Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

16 files changed, 9958 insertions, 0 deletions

diff --git a/src/rocksdb/env/composite_env_wrapper.h b/src/rocksdb/env/composite_env_wrapper.h
new file mode 100644
index 000000000..fbc0b93fa
--- /dev/null
+++ b/src/rocksdb/env/composite_env_wrapper.h
@@ -0,0 +1,1117 @@
+// Copyright (c) 2019-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include "rocksdb/env.h"
+#include "rocksdb/file_system.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// The CompositeEnvWrapper class provides an interface that is compatible
+// with the old monolithic Env API, and an implementation that wraps around
+// the new Env that provides threading and other OS related functionality, and
+// the new FileSystem API that provides storage functionality. By
+// providing the old Env interface, it allows the rest of RocksDB code to
+// be agnostic of whether the underlying Env implementation is a monolithic
+// Env or an Env + FileSystem. In the former case, the user will specify
+// Options::env only, whereas in the latter case, the user will specify
+// Options::env and Options::file_system.
+
+inline IOStatus status_to_io_status(Status&& status) {
+  if (status.ok()) {
+    // Fast path
+    return IOStatus::OK();
+  } else {
+    const char* state = status.getState();
+    if (state) {
+      return IOStatus(status.code(), status.subcode(),
+                      Slice(state, strlen(status.getState()) + 1),
+                      Slice());
+    } else {
+      return IOStatus(status.code(), status.subcode());
+    }
+  }
+}
+
+class CompositeSequentialFileWrapper : public SequentialFile {
+ public:
+  explicit CompositeSequentialFileWrapper(
+      std::unique_ptr<FSSequentialFile>& target)
+      : target_(std::move(target)) {}
+
+  Status Read(size_t n, Slice* result, char* scratch) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Read(n, io_opts, result, scratch, &dbg);
+  }
+  Status Skip(uint64_t n) override { return target_->Skip(n); }
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+  Status InvalidateCache(size_t offset, size_t length) override {
+    return target_->InvalidateCache(offset, length);
+  }
+  Status PositionedRead(uint64_t offset, size_t n, Slice* result,
+                        char* scratch) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->PositionedRead(offset, n, io_opts, result, scratch, &dbg);
+  }
+
+ private:
+  std::unique_ptr<FSSequentialFile> target_;
+};
+
+class CompositeRandomAccessFileWrapper : public RandomAccessFile {
+ public:
+  explicit CompositeRandomAccessFileWrapper(
+      std::unique_ptr<FSRandomAccessFile>& target)
+      : target_(std::move(target)) {}
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Read(offset, n, io_opts, result, scratch, &dbg);
+  }
+  Status MultiRead(ReadRequest* reqs, size_t num_reqs) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    std::vector<FSReadRequest> fs_reqs;
+    Status status;
+
+    fs_reqs.resize(num_reqs);
+    for (size_t i = 0; i < num_reqs; ++i) {
+      fs_reqs[i].offset = reqs[i].offset;
+      fs_reqs[i].len = reqs[i].len;
+      fs_reqs[i].scratch = reqs[i].scratch;
+      fs_reqs[i].status = IOStatus::OK();
+    }
+    status = target_->MultiRead(fs_reqs.data(), num_reqs, io_opts, &dbg);
+    for (size_t i = 0; i < num_reqs; ++i) {
+      reqs[i].result = fs_reqs[i].result;
+      reqs[i].status = fs_reqs[i].status;
+    }
+    return status;
+  }
+  Status Prefetch(uint64_t offset, size_t n) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Prefetch(offset, n, io_opts, &dbg);
+  }
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return target_->GetUniqueId(id, max_size);
+  };
+  void Hint(AccessPattern pattern) override {
+    target_->Hint((FSRandomAccessFile::AccessPattern)pattern);
+  }
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+  Status InvalidateCache(size_t offset, size_t length) override {
+    return target_->InvalidateCache(offset, length);
+  }
+
+ private:
+  std::unique_ptr<FSRandomAccessFile> target_;
+};
+
+class CompositeWritableFileWrapper : public WritableFile {
+ public:
+  explicit CompositeWritableFileWrapper(std::unique_ptr<FSWritableFile>& t)
+      : target_(std::move(t)) {}
+
+  Status Append(const Slice& data) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Append(data, io_opts, &dbg);
+  }
+  Status PositionedAppend(const Slice& data, uint64_t offset) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->PositionedAppend(data, offset, io_opts, &dbg);
+  }
+  Status Truncate(uint64_t size) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Truncate(size, io_opts, &dbg);
+  }
+  Status Close() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Close(io_opts, &dbg);
+  }
+  Status Flush() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Flush(io_opts, &dbg);
+  }
+  Status Sync() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Sync(io_opts, &dbg);
+  }
+  Status Fsync() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Fsync(io_opts, &dbg);
+  }
+  bool IsSyncThreadSafe() const override { return target_->IsSyncThreadSafe(); }
+
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+
+  void SetWriteLifeTimeHint(Env::WriteLifeTimeHint hint) override {
+    target_->SetWriteLifeTimeHint(hint);
+  }
+
+  Env::WriteLifeTimeHint GetWriteLifeTimeHint() override {
+    return target_->GetWriteLifeTimeHint();
+  }
+
+  uint64_t GetFileSize() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->GetFileSize(io_opts, &dbg);
+  }
+
+  void SetPreallocationBlockSize(size_t size) override {
+    target_->SetPreallocationBlockSize(size);
+  }
+
+  void GetPreallocationStatus(size_t* block_size,
+                              size_t* last_allocated_block) override {
+    target_->GetPreallocationStatus(block_size, last_allocated_block);
+  }
+
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return target_->GetUniqueId(id, max_size);
+  }
+
+  Status InvalidateCache(size_t offset, size_t length) override {
+    return target_->InvalidateCache(offset, length);
+  }
+
+  Status RangeSync(uint64_t offset, uint64_t nbytes) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->RangeSync(offset, nbytes, io_opts, &dbg);
+  }
+
+  void PrepareWrite(size_t offset, size_t len) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    target_->PrepareWrite(offset, len, io_opts, &dbg);
+  }
+
+  Status Allocate(uint64_t offset, uint64_t len) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Allocate(offset, len, io_opts, &dbg);
+  }
+
+  std::unique_ptr<FSWritableFile>* target() { return &target_; }
+
+ private:
+  std::unique_ptr<FSWritableFile> target_;
+};
+
+class CompositeRandomRWFileWrapper : public RandomRWFile {
+ public:
+  explicit CompositeRandomRWFileWrapper(std::unique_ptr<FSRandomRWFile>& target)
+      : target_(std::move(target)) {}
+
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+  Status Write(uint64_t offset, const Slice& data) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Write(offset, data, io_opts, &dbg);
+  }
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Read(offset, n, io_opts, result, scratch, &dbg);
+  }
+  Status Flush() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Flush(io_opts, &dbg);
+  }
+  Status Sync() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Sync(io_opts, &dbg);
+  }
+  Status Fsync() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Fsync(io_opts, &dbg);
+  }
+  Status Close() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Close(io_opts, &dbg);
+  }
+
+ private:
+  std::unique_ptr<FSRandomRWFile> target_;
+};
+
+class CompositeDirectoryWrapper : public Directory {
+ public:
+  explicit CompositeDirectoryWrapper(std::unique_ptr<FSDirectory>& target)
+      : target_(std::move(target)) {}
+
+  Status Fsync() override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return target_->Fsync(io_opts, &dbg);
+  }
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return target_->GetUniqueId(id, max_size);
+  }
+
+ private:
+  std::unique_ptr<FSDirectory> target_;
+};
+
+class CompositeEnvWrapper : public Env {
+ public:
+  // Initialize a CompositeEnvWrapper that delegates all thread/time related
+  // calls to env, and all file operations to fs
+  explicit CompositeEnvWrapper(Env* env, FileSystem* fs)
+      : env_target_(env), fs_env_target_(fs) {}
+  ~CompositeEnvWrapper() {}
+
+  // Return the target to which this Env forwards all calls
+  Env* env_target() const { return env_target_; }
+
+  FileSystem* fs_env_target() const { return fs_env_target_; }
+
+  // The following text is boilerplate that forwards all methods to target()
+  Status NewSequentialFile(const std::string& f,
+                           std::unique_ptr<SequentialFile>* r,
+                           const EnvOptions& options) override {
+    IODebugContext dbg;
+    std::unique_ptr<FSSequentialFile> file;
+    Status status;
+    status =
+        fs_env_target_->NewSequentialFile(f, FileOptions(options), &file, &dbg);
+    if (status.ok()) {
+      r->reset(new CompositeSequentialFileWrapper(file));
+    }
+    return status;
+  }
+  Status NewRandomAccessFile(const std::string& f,
+                             std::unique_ptr<RandomAccessFile>* r,
+                             const EnvOptions& options) override {
+    IODebugContext dbg;
+    std::unique_ptr<FSRandomAccessFile> file;
+    Status status;
+    status = fs_env_target_->NewRandomAccessFile(f, FileOptions(options), &file,
+                                                 &dbg);
+    if (status.ok()) {
+      r->reset(new CompositeRandomAccessFileWrapper(file));
+    }
+    return status;
+  }
+  Status NewWritableFile(const std::string& f, std::unique_ptr<WritableFile>* r,
+                         const EnvOptions& options) override {
+    IODebugContext dbg;
+    std::unique_ptr<FSWritableFile> file;
+    Status status;
+    status =
+        fs_env_target_->NewWritableFile(f, FileOptions(options), &file, &dbg);
+    if (status.ok()) {
+      r->reset(new CompositeWritableFileWrapper(file));
+    }
+    return status;
+  }
+  Status ReopenWritableFile(const std::string& fname,
+                            std::unique_ptr<WritableFile>* result,
+                            const EnvOptions& options) override {
+    IODebugContext dbg;
+    Status status;
+    std::unique_ptr<FSWritableFile> file;
+    status = fs_env_target_->ReopenWritableFile(fname, FileOptions(options),
+                                                &file, &dbg);
+    if (status.ok()) {
+      result->reset(new CompositeWritableFileWrapper(file));
+    }
+    return status;
+  }
+  Status ReuseWritableFile(const std::string& fname,
+                           const std::string& old_fname,
+                           std::unique_ptr<WritableFile>* r,
+                           const EnvOptions& options) override {
+    IODebugContext dbg;
+    Status status;
+    std::unique_ptr<FSWritableFile> file;
+    status = fs_env_target_->ReuseWritableFile(
+        fname, old_fname, FileOptions(options), &file, &dbg);
+    if (status.ok()) {
+      r->reset(new CompositeWritableFileWrapper(file));
+    }
+    return status;
+  }
+  Status NewRandomRWFile(const std::string& fname,
+                         std::unique_ptr<RandomRWFile>* result,
+                         const EnvOptions& options) override {
+    IODebugContext dbg;
+    std::unique_ptr<FSRandomRWFile> file;
+    Status status;
+    status = fs_env_target_->NewRandomRWFile(fname, FileOptions(options), &file,
+                                             &dbg);
+    if (status.ok()) {
+      result->reset(new CompositeRandomRWFileWrapper(file));
+    }
+    return status;
+  }
+  Status NewMemoryMappedFileBuffer(
+      const std::string& fname,
+      std::unique_ptr<MemoryMappedFileBuffer>* result) override {
+    return fs_env_target_->NewMemoryMappedFileBuffer(fname, result);
+  }
+  Status NewDirectory(const std::string& name,
+                      std::unique_ptr<Directory>* result) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    std::unique_ptr<FSDirectory> dir;
+    Status status;
+    status = fs_env_target_->NewDirectory(name, io_opts, &dir, &dbg);
+    if (status.ok()) {
+      result->reset(new CompositeDirectoryWrapper(dir));
+    }
+    return status;
+  }
+  Status FileExists(const std::string& f) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->FileExists(f, io_opts, &dbg);
+  }
+  Status GetChildren(const std::string& dir,
+                     std::vector<std::string>* r) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->GetChildren(dir, io_opts, r, &dbg);
+  }
+  Status GetChildrenFileAttributes(
+      const std::string& dir, std::vector<FileAttributes>* result) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->GetChildrenFileAttributes(dir, io_opts, result,
+                                                     &dbg);
+  }
+  Status DeleteFile(const std::string& f) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->DeleteFile(f, io_opts, &dbg);
+  }
+  Status Truncate(const std::string& fname, size_t size) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->Truncate(fname, size, io_opts, &dbg);
+  }
+  Status CreateDir(const std::string& d) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->CreateDir(d, io_opts, &dbg);
+  }
+  Status CreateDirIfMissing(const std::string& d) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->CreateDirIfMissing(d, io_opts, &dbg);
+  }
+  Status DeleteDir(const std::string& d) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->DeleteDir(d, io_opts, &dbg);
+  }
+  Status GetFileSize(const std::string& f, uint64_t* s) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->GetFileSize(f, io_opts, s, &dbg);
+  }
+
+  Status GetFileModificationTime(const std::string& fname,
+                                 uint64_t* file_mtime) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->GetFileModificationTime(fname, io_opts, file_mtime,
+                                                   &dbg);
+  }
+
+  Status RenameFile(const std::string& s, const std::string& t) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->RenameFile(s, t, io_opts, &dbg);
+  }
+
+  Status LinkFile(const std::string& s, const std::string& t) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->LinkFile(s, t, io_opts, &dbg);
+  }
+
+  Status NumFileLinks(const std::string& fname, uint64_t* count) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->NumFileLinks(fname, io_opts, count, &dbg);
+  }
+
+  Status AreFilesSame(const std::string& first, const std::string& second,
+                      bool* res) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->AreFilesSame(first, second, io_opts, res, &dbg);
+  }
+
+  Status LockFile(const std::string& f, FileLock** l) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->LockFile(f, io_opts, l, &dbg);
+  }
+
+  Status UnlockFile(FileLock* l) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->UnlockFile(l, io_opts, &dbg);
+  }
+
+  Status GetAbsolutePath(const std::string& db_path,
+                         std::string* output_path) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->GetAbsolutePath(db_path, io_opts, output_path, &dbg);
+  }
+
+#if !defined(OS_WIN) && !defined(ROCKSDB_NO_DYNAMIC_EXTENSION)
+  Status LoadLibrary(const std::string& lib_name,
+                     const std::string& search_path,
+                     std::shared_ptr<DynamicLibrary>* result) override {
+    return env_target_->LoadLibrary(lib_name, search_path, result);
+  }
+#endif
+
+  void Schedule(void (*f)(void* arg), void* a, Priority pri,
+                void* tag = nullptr, void (*u)(void* arg) = nullptr) override {
+    return env_target_->Schedule(f, a, pri, tag, u);
+  }
+
+  int UnSchedule(void* tag, Priority pri) override {
+    return env_target_->UnSchedule(tag, pri);
+  }
+
+  void StartThread(void (*f)(void*), void* a) override {
+    return env_target_->StartThread(f, a);
+  }
+  void WaitForJoin() override { return env_target_->WaitForJoin(); }
+  unsigned int GetThreadPoolQueueLen(Priority pri = LOW) const override {
+    return env_target_->GetThreadPoolQueueLen(pri);
+  }
+  Status GetTestDirectory(std::string* path) override {
+    return env_target_->GetTestDirectory(path);
+  }
+  Status NewLogger(const std::string& fname,
+                   std::shared_ptr<Logger>* result) override {
+    return env_target_->NewLogger(fname, result);
+  }
+  uint64_t NowMicros() override { return env_target_->NowMicros(); }
+  uint64_t NowNanos() override { return env_target_->NowNanos(); }
+  uint64_t NowCPUNanos() override { return env_target_->NowCPUNanos(); }
+
+  void SleepForMicroseconds(int micros) override {
+    env_target_->SleepForMicroseconds(micros);
+  }
+  Status GetHostName(char* name, uint64_t len) override {
+    return env_target_->GetHostName(name, len);
+  }
+  Status GetCurrentTime(int64_t* unix_time) override {
+    return env_target_->GetCurrentTime(unix_time);
+  }
+  void SetBackgroundThreads(int num, Priority pri) override {
+    return env_target_->SetBackgroundThreads(num, pri);
+  }
+  int GetBackgroundThreads(Priority pri) override {
+    return env_target_->GetBackgroundThreads(pri);
+  }
+
+  Status SetAllowNonOwnerAccess(bool allow_non_owner_access) override {
+    return env_target_->SetAllowNonOwnerAccess(allow_non_owner_access);
+  }
+
+  void IncBackgroundThreadsIfNeeded(int num, Priority pri) override {
+    return env_target_->IncBackgroundThreadsIfNeeded(num, pri);
+  }
+
+  void LowerThreadPoolIOPriority(Priority pool = LOW) override {
+    env_target_->LowerThreadPoolIOPriority(pool);
+  }
+
+  void LowerThreadPoolCPUPriority(Priority pool = LOW) override {
+    env_target_->LowerThreadPoolCPUPriority(pool);
+  }
+
+  std::string TimeToString(uint64_t time) override {
+    return env_target_->TimeToString(time);
+  }
+
+  Status GetThreadList(std::vector<ThreadStatus>* thread_list) override {
+    return env_target_->GetThreadList(thread_list);
+  }
+
+  ThreadStatusUpdater* GetThreadStatusUpdater() const override {
+    return env_target_->GetThreadStatusUpdater();
+  }
+
+  uint64_t GetThreadID() const override { return env_target_->GetThreadID(); }
+
+  std::string GenerateUniqueId() override {
+    return env_target_->GenerateUniqueId();
+  }
+
+  EnvOptions OptimizeForLogRead(const EnvOptions& env_options) const override {
+    return fs_env_target_->OptimizeForLogRead(FileOptions(env_options));
+  }
+  EnvOptions OptimizeForManifestRead(
+      const EnvOptions& env_options) const override {
+    return fs_env_target_->OptimizeForManifestRead(
+                                FileOptions(env_options));
+  }
+  EnvOptions OptimizeForLogWrite(const EnvOptions& env_options,
+                                 const DBOptions& db_options) const override {
+    return fs_env_target_->OptimizeForLogWrite(FileOptions(env_options),
+                                               db_options);
+  }
+  EnvOptions OptimizeForManifestWrite(
+      const EnvOptions& env_options) const override {
+    return fs_env_target_->OptimizeForManifestWrite(
+                                FileOptions(env_options));
+  }
+  EnvOptions OptimizeForCompactionTableWrite(
+      const EnvOptions& env_options,
+      const ImmutableDBOptions& immutable_ops) const override {
+    return fs_env_target_->OptimizeForCompactionTableWrite(
+                                FileOptions(env_options),
+                                immutable_ops);
+  }
+  EnvOptions OptimizeForCompactionTableRead(
+      const EnvOptions& env_options,
+      const ImmutableDBOptions& db_options) const override {
+    return fs_env_target_->OptimizeForCompactionTableRead(
+                                FileOptions(env_options),
+                                db_options);
+  }
+  Status GetFreeSpace(const std::string& path, uint64_t* diskfree) override {
+    IOOptions io_opts;
+    IODebugContext dbg;
+    return fs_env_target_->GetFreeSpace(path, io_opts, diskfree, &dbg);
+  }
+
+ private:
+  Env* env_target_;
+  FileSystem* fs_env_target_;
+};
+
+class LegacySequentialFileWrapper : public FSSequentialFile {
+ public:
+  explicit LegacySequentialFileWrapper(
+      std::unique_ptr<SequentialFile>&& _target)
+      : target_(std::move(_target)) {}
+
+  IOStatus Read(size_t n, const IOOptions& /*options*/, Slice* result,
+                char* scratch, IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Read(n, result, scratch));
+  }
+  IOStatus Skip(uint64_t n) override {
+    return status_to_io_status(target_->Skip(n));
+  }
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+  IOStatus InvalidateCache(size_t offset, size_t length) override {
+    return status_to_io_status(target_->InvalidateCache(offset, length));
+  }
+  IOStatus PositionedRead(uint64_t offset, size_t n,
+                          const IOOptions& /*options*/, Slice* result,
+                          char* scratch, IODebugContext* /*dbg*/) override {
+    return status_to_io_status(
+        target_->PositionedRead(offset, n, result, scratch));
+  }
+  SequentialFile* target() { return target_.get(); }
+
+ private:
+  std::unique_ptr<SequentialFile> target_;
+};
+
+class LegacyRandomAccessFileWrapper : public FSRandomAccessFile {
+ public:
+  explicit LegacyRandomAccessFileWrapper(
+      std::unique_ptr<RandomAccessFile>&& target)
+      : target_(std::move(target)) {}
+
+  IOStatus Read(uint64_t offset, size_t n, const IOOptions& /*options*/,
+                Slice* result, char* scratch,
+                IODebugContext* /*dbg*/) const override {
+    return status_to_io_status(target_->Read(offset, n, result, scratch));
+  }
+  IOStatus MultiRead(FSReadRequest* fs_reqs, size_t num_reqs,
+                     const IOOptions& /*options*/,
+                     IODebugContext* /*dbg*/) override {
+    std::vector<ReadRequest> reqs;
+    Status status;
+
+    reqs.reserve(num_reqs);
+    for (size_t i = 0; i < num_reqs; ++i) {
+      ReadRequest req;
+
+      req.offset = fs_reqs[i].offset;
+      req.len = fs_reqs[i].len;
+      req.scratch = fs_reqs[i].scratch;
+      req.status = Status::OK();
+
+      reqs.emplace_back(req);
+    }
+    status = target_->MultiRead(reqs.data(), num_reqs);
+    for (size_t i = 0; i < num_reqs; ++i) {
+      fs_reqs[i].result = reqs[i].result;
+      fs_reqs[i].status = status_to_io_status(std::move(reqs[i].status));
+    }
+    return status_to_io_status(std::move(status));
+    ;
+  }
+  IOStatus Prefetch(uint64_t offset, size_t n, const IOOptions& /*options*/,
+                    IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Prefetch(offset, n));
+  }
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return target_->GetUniqueId(id, max_size);
+  };
+  void Hint(AccessPattern pattern) override {
+    target_->Hint((RandomAccessFile::AccessPattern)pattern);
+  }
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+  IOStatus InvalidateCache(size_t offset, size_t length) override {
+    return status_to_io_status(target_->InvalidateCache(offset, length));
+  }
+
+ private:
+  std::unique_ptr<RandomAccessFile> target_;
+};
+
+class LegacyWritableFileWrapper : public FSWritableFile {
+ public:
+  explicit LegacyWritableFileWrapper(std::unique_ptr<WritableFile>&& _target)
+      : target_(std::move(_target)) {}
+
+  IOStatus Append(const Slice& data, const IOOptions& /*options*/,
+                  IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Append(data));
+  }
+  IOStatus PositionedAppend(const Slice& data, uint64_t offset,
+                            const IOOptions& /*options*/,
+                            IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->PositionedAppend(data, offset));
+  }
+  IOStatus Truncate(uint64_t size, const IOOptions& /*options*/,
+                    IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Truncate(size));
+  }
+  IOStatus Close(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Close());
+  }
+  IOStatus Flush(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Flush());
+  }
+  IOStatus Sync(const IOOptions& /*options*/,
+                IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Sync());
+  }
+  IOStatus Fsync(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Fsync());
+  }
+  bool IsSyncThreadSafe() const override { return target_->IsSyncThreadSafe(); }
+
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+
+  void SetWriteLifeTimeHint(Env::WriteLifeTimeHint hint) override {
+    target_->SetWriteLifeTimeHint(hint);
+  }
+
+  Env::WriteLifeTimeHint GetWriteLifeTimeHint() override {
+    return target_->GetWriteLifeTimeHint();
+  }
+
+  uint64_t GetFileSize(const IOOptions& /*options*/,
+                       IODebugContext* /*dbg*/) override {
+    return target_->GetFileSize();
+  }
+
+  void SetPreallocationBlockSize(size_t size) override {
+    target_->SetPreallocationBlockSize(size);
+  }
+
+  void GetPreallocationStatus(size_t* block_size,
+                              size_t* last_allocated_block) override {
+    target_->GetPreallocationStatus(block_size, last_allocated_block);
+  }
+
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return target_->GetUniqueId(id, max_size);
+  }
+
+  IOStatus InvalidateCache(size_t offset, size_t length) override {
+    return status_to_io_status(target_->InvalidateCache(offset, length));
+  }
+
+  IOStatus RangeSync(uint64_t offset, uint64_t nbytes,
+                     const IOOptions& /*options*/,
+                     IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->RangeSync(offset, nbytes));
+  }
+
+  void PrepareWrite(size_t offset, size_t len, const IOOptions& /*options*/,
+                    IODebugContext* /*dbg*/) override {
+    target_->PrepareWrite(offset, len);
+  }
+
+  IOStatus Allocate(uint64_t offset, uint64_t len, const IOOptions& /*options*/,
+                    IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Allocate(offset, len));
+  }
+
+  WritableFile* target() { return target_.get(); }
+
+ private:
+  std::unique_ptr<WritableFile> target_;
+};
+
+class LegacyRandomRWFileWrapper : public FSRandomRWFile {
+ public:
+  explicit LegacyRandomRWFileWrapper(std::unique_ptr<RandomRWFile>&& target)
+      : target_(std::move(target)) {}
+
+  bool use_direct_io() const override { return target_->use_direct_io(); }
+  size_t GetRequiredBufferAlignment() const override {
+    return target_->GetRequiredBufferAlignment();
+  }
+  IOStatus Write(uint64_t offset, const Slice& data,
+                 const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Write(offset, data));
+  }
+  IOStatus Read(uint64_t offset, size_t n, const IOOptions& /*options*/,
+                Slice* result, char* scratch,
+                IODebugContext* /*dbg*/) const override {
+    return status_to_io_status(target_->Read(offset, n, result, scratch));
+  }
+  IOStatus Flush(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Flush());
+  }
+  IOStatus Sync(const IOOptions& /*options*/,
+                IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Sync());
+  }
+  IOStatus Fsync(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Fsync());
+  }
+  IOStatus Close(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Close());
+  }
+
+ private:
+  std::unique_ptr<RandomRWFile> target_;
+};
+
+class LegacyDirectoryWrapper : public FSDirectory {
+ public:
+  explicit LegacyDirectoryWrapper(std::unique_ptr<Directory>&& target)
+      : target_(std::move(target)) {}
+
+  IOStatus Fsync(const IOOptions& /*options*/,
+                 IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Fsync());
+  }
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return target_->GetUniqueId(id, max_size);
+  }
+
+ private:
+  std::unique_ptr<Directory> target_;
+};
+
+class LegacyFileSystemWrapper : public FileSystem {
+ public:
+  // Initialize an EnvWrapper that delegates all calls to *t
+  explicit LegacyFileSystemWrapper(Env* t) : target_(t) {}
+  ~LegacyFileSystemWrapper() override {}
+
+  const char* Name() const override { return "Legacy File System"; }
+
+  // Return the target to which this Env forwards all calls
+  Env* target() const { return target_; }
+
+  // The following text is boilerplate that forwards all methods to target()
+  IOStatus NewSequentialFile(const std::string& f,
+                             const FileOptions& file_opts,
+                             std::unique_ptr<FSSequentialFile>* r,
+                             IODebugContext* /*dbg*/) override {
+    std::unique_ptr<SequentialFile> file;
+    Status s = target_->NewSequentialFile(f, &file, file_opts);
+    if (s.ok()) {
+      r->reset(new LegacySequentialFileWrapper(std::move(file)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus NewRandomAccessFile(const std::string& f,
+      const FileOptions& file_opts,
+                               std::unique_ptr<FSRandomAccessFile>* r,
+                               IODebugContext* /*dbg*/) override {
+    std::unique_ptr<RandomAccessFile> file;
+    Status s = target_->NewRandomAccessFile(f, &file, file_opts);
+    if (s.ok()) {
+      r->reset(new LegacyRandomAccessFileWrapper(std::move(file)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus NewWritableFile(const std::string& f, const FileOptions& file_opts,
+                           std::unique_ptr<FSWritableFile>* r,
+                           IODebugContext* /*dbg*/) override {
+    std::unique_ptr<WritableFile> file;
+    Status s = target_->NewWritableFile(f, &file, file_opts);
+    if (s.ok()) {
+      r->reset(new LegacyWritableFileWrapper(std::move(file)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus ReopenWritableFile(const std::string& fname,
+                              const FileOptions& file_opts,
+                              std::unique_ptr<FSWritableFile>* result,
+                              IODebugContext* /*dbg*/) override {
+    std::unique_ptr<WritableFile> file;
+    Status s = target_->ReopenWritableFile(fname, &file, file_opts);
+    if (s.ok()) {
+      result->reset(new LegacyWritableFileWrapper(std::move(file)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus ReuseWritableFile(const std::string& fname,
+                             const std::string& old_fname,
+                             const FileOptions& file_opts,
+                             std::unique_ptr<FSWritableFile>* r,
+                             IODebugContext* /*dbg*/) override {
+    std::unique_ptr<WritableFile> file;
+    Status s = target_->ReuseWritableFile(fname, old_fname, &file, file_opts);
+    if (s.ok()) {
+      r->reset(new LegacyWritableFileWrapper(std::move(file)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus NewRandomRWFile(const std::string& fname,
+      const FileOptions& file_opts,
+                           std::unique_ptr<FSRandomRWFile>* result,
+                           IODebugContext* /*dbg*/) override {
+    std::unique_ptr<RandomRWFile> file;
+    Status s = target_->NewRandomRWFile(fname, &file, file_opts);
+    if (s.ok()) {
+      result->reset(new LegacyRandomRWFileWrapper(std::move(file)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus NewMemoryMappedFileBuffer(
+      const std::string& fname,
+      std::unique_ptr<MemoryMappedFileBuffer>* result) override {
+    return status_to_io_status(
+        target_->NewMemoryMappedFileBuffer(fname, result));
+  }
+  IOStatus NewDirectory(const std::string& name, const IOOptions& /*io_opts*/,
+                        std::unique_ptr<FSDirectory>* result,
+                        IODebugContext* /*dbg*/) override {
+    std::unique_ptr<Directory> dir;
+    Status s = target_->NewDirectory(name, &dir);
+    if (s.ok()) {
+      result->reset(new LegacyDirectoryWrapper(std::move(dir)));
+    }
+    return status_to_io_status(std::move(s));
+  }
+  IOStatus FileExists(const std::string& f, const IOOptions& /*io_opts*/,
+                      IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->FileExists(f));
+  }
+  IOStatus GetChildren(const std::string& dir, const IOOptions& /*io_opts*/,
+                       std::vector<std::string>* r,
+                       IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->GetChildren(dir, r));
+  }
+  IOStatus GetChildrenFileAttributes(const std::string& dir,
+                                     const IOOptions& /*options*/,
+                                     std::vector<FileAttributes>* result,
+                                     IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->GetChildrenFileAttributes(dir, result));
+  }
+  IOStatus DeleteFile(const std::string& f, const IOOptions& /*options*/,
+                      IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->DeleteFile(f));
+  }
+  IOStatus Truncate(const std::string& fname, size_t size,
+                    const IOOptions& /*options*/,
+                    IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->Truncate(fname, size));
+  }
+  IOStatus CreateDir(const std::string& d, const IOOptions& /*options*/,
+                     IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->CreateDir(d));
+  }
+  IOStatus CreateDirIfMissing(const std::string& d,
+                              const IOOptions& /*options*/,
+                              IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->CreateDirIfMissing(d));
+  }
+  IOStatus DeleteDir(const std::string& d, const IOOptions& /*options*/,
+                     IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->DeleteDir(d));
+  }
+  IOStatus GetFileSize(const std::string& f, const IOOptions& /*options*/,
+                       uint64_t* s, IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->GetFileSize(f, s));
+  }
+
+  IOStatus GetFileModificationTime(const std::string& fname,
+                                   const IOOptions& /*options*/,
+                                   uint64_t* file_mtime,
+                                   IODebugContext* /*dbg*/) override {
+    return status_to_io_status(
+        target_->GetFileModificationTime(fname, file_mtime));
+  }
+
+  IOStatus GetAbsolutePath(const std::string& db_path,
+                           const IOOptions& /*options*/,
+                           std::string* output_path,
+                           IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->GetAbsolutePath(db_path, output_path));
+  }
+
+  IOStatus RenameFile(const std::string& s, const std::string& t,
+                      const IOOptions& /*options*/,
+                      IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->RenameFile(s, t));
+  }
+
+  IOStatus LinkFile(const std::string& s, const std::string& t,
+                    const IOOptions& /*options*/,
+                    IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->LinkFile(s, t));
+  }
+
+  IOStatus NumFileLinks(const std::string& fname, const IOOptions& /*options*/,
+                        uint64_t* count, IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->NumFileLinks(fname, count));
+  }
+
+  IOStatus AreFilesSame(const std::string& first, const std::string& second,
+                        const IOOptions& /*options*/, bool* res,
+                        IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->AreFilesSame(first, second, res));
+  }
+
+  IOStatus LockFile(const std::string& f, const IOOptions& /*options*/,
+                    FileLock** l, IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->LockFile(f, l));
+  }
+
+  IOStatus UnlockFile(FileLock* l, const IOOptions& /*options*/,
+                      IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->UnlockFile(l));
+  }
+
+  IOStatus GetTestDirectory(const IOOptions& /*options*/, std::string* path,
+                            IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->GetTestDirectory(path));
+  }
+  IOStatus NewLogger(const std::string& fname, const IOOptions& /*options*/,
+                     std::shared_ptr<Logger>* result,
+                     IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->NewLogger(fname, result));
+  }
+
+  FileOptions OptimizeForLogRead(
+                  const FileOptions& file_options) const override {
+    return target_->OptimizeForLogRead(file_options);
+  }
+  FileOptions OptimizeForManifestRead(
+      const FileOptions& file_options) const override {
+    return target_->OptimizeForManifestRead(file_options);
+  }
+  FileOptions OptimizeForLogWrite(const FileOptions& file_options,
+                                 const DBOptions& db_options) const override {
+    return target_->OptimizeForLogWrite(file_options, db_options);
+  }
+  FileOptions OptimizeForManifestWrite(
+      const FileOptions& file_options) const override {
+    return target_->OptimizeForManifestWrite(file_options);
+  }
+  FileOptions OptimizeForCompactionTableWrite(
+      const FileOptions& file_options,
+      const ImmutableDBOptions& immutable_ops) const override {
+    return target_->OptimizeForCompactionTableWrite(file_options,
+                                                     immutable_ops);
+  }
+  FileOptions OptimizeForCompactionTableRead(
+      const FileOptions& file_options,
+      const ImmutableDBOptions& db_options) const override {
+    return target_->OptimizeForCompactionTableRead(file_options, db_options);
+  }
+  IOStatus GetFreeSpace(const std::string& path, const IOOptions& /*options*/,
+                        uint64_t* diskfree, IODebugContext* /*dbg*/) override {
+    return status_to_io_status(target_->GetFreeSpace(path, diskfree));
+  }
+
+ private:
+  Env* target_;
+};
+
+inline std::unique_ptr<FSSequentialFile> NewLegacySequentialFileWrapper(
+    std::unique_ptr<SequentialFile>& file) {
+  return std::unique_ptr<FSSequentialFile>(
+      new LegacySequentialFileWrapper(std::move(file)));
+}
+
+inline std::unique_ptr<FSRandomAccessFile> NewLegacyRandomAccessFileWrapper(
+    std::unique_ptr<RandomAccessFile>& file) {
+  return std::unique_ptr<FSRandomAccessFile>(
+      new LegacyRandomAccessFileWrapper(std::move(file)));
+}
+
+inline std::unique_ptr<FSWritableFile> NewLegacyWritableFileWrapper(
+    std::unique_ptr<WritableFile>&& file) {
+  return std::unique_ptr<FSWritableFile>(
+      new LegacyWritableFileWrapper(std::move(file)));
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/env.cc b/src/rocksdb/env/env.cc
new file mode 100644
index 000000000..70f4b29f7
--- /dev/null
+++ b/src/rocksdb/env/env.cc
@@ -0,0 +1,475 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "rocksdb/env.h"
+
+#include <thread>
+#include "env/composite_env_wrapper.h"
+#include "logging/env_logger.h"
+#include "memory/arena.h"
+#include "options/db_options.h"
+#include "port/port.h"
+#include "port/sys_time.h"
+#include "rocksdb/options.h"
+#include "rocksdb/utilities/object_registry.h"
+#include "util/autovector.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+Env::~Env() {
+}
+
+Status Env::NewLogger(const std::string& fname,
+                      std::shared_ptr<Logger>* result) {
+  return NewEnvLogger(fname, this, result);
+}
+
+Status Env::LoadEnv(const std::string& value, Env** result) {
+  Env* env = *result;
+  Status s;
+#ifndef ROCKSDB_LITE
+  s = ObjectRegistry::NewInstance()->NewStaticObject<Env>(value, &env);
+#else
+  s = Status::NotSupported("Cannot load environment in LITE mode: ", value);
+#endif
+  if (s.ok()) {
+    *result = env;
+  }
+  return s;
+}
+
+Status Env::LoadEnv(const std::string& value, Env** result,
+                    std::shared_ptr<Env>* guard) {
+  assert(result);
+  Status s;
+#ifndef ROCKSDB_LITE
+  Env* env = nullptr;
+  std::unique_ptr<Env> uniq_guard;
+  std::string err_msg;
+  assert(guard != nullptr);
+  env = ObjectRegistry::NewInstance()->NewObject<Env>(value, &uniq_guard,
+                                                      &err_msg);
+  if (!env) {
+    s = Status::NotFound(std::string("Cannot load ") + Env::Type() + ": " +
+                         value);
+    env = Env::Default();
+  }
+  if (s.ok() && uniq_guard) {
+    guard->reset(uniq_guard.release());
+    *result = guard->get();
+  } else {
+    *result = env;
+  }
+#else
+  (void)result;
+  (void)guard;
+  s = Status::NotSupported("Cannot load environment in LITE mode: ", value);
+#endif
+  return s;
+}
+
+std::string Env::PriorityToString(Env::Priority priority) {
+  switch (priority) {
+    case Env::Priority::BOTTOM:
+      return "Bottom";
+    case Env::Priority::LOW:
+      return "Low";
+    case Env::Priority::HIGH:
+      return "High";
+    case Env::Priority::USER:
+      return "User";
+    case Env::Priority::TOTAL:
+      assert(false);
+  }
+  return "Invalid";
+}
+
+uint64_t Env::GetThreadID() const {
+  std::hash<std::thread::id> hasher;
+  return hasher(std::this_thread::get_id());
+}
+
+Status Env::ReuseWritableFile(const std::string& fname,
+                              const std::string& old_fname,
+                              std::unique_ptr<WritableFile>* result,
+                              const EnvOptions& options) {
+  Status s = RenameFile(old_fname, fname);
+  if (!s.ok()) {
+    return s;
+  }
+  return NewWritableFile(fname, result, options);
+}
+
+Status Env::GetChildrenFileAttributes(const std::string& dir,
+                                      std::vector<FileAttributes>* result) {
+  assert(result != nullptr);
+  std::vector<std::string> child_fnames;
+  Status s = GetChildren(dir, &child_fnames);
+  if (!s.ok()) {
+    return s;
+  }
+  result->resize(child_fnames.size());
+  size_t result_size = 0;
+  for (size_t i = 0; i < child_fnames.size(); ++i) {
+    const std::string path = dir + "/" + child_fnames[i];
+    if (!(s = GetFileSize(path, &(*result)[result_size].size_bytes)).ok()) {
+      if (FileExists(path).IsNotFound()) {
+        // The file may have been deleted since we listed the directory
+        continue;
+      }
+      return s;
+    }
+    (*result)[result_size].name = std::move(child_fnames[i]);
+    result_size++;
+  }
+  result->resize(result_size);
+  return Status::OK();
+}
+
+SequentialFile::~SequentialFile() {
+}
+
+RandomAccessFile::~RandomAccessFile() {
+}
+
+WritableFile::~WritableFile() {
+}
+
+MemoryMappedFileBuffer::~MemoryMappedFileBuffer() {}
+
+Logger::~Logger() {}
+
+Status Logger::Close() {
+  if (!closed_) {
+    closed_ = true;
+    return CloseImpl();
+  } else {
+    return Status::OK();
+  }
+}
+
+Status Logger::CloseImpl() { return Status::NotSupported(); }
+
+FileLock::~FileLock() {
+}
+
+void LogFlush(Logger *info_log) {
+  if (info_log) {
+    info_log->Flush();
+  }
+}
+
+static void Logv(Logger *info_log, const char* format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= InfoLogLevel::INFO_LEVEL) {
+    info_log->Logv(InfoLogLevel::INFO_LEVEL, format, ap);
+  }
+}
+
+void Log(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Logv(info_log, format, ap);
+  va_end(ap);
+}
+
+void Logger::Logv(const InfoLogLevel log_level, const char* format, va_list ap) {
+  static const char* kInfoLogLevelNames[5] = { "DEBUG", "INFO", "WARN",
+    "ERROR", "FATAL" };
+  if (log_level < log_level_) {
+    return;
+  }
+
+  if (log_level == InfoLogLevel::INFO_LEVEL) {
+    // Doesn't print log level if it is INFO level.
+    // This is to avoid unexpected performance regression after we add
+    // the feature of log level. All the logs before we add the feature
+    // are INFO level. We don't want to add extra costs to those existing
+    // logging.
+    Logv(format, ap);
+  } else if (log_level == InfoLogLevel::HEADER_LEVEL) {
+    LogHeader(format, ap);
+  } else {
+    char new_format[500];
+    snprintf(new_format, sizeof(new_format) - 1, "[%s] %s",
+      kInfoLogLevelNames[log_level], format);
+    Logv(new_format, ap);
+  }
+}
+
+static void Logv(const InfoLogLevel log_level, Logger *info_log, const char *format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= log_level) {
+    if (log_level == InfoLogLevel::HEADER_LEVEL) {
+      info_log->LogHeader(format, ap);
+    } else {
+      info_log->Logv(log_level, format, ap);
+    }
+  }
+}
+
+void Log(const InfoLogLevel log_level, Logger* info_log, const char* format,
+         ...) {
+  va_list ap;
+  va_start(ap, format);
+  Logv(log_level, info_log, format, ap);
+  va_end(ap);
+}
+
+static void Headerv(Logger *info_log, const char *format, va_list ap) {
+  if (info_log) {
+    info_log->LogHeader(format, ap);
+  }
+}
+
+void Header(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Headerv(info_log, format, ap);
+  va_end(ap);
+}
+
+static void Debugv(Logger* info_log, const char* format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= InfoLogLevel::DEBUG_LEVEL) {
+    info_log->Logv(InfoLogLevel::DEBUG_LEVEL, format, ap);
+  }
+}
+
+void Debug(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Debugv(info_log, format, ap);
+  va_end(ap);
+}
+
+static void Infov(Logger* info_log, const char* format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= InfoLogLevel::INFO_LEVEL) {
+    info_log->Logv(InfoLogLevel::INFO_LEVEL, format, ap);
+  }
+}
+
+void Info(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Infov(info_log, format, ap);
+  va_end(ap);
+}
+
+static void Warnv(Logger* info_log, const char* format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= InfoLogLevel::WARN_LEVEL) {
+    info_log->Logv(InfoLogLevel::WARN_LEVEL, format, ap);
+  }
+}
+
+void Warn(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Warnv(info_log, format, ap);
+  va_end(ap);
+}
+
+static void Errorv(Logger* info_log, const char* format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= InfoLogLevel::ERROR_LEVEL) {
+    info_log->Logv(InfoLogLevel::ERROR_LEVEL, format, ap);
+  }
+}
+
+void Error(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Errorv(info_log, format, ap);
+  va_end(ap);
+}
+
+static void Fatalv(Logger* info_log, const char* format, va_list ap) {
+  if (info_log && info_log->GetInfoLogLevel() <= InfoLogLevel::FATAL_LEVEL) {
+    info_log->Logv(InfoLogLevel::FATAL_LEVEL, format, ap);
+  }
+}
+
+void Fatal(Logger* info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Fatalv(info_log, format, ap);
+  va_end(ap);
+}
+
+void LogFlush(const std::shared_ptr<Logger>& info_log) {
+  LogFlush(info_log.get());
+}
+
+void Log(const InfoLogLevel log_level, const std::shared_ptr<Logger>& info_log,
+         const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Logv(log_level, info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Header(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Headerv(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Debug(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Debugv(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Info(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Infov(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Warn(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Warnv(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Error(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Errorv(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Fatal(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Fatalv(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+void Log(const std::shared_ptr<Logger>& info_log, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  Logv(info_log.get(), format, ap);
+  va_end(ap);
+}
+
+Status WriteStringToFile(Env* env, const Slice& data, const std::string& fname,
+                         bool should_sync) {
+  std::unique_ptr<WritableFile> file;
+  EnvOptions soptions;
+  Status s = env->NewWritableFile(fname, &file, soptions);
+  if (!s.ok()) {
+    return s;
+  }
+  s = file->Append(data);
+  if (s.ok() && should_sync) {
+    s = file->Sync();
+  }
+  if (!s.ok()) {
+    env->DeleteFile(fname);
+  }
+  return s;
+}
+
+Status ReadFileToString(Env* env, const std::string& fname, std::string* data) {
+  LegacyFileSystemWrapper lfsw(env);
+  return ReadFileToString(&lfsw, fname, data);
+}
+
+EnvWrapper::~EnvWrapper() {
+}
+
+namespace {  // anonymous namespace
+
+void AssignEnvOptions(EnvOptions* env_options, const DBOptions& options) {
+  env_options->use_mmap_reads = options.allow_mmap_reads;
+  env_options->use_mmap_writes = options.allow_mmap_writes;
+  env_options->use_direct_reads = options.use_direct_reads;
+  env_options->set_fd_cloexec = options.is_fd_close_on_exec;
+  env_options->bytes_per_sync = options.bytes_per_sync;
+  env_options->compaction_readahead_size = options.compaction_readahead_size;
+  env_options->random_access_max_buffer_size =
+      options.random_access_max_buffer_size;
+  env_options->rate_limiter = options.rate_limiter.get();
+  env_options->writable_file_max_buffer_size =
+      options.writable_file_max_buffer_size;
+  env_options->allow_fallocate = options.allow_fallocate;
+  env_options->strict_bytes_per_sync = options.strict_bytes_per_sync;
+  options.env->SanitizeEnvOptions(env_options);
+}
+
+}
+
+EnvOptions Env::OptimizeForLogWrite(const EnvOptions& env_options,
+                                    const DBOptions& db_options) const {
+  EnvOptions optimized_env_options(env_options);
+  optimized_env_options.bytes_per_sync = db_options.wal_bytes_per_sync;
+  optimized_env_options.writable_file_max_buffer_size =
+      db_options.writable_file_max_buffer_size;
+  return optimized_env_options;
+}
+
+EnvOptions Env::OptimizeForManifestWrite(const EnvOptions& env_options) const {
+  return env_options;
+}
+
+EnvOptions Env::OptimizeForLogRead(const EnvOptions& env_options) const {
+  EnvOptions optimized_env_options(env_options);
+  optimized_env_options.use_direct_reads = false;
+  return optimized_env_options;
+}
+
+EnvOptions Env::OptimizeForManifestRead(const EnvOptions& env_options) const {
+  EnvOptions optimized_env_options(env_options);
+  optimized_env_options.use_direct_reads = false;
+  return optimized_env_options;
+}
+
+EnvOptions Env::OptimizeForCompactionTableWrite(
+    const EnvOptions& env_options, const ImmutableDBOptions& db_options) const {
+  EnvOptions optimized_env_options(env_options);
+  optimized_env_options.use_direct_writes =
+      db_options.use_direct_io_for_flush_and_compaction;
+  return optimized_env_options;
+}
+
+EnvOptions Env::OptimizeForCompactionTableRead(
+    const EnvOptions& env_options, const ImmutableDBOptions& db_options) const {
+  EnvOptions optimized_env_options(env_options);
+  optimized_env_options.use_direct_reads = db_options.use_direct_reads;
+  return optimized_env_options;
+}
+
+EnvOptions::EnvOptions(const DBOptions& options) {
+  AssignEnvOptions(this, options);
+}
+
+EnvOptions::EnvOptions() {
+  DBOptions options;
+  AssignEnvOptions(this, options);
+}
+
+Status NewEnvLogger(const std::string& fname, Env* env,
+                    std::shared_ptr<Logger>* result) {
+  EnvOptions options;
+  // TODO: Tune the buffer size.
+  options.writable_file_max_buffer_size = 1024 * 1024;
+  std::unique_ptr<WritableFile> writable_file;
+  const auto status = env->NewWritableFile(fname, &writable_file, options);
+  if (!status.ok()) {
+    return status;
+  }
+
+  *result = std::make_shared<EnvLogger>(
+      NewLegacyWritableFileWrapper(std::move(writable_file)), fname, options,
+      env);
+  return Status::OK();
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/env_basic_test.cc b/src/rocksdb/env/env_basic_test.cc
new file mode 100644
index 000000000..d2041f780
--- /dev/null
+++ b/src/rocksdb/env/env_basic_test.cc
@@ -0,0 +1,354 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+
+#include <memory>
+#include <string>
+#include <vector>
+#include <algorithm>
+
+#include "env/mock_env.h"
+#include "rocksdb/env.h"
+#include "test_util/testharness.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Normalizes trivial differences across Envs such that these test cases can
+// run on all Envs.
+class NormalizingEnvWrapper : public EnvWrapper {
+ public:
+  explicit NormalizingEnvWrapper(Env* base) : EnvWrapper(base) {}
+
+  // Removes . and .. from directory listing
+  Status GetChildren(const std::string& dir,
+                     std::vector<std::string>* result) override {
+    Status status = EnvWrapper::GetChildren(dir, result);
+    if (status.ok()) {
+      result->erase(std::remove_if(result->begin(), result->end(),
+                                   [](const std::string& s) {
+                                     return s == "." || s == "..";
+                                   }),
+                    result->end());
+    }
+    return status;
+  }
+
+  // Removes . and .. from directory listing
+  Status GetChildrenFileAttributes(
+      const std::string& dir, std::vector<FileAttributes>* result) override {
+    Status status = EnvWrapper::GetChildrenFileAttributes(dir, result);
+    if (status.ok()) {
+      result->erase(std::remove_if(result->begin(), result->end(),
+                                   [](const FileAttributes& fa) {
+                                     return fa.name == "." || fa.name == "..";
+                                   }),
+                    result->end());
+    }
+    return status;
+  }
+};
+
+class EnvBasicTestWithParam : public testing::Test,
+                              public ::testing::WithParamInterface<Env*> {
+ public:
+  Env* env_;
+  const EnvOptions soptions_;
+  std::string test_dir_;
+
+  EnvBasicTestWithParam() : env_(GetParam()) {
+    test_dir_ = test::PerThreadDBPath(env_, "env_basic_test");
+  }
+
+  void SetUp() override { env_->CreateDirIfMissing(test_dir_); }
+
+  void TearDown() override {
+    std::vector<std::string> files;
+    env_->GetChildren(test_dir_, &files);
+    for (const auto& file : files) {
+      // don't know whether it's file or directory, try both. The tests must
+      // only create files or empty directories, so one must succeed, else the
+      // directory's corrupted.
+      Status s = env_->DeleteFile(test_dir_ + "/" + file);
+      if (!s.ok()) {
+        ASSERT_OK(env_->DeleteDir(test_dir_ + "/" + file));
+      }
+    }
+  }
+};
+
+class EnvMoreTestWithParam : public EnvBasicTestWithParam {};
+
+static std::unique_ptr<Env> def_env(new NormalizingEnvWrapper(Env::Default()));
+INSTANTIATE_TEST_CASE_P(EnvDefault, EnvBasicTestWithParam,
+                        ::testing::Values(def_env.get()));
+INSTANTIATE_TEST_CASE_P(EnvDefault, EnvMoreTestWithParam,
+                        ::testing::Values(def_env.get()));
+
+static std::unique_ptr<Env> mock_env(new MockEnv(Env::Default()));
+INSTANTIATE_TEST_CASE_P(MockEnv, EnvBasicTestWithParam,
+                        ::testing::Values(mock_env.get()));
+#ifndef ROCKSDB_LITE
+static std::unique_ptr<Env> mem_env(NewMemEnv(Env::Default()));
+INSTANTIATE_TEST_CASE_P(MemEnv, EnvBasicTestWithParam,
+                        ::testing::Values(mem_env.get()));
+
+namespace {
+
+// Returns a vector of 0 or 1 Env*, depending whether an Env is registered for
+// TEST_ENV_URI.
+//
+// The purpose of returning an empty vector (instead of nullptr) is that gtest
+// ValuesIn() will skip running tests when given an empty collection.
+std::vector<Env*> GetCustomEnvs() {
+  static Env* custom_env;
+  static bool init = false;
+  if (!init) {
+    init = true;
+    const char* uri = getenv("TEST_ENV_URI");
+    if (uri != nullptr) {
+      Env::LoadEnv(uri, &custom_env);
+    }
+  }
+
+  std::vector<Env*> res;
+  if (custom_env != nullptr) {
+    res.emplace_back(custom_env);
+  }
+  return res;
+}
+
+}  // anonymous namespace
+
+INSTANTIATE_TEST_CASE_P(CustomEnv, EnvBasicTestWithParam,
+                        ::testing::ValuesIn(GetCustomEnvs()));
+
+INSTANTIATE_TEST_CASE_P(CustomEnv, EnvMoreTestWithParam,
+                        ::testing::ValuesIn(GetCustomEnvs()));
+
+#endif  // ROCKSDB_LITE
+
+TEST_P(EnvBasicTestWithParam, Basics) {
+  uint64_t file_size;
+  std::unique_ptr<WritableFile> writable_file;
+  std::vector<std::string> children;
+
+  // Check that the directory is empty.
+  ASSERT_EQ(Status::NotFound(), env_->FileExists(test_dir_ + "/non_existent"));
+  ASSERT_TRUE(!env_->GetFileSize(test_dir_ + "/non_existent", &file_size).ok());
+  ASSERT_OK(env_->GetChildren(test_dir_, &children));
+  ASSERT_EQ(0U, children.size());
+
+  // Create a file.
+  ASSERT_OK(env_->NewWritableFile(test_dir_ + "/f", &writable_file, soptions_));
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+
+  // Check that the file exists.
+  ASSERT_OK(env_->FileExists(test_dir_ + "/f"));
+  ASSERT_OK(env_->GetFileSize(test_dir_ + "/f", &file_size));
+  ASSERT_EQ(0U, file_size);
+  ASSERT_OK(env_->GetChildren(test_dir_, &children));
+  ASSERT_EQ(1U, children.size());
+  ASSERT_EQ("f", children[0]);
+  ASSERT_OK(env_->DeleteFile(test_dir_ + "/f"));
+
+  // Write to the file.
+  ASSERT_OK(
+      env_->NewWritableFile(test_dir_ + "/f1", &writable_file, soptions_));
+  ASSERT_OK(writable_file->Append("abc"));
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+  ASSERT_OK(
+      env_->NewWritableFile(test_dir_ + "/f2", &writable_file, soptions_));
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+
+  // Check for expected size.
+  ASSERT_OK(env_->GetFileSize(test_dir_ + "/f1", &file_size));
+  ASSERT_EQ(3U, file_size);
+
+  // Check that renaming works.
+  ASSERT_TRUE(
+      !env_->RenameFile(test_dir_ + "/non_existent", test_dir_ + "/g").ok());
+  ASSERT_OK(env_->RenameFile(test_dir_ + "/f1", test_dir_ + "/g"));
+  ASSERT_EQ(Status::NotFound(), env_->FileExists(test_dir_ + "/f1"));
+  ASSERT_OK(env_->FileExists(test_dir_ + "/g"));
+  ASSERT_OK(env_->GetFileSize(test_dir_ + "/g", &file_size));
+  ASSERT_EQ(3U, file_size);
+
+  // Check that renaming overwriting works
+  ASSERT_OK(env_->RenameFile(test_dir_ + "/f2", test_dir_ + "/g"));
+  ASSERT_OK(env_->GetFileSize(test_dir_ + "/g", &file_size));
+  ASSERT_EQ(0U, file_size);
+
+  // Check that opening non-existent file fails.
+  std::unique_ptr<SequentialFile> seq_file;
+  std::unique_ptr<RandomAccessFile> rand_file;
+  ASSERT_TRUE(!env_->NewSequentialFile(test_dir_ + "/non_existent", &seq_file,
+                                       soptions_)
+                   .ok());
+  ASSERT_TRUE(!seq_file);
+  ASSERT_TRUE(!env_->NewRandomAccessFile(test_dir_ + "/non_existent",
+                                         &rand_file, soptions_)
+                   .ok());
+  ASSERT_TRUE(!rand_file);
+
+  // Check that deleting works.
+  ASSERT_TRUE(!env_->DeleteFile(test_dir_ + "/non_existent").ok());
+  ASSERT_OK(env_->DeleteFile(test_dir_ + "/g"));
+  ASSERT_EQ(Status::NotFound(), env_->FileExists(test_dir_ + "/g"));
+  ASSERT_OK(env_->GetChildren(test_dir_, &children));
+  ASSERT_EQ(0U, children.size());
+  ASSERT_TRUE(
+      env_->GetChildren(test_dir_ + "/non_existent", &children).IsNotFound());
+}
+
+TEST_P(EnvBasicTestWithParam, ReadWrite) {
+  std::unique_ptr<WritableFile> writable_file;
+  std::unique_ptr<SequentialFile> seq_file;
+  std::unique_ptr<RandomAccessFile> rand_file;
+  Slice result;
+  char scratch[100];
+
+  ASSERT_OK(env_->NewWritableFile(test_dir_ + "/f", &writable_file, soptions_));
+  ASSERT_OK(writable_file->Append("hello "));
+  ASSERT_OK(writable_file->Append("world"));
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+
+  // Read sequentially.
+  ASSERT_OK(env_->NewSequentialFile(test_dir_ + "/f", &seq_file, soptions_));
+  ASSERT_OK(seq_file->Read(5, &result, scratch));  // Read "hello".
+  ASSERT_EQ(0, result.compare("hello"));
+  ASSERT_OK(seq_file->Skip(1));
+  ASSERT_OK(seq_file->Read(1000, &result, scratch));  // Read "world".
+  ASSERT_EQ(0, result.compare("world"));
+  ASSERT_OK(seq_file->Read(1000, &result, scratch));  // Try reading past EOF.
+  ASSERT_EQ(0U, result.size());
+  ASSERT_OK(seq_file->Skip(100));  // Try to skip past end of file.
+  ASSERT_OK(seq_file->Read(1000, &result, scratch));
+  ASSERT_EQ(0U, result.size());
+
+  // Random reads.
+  ASSERT_OK(env_->NewRandomAccessFile(test_dir_ + "/f", &rand_file, soptions_));
+  ASSERT_OK(rand_file->Read(6, 5, &result, scratch));  // Read "world".
+  ASSERT_EQ(0, result.compare("world"));
+  ASSERT_OK(rand_file->Read(0, 5, &result, scratch));  // Read "hello".
+  ASSERT_EQ(0, result.compare("hello"));
+  ASSERT_OK(rand_file->Read(10, 100, &result, scratch));  // Read "d".
+  ASSERT_EQ(0, result.compare("d"));
+
+  // Too high offset.
+  ASSERT_TRUE(rand_file->Read(1000, 5, &result, scratch).ok());
+}
+
+TEST_P(EnvBasicTestWithParam, Misc) {
+  std::unique_ptr<WritableFile> writable_file;
+  ASSERT_OK(env_->NewWritableFile(test_dir_ + "/b", &writable_file, soptions_));
+
+  // These are no-ops, but we test they return success.
+  ASSERT_OK(writable_file->Sync());
+  ASSERT_OK(writable_file->Flush());
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+}
+
+TEST_P(EnvBasicTestWithParam, LargeWrite) {
+  const size_t kWriteSize = 300 * 1024;
+  char* scratch = new char[kWriteSize * 2];
+
+  std::string write_data;
+  for (size_t i = 0; i < kWriteSize; ++i) {
+    write_data.append(1, static_cast<char>(i));
+  }
+
+  std::unique_ptr<WritableFile> writable_file;
+  ASSERT_OK(env_->NewWritableFile(test_dir_ + "/f", &writable_file, soptions_));
+  ASSERT_OK(writable_file->Append("foo"));
+  ASSERT_OK(writable_file->Append(write_data));
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+
+  std::unique_ptr<SequentialFile> seq_file;
+  Slice result;
+  ASSERT_OK(env_->NewSequentialFile(test_dir_ + "/f", &seq_file, soptions_));
+  ASSERT_OK(seq_file->Read(3, &result, scratch));  // Read "foo".
+  ASSERT_EQ(0, result.compare("foo"));
+
+  size_t read = 0;
+  std::string read_data;
+  while (read < kWriteSize) {
+    ASSERT_OK(seq_file->Read(kWriteSize - read, &result, scratch));
+    read_data.append(result.data(), result.size());
+    read += result.size();
+  }
+  ASSERT_TRUE(write_data == read_data);
+  delete [] scratch;
+}
+
+TEST_P(EnvMoreTestWithParam, GetModTime) {
+  ASSERT_OK(env_->CreateDirIfMissing(test_dir_ + "/dir1"));
+  uint64_t mtime1 = 0x0;
+  ASSERT_OK(env_->GetFileModificationTime(test_dir_ + "/dir1", &mtime1));
+}
+
+TEST_P(EnvMoreTestWithParam, MakeDir) {
+  ASSERT_OK(env_->CreateDir(test_dir_ + "/j"));
+  ASSERT_OK(env_->FileExists(test_dir_ + "/j"));
+  std::vector<std::string> children;
+  env_->GetChildren(test_dir_, &children);
+  ASSERT_EQ(1U, children.size());
+  // fail because file already exists
+  ASSERT_TRUE(!env_->CreateDir(test_dir_ + "/j").ok());
+  ASSERT_OK(env_->CreateDirIfMissing(test_dir_ + "/j"));
+  ASSERT_OK(env_->DeleteDir(test_dir_ + "/j"));
+  ASSERT_EQ(Status::NotFound(), env_->FileExists(test_dir_ + "/j"));
+}
+
+TEST_P(EnvMoreTestWithParam, GetChildren) {
+  // empty folder returns empty vector
+  std::vector<std::string> children;
+  std::vector<Env::FileAttributes> childAttr;
+  ASSERT_OK(env_->CreateDirIfMissing(test_dir_));
+  ASSERT_OK(env_->GetChildren(test_dir_, &children));
+  ASSERT_OK(env_->FileExists(test_dir_));
+  ASSERT_OK(env_->GetChildrenFileAttributes(test_dir_, &childAttr));
+  ASSERT_EQ(0U, children.size());
+  ASSERT_EQ(0U, childAttr.size());
+
+  // folder with contents returns relative path to test dir
+  ASSERT_OK(env_->CreateDirIfMissing(test_dir_ + "/niu"));
+  ASSERT_OK(env_->CreateDirIfMissing(test_dir_ + "/you"));
+  ASSERT_OK(env_->CreateDirIfMissing(test_dir_ + "/guo"));
+  ASSERT_OK(env_->GetChildren(test_dir_, &children));
+  ASSERT_OK(env_->GetChildrenFileAttributes(test_dir_, &childAttr));
+  ASSERT_EQ(3U, children.size());
+  ASSERT_EQ(3U, childAttr.size());
+  for (auto each : children) {
+    env_->DeleteDir(test_dir_ + "/" + each);
+  }  // necessary for default POSIX env
+
+  // non-exist directory returns IOError
+  ASSERT_OK(env_->DeleteDir(test_dir_));
+  ASSERT_TRUE(!env_->FileExists(test_dir_).ok());
+  ASSERT_TRUE(!env_->GetChildren(test_dir_, &children).ok());
+  ASSERT_TRUE(!env_->GetChildrenFileAttributes(test_dir_, &childAttr).ok());
+
+  // if dir is a file, returns IOError
+  ASSERT_OK(env_->CreateDir(test_dir_));
+  std::unique_ptr<WritableFile> writable_file;
+  ASSERT_OK(
+      env_->NewWritableFile(test_dir_ + "/file", &writable_file, soptions_));
+  ASSERT_OK(writable_file->Close());
+  writable_file.reset();
+  ASSERT_TRUE(!env_->GetChildren(test_dir_ + "/file", &children).ok());
+  ASSERT_EQ(0U, children.size());
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/env/env_chroot.cc b/src/rocksdb/env/env_chroot.cc
new file mode 100644
index 000000000..246437bdd
--- /dev/null
+++ b/src/rocksdb/env/env_chroot.cc
@@ -0,0 +1,321 @@
+//  Copyright (c) 2016-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#if !defined(ROCKSDB_LITE) && !defined(OS_WIN)
+
+#include "env/env_chroot.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "rocksdb/status.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class ChrootEnv : public EnvWrapper {
+ public:
+  ChrootEnv(Env* base_env, const std::string& chroot_dir)
+      : EnvWrapper(base_env) {
+#if defined(OS_AIX)
+    char resolvedName[PATH_MAX];
+    char* real_chroot_dir = realpath(chroot_dir.c_str(), resolvedName);
+#else
+    char* real_chroot_dir = realpath(chroot_dir.c_str(), nullptr);
+#endif
+    // chroot_dir must exist so realpath() returns non-nullptr.
+    assert(real_chroot_dir != nullptr);
+    chroot_dir_ = real_chroot_dir;
+#if !defined(OS_AIX)
+    free(real_chroot_dir);
+#endif
+  }
+
+  Status NewSequentialFile(const std::string& fname,
+                           std::unique_ptr<SequentialFile>* result,
+                           const EnvOptions& options) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::NewSequentialFile(status_and_enc_path.second, result,
+                                         options);
+  }
+
+  Status NewRandomAccessFile(const std::string& fname,
+                             std::unique_ptr<RandomAccessFile>* result,
+                             const EnvOptions& options) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::NewRandomAccessFile(status_and_enc_path.second, result,
+                                           options);
+  }
+
+  Status NewWritableFile(const std::string& fname,
+                         std::unique_ptr<WritableFile>* result,
+                         const EnvOptions& options) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::NewWritableFile(status_and_enc_path.second, result,
+                                       options);
+  }
+
+  Status ReuseWritableFile(const std::string& fname,
+                           const std::string& old_fname,
+                           std::unique_ptr<WritableFile>* result,
+                           const EnvOptions& options) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    auto status_and_old_enc_path = EncodePath(old_fname);
+    if (!status_and_old_enc_path.first.ok()) {
+      return status_and_old_enc_path.first;
+    }
+    return EnvWrapper::ReuseWritableFile(status_and_old_enc_path.second,
+                                         status_and_old_enc_path.second, result,
+                                         options);
+  }
+
+  Status NewRandomRWFile(const std::string& fname,
+                         std::unique_ptr<RandomRWFile>* result,
+                         const EnvOptions& options) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::NewRandomRWFile(status_and_enc_path.second, result,
+                                       options);
+  }
+
+  Status NewDirectory(const std::string& dir,
+                      std::unique_ptr<Directory>* result) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(dir);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::NewDirectory(status_and_enc_path.second, result);
+  }
+
+  Status FileExists(const std::string& fname) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::FileExists(status_and_enc_path.second);
+  }
+
+  Status GetChildren(const std::string& dir,
+                     std::vector<std::string>* result) override {
+    auto status_and_enc_path = EncodePath(dir);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::GetChildren(status_and_enc_path.second, result);
+  }
+
+  Status GetChildrenFileAttributes(
+      const std::string& dir, std::vector<FileAttributes>* result) override {
+    auto status_and_enc_path = EncodePath(dir);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::GetChildrenFileAttributes(status_and_enc_path.second,
+                                                 result);
+  }
+
+  Status DeleteFile(const std::string& fname) override {
+    auto status_and_enc_path = EncodePath(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::DeleteFile(status_and_enc_path.second);
+  }
+
+  Status CreateDir(const std::string& dirname) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(dirname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::CreateDir(status_and_enc_path.second);
+  }
+
+  Status CreateDirIfMissing(const std::string& dirname) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(dirname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::CreateDirIfMissing(status_and_enc_path.second);
+  }
+
+  Status DeleteDir(const std::string& dirname) override {
+    auto status_and_enc_path = EncodePath(dirname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::DeleteDir(status_and_enc_path.second);
+  }
+
+  Status GetFileSize(const std::string& fname, uint64_t* file_size) override {
+    auto status_and_enc_path = EncodePath(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::GetFileSize(status_and_enc_path.second, file_size);
+  }
+
+  Status GetFileModificationTime(const std::string& fname,
+                                 uint64_t* file_mtime) override {
+    auto status_and_enc_path = EncodePath(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::GetFileModificationTime(status_and_enc_path.second,
+                                               file_mtime);
+  }
+
+  Status RenameFile(const std::string& src, const std::string& dest) override {
+    auto status_and_src_enc_path = EncodePath(src);
+    if (!status_and_src_enc_path.first.ok()) {
+      return status_and_src_enc_path.first;
+    }
+    auto status_and_dest_enc_path = EncodePathWithNewBasename(dest);
+    if (!status_and_dest_enc_path.first.ok()) {
+      return status_and_dest_enc_path.first;
+    }
+    return EnvWrapper::RenameFile(status_and_src_enc_path.second,
+                                  status_and_dest_enc_path.second);
+  }
+
+  Status LinkFile(const std::string& src, const std::string& dest) override {
+    auto status_and_src_enc_path = EncodePath(src);
+    if (!status_and_src_enc_path.first.ok()) {
+      return status_and_src_enc_path.first;
+    }
+    auto status_and_dest_enc_path = EncodePathWithNewBasename(dest);
+    if (!status_and_dest_enc_path.first.ok()) {
+      return status_and_dest_enc_path.first;
+    }
+    return EnvWrapper::LinkFile(status_and_src_enc_path.second,
+                                status_and_dest_enc_path.second);
+  }
+
+  Status LockFile(const std::string& fname, FileLock** lock) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    // FileLock subclasses may store path (e.g., PosixFileLock stores it). We
+    // can skip stripping the chroot directory from this path because callers
+    // shouldn't use it.
+    return EnvWrapper::LockFile(status_and_enc_path.second, lock);
+  }
+
+  Status GetTestDirectory(std::string* path) override {
+    // Adapted from PosixEnv's implementation since it doesn't provide a way to
+    // create directory in the chroot.
+    char buf[256];
+    snprintf(buf, sizeof(buf), "/rocksdbtest-%d", static_cast<int>(geteuid()));
+    *path = buf;
+
+    // Directory may already exist, so ignore return
+    CreateDir(*path);
+    return Status::OK();
+  }
+
+  Status NewLogger(const std::string& fname,
+                   std::shared_ptr<Logger>* result) override {
+    auto status_and_enc_path = EncodePathWithNewBasename(fname);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::NewLogger(status_and_enc_path.second, result);
+  }
+
+  Status GetAbsolutePath(const std::string& db_path,
+                         std::string* output_path) override {
+    auto status_and_enc_path = EncodePath(db_path);
+    if (!status_and_enc_path.first.ok()) {
+      return status_and_enc_path.first;
+    }
+    return EnvWrapper::GetAbsolutePath(status_and_enc_path.second, output_path);
+  }
+
+ private:
+  // Returns status and expanded absolute path including the chroot directory.
+  // Checks whether the provided path breaks out of the chroot. If it returns
+  // non-OK status, the returned path should not be used.
+  std::pair<Status, std::string> EncodePath(const std::string& path) {
+    if (path.empty() || path[0] != '/') {
+      return {Status::InvalidArgument(path, "Not an absolute path"), ""};
+    }
+    std::pair<Status, std::string> res;
+    res.second = chroot_dir_ + path;
+#if defined(OS_AIX)
+    char resolvedName[PATH_MAX];
+    char* normalized_path = realpath(res.second.c_str(), resolvedName);
+#else
+    char* normalized_path = realpath(res.second.c_str(), nullptr);
+#endif
+    if (normalized_path == nullptr) {
+      res.first = Status::NotFound(res.second, strerror(errno));
+    } else if (strlen(normalized_path) < chroot_dir_.size() ||
+               strncmp(normalized_path, chroot_dir_.c_str(),
+                       chroot_dir_.size()) != 0) {
+      res.first = Status::IOError(res.second,
+                                  "Attempted to access path outside chroot");
+    } else {
+      res.first = Status::OK();
+    }
+#if !defined(OS_AIX)
+    free(normalized_path);
+#endif
+    return res;
+  }
+
+  // Similar to EncodePath() except assumes the basename in the path hasn't been
+  // created yet.
+  std::pair<Status, std::string> EncodePathWithNewBasename(
+      const std::string& path) {
+    if (path.empty() || path[0] != '/') {
+      return {Status::InvalidArgument(path, "Not an absolute path"), ""};
+    }
+    // Basename may be followed by trailing slashes
+    size_t final_idx = path.find_last_not_of('/');
+    if (final_idx == std::string::npos) {
+      // It's only slashes so no basename to extract
+      return EncodePath(path);
+    }
+
+    // Pull off the basename temporarily since realname(3) (used by
+    // EncodePath()) requires a path that exists
+    size_t base_sep = path.rfind('/', final_idx);
+    auto status_and_enc_path = EncodePath(path.substr(0, base_sep + 1));
+    status_and_enc_path.second.append(path.substr(base_sep + 1));
+    return status_and_enc_path;
+  }
+
+  std::string chroot_dir_;
+};
+
+Env* NewChrootEnv(Env* base_env, const std::string& chroot_dir) {
+  if (!base_env->FileExists(chroot_dir).ok()) {
+    return nullptr;
+  }
+  return new ChrootEnv(base_env, chroot_dir);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif  // !defined(ROCKSDB_LITE) && !defined(OS_WIN)
diff --git a/src/rocksdb/env/env_chroot.h b/src/rocksdb/env/env_chroot.h
new file mode 100644
index 000000000..cb5585b3b
--- /dev/null
+++ b/src/rocksdb/env/env_chroot.h
@@ -0,0 +1,22 @@
+//  Copyright (c) 2016-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#if !defined(ROCKSDB_LITE) && !defined(OS_WIN)
+
+#include <string>
+
+#include "rocksdb/env.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Returns an Env that translates paths such that the root directory appears to
+// be chroot_dir. chroot_dir should refer to an existing directory.
+Env* NewChrootEnv(Env* base_env, const std::string& chroot_dir);
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif  // !defined(ROCKSDB_LITE) && !defined(OS_WIN)
diff --git a/src/rocksdb/env/env_encryption.cc b/src/rocksdb/env/env_encryption.cc
new file mode 100644
index 000000000..5f4f65d75
--- /dev/null
+++ b/src/rocksdb/env/env_encryption.cc
@@ -0,0 +1,937 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#ifndef ROCKSDB_LITE
+
+#include <algorithm>
+#include <cassert>
+#include <cctype>
+#include <iostream>
+
+#include "rocksdb/env_encryption.h"
+#include "util/aligned_buffer.h"
+#include "util/coding.h"
+#include "util/random.h"
+
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+#ifndef ROCKSDB_LITE
+
+class EncryptedSequentialFile : public SequentialFile {
+  private:
+    std::unique_ptr<SequentialFile> file_;
+    std::unique_ptr<BlockAccessCipherStream> stream_;
+    uint64_t offset_;
+    size_t prefixLength_;
+
+     public:
+  // Default ctor. Given underlying sequential file is supposed to be at
+  // offset == prefixLength.
+  EncryptedSequentialFile(SequentialFile* f, BlockAccessCipherStream* s, size_t prefixLength)
+      : file_(f), stream_(s), offset_(prefixLength), prefixLength_(prefixLength) {
+  }
+
+  // Read up to "n" bytes from the file.  "scratch[0..n-1]" may be
+  // written by this routine.  Sets "*result" to the data that was
+  // read (including if fewer than "n" bytes were successfully read).
+  // May set "*result" to point at data in "scratch[0..n-1]", so
+  // "scratch[0..n-1]" must be live when "*result" is used.
+  // If an error was encountered, returns a non-OK status.
+  //
+  // REQUIRES: External synchronization
+  Status Read(size_t n, Slice* result, char* scratch) override {
+    assert(scratch);
+    Status status = file_->Read(n, result, scratch);
+    if (!status.ok()) {
+      return status;
+    }
+    status = stream_->Decrypt(offset_, (char*)result->data(), result->size());
+    offset_ += result->size(); // We've already ready data from disk, so update offset_ even if decryption fails.
+    return status;
+  }
+
+  // Skip "n" bytes from the file. This is guaranteed to be no
+  // slower that reading the same data, but may be faster.
+  //
+  // If end of file is reached, skipping will stop at the end of the
+  // file, and Skip will return OK.
+  //
+  // REQUIRES: External synchronization
+  Status Skip(uint64_t n) override {
+    auto status = file_->Skip(n);
+    if (!status.ok()) {
+      return status;
+    }
+    offset_ += n;
+    return status;
+  }
+
+  // Indicates the upper layers if the current SequentialFile implementation
+  // uses direct IO.
+  bool use_direct_io() const override { return file_->use_direct_io(); }
+
+  // Use the returned alignment value to allocate
+  // aligned buffer for Direct I/O
+  size_t GetRequiredBufferAlignment() const override {
+    return file_->GetRequiredBufferAlignment();
+  }
+
+  // Remove any kind of caching of data from the offset to offset+length
+  // of this file. If the length is 0, then it refers to the end of file.
+  // If the system is not caching the file contents, then this is a noop.
+  Status InvalidateCache(size_t offset, size_t length) override {
+    return file_->InvalidateCache(offset + prefixLength_, length);
+  }
+
+  // Positioned Read for direct I/O
+  // If Direct I/O enabled, offset, n, and scratch should be properly aligned
+  Status PositionedRead(uint64_t offset, size_t n, Slice* result,
+                        char* scratch) override {
+    assert(scratch);
+    offset += prefixLength_; // Skip prefix
+    auto status = file_->PositionedRead(offset, n, result, scratch);
+    if (!status.ok()) {
+      return status;
+    }
+    offset_ = offset + result->size();
+    status = stream_->Decrypt(offset, (char*)result->data(), result->size());
+    return status;
+  }
+};
+
+// A file abstraction for randomly reading the contents of a file.
+class EncryptedRandomAccessFile : public RandomAccessFile {
+  private:
+    std::unique_ptr<RandomAccessFile> file_;
+    std::unique_ptr<BlockAccessCipherStream> stream_;
+    size_t prefixLength_;
+
+ public:
+  EncryptedRandomAccessFile(RandomAccessFile* f, BlockAccessCipherStream* s, size_t prefixLength)
+    : file_(f), stream_(s), prefixLength_(prefixLength) { }
+
+  // Read up to "n" bytes from the file starting at "offset".
+  // "scratch[0..n-1]" may be written by this routine.  Sets "*result"
+  // to the data that was read (including if fewer than "n" bytes were
+  // successfully read).  May set "*result" to point at data in
+  // "scratch[0..n-1]", so "scratch[0..n-1]" must be live when
+  // "*result" is used.  If an error was encountered, returns a non-OK
+  // status.
+  //
+  // Safe for concurrent use by multiple threads.
+  // If Direct I/O enabled, offset, n, and scratch should be aligned properly.
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    assert(scratch);
+    offset += prefixLength_;
+    auto status = file_->Read(offset, n, result, scratch);
+    if (!status.ok()) {
+      return status;
+    }
+    status = stream_->Decrypt(offset, (char*)result->data(), result->size());
+    return status;
+  }
+
+  // Readahead the file starting from offset by n bytes for caching.
+  Status Prefetch(uint64_t offset, size_t n) override {
+    //return Status::OK();
+    return file_->Prefetch(offset + prefixLength_, n);
+  }
+
+  // Tries to get an unique ID for this file that will be the same each time
+  // the file is opened (and will stay the same while the file is open).
+  // Furthermore, it tries to make this ID at most "max_size" bytes. If such an
+  // ID can be created this function returns the length of the ID and places it
+  // in "id"; otherwise, this function returns 0, in which case "id"
+  // may not have been modified.
+  //
+  // This function guarantees, for IDs from a given environment, two unique ids
+  // cannot be made equal to each other by adding arbitrary bytes to one of
+  // them. That is, no unique ID is the prefix of another.
+  //
+  // This function guarantees that the returned ID will not be interpretable as
+  // a single varint.
+  //
+  // Note: these IDs are only valid for the duration of the process.
+  size_t GetUniqueId(char* id, size_t max_size) const override {
+    return file_->GetUniqueId(id, max_size);
+  };
+
+  void Hint(AccessPattern pattern) override { file_->Hint(pattern); }
+
+  // Indicates the upper layers if the current RandomAccessFile implementation
+  // uses direct IO.
+  bool use_direct_io() const override { return file_->use_direct_io(); }
+
+  // Use the returned alignment value to allocate
+  // aligned buffer for Direct I/O
+  size_t GetRequiredBufferAlignment() const override {
+    return file_->GetRequiredBufferAlignment();
+  }
+
+  // Remove any kind of caching of data from the offset to offset+length
+  // of this file. If the length is 0, then it refers to the end of file.
+  // If the system is not caching the file contents, then this is a noop.
+  Status InvalidateCache(size_t offset, size_t length) override {
+    return file_->InvalidateCache(offset + prefixLength_, length);
+  }
+};
+
+// A file abstraction for sequential writing.  The implementation
+// must provide buffering since callers may append small fragments
+// at a time to the file.
+class EncryptedWritableFile : public WritableFileWrapper {
+  private:
+    std::unique_ptr<WritableFile> file_;
+    std::unique_ptr<BlockAccessCipherStream> stream_;
+    size_t prefixLength_;
+
+ public:
+  // Default ctor. Prefix is assumed to be written already.
+  EncryptedWritableFile(WritableFile* f, BlockAccessCipherStream* s, size_t prefixLength)
+    : WritableFileWrapper(f), file_(f), stream_(s), prefixLength_(prefixLength) { }
+
+  Status Append(const Slice& data) override {
+    AlignedBuffer buf;
+    Status status;
+    Slice dataToAppend(data);
+    if (data.size() > 0) {
+      auto offset = file_->GetFileSize(); // size including prefix
+      // Encrypt in cloned buffer
+      buf.Alignment(GetRequiredBufferAlignment());
+      buf.AllocateNewBuffer(data.size());
+      // TODO (sagar0): Modify AlignedBuffer.Append to allow doing a memmove
+      // so that the next two lines can be replaced with buf.Append().
+      memmove(buf.BufferStart(), data.data(), data.size());
+      buf.Size(data.size());
+      status = stream_->Encrypt(offset, buf.BufferStart(), buf.CurrentSize());
+      if (!status.ok()) {
+        return status;
+      }
+      dataToAppend = Slice(buf.BufferStart(), buf.CurrentSize());
+    }
+    status = file_->Append(dataToAppend);
+    if (!status.ok()) {
+      return status;
+    }
+    return status;
+  }
+
+  Status PositionedAppend(const Slice& data, uint64_t offset) override {
+    AlignedBuffer buf;
+    Status status;
+    Slice dataToAppend(data);
+    offset += prefixLength_;
+    if (data.size() > 0) {
+      // Encrypt in cloned buffer
+      buf.Alignment(GetRequiredBufferAlignment());
+      buf.AllocateNewBuffer(data.size());
+      memmove(buf.BufferStart(), data.data(), data.size());
+      buf.Size(data.size());
+      status = stream_->Encrypt(offset, buf.BufferStart(), buf.CurrentSize());
+      if (!status.ok()) {
+        return status;
+      }
+      dataToAppend = Slice(buf.BufferStart(), buf.CurrentSize());
+    }
+    status = file_->PositionedAppend(dataToAppend, offset);
+    if (!status.ok()) {
+      return status;
+    }
+    return status;
+  }
+
+  // Indicates the upper layers if the current WritableFile implementation
+  // uses direct IO.
+  bool use_direct_io() const override { return file_->use_direct_io(); }
+
+  // Use the returned alignment value to allocate
+  // aligned buffer for Direct I/O
+  size_t GetRequiredBufferAlignment() const override {
+    return file_->GetRequiredBufferAlignment();
+  }
+
+    /*
+   * Get the size of valid data in the file.
+   */
+  uint64_t GetFileSize() override {
+    return file_->GetFileSize() - prefixLength_;
+  }
+
+  // Truncate is necessary to trim the file to the correct size
+  // before closing. It is not always possible to keep track of the file
+  // size due to whole pages writes. The behavior is undefined if called
+  // with other writes to follow.
+  Status Truncate(uint64_t size) override {
+    return file_->Truncate(size + prefixLength_);
+  }
+
+    // Remove any kind of caching of data from the offset to offset+length
+  // of this file. If the length is 0, then it refers to the end of file.
+  // If the system is not caching the file contents, then this is a noop.
+  // This call has no effect on dirty pages in the cache.
+  Status InvalidateCache(size_t offset, size_t length) override {
+    return file_->InvalidateCache(offset + prefixLength_, length);
+  }
+
+  // Sync a file range with disk.
+  // offset is the starting byte of the file range to be synchronized.
+  // nbytes specifies the length of the range to be synchronized.
+  // This asks the OS to initiate flushing the cached data to disk,
+  // without waiting for completion.
+  // Default implementation does nothing.
+  Status RangeSync(uint64_t offset, uint64_t nbytes) override {
+    return file_->RangeSync(offset + prefixLength_, nbytes);
+  }
+
+  // PrepareWrite performs any necessary preparation for a write
+  // before the write actually occurs.  This allows for pre-allocation
+  // of space on devices where it can result in less file
+  // fragmentation and/or less waste from over-zealous filesystem
+  // pre-allocation.
+  void PrepareWrite(size_t offset, size_t len) override {
+    file_->PrepareWrite(offset + prefixLength_, len);
+  }
+
+  // Pre-allocates space for a file.
+  Status Allocate(uint64_t offset, uint64_t len) override {
+    return file_->Allocate(offset + prefixLength_, len);
+  }
+};
+
+// A file abstraction for random reading and writing.
+class EncryptedRandomRWFile : public RandomRWFile {
+  private:
+    std::unique_ptr<RandomRWFile> file_;
+    std::unique_ptr<BlockAccessCipherStream> stream_;
+    size_t prefixLength_;
+
+ public:
+  EncryptedRandomRWFile(RandomRWFile* f, BlockAccessCipherStream* s, size_t prefixLength)
+    : file_(f), stream_(s), prefixLength_(prefixLength) {}
+
+  // Indicates if the class makes use of direct I/O
+  // If false you must pass aligned buffer to Write()
+  bool use_direct_io() const override { return file_->use_direct_io(); }
+
+  // Use the returned alignment value to allocate
+  // aligned buffer for Direct I/O
+  size_t GetRequiredBufferAlignment() const override {
+    return file_->GetRequiredBufferAlignment();
+  }
+
+  // Write bytes in `data` at  offset `offset`, Returns Status::OK() on success.
+  // Pass aligned buffer when use_direct_io() returns true.
+  Status Write(uint64_t offset, const Slice& data) override {
+    AlignedBuffer buf;
+    Status status;
+    Slice dataToWrite(data);
+    offset += prefixLength_;
+    if (data.size() > 0) {
+      // Encrypt in cloned buffer
+      buf.Alignment(GetRequiredBufferAlignment());
+      buf.AllocateNewBuffer(data.size());
+      memmove(buf.BufferStart(), data.data(), data.size());
+      buf.Size(data.size());
+      status = stream_->Encrypt(offset, buf.BufferStart(), buf.CurrentSize());
+      if (!status.ok()) {
+        return status;
+      }
+      dataToWrite = Slice(buf.BufferStart(), buf.CurrentSize());
+    }
+    status = file_->Write(offset, dataToWrite);
+    return status;
+  }
+
+  // Read up to `n` bytes starting from offset `offset` and store them in
+  // result, provided `scratch` size should be at least `n`.
+  // Returns Status::OK() on success.
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    assert(scratch);
+    offset += prefixLength_;
+    auto status = file_->Read(offset, n, result, scratch);
+    if (!status.ok()) {
+      return status;
+    }
+    status = stream_->Decrypt(offset, (char*)result->data(), result->size());
+    return status;
+  }
+
+  Status Flush() override { return file_->Flush(); }
+
+  Status Sync() override { return file_->Sync(); }
+
+  Status Fsync() override { return file_->Fsync(); }
+
+  Status Close() override { return file_->Close(); }
+};
+
+// EncryptedEnv implements an Env wrapper that adds encryption to files stored on disk.
+class EncryptedEnv : public EnvWrapper {
+ public:
+  EncryptedEnv(Env* base_env, EncryptionProvider *provider)
+      : EnvWrapper(base_env) {
+    provider_ = provider;
+  }
+
+  // NewSequentialFile opens a file for sequential reading.
+  Status NewSequentialFile(const std::string& fname,
+                           std::unique_ptr<SequentialFile>* result,
+                           const EnvOptions& options) override {
+    result->reset();
+    if (options.use_mmap_reads) {
+      return Status::InvalidArgument();
+    }
+    // Open file using underlying Env implementation
+    std::unique_ptr<SequentialFile> underlying;
+    auto status = EnvWrapper::NewSequentialFile(fname, &underlying, options);
+    if (!status.ok()) {
+      return status;
+    }
+    // Read prefix (if needed)
+    AlignedBuffer prefixBuf;
+    Slice prefixSlice;
+    size_t prefixLength = provider_->GetPrefixLength();
+    if (prefixLength > 0) {
+      // Read prefix
+      prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
+      prefixBuf.AllocateNewBuffer(prefixLength);
+      status = underlying->Read(prefixLength, &prefixSlice, prefixBuf.BufferStart());
+      if (!status.ok()) {
+        return status;
+      }
+      prefixBuf.Size(prefixLength);
+    }
+    // Create cipher stream
+    std::unique_ptr<BlockAccessCipherStream> stream;
+    status = provider_->CreateCipherStream(fname, options, prefixSlice, &stream);
+    if (!status.ok()) {
+      return status;
+    }
+    (*result) = std::unique_ptr<SequentialFile>(new EncryptedSequentialFile(underlying.release(), stream.release(), prefixLength));
+    return Status::OK();
+  }
+
+  // NewRandomAccessFile opens a file for random read access.
+  Status NewRandomAccessFile(const std::string& fname,
+                             std::unique_ptr<RandomAccessFile>* result,
+                             const EnvOptions& options) override {
+    result->reset();
+    if (options.use_mmap_reads) {
+      return Status::InvalidArgument();
+    }
+    // Open file using underlying Env implementation
+    std::unique_ptr<RandomAccessFile> underlying;
+    auto status = EnvWrapper::NewRandomAccessFile(fname, &underlying, options);
+    if (!status.ok()) {
+      return status;
+    }
+    // Read prefix (if needed)
+    AlignedBuffer prefixBuf;
+    Slice prefixSlice;
+    size_t prefixLength = provider_->GetPrefixLength();
+    if (prefixLength > 0) {
+      // Read prefix
+      prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
+      prefixBuf.AllocateNewBuffer(prefixLength);
+      status = underlying->Read(0, prefixLength, &prefixSlice, prefixBuf.BufferStart());
+      if (!status.ok()) {
+        return status;
+      }
+      prefixBuf.Size(prefixLength);
+    }
+    // Create cipher stream
+    std::unique_ptr<BlockAccessCipherStream> stream;
+    status = provider_->CreateCipherStream(fname, options, prefixSlice, &stream);
+    if (!status.ok()) {
+      return status;
+    }
+    (*result) = std::unique_ptr<RandomAccessFile>(new EncryptedRandomAccessFile(underlying.release(), stream.release(), prefixLength));
+    return Status::OK();
+  }
+
+  // NewWritableFile opens a file for sequential writing.
+  Status NewWritableFile(const std::string& fname,
+                         std::unique_ptr<WritableFile>* result,
+                         const EnvOptions& options) override {
+    result->reset();
+    if (options.use_mmap_writes) {
+      return Status::InvalidArgument();
+    }
+    // Open file using underlying Env implementation
+    std::unique_ptr<WritableFile> underlying;
+    Status status = EnvWrapper::NewWritableFile(fname, &underlying, options);
+    if (!status.ok()) {
+      return status;
+    }
+    // Initialize & write prefix (if needed)
+    AlignedBuffer prefixBuf;
+    Slice prefixSlice;
+    size_t prefixLength = provider_->GetPrefixLength();
+    if (prefixLength > 0) {
+      // Initialize prefix
+      prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
+      prefixBuf.AllocateNewBuffer(prefixLength);
+      provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
+      prefixBuf.Size(prefixLength);
+      prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
+      // Write prefix
+      status = underlying->Append(prefixSlice);
+      if (!status.ok()) {
+        return status;
+      }
+    }
+    // Create cipher stream
+    std::unique_ptr<BlockAccessCipherStream> stream;
+    status = provider_->CreateCipherStream(fname, options, prefixSlice, &stream);
+    if (!status.ok()) {
+      return status;
+    }
+    (*result) = std::unique_ptr<WritableFile>(new EncryptedWritableFile(underlying.release(), stream.release(), prefixLength));
+    return Status::OK();
+  }
+
+  // Create an object that writes to a new file with the specified
+  // name.  Deletes any existing file with the same name and creates a
+  // new file.  On success, stores a pointer to the new file in
+  // *result and returns OK.  On failure stores nullptr in *result and
+  // returns non-OK.
+  //
+  // The returned file will only be accessed by one thread at a time.
+  Status ReopenWritableFile(const std::string& fname,
+                            std::unique_ptr<WritableFile>* result,
+                            const EnvOptions& options) override {
+    result->reset();
+    if (options.use_mmap_writes) {
+      return Status::InvalidArgument();
+    }
+    // Open file using underlying Env implementation
+    std::unique_ptr<WritableFile> underlying;
+    Status status = EnvWrapper::ReopenWritableFile(fname, &underlying, options);
+    if (!status.ok()) {
+      return status;
+    }
+    // Initialize & write prefix (if needed)
+    AlignedBuffer prefixBuf;
+    Slice prefixSlice;
+    size_t prefixLength = provider_->GetPrefixLength();
+    if (prefixLength > 0) {
+      // Initialize prefix
+      prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
+      prefixBuf.AllocateNewBuffer(prefixLength);
+      provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
+      prefixBuf.Size(prefixLength);
+      prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
+      // Write prefix
+      status = underlying->Append(prefixSlice);
+      if (!status.ok()) {
+        return status;
+      }
+    }
+    // Create cipher stream
+    std::unique_ptr<BlockAccessCipherStream> stream;
+    status = provider_->CreateCipherStream(fname, options, prefixSlice, &stream);
+    if (!status.ok()) {
+      return status;
+    }
+    (*result) = std::unique_ptr<WritableFile>(new EncryptedWritableFile(underlying.release(), stream.release(), prefixLength));
+    return Status::OK();
+  }
+
+  // Reuse an existing file by renaming it and opening it as writable.
+  Status ReuseWritableFile(const std::string& fname,
+                           const std::string& old_fname,
+                           std::unique_ptr<WritableFile>* result,
+                           const EnvOptions& options) override {
+    result->reset();
+    if (options.use_mmap_writes) {
+      return Status::InvalidArgument();
+    }
+    // Open file using underlying Env implementation
+    std::unique_ptr<WritableFile> underlying;
+    Status status = EnvWrapper::ReuseWritableFile(fname, old_fname, &underlying, options);
+    if (!status.ok()) {
+      return status;
+    }
+    // Initialize & write prefix (if needed)
+    AlignedBuffer prefixBuf;
+    Slice prefixSlice;
+    size_t prefixLength = provider_->GetPrefixLength();
+    if (prefixLength > 0) {
+      // Initialize prefix
+      prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
+      prefixBuf.AllocateNewBuffer(prefixLength);
+      provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
+      prefixBuf.Size(prefixLength);
+      prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
+      // Write prefix
+      status = underlying->Append(prefixSlice);
+      if (!status.ok()) {
+        return status;
+      }
+    }
+    // Create cipher stream
+    std::unique_ptr<BlockAccessCipherStream> stream;
+    status = provider_->CreateCipherStream(fname, options, prefixSlice, &stream);
+    if (!status.ok()) {
+      return status;
+    }
+    (*result) = std::unique_ptr<WritableFile>(new EncryptedWritableFile(underlying.release(), stream.release(), prefixLength));
+    return Status::OK();
+  }
+
+  // Open `fname` for random read and write, if file doesn't exist the file
+  // will be created.  On success, stores a pointer to the new file in
+  // *result and returns OK.  On failure returns non-OK.
+  //
+  // The returned file will only be accessed by one thread at a time.
+  Status NewRandomRWFile(const std::string& fname,
+                         std::unique_ptr<RandomRWFile>* result,
+                         const EnvOptions& options) override {
+    result->reset();
+    if (options.use_mmap_reads || options.use_mmap_writes) {
+      return Status::InvalidArgument();
+    }
+    // Check file exists
+    bool isNewFile = !FileExists(fname).ok();
+
+    // Open file using underlying Env implementation
+    std::unique_ptr<RandomRWFile> underlying;
+    Status status = EnvWrapper::NewRandomRWFile(fname, &underlying, options);
+    if (!status.ok()) {
+      return status;
+    }
+    // Read or Initialize & write prefix (if needed)
+    AlignedBuffer prefixBuf;
+    Slice prefixSlice;
+    size_t prefixLength = provider_->GetPrefixLength();
+    if (prefixLength > 0) {
+      prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
+      prefixBuf.AllocateNewBuffer(prefixLength);
+      if (!isNewFile) {
+        // File already exists, read prefix
+        status = underlying->Read(0, prefixLength, &prefixSlice, prefixBuf.BufferStart());
+        if (!status.ok()) {
+          return status;
+        }
+        prefixBuf.Size(prefixLength);
+      } else {
+        // File is new, initialize & write prefix
+        provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
+        prefixBuf.Size(prefixLength);
+        prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
+        // Write prefix
+        status = underlying->Write(0, prefixSlice);
+        if (!status.ok()) {
+          return status;
+        }
+      }
+    }
+    // Create cipher stream
+    std::unique_ptr<BlockAccessCipherStream> stream;
+    status = provider_->CreateCipherStream(fname, options, prefixSlice, &stream);
+    if (!status.ok()) {
+      return status;
+    }
+    (*result) = std::unique_ptr<RandomRWFile>(new EncryptedRandomRWFile(underlying.release(), stream.release(), prefixLength));
+    return Status::OK();
+  }
+
+  // Store in *result the attributes of the children of the specified directory.
+  // In case the implementation lists the directory prior to iterating the files
+  // and files are concurrently deleted, the deleted files will be omitted from
+  // result.
+  // The name attributes are relative to "dir".
+  // Original contents of *results are dropped.
+  // Returns OK if "dir" exists and "*result" contains its children.
+  //         NotFound if "dir" does not exist, the calling process does not have
+  //                  permission to access "dir", or if "dir" is invalid.
+  //         IOError if an IO Error was encountered
+  Status GetChildrenFileAttributes(
+      const std::string& dir, std::vector<FileAttributes>* result) override {
+    auto status = EnvWrapper::GetChildrenFileAttributes(dir, result);
+    if (!status.ok()) {
+      return status;
+    }
+    size_t prefixLength = provider_->GetPrefixLength();
+    for (auto it = std::begin(*result); it!=std::end(*result); ++it) {
+      assert(it->size_bytes >= prefixLength);
+      it->size_bytes -= prefixLength;
+    }
+    return Status::OK();
+  }
+
+  // Store the size of fname in *file_size.
+  Status GetFileSize(const std::string& fname, uint64_t* file_size) override {
+    auto status = EnvWrapper::GetFileSize(fname, file_size);
+    if (!status.ok()) {
+      return status;
+    }
+    size_t prefixLength = provider_->GetPrefixLength();
+    assert(*file_size >= prefixLength);
+    *file_size -= prefixLength;
+    return Status::OK();
+  }
+
+ private:
+  EncryptionProvider *provider_;
+};
+
+// Returns an Env that encrypts data when stored on disk and decrypts data when
+// read from disk.
+Env* NewEncryptedEnv(Env* base_env, EncryptionProvider* provider) {
+  return new EncryptedEnv(base_env, provider);
+}
+
+// Encrypt one or more (partial) blocks of data at the file offset.
+// Length of data is given in dataSize.
+Status BlockAccessCipherStream::Encrypt(uint64_t fileOffset, char *data, size_t dataSize) {
+  // Calculate block index
+  auto blockSize = BlockSize();
+  uint64_t blockIndex = fileOffset / blockSize;
+  size_t blockOffset = fileOffset % blockSize;
+  std::unique_ptr<char[]> blockBuffer;
+
+  std::string scratch;
+  AllocateScratch(scratch);
+
+  // Encrypt individual blocks.
+  while (1) {
+    char *block = data;
+    size_t n = std::min(dataSize, blockSize - blockOffset);
+    if (n != blockSize) {
+      // We're not encrypting a full block.
+      // Copy data to blockBuffer
+      if (!blockBuffer.get()) {
+        // Allocate buffer
+        blockBuffer = std::unique_ptr<char[]>(new char[blockSize]);
+      }
+      block = blockBuffer.get();
+      // Copy plain data to block buffer
+      memmove(block + blockOffset, data, n);
+    }
+    auto status = EncryptBlock(blockIndex, block, (char*)scratch.data());
+    if (!status.ok()) {
+      return status;
+    }
+    if (block != data) {
+      // Copy encrypted data back to `data`.
+      memmove(data, block + blockOffset, n);
+    }
+    dataSize -= n;
+    if (dataSize == 0) {
+      return Status::OK();
+    }
+    data += n;
+    blockOffset = 0;
+    blockIndex++;
+  }
+}
+
+// Decrypt one or more (partial) blocks of data at the file offset.
+// Length of data is given in dataSize.
+Status BlockAccessCipherStream::Decrypt(uint64_t fileOffset, char *data, size_t dataSize) {
+  // Calculate block index
+  auto blockSize = BlockSize();
+  uint64_t blockIndex = fileOffset / blockSize;
+  size_t blockOffset = fileOffset % blockSize;
+  std::unique_ptr<char[]> blockBuffer;
+
+  std::string scratch;
+  AllocateScratch(scratch);
+
+  // Decrypt individual blocks.
+  while (1) {
+    char *block = data;
+    size_t n = std::min(dataSize, blockSize - blockOffset);
+    if (n != blockSize) {
+      // We're not decrypting a full block.
+      // Copy data to blockBuffer
+      if (!blockBuffer.get()) {
+        // Allocate buffer
+        blockBuffer = std::unique_ptr<char[]>(new char[blockSize]);
+      }
+      block = blockBuffer.get();
+      // Copy encrypted data to block buffer
+      memmove(block + blockOffset, data, n);
+    }
+    auto status = DecryptBlock(blockIndex, block, (char*)scratch.data());
+    if (!status.ok()) {
+      return status;
+    }
+    if (block != data) {
+      // Copy decrypted data back to `data`.
+      memmove(data, block + blockOffset, n);
+    }
+
+    // Simply decrementing dataSize by n could cause it to underflow,
+    // which will very likely make it read over the original bounds later
+    assert(dataSize >= n);
+    if (dataSize < n) {
+      return Status::Corruption("Cannot decrypt data at given offset");
+    }
+
+    dataSize -= n;
+    if (dataSize == 0) {
+      return Status::OK();
+    }
+    data += n;
+    blockOffset = 0;
+    blockIndex++;
+  }
+}
+
+// Encrypt a block of data.
+// Length of data is equal to BlockSize().
+Status ROT13BlockCipher::Encrypt(char *data) {
+  for (size_t i = 0; i < blockSize_; ++i) {
+      data[i] += 13;
+  }
+  return Status::OK();
+}
+
+// Decrypt a block of data.
+// Length of data is equal to BlockSize().
+Status ROT13BlockCipher::Decrypt(char *data) {
+  return Encrypt(data);
+}
+
+// Allocate scratch space which is passed to EncryptBlock/DecryptBlock.
+void CTRCipherStream::AllocateScratch(std::string& scratch) {
+  auto blockSize = cipher_.BlockSize();
+  scratch.reserve(blockSize);
+}
+
+// Encrypt a block of data at the given block index.
+// Length of data is equal to BlockSize();
+Status CTRCipherStream::EncryptBlock(uint64_t blockIndex, char *data, char* scratch) {
+
+  // Create nonce + counter
+  auto blockSize = cipher_.BlockSize();
+  memmove(scratch, iv_.data(), blockSize);
+  EncodeFixed64(scratch, blockIndex + initialCounter_);
+
+  // Encrypt nonce+counter
+  auto status = cipher_.Encrypt(scratch);
+  if (!status.ok()) {
+    return status;
+  }
+
+  // XOR data with ciphertext.
+  for (size_t i = 0; i < blockSize; i++) {
+    data[i] = data[i] ^ scratch[i];
+  }
+  return Status::OK();
+}
+
+// Decrypt a block of data at the given block index.
+// Length of data is equal to BlockSize();
+Status CTRCipherStream::DecryptBlock(uint64_t blockIndex, char *data, char* scratch) {
+  // For CTR decryption & encryption are the same
+  return EncryptBlock(blockIndex, data, scratch);
+}
+
+// GetPrefixLength returns the length of the prefix that is added to every file
+// and used for storing encryption options.
+// For optimal performance, the prefix length should be a multiple of
+// the page size.
+size_t CTREncryptionProvider::GetPrefixLength() {
+  return defaultPrefixLength;
+}
+
+// decodeCTRParameters decodes the initial counter & IV from the given
+// (plain text) prefix.
+static void decodeCTRParameters(const char *prefix, size_t blockSize, uint64_t &initialCounter, Slice &iv) {
+  // First block contains 64-bit initial counter
+  initialCounter = DecodeFixed64(prefix);
+  // Second block contains IV
+  iv = Slice(prefix + blockSize, blockSize);
+}
+
+// CreateNewPrefix initialized an allocated block of prefix memory
+// for a new file.
+Status CTREncryptionProvider::CreateNewPrefix(const std::string& /*fname*/,
+                                              char* prefix,
+                                              size_t prefixLength) {
+  // Create & seed rnd.
+  Random rnd((uint32_t)Env::Default()->NowMicros());
+  // Fill entire prefix block with random values.
+  for (size_t i = 0; i < prefixLength; i++) {
+    prefix[i] = rnd.Uniform(256) & 0xFF;
+  }
+  // Take random data to extract initial counter & IV
+  auto blockSize = cipher_.BlockSize();
+  uint64_t initialCounter;
+  Slice prefixIV;
+  decodeCTRParameters(prefix, blockSize, initialCounter, prefixIV);
+
+  // Now populate the rest of the prefix, starting from the third block.
+  PopulateSecretPrefixPart(prefix + (2 * blockSize), prefixLength - (2 * blockSize), blockSize);
+
+  // Encrypt the prefix, starting from block 2 (leave block 0, 1 with initial counter & IV unencrypted)
+  CTRCipherStream cipherStream(cipher_, prefixIV.data(), initialCounter);
+  auto status = cipherStream.Encrypt(0, prefix + (2 * blockSize), prefixLength - (2 * blockSize));
+  if (!status.ok()) {
+    return status;
+  }
+  return Status::OK();
+}
+
+// PopulateSecretPrefixPart initializes the data into a new prefix block
+// in plain text.
+// Returns the amount of space (starting from the start of the prefix)
+// that has been initialized.
+size_t CTREncryptionProvider::PopulateSecretPrefixPart(char* /*prefix*/,
+                                                       size_t /*prefixLength*/,
+                                                       size_t /*blockSize*/) {
+  // Nothing to do here, put in custom data in override when needed.
+  return 0;
+}
+
+Status CTREncryptionProvider::CreateCipherStream(
+    const std::string& fname, const EnvOptions& options, Slice& prefix,
+    std::unique_ptr<BlockAccessCipherStream>* result) {
+  // Read plain text part of prefix.
+  auto blockSize = cipher_.BlockSize();
+  uint64_t initialCounter;
+  Slice iv;
+  decodeCTRParameters(prefix.data(), blockSize, initialCounter, iv);
+
+  // If the prefix is smaller than twice the block size, we would below read a
+  // very large chunk of the file (and very likely read over the bounds)
+  assert(prefix.size() >= 2 * blockSize);
+  if (prefix.size() < 2 * blockSize) {
+    return Status::Corruption("Unable to read from file " + fname +
+                              ": read attempt would read beyond file bounds");
+  }
+
+  // Decrypt the encrypted part of the prefix, starting from block 2 (block 0, 1 with initial counter & IV are unencrypted)
+  CTRCipherStream cipherStream(cipher_, iv.data(), initialCounter);
+  auto status = cipherStream.Decrypt(0, (char*)prefix.data() + (2 * blockSize), prefix.size() - (2 * blockSize));
+  if (!status.ok()) {
+    return status;
+  }
+
+  // Create cipher stream
+  return CreateCipherStreamFromPrefix(fname, options, initialCounter, iv, prefix, result);
+}
+
+// CreateCipherStreamFromPrefix creates a block access cipher stream for a file given
+// given name and options. The given prefix is already decrypted.
+Status CTREncryptionProvider::CreateCipherStreamFromPrefix(
+    const std::string& /*fname*/, const EnvOptions& /*options*/,
+    uint64_t initialCounter, const Slice& iv, const Slice& /*prefix*/,
+    std::unique_ptr<BlockAccessCipherStream>* result) {
+  (*result) = std::unique_ptr<BlockAccessCipherStream>(
+      new CTRCipherStream(cipher_, iv.data(), initialCounter));
+  return Status::OK();
+}
+
+#endif // ROCKSDB_LITE
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/env_hdfs.cc b/src/rocksdb/env/env_hdfs.cc
new file mode 100644
index 000000000..cb84dcc64
--- /dev/null
+++ b/src/rocksdb/env/env_hdfs.cc
@@ -0,0 +1,636 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+
+#include "rocksdb/env.h"
+#include "hdfs/env_hdfs.h"
+
+#ifdef USE_HDFS
+#ifndef ROCKSDB_HDFS_FILE_C
+#define ROCKSDB_HDFS_FILE_C
+
+#include <stdio.h>
+#include <sys/time.h>
+#include <time.h>
+#include <algorithm>
+#include <iostream>
+#include <sstream>
+#include "logging/logging.h"
+#include "rocksdb/status.h"
+#include "util/string_util.h"
+
+#define HDFS_EXISTS 0
+#define HDFS_DOESNT_EXIST -1
+#define HDFS_SUCCESS 0
+
+//
+// This file defines an HDFS environment for rocksdb. It uses the libhdfs
+// api to access HDFS. All HDFS files created by one instance of rocksdb
+// will reside on the same HDFS cluster.
+//
+
+namespace ROCKSDB_NAMESPACE {
+
+namespace {
+
+// Log error message
+static Status IOError(const std::string& context, int err_number) {
+  return (err_number == ENOSPC)
+             ? Status::NoSpace(context, strerror(err_number))
+             : (err_number == ENOENT)
+                   ? Status::PathNotFound(context, strerror(err_number))
+                   : Status::IOError(context, strerror(err_number));
+}
+
+// assume that there is one global logger for now. It is not thread-safe,
+// but need not be because the logger is initialized at db-open time.
+static Logger* mylog = nullptr;
+
+// Used for reading a file from HDFS. It implements both sequential-read
+// access methods as well as random read access methods.
+class HdfsReadableFile : virtual public SequentialFile,
+                         virtual public RandomAccessFile {
+ private:
+  hdfsFS fileSys_;
+  std::string filename_;
+  hdfsFile hfile_;
+
+ public:
+  HdfsReadableFile(hdfsFS fileSys, const std::string& fname)
+      : fileSys_(fileSys), filename_(fname), hfile_(nullptr) {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile opening file %s\n",
+                    filename_.c_str());
+    hfile_ = hdfsOpenFile(fileSys_, filename_.c_str(), O_RDONLY, 0, 0, 0);
+    ROCKS_LOG_DEBUG(mylog,
+                    "[hdfs] HdfsReadableFile opened file %s hfile_=0x%p\n",
+                    filename_.c_str(), hfile_);
+  }
+
+  virtual ~HdfsReadableFile() {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile closing file %s\n",
+                    filename_.c_str());
+    hdfsCloseFile(fileSys_, hfile_);
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile closed file %s\n",
+                    filename_.c_str());
+    hfile_ = nullptr;
+  }
+
+  bool isValid() {
+    return hfile_ != nullptr;
+  }
+
+  // sequential access, read data at current offset in file
+  virtual Status Read(size_t n, Slice* result, char* scratch) {
+    Status s;
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile reading %s %ld\n",
+                    filename_.c_str(), n);
+
+    char* buffer = scratch;
+    size_t total_bytes_read = 0;
+    tSize bytes_read = 0;
+    tSize remaining_bytes = (tSize)n;
+
+    // Read a total of n bytes repeatedly until we hit error or eof
+    while (remaining_bytes > 0) {
+      bytes_read = hdfsRead(fileSys_, hfile_, buffer, remaining_bytes);
+      if (bytes_read <= 0) {
+        break;
+      }
+      assert(bytes_read <= remaining_bytes);
+
+      total_bytes_read += bytes_read;
+      remaining_bytes -= bytes_read;
+      buffer += bytes_read;
+    }
+    assert(total_bytes_read <= n);
+
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile read %s\n",
+                    filename_.c_str());
+
+    if (bytes_read < 0) {
+      s = IOError(filename_, errno);
+    } else {
+      *result = Slice(scratch, total_bytes_read);
+    }
+
+    return s;
+  }
+
+  // random access, read data from specified offset in file
+  virtual Status Read(uint64_t offset, size_t n, Slice* result,
+                      char* scratch) const {
+    Status s;
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile preading %s\n",
+                    filename_.c_str());
+    ssize_t bytes_read = hdfsPread(fileSys_, hfile_, offset,
+                                   (void*)scratch, (tSize)n);
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile pread %s\n",
+                    filename_.c_str());
+    *result = Slice(scratch, (bytes_read < 0) ? 0 : bytes_read);
+    if (bytes_read < 0) {
+      // An error: return a non-ok status
+      s = IOError(filename_, errno);
+    }
+    return s;
+  }
+
+  virtual Status Skip(uint64_t n) {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile skip %s\n",
+                    filename_.c_str());
+    // get current offset from file
+    tOffset current = hdfsTell(fileSys_, hfile_);
+    if (current < 0) {
+      return IOError(filename_, errno);
+    }
+    // seek to new offset in file
+    tOffset newoffset = current + n;
+    int val = hdfsSeek(fileSys_, hfile_, newoffset);
+    if (val < 0) {
+      return IOError(filename_, errno);
+    }
+    return Status::OK();
+  }
+
+ private:
+
+  // returns true if we are at the end of file, false otherwise
+  bool feof() {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile feof %s\n",
+                    filename_.c_str());
+    if (hdfsTell(fileSys_, hfile_) == fileSize()) {
+      return true;
+    }
+    return false;
+  }
+
+  // the current size of the file
+  tOffset fileSize() {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsReadableFile fileSize %s\n",
+                    filename_.c_str());
+    hdfsFileInfo* pFileInfo = hdfsGetPathInfo(fileSys_, filename_.c_str());
+    tOffset size = 0L;
+    if (pFileInfo != nullptr) {
+      size = pFileInfo->mSize;
+      hdfsFreeFileInfo(pFileInfo, 1);
+    } else {
+      throw HdfsFatalException("fileSize on unknown file " + filename_);
+    }
+    return size;
+  }
+};
+
+// Appends to an existing file in HDFS.
+class HdfsWritableFile: public WritableFile {
+ private:
+  hdfsFS fileSys_;
+  std::string filename_;
+  hdfsFile hfile_;
+
+ public:
+  HdfsWritableFile(hdfsFS fileSys, const std::string& fname,
+                   const EnvOptions& options)
+      : WritableFile(options),
+        fileSys_(fileSys),
+        filename_(fname),
+        hfile_(nullptr) {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile opening %s\n",
+                    filename_.c_str());
+    hfile_ = hdfsOpenFile(fileSys_, filename_.c_str(), O_WRONLY, 0, 0, 0);
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile opened %s\n",
+                    filename_.c_str());
+    assert(hfile_ != nullptr);
+  }
+  virtual ~HdfsWritableFile() {
+    if (hfile_ != nullptr) {
+      ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile closing %s\n",
+                      filename_.c_str());
+      hdfsCloseFile(fileSys_, hfile_);
+      ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile closed %s\n",
+                      filename_.c_str());
+      hfile_ = nullptr;
+    }
+  }
+
+  // If the file was successfully created, then this returns true.
+  // Otherwise returns false.
+  bool isValid() {
+    return hfile_ != nullptr;
+  }
+
+  // The name of the file, mostly needed for debug logging.
+  const std::string& getName() {
+    return filename_;
+  }
+
+  virtual Status Append(const Slice& data) {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile Append %s\n",
+                    filename_.c_str());
+    const char* src = data.data();
+    size_t left = data.size();
+    size_t ret = hdfsWrite(fileSys_, hfile_, src, static_cast<tSize>(left));
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile Appended %s\n",
+                    filename_.c_str());
+    if (ret != left) {
+      return IOError(filename_, errno);
+    }
+    return Status::OK();
+  }
+
+  virtual Status Flush() {
+    return Status::OK();
+  }
+
+  virtual Status Sync() {
+    Status s;
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile Sync %s\n",
+                    filename_.c_str());
+    if (hdfsFlush(fileSys_, hfile_) == -1) {
+      return IOError(filename_, errno);
+    }
+    if (hdfsHSync(fileSys_, hfile_) == -1) {
+      return IOError(filename_, errno);
+    }
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile Synced %s\n",
+                    filename_.c_str());
+    return Status::OK();
+  }
+
+  // This is used by HdfsLogger to write data to the debug log file
+  virtual Status Append(const char* src, size_t size) {
+    if (hdfsWrite(fileSys_, hfile_, src, static_cast<tSize>(size)) !=
+        static_cast<tSize>(size)) {
+      return IOError(filename_, errno);
+    }
+    return Status::OK();
+  }
+
+  virtual Status Close() {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile closing %s\n",
+                    filename_.c_str());
+    if (hdfsCloseFile(fileSys_, hfile_) != 0) {
+      return IOError(filename_, errno);
+    }
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsWritableFile closed %s\n",
+                    filename_.c_str());
+    hfile_ = nullptr;
+    return Status::OK();
+  }
+};
+
+// The object that implements the debug logs to reside in HDFS.
+class HdfsLogger : public Logger {
+ private:
+  HdfsWritableFile* file_;
+  uint64_t (*gettid_)();  // Return the thread id for the current thread
+
+  Status HdfsCloseHelper() {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsLogger closed %s\n",
+                    file_->getName().c_str());
+    if (mylog != nullptr && mylog == this) {
+      mylog = nullptr;
+    }
+    return Status::OK();
+  }
+
+ protected:
+  virtual Status CloseImpl() override { return HdfsCloseHelper(); }
+
+ public:
+  HdfsLogger(HdfsWritableFile* f, uint64_t (*gettid)())
+      : file_(f), gettid_(gettid) {
+    ROCKS_LOG_DEBUG(mylog, "[hdfs] HdfsLogger opened %s\n",
+                    file_->getName().c_str());
+  }
+
+  ~HdfsLogger() override {
+    if (!closed_) {
+      closed_ = true;
+      HdfsCloseHelper();
+    }
+  }
+
+  using Logger::Logv;
+  void Logv(const char* format, va_list ap) override {
+    const uint64_t thread_id = (*gettid_)();
+
+    // We try twice: the first time with a fixed-size stack allocated buffer,
+    // and the second time with a much larger dynamically allocated buffer.
+    char buffer[500];
+    for (int iter = 0; iter < 2; iter++) {
+      char* base;
+      int bufsize;
+      if (iter == 0) {
+        bufsize = sizeof(buffer);
+        base = buffer;
+      } else {
+        bufsize = 30000;
+        base = new char[bufsize];
+      }
+      char* p = base;
+      char* limit = base + bufsize;
+
+      struct timeval now_tv;
+      gettimeofday(&now_tv, nullptr);
+      const time_t seconds = now_tv.tv_sec;
+      struct tm t;
+      localtime_r(&seconds, &t);
+      p += snprintf(p, limit - p,
+                    "%04d/%02d/%02d-%02d:%02d:%02d.%06d %llx ",
+                    t.tm_year + 1900,
+                    t.tm_mon + 1,
+                    t.tm_mday,
+                    t.tm_hour,
+                    t.tm_min,
+                    t.tm_sec,
+                    static_cast<int>(now_tv.tv_usec),
+                    static_cast<long long unsigned int>(thread_id));
+
+      // Print the message
+      if (p < limit) {
+        va_list backup_ap;
+        va_copy(backup_ap, ap);
+        p += vsnprintf(p, limit - p, format, backup_ap);
+        va_end(backup_ap);
+      }
+
+      // Truncate to available space if necessary
+      if (p >= limit) {
+        if (iter == 0) {
+          continue;       // Try again with larger buffer
+        } else {
+          p = limit - 1;
+        }
+      }
+
+      // Add newline if necessary
+      if (p == base || p[-1] != '\n') {
+        *p++ = '\n';
+      }
+
+      assert(p <= limit);
+      file_->Append(base, p-base);
+      file_->Flush();
+      if (base != buffer) {
+        delete[] base;
+      }
+      break;
+    }
+  }
+};
+
+}  // namespace
+
+// Finally, the hdfs environment
+
+const std::string HdfsEnv::kProto = "hdfs://";
+const std::string HdfsEnv::pathsep = "/";
+
+// open a file for sequential reading
+Status HdfsEnv::NewSequentialFile(const std::string& fname,
+                                  std::unique_ptr<SequentialFile>* result,
+                                  const EnvOptions& /*options*/) {
+  result->reset();
+  HdfsReadableFile* f = new HdfsReadableFile(fileSys_, fname);
+  if (f == nullptr || !f->isValid()) {
+    delete f;
+    *result = nullptr;
+    return IOError(fname, errno);
+  }
+  result->reset(dynamic_cast<SequentialFile*>(f));
+  return Status::OK();
+}
+
+// open a file for random reading
+Status HdfsEnv::NewRandomAccessFile(const std::string& fname,
+                                    std::unique_ptr<RandomAccessFile>* result,
+                                    const EnvOptions& /*options*/) {
+  result->reset();
+  HdfsReadableFile* f = new HdfsReadableFile(fileSys_, fname);
+  if (f == nullptr || !f->isValid()) {
+    delete f;
+    *result = nullptr;
+    return IOError(fname, errno);
+  }
+  result->reset(dynamic_cast<RandomAccessFile*>(f));
+  return Status::OK();
+}
+
+// create a new file for writing
+Status HdfsEnv::NewWritableFile(const std::string& fname,
+                                std::unique_ptr<WritableFile>* result,
+                                const EnvOptions& options) {
+  result->reset();
+  Status s;
+  HdfsWritableFile* f = new HdfsWritableFile(fileSys_, fname, options);
+  if (f == nullptr || !f->isValid()) {
+    delete f;
+    *result = nullptr;
+    return IOError(fname, errno);
+  }
+  result->reset(dynamic_cast<WritableFile*>(f));
+  return Status::OK();
+}
+
+class HdfsDirectory : public Directory {
+ public:
+  explicit HdfsDirectory(int fd) : fd_(fd) {}
+  ~HdfsDirectory() {}
+
+  Status Fsync() override { return Status::OK(); }
+
+  int GetFd() const { return fd_; }
+
+ private:
+  int fd_;
+};
+
+Status HdfsEnv::NewDirectory(const std::string& name,
+                             std::unique_ptr<Directory>* result) {
+  int value = hdfsExists(fileSys_, name.c_str());
+  switch (value) {
+    case HDFS_EXISTS:
+      result->reset(new HdfsDirectory(0));
+      return Status::OK();
+    default:  // fail if the directory doesn't exist
+      ROCKS_LOG_FATAL(mylog, "NewDirectory hdfsExists call failed");
+      throw HdfsFatalException("hdfsExists call failed with error " +
+                               ToString(value) + " on path " + name +
+                               ".\n");
+  }
+}
+
+Status HdfsEnv::FileExists(const std::string& fname) {
+  int value = hdfsExists(fileSys_, fname.c_str());
+  switch (value) {
+    case HDFS_EXISTS:
+      return Status::OK();
+    case HDFS_DOESNT_EXIST:
+      return Status::NotFound();
+    default:  // anything else should be an error
+      ROCKS_LOG_FATAL(mylog, "FileExists hdfsExists call failed");
+      return Status::IOError("hdfsExists call failed with error " +
+                             ToString(value) + " on path " + fname + ".\n");
+  }
+}
+
+Status HdfsEnv::GetChildren(const std::string& path,
+                            std::vector<std::string>* result) {
+  int value = hdfsExists(fileSys_, path.c_str());
+  switch (value) {
+    case HDFS_EXISTS: {  // directory exists
+    int numEntries = 0;
+    hdfsFileInfo* pHdfsFileInfo = 0;
+    pHdfsFileInfo = hdfsListDirectory(fileSys_, path.c_str(), &numEntries);
+    if (numEntries >= 0) {
+      for(int i = 0; i < numEntries; i++) {
+        std::string pathname(pHdfsFileInfo[i].mName);
+        size_t pos = pathname.rfind("/");
+        if (std::string::npos != pos) {
+          result->push_back(pathname.substr(pos + 1));
+        }
+      }
+      if (pHdfsFileInfo != nullptr) {
+        hdfsFreeFileInfo(pHdfsFileInfo, numEntries);
+      }
+    } else {
+      // numEntries < 0 indicates error
+      ROCKS_LOG_FATAL(mylog, "hdfsListDirectory call failed with error ");
+      throw HdfsFatalException(
+          "hdfsListDirectory call failed negative error.\n");
+    }
+    break;
+  }
+  case HDFS_DOESNT_EXIST:  // directory does not exist, exit
+    return Status::NotFound();
+  default:          // anything else should be an error
+    ROCKS_LOG_FATAL(mylog, "GetChildren hdfsExists call failed");
+    throw HdfsFatalException("hdfsExists call failed with error " +
+                             ToString(value) + ".\n");
+  }
+  return Status::OK();
+}
+
+Status HdfsEnv::DeleteFile(const std::string& fname) {
+  if (hdfsDelete(fileSys_, fname.c_str(), 1) == 0) {
+    return Status::OK();
+  }
+  return IOError(fname, errno);
+};
+
+Status HdfsEnv::CreateDir(const std::string& name) {
+  if (hdfsCreateDirectory(fileSys_, name.c_str()) == 0) {
+    return Status::OK();
+  }
+  return IOError(name, errno);
+};
+
+Status HdfsEnv::CreateDirIfMissing(const std::string& name) {
+  const int value = hdfsExists(fileSys_, name.c_str());
+  //  Not atomic. state might change b/w hdfsExists and CreateDir.
+  switch (value) {
+    case HDFS_EXISTS:
+    return Status::OK();
+    case HDFS_DOESNT_EXIST:
+    return CreateDir(name);
+    default:  // anything else should be an error
+      ROCKS_LOG_FATAL(mylog, "CreateDirIfMissing hdfsExists call failed");
+      throw HdfsFatalException("hdfsExists call failed with error " +
+                               ToString(value) + ".\n");
+  }
+};
+
+Status HdfsEnv::DeleteDir(const std::string& name) {
+  return DeleteFile(name);
+};
+
+Status HdfsEnv::GetFileSize(const std::string& fname, uint64_t* size) {
+  *size = 0L;
+  hdfsFileInfo* pFileInfo = hdfsGetPathInfo(fileSys_, fname.c_str());
+  if (pFileInfo != nullptr) {
+    *size = pFileInfo->mSize;
+    hdfsFreeFileInfo(pFileInfo, 1);
+    return Status::OK();
+  }
+  return IOError(fname, errno);
+}
+
+Status HdfsEnv::GetFileModificationTime(const std::string& fname,
+                                        uint64_t* time) {
+  hdfsFileInfo* pFileInfo = hdfsGetPathInfo(fileSys_, fname.c_str());
+  if (pFileInfo != nullptr) {
+    *time = static_cast<uint64_t>(pFileInfo->mLastMod);
+    hdfsFreeFileInfo(pFileInfo, 1);
+    return Status::OK();
+  }
+  return IOError(fname, errno);
+
+}
+
+// The rename is not atomic. HDFS does not allow a renaming if the
+// target already exists. So, we delete the target before attempting the
+// rename.
+Status HdfsEnv::RenameFile(const std::string& src, const std::string& target) {
+  hdfsDelete(fileSys_, target.c_str(), 1);
+  if (hdfsRename(fileSys_, src.c_str(), target.c_str()) == 0) {
+    return Status::OK();
+  }
+  return IOError(src, errno);
+}
+
+Status HdfsEnv::LockFile(const std::string& /*fname*/, FileLock** lock) {
+  // there isn's a very good way to atomically check and create
+  // a file via libhdfs
+  *lock = nullptr;
+  return Status::OK();
+}
+
+Status HdfsEnv::UnlockFile(FileLock* /*lock*/) { return Status::OK(); }
+
+Status HdfsEnv::NewLogger(const std::string& fname,
+                          std::shared_ptr<Logger>* result) {
+  // EnvOptions is used exclusively for its `strict_bytes_per_sync` value. That
+  // option is only intended for WAL/flush/compaction writes, so turn it off in
+  // the logger.
+  EnvOptions options;
+  options.strict_bytes_per_sync = false;
+  HdfsWritableFile* f = new HdfsWritableFile(fileSys_, fname, options);
+  if (f == nullptr || !f->isValid()) {
+    delete f;
+    *result = nullptr;
+    return IOError(fname, errno);
+  }
+  HdfsLogger* h = new HdfsLogger(f, &HdfsEnv::gettid);
+  result->reset(h);
+  if (mylog == nullptr) {
+    // mylog = h; // uncomment this for detailed logging
+  }
+  return Status::OK();
+}
+
+// The factory method for creating an HDFS Env
+Status NewHdfsEnv(Env** hdfs_env, const std::string& fsname) {
+  *hdfs_env = new HdfsEnv(fsname);
+  return Status::OK();
+}
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif // ROCKSDB_HDFS_FILE_C
+
+#else // USE_HDFS
+
+// dummy placeholders used when HDFS is not available
+namespace ROCKSDB_NAMESPACE {
+Status HdfsEnv::NewSequentialFile(const std::string& /*fname*/,
+                                  std::unique_ptr<SequentialFile>* /*result*/,
+                                  const EnvOptions& /*options*/) {
+  return Status::NotSupported("Not compiled with hdfs support");
+}
+
+ Status NewHdfsEnv(Env** /*hdfs_env*/, const std::string& /*fsname*/) {
+   return Status::NotSupported("Not compiled with hdfs support");
+ }
+ }  // namespace ROCKSDB_NAMESPACE
+
+#endif
diff --git a/src/rocksdb/env/env_posix.cc b/src/rocksdb/env/env_posix.cc
new file mode 100644
index 000000000..861fbcf62
--- /dev/null
+++ b/src/rocksdb/env/env_posix.cc
@@ -0,0 +1,527 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors
+#include <dirent.h>
+#ifndef ROCKSDB_NO_DYNAMIC_EXTENSION
+#include <dlfcn.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+
+#if defined(OS_LINUX)
+#include <linux/fs.h>
+#endif
+#if defined(ROCKSDB_IOURING_PRESENT)
+#include <liburing.h>
+#endif
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#if defined(OS_LINUX) || defined(OS_SOLARIS) || defined(OS_ANDROID)
+#include <sys/statfs.h>
+#include <sys/syscall.h>
+#include <sys/sysmacros.h>
+#endif
+#include <sys/statvfs.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#if defined(ROCKSDB_IOURING_PRESENT)
+#include <sys/uio.h>
+#endif
+#include <time.h>
+#include <algorithm>
+// Get nano time includes
+#if defined(OS_LINUX) || defined(OS_FREEBSD)
+#elif defined(__MACH__)
+#include <Availability.h>
+#include <mach/clock.h>
+#include <mach/mach.h>
+#else
+#include <chrono>
+#endif
+#include <deque>
+#include <set>
+#include <vector>
+
+#include "env/composite_env_wrapper.h"
+#include "env/io_posix.h"
+#include "logging/logging.h"
+#include "logging/posix_logger.h"
+#include "monitoring/iostats_context_imp.h"
+#include "monitoring/thread_status_updater.h"
+#include "port/port.h"
+#include "rocksdb/options.h"
+#include "rocksdb/slice.h"
+#include "test_util/sync_point.h"
+#include "util/coding.h"
+#include "util/compression_context_cache.h"
+#include "util/random.h"
+#include "util/string_util.h"
+#include "util/thread_local.h"
+#include "util/threadpool_imp.h"
+
+#if !defined(TMPFS_MAGIC)
+#define TMPFS_MAGIC 0x01021994
+#endif
+#if !defined(XFS_SUPER_MAGIC)
+#define XFS_SUPER_MAGIC 0x58465342
+#endif
+#if !defined(EXT4_SUPER_MAGIC)
+#define EXT4_SUPER_MAGIC 0xEF53
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+#if defined(OS_WIN)
+static const std::string kSharedLibExt = ".dll";
+static const char kPathSeparator = ';';
+#else
+static const char kPathSeparator = ':';
+#if defined(OS_MACOSX)
+static const std::string kSharedLibExt = ".dylib";
+#else
+static const std::string kSharedLibExt = ".so";
+#endif
+#endif
+
+namespace {
+
+ThreadStatusUpdater* CreateThreadStatusUpdater() {
+  return new ThreadStatusUpdater();
+}
+
+#ifndef ROCKSDB_NO_DYNAMIC_EXTENSION
+class PosixDynamicLibrary : public DynamicLibrary {
+ public:
+  PosixDynamicLibrary(const std::string& name, void* handle)
+      : name_(name), handle_(handle) {}
+  ~PosixDynamicLibrary() override { dlclose(handle_); }
+
+  Status LoadSymbol(const std::string& sym_name, void** func) override {
+    assert(nullptr != func);
+    dlerror();  // Clear any old error
+    *func = dlsym(handle_, sym_name.c_str());
+    if (*func != nullptr) {
+      return Status::OK();
+    } else {
+      char* err = dlerror();
+      return Status::NotFound("Error finding symbol: " + sym_name, err);
+    }
+  }
+
+  const char* Name() const override { return name_.c_str(); }
+
+ private:
+  std::string name_;
+  void* handle_;
+};
+#endif  // !ROCKSDB_NO_DYNAMIC_EXTENSION
+
+class PosixEnv : public CompositeEnvWrapper {
+ public:
+  PosixEnv();
+
+  ~PosixEnv() override {
+    for (const auto tid : threads_to_join_) {
+      pthread_join(tid, nullptr);
+    }
+    for (int pool_id = 0; pool_id < Env::Priority::TOTAL; ++pool_id) {
+      thread_pools_[pool_id].JoinAllThreads();
+    }
+    // Delete the thread_status_updater_ only when the current Env is not
+    // Env::Default().  This is to avoid the free-after-use error when
+    // Env::Default() is destructed while some other child threads are
+    // still trying to update thread status.
+    if (this != Env::Default()) {
+      delete thread_status_updater_;
+    }
+  }
+
+  void SetFD_CLOEXEC(int fd, const EnvOptions* options) {
+    if ((options == nullptr || options->set_fd_cloexec) && fd > 0) {
+      fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
+    }
+  }
+
+#ifndef ROCKSDB_NO_DYNAMIC_EXTENSION
+  // Loads the named library into the result.
+  // If the input name is empty, the current executable is loaded
+  // On *nix systems, a "lib" prefix is added to the name if one is not supplied
+  // Comparably, the appropriate shared library extension is added to the name
+  // if not supplied. If search_path is not specified, the shared library will
+  // be loaded using the default path (LD_LIBRARY_PATH) If search_path is
+  // specified, the shared library will be searched for in the directories
+  // provided by the search path
+  Status LoadLibrary(const std::string& name, const std::string& path,
+                     std::shared_ptr<DynamicLibrary>* result) override {
+    Status status;
+    assert(result != nullptr);
+    if (name.empty()) {
+      void* hndl = dlopen(NULL, RTLD_NOW);
+      if (hndl != nullptr) {
+        result->reset(new PosixDynamicLibrary(name, hndl));
+        return Status::OK();
+      }
+    } else {
+      std::string library_name = name;
+      if (library_name.find(kSharedLibExt) == std::string::npos) {
+        library_name = library_name + kSharedLibExt;
+      }
+#if !defined(OS_WIN)
+      if (library_name.find('/') == std::string::npos &&
+          library_name.compare(0, 3, "lib") != 0) {
+        library_name = "lib" + library_name;
+      }
+#endif
+      if (path.empty()) {
+        void* hndl = dlopen(library_name.c_str(), RTLD_NOW);
+        if (hndl != nullptr) {
+          result->reset(new PosixDynamicLibrary(library_name, hndl));
+          return Status::OK();
+        }
+      } else {
+        std::string local_path;
+        std::stringstream ss(path);
+        while (getline(ss, local_path, kPathSeparator)) {
+          if (!path.empty()) {
+            std::string full_name = local_path + "/" + library_name;
+            void* hndl = dlopen(full_name.c_str(), RTLD_NOW);
+            if (hndl != nullptr) {
+              result->reset(new PosixDynamicLibrary(full_name, hndl));
+              return Status::OK();
+            }
+          }
+        }
+      }
+    }
+    return Status::IOError(
+        IOErrorMsg("Failed to open shared library: xs", name), dlerror());
+  }
+#endif  // !ROCKSDB_NO_DYNAMIC_EXTENSION
+
+  void Schedule(void (*function)(void* arg1), void* arg, Priority pri = LOW,
+                void* tag = nullptr,
+                void (*unschedFunction)(void* arg) = nullptr) override;
+
+  int UnSchedule(void* arg, Priority pri) override;
+
+  void StartThread(void (*function)(void* arg), void* arg) override;
+
+  void WaitForJoin() override;
+
+  unsigned int GetThreadPoolQueueLen(Priority pri = LOW) const override;
+
+  Status GetTestDirectory(std::string* result) override {
+    const char* env = getenv("TEST_TMPDIR");
+    if (env && env[0] != '\0') {
+      *result = env;
+    } else {
+      char buf[100];
+      snprintf(buf, sizeof(buf), "/tmp/rocksdbtest-%d", int(geteuid()));
+      *result = buf;
+    }
+    // Directory may already exist
+    CreateDir(*result);
+    return Status::OK();
+  }
+
+  Status GetThreadList(std::vector<ThreadStatus>* thread_list) override {
+    assert(thread_status_updater_);
+    return thread_status_updater_->GetThreadList(thread_list);
+  }
+
+  static uint64_t gettid(pthread_t tid) {
+    uint64_t thread_id = 0;
+    memcpy(&thread_id, &tid, std::min(sizeof(thread_id), sizeof(tid)));
+    return thread_id;
+  }
+
+  static uint64_t gettid() {
+    pthread_t tid = pthread_self();
+    return gettid(tid);
+  }
+
+  uint64_t GetThreadID() const override { return gettid(pthread_self()); }
+
+  Status NewLogger(const std::string& fname,
+                   std::shared_ptr<Logger>* result) override {
+    FILE* f;
+    {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      f = fopen(fname.c_str(),
+                "w"
+#ifdef __GLIBC_PREREQ
+#if __GLIBC_PREREQ(2, 7)
+                "e"  // glibc extension to enable O_CLOEXEC
+#endif
+#endif
+      );
+    }
+    if (f == nullptr) {
+      result->reset();
+      return IOError("when fopen a file for new logger", fname, errno);
+    } else {
+      int fd = fileno(f);
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+      fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 4 * 1024);
+#endif
+      SetFD_CLOEXEC(fd, nullptr);
+      result->reset(new PosixLogger(f, &PosixEnv::gettid, this));
+      return Status::OK();
+    }
+  }
+
+  uint64_t NowMicros() override {
+    struct timeval tv;
+    gettimeofday(&tv, nullptr);
+    return static_cast<uint64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
+  }
+
+  uint64_t NowNanos() override {
+#if defined(OS_LINUX) || defined(OS_FREEBSD) || defined(OS_AIX)
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    return static_cast<uint64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
+#elif defined(OS_SOLARIS)
+    return gethrtime();
+#elif defined(__MACH__)
+    clock_serv_t cclock;
+    mach_timespec_t ts;
+    host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
+    clock_get_time(cclock, &ts);
+    mach_port_deallocate(mach_task_self(), cclock);
+    return static_cast<uint64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
+#else
+    return std::chrono::duration_cast<std::chrono::nanoseconds>(
+       std::chrono::steady_clock::now().time_since_epoch()).count();
+#endif
+  }
+
+  uint64_t NowCPUNanos() override {
+#if defined(OS_LINUX) || defined(OS_FREEBSD) || defined(OS_AIX) || \
+    (defined(__MACH__) && defined(__MAC_10_12))
+    struct timespec ts;
+    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
+    return static_cast<uint64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
+#endif
+    return 0;
+  }
+
+  void SleepForMicroseconds(int micros) override { usleep(micros); }
+
+  Status GetHostName(char* name, uint64_t len) override {
+    int ret = gethostname(name, static_cast<size_t>(len));
+    if (ret < 0) {
+      if (errno == EFAULT || errno == EINVAL) {
+        return Status::InvalidArgument(strerror(errno));
+      } else {
+        return IOError("GetHostName", name, errno);
+      }
+    }
+    return Status::OK();
+  }
+
+  Status GetCurrentTime(int64_t* unix_time) override {
+    time_t ret = time(nullptr);
+    if (ret == (time_t) -1) {
+      return IOError("GetCurrentTime", "", errno);
+    }
+    *unix_time = (int64_t) ret;
+    return Status::OK();
+  }
+
+  ThreadStatusUpdater* GetThreadStatusUpdater() const override {
+    return Env::GetThreadStatusUpdater();
+  }
+
+  std::string GenerateUniqueId() override { return Env::GenerateUniqueId(); }
+
+  // Allow increasing the number of worker threads.
+  void SetBackgroundThreads(int num, Priority pri) override {
+    assert(pri >= Priority::BOTTOM && pri <= Priority::HIGH);
+    thread_pools_[pri].SetBackgroundThreads(num);
+  }
+
+  int GetBackgroundThreads(Priority pri) override {
+    assert(pri >= Priority::BOTTOM && pri <= Priority::HIGH);
+    return thread_pools_[pri].GetBackgroundThreads();
+  }
+
+  Status SetAllowNonOwnerAccess(bool allow_non_owner_access) override {
+    allow_non_owner_access_ = allow_non_owner_access;
+    return Status::OK();
+  }
+
+  // Allow increasing the number of worker threads.
+  void IncBackgroundThreadsIfNeeded(int num, Priority pri) override {
+    assert(pri >= Priority::BOTTOM && pri <= Priority::HIGH);
+    thread_pools_[pri].IncBackgroundThreadsIfNeeded(num);
+  }
+
+  void LowerThreadPoolIOPriority(Priority pool = LOW) override {
+    assert(pool >= Priority::BOTTOM && pool <= Priority::HIGH);
+#ifdef OS_LINUX
+    thread_pools_[pool].LowerIOPriority();
+#else
+    (void)pool;
+#endif
+  }
+
+  void LowerThreadPoolCPUPriority(Priority pool = LOW) override {
+    assert(pool >= Priority::BOTTOM && pool <= Priority::HIGH);
+#ifdef OS_LINUX
+    thread_pools_[pool].LowerCPUPriority();
+#else
+    (void)pool;
+#endif
+  }
+
+  std::string TimeToString(uint64_t secondsSince1970) override {
+    const time_t seconds = (time_t)secondsSince1970;
+    struct tm t;
+    int maxsize = 64;
+    std::string dummy;
+    dummy.reserve(maxsize);
+    dummy.resize(maxsize);
+    char* p = &dummy[0];
+    localtime_r(&seconds, &t);
+    snprintf(p, maxsize,
+             "%04d/%02d/%02d-%02d:%02d:%02d ",
+             t.tm_year + 1900,
+             t.tm_mon + 1,
+             t.tm_mday,
+             t.tm_hour,
+             t.tm_min,
+             t.tm_sec);
+    return dummy;
+  }
+
+ private:
+  std::vector<ThreadPoolImpl> thread_pools_;
+  pthread_mutex_t mu_;
+  std::vector<pthread_t> threads_to_join_;
+  // If true, allow non owner read access for db files. Otherwise, non-owner
+  //  has no access to db files.
+  bool allow_non_owner_access_;
+};
+
+PosixEnv::PosixEnv()
+    : CompositeEnvWrapper(this, FileSystem::Default().get()),
+      thread_pools_(Priority::TOTAL),
+      allow_non_owner_access_(true) {
+  ThreadPoolImpl::PthreadCall("mutex_init", pthread_mutex_init(&mu_, nullptr));
+  for (int pool_id = 0; pool_id < Env::Priority::TOTAL; ++pool_id) {
+    thread_pools_[pool_id].SetThreadPriority(
+        static_cast<Env::Priority>(pool_id));
+    // This allows later initializing the thread-local-env of each thread.
+    thread_pools_[pool_id].SetHostEnv(this);
+  }
+  thread_status_updater_ = CreateThreadStatusUpdater();
+}
+
+void PosixEnv::Schedule(void (*function)(void* arg1), void* arg, Priority pri,
+                        void* tag, void (*unschedFunction)(void* arg)) {
+  assert(pri >= Priority::BOTTOM && pri <= Priority::HIGH);
+  thread_pools_[pri].Schedule(function, arg, tag, unschedFunction);
+}
+
+int PosixEnv::UnSchedule(void* arg, Priority pri) {
+  return thread_pools_[pri].UnSchedule(arg);
+}
+
+unsigned int PosixEnv::GetThreadPoolQueueLen(Priority pri) const {
+  assert(pri >= Priority::BOTTOM && pri <= Priority::HIGH);
+  return thread_pools_[pri].GetQueueLen();
+}
+
+struct StartThreadState {
+  void (*user_function)(void*);
+  void* arg;
+};
+
+static void* StartThreadWrapper(void* arg) {
+  StartThreadState* state = reinterpret_cast<StartThreadState*>(arg);
+  state->user_function(state->arg);
+  delete state;
+  return nullptr;
+}
+
+void PosixEnv::StartThread(void (*function)(void* arg), void* arg) {
+  pthread_t t;
+  StartThreadState* state = new StartThreadState;
+  state->user_function = function;
+  state->arg = arg;
+  ThreadPoolImpl::PthreadCall(
+      "start thread", pthread_create(&t, nullptr, &StartThreadWrapper, state));
+  ThreadPoolImpl::PthreadCall("lock", pthread_mutex_lock(&mu_));
+  threads_to_join_.push_back(t);
+  ThreadPoolImpl::PthreadCall("unlock", pthread_mutex_unlock(&mu_));
+}
+
+void PosixEnv::WaitForJoin() {
+  for (const auto tid : threads_to_join_) {
+    pthread_join(tid, nullptr);
+  }
+  threads_to_join_.clear();
+}
+
+}  // namespace
+
+std::string Env::GenerateUniqueId() {
+  std::string uuid_file = "/proc/sys/kernel/random/uuid";
+
+  Status s = FileExists(uuid_file);
+  if (s.ok()) {
+    std::string uuid;
+    s = ReadFileToString(this, uuid_file, &uuid);
+    if (s.ok()) {
+      return uuid;
+    }
+  }
+  // Could not read uuid_file - generate uuid using "nanos-random"
+  Random64 r(time(nullptr));
+  uint64_t random_uuid_portion =
+    r.Uniform(std::numeric_limits<uint64_t>::max());
+  uint64_t nanos_uuid_portion = NowNanos();
+  char uuid2[200];
+  snprintf(uuid2,
+           200,
+           "%lx-%lx",
+           (unsigned long)nanos_uuid_portion,
+           (unsigned long)random_uuid_portion);
+  return uuid2;
+}
+
+//
+// Default Posix Env
+//
+Env* Env::Default() {
+  // The following function call initializes the singletons of ThreadLocalPtr
+  // right before the static default_env.  This guarantees default_env will
+  // always being destructed before the ThreadLocalPtr singletons get
+  // destructed as C++ guarantees that the destructions of static variables
+  // is in the reverse order of their constructions.
+  //
+  // Since static members are destructed in the reverse order
+  // of their construction, having this call here guarantees that
+  // the destructor of static PosixEnv will go first, then the
+  // the singletons of ThreadLocalPtr.
+  ThreadLocalPtr::InitSingletons();
+  CompressionContextCache::InitSingleton();
+  INIT_SYNC_POINT_SINGLETONS();
+  static PosixEnv default_env;
+  static CompositeEnvWrapper composite_env(&default_env,
+                                           FileSystem::Default().get());
+  return &composite_env;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/env_test.cc b/src/rocksdb/env/env_test.cc
new file mode 100644
index 000000000..98f73d9a9
--- /dev/null
+++ b/src/rocksdb/env/env_test.cc
@@ -0,0 +1,1895 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef OS_WIN
+#include <sys/ioctl.h>
+#endif
+
+#include <sys/types.h>
+
+#include <iostream>
+#include <unordered_set>
+#include <atomic>
+#include <list>
+
+#ifdef OS_LINUX
+#include <fcntl.h>
+#include <linux/fs.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#endif
+
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+#include <errno.h>
+#endif
+
+#include "env/env_chroot.h"
+#include "logging/log_buffer.h"
+#include "port/malloc.h"
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "test_util/sync_point.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/coding.h"
+#include "util/mutexlock.h"
+#include "util/string_util.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+using port::kPageSize;
+
+static const int kDelayMicros = 100000;
+
+struct Deleter {
+  explicit Deleter(void (*fn)(void*)) : fn_(fn) {}
+
+  void operator()(void* ptr) {
+    assert(fn_);
+    assert(ptr);
+    (*fn_)(ptr);
+  }
+
+  void (*fn_)(void*);
+};
+
+std::unique_ptr<char, Deleter> NewAligned(const size_t size, const char ch) {
+  char* ptr = nullptr;
+#ifdef OS_WIN
+  if (nullptr == (ptr = reinterpret_cast<char*>(_aligned_malloc(size, kPageSize)))) {
+    return std::unique_ptr<char, Deleter>(nullptr, Deleter(_aligned_free));
+  }
+  std::unique_ptr<char, Deleter> uptr(ptr, Deleter(_aligned_free));
+#else
+  if (posix_memalign(reinterpret_cast<void**>(&ptr), kPageSize, size) != 0) {
+    return std::unique_ptr<char, Deleter>(nullptr, Deleter(free));
+  }
+  std::unique_ptr<char, Deleter> uptr(ptr, Deleter(free));
+#endif
+  memset(uptr.get(), ch, size);
+  return uptr;
+}
+
+class EnvPosixTest : public testing::Test {
+ private:
+  port::Mutex mu_;
+  std::string events_;
+
+ public:
+  Env* env_;
+  bool direct_io_;
+  EnvPosixTest() : env_(Env::Default()), direct_io_(false) {}
+};
+
+class EnvPosixTestWithParam
+    : public EnvPosixTest,
+      public ::testing::WithParamInterface<std::pair<Env*, bool>> {
+ public:
+  EnvPosixTestWithParam() {
+    std::pair<Env*, bool> param_pair = GetParam();
+    env_ = param_pair.first;
+    direct_io_ = param_pair.second;
+  }
+
+  void WaitThreadPoolsEmpty() {
+    // Wait until the thread pools are empty.
+    while (env_->GetThreadPoolQueueLen(Env::Priority::LOW) != 0) {
+      Env::Default()->SleepForMicroseconds(kDelayMicros);
+    }
+    while (env_->GetThreadPoolQueueLen(Env::Priority::HIGH) != 0) {
+      Env::Default()->SleepForMicroseconds(kDelayMicros);
+    }
+  }
+
+  ~EnvPosixTestWithParam() override { WaitThreadPoolsEmpty(); }
+};
+
+static void SetBool(void* ptr) {
+  reinterpret_cast<std::atomic<bool>*>(ptr)->store(true);
+}
+
+TEST_F(EnvPosixTest, DISABLED_RunImmediately) {
+  for (int pri = Env::BOTTOM; pri < Env::TOTAL; ++pri) {
+    std::atomic<bool> called(false);
+    env_->SetBackgroundThreads(1, static_cast<Env::Priority>(pri));
+    env_->Schedule(&SetBool, &called, static_cast<Env::Priority>(pri));
+    Env::Default()->SleepForMicroseconds(kDelayMicros);
+    ASSERT_TRUE(called.load());
+  }
+}
+
+TEST_F(EnvPosixTest, RunEventually) {
+  std::atomic<bool> called(false);
+  env_->StartThread(&SetBool, &called);
+  env_->WaitForJoin();
+  ASSERT_TRUE(called.load());
+}
+
+#ifdef OS_WIN
+TEST_F(EnvPosixTest, AreFilesSame) {
+  {
+    bool tmp;
+    if (env_->AreFilesSame("", "", &tmp).IsNotSupported()) {
+      fprintf(stderr,
+              "skipping EnvBasicTestWithParam.AreFilesSame due to "
+              "unsupported Env::AreFilesSame\n");
+      return;
+    }
+  }
+
+  const EnvOptions soptions;
+  auto* env = Env::Default();
+  std::string same_file_name = test::PerThreadDBPath(env, "same_file");
+  std::string same_file_link_name = same_file_name + "_link";
+
+  std::unique_ptr<WritableFile> same_file;
+  ASSERT_OK(env->NewWritableFile(same_file_name,
+    &same_file, soptions));
+  same_file->Append("random_data");
+  ASSERT_OK(same_file->Flush());
+  same_file.reset();
+
+  ASSERT_OK(env->LinkFile(same_file_name, same_file_link_name));
+  bool result = false;
+  ASSERT_OK(env->AreFilesSame(same_file_name, same_file_link_name, &result));
+  ASSERT_TRUE(result);
+}
+#endif
+
+#ifdef OS_LINUX
+TEST_F(EnvPosixTest, DISABLED_FilePermission) {
+  // Only works for Linux environment
+  if (env_ == Env::Default()) {
+    EnvOptions soptions;
+    std::vector<std::string> fileNames{
+        test::PerThreadDBPath(env_, "testfile"),
+        test::PerThreadDBPath(env_, "testfile1")};
+    std::unique_ptr<WritableFile> wfile;
+    ASSERT_OK(env_->NewWritableFile(fileNames[0], &wfile, soptions));
+    ASSERT_OK(env_->NewWritableFile(fileNames[1], &wfile, soptions));
+    wfile.reset();
+    std::unique_ptr<RandomRWFile> rwfile;
+    ASSERT_OK(env_->NewRandomRWFile(fileNames[1], &rwfile, soptions));
+
+    struct stat sb;
+    for (const auto& filename : fileNames) {
+      if (::stat(filename.c_str(), &sb) == 0) {
+        ASSERT_EQ(sb.st_mode & 0777, 0644);
+      }
+      env_->DeleteFile(filename);
+    }
+
+    env_->SetAllowNonOwnerAccess(false);
+    ASSERT_OK(env_->NewWritableFile(fileNames[0], &wfile, soptions));
+    ASSERT_OK(env_->NewWritableFile(fileNames[1], &wfile, soptions));
+    wfile.reset();
+    ASSERT_OK(env_->NewRandomRWFile(fileNames[1], &rwfile, soptions));
+
+    for (const auto& filename : fileNames) {
+      if (::stat(filename.c_str(), &sb) == 0) {
+        ASSERT_EQ(sb.st_mode & 0777, 0600);
+      }
+      env_->DeleteFile(filename);
+    }
+  }
+}
+#endif
+
+TEST_F(EnvPosixTest, MemoryMappedFileBuffer) {
+  const int kFileBytes = 1 << 15;  // 32 KB
+  std::string expected_data;
+  std::string fname = test::PerThreadDBPath(env_, "testfile");
+  {
+    std::unique_ptr<WritableFile> wfile;
+    const EnvOptions soptions;
+    ASSERT_OK(env_->NewWritableFile(fname, &wfile, soptions));
+
+    Random rnd(301);
+    test::RandomString(&rnd, kFileBytes, &expected_data);
+    ASSERT_OK(wfile->Append(expected_data));
+  }
+
+  std::unique_ptr<MemoryMappedFileBuffer> mmap_buffer;
+  Status status = env_->NewMemoryMappedFileBuffer(fname, &mmap_buffer);
+  // it should be supported at least on linux
+#if !defined(OS_LINUX)
+  if (status.IsNotSupported()) {
+    fprintf(stderr,
+            "skipping EnvPosixTest.MemoryMappedFileBuffer due to "
+            "unsupported Env::NewMemoryMappedFileBuffer\n");
+    return;
+  }
+#endif  // !defined(OS_LINUX)
+
+  ASSERT_OK(status);
+  ASSERT_NE(nullptr, mmap_buffer.get());
+  ASSERT_NE(nullptr, mmap_buffer->GetBase());
+  ASSERT_EQ(kFileBytes, mmap_buffer->GetLen());
+  std::string actual_data(reinterpret_cast<const char*>(mmap_buffer->GetBase()),
+                          mmap_buffer->GetLen());
+  ASSERT_EQ(expected_data, actual_data);
+}
+
+#ifndef ROCKSDB_NO_DYNAMIC_EXTENSION
+TEST_F(EnvPosixTest, LoadRocksDBLibrary) {
+  std::shared_ptr<DynamicLibrary> library;
+  std::function<void*(void*, const char*)> function;
+  Status status = env_->LoadLibrary("no-such-library", "", &library);
+  ASSERT_NOK(status);
+  ASSERT_EQ(nullptr, library.get());
+  status = env_->LoadLibrary("rocksdb", "", &library);
+  if (status.ok()) {  // If we have can find a rocksdb shared library
+    ASSERT_NE(nullptr, library.get());
+    ASSERT_OK(library->LoadFunction("rocksdb_create_default_env",
+                                    &function));  // from C definition
+    ASSERT_NE(nullptr, function);
+    ASSERT_NOK(library->LoadFunction("no-such-method", &function));
+    ASSERT_EQ(nullptr, function);
+    ASSERT_OK(env_->LoadLibrary(library->Name(), "", &library));
+  } else {
+    ASSERT_EQ(nullptr, library.get());
+  }
+}
+#endif  // !ROCKSDB_NO_DYNAMIC_EXTENSION
+
+#if !defined(OS_WIN) && !defined(ROCKSDB_NO_DYNAMIC_EXTENSION)
+TEST_F(EnvPosixTest, LoadRocksDBLibraryWithSearchPath) {
+  std::shared_ptr<DynamicLibrary> library;
+  std::function<void*(void*, const char*)> function;
+  ASSERT_NOK(env_->LoadLibrary("no-such-library", "/tmp", &library));
+  ASSERT_EQ(nullptr, library.get());
+  ASSERT_NOK(env_->LoadLibrary("dl", "/tmp", &library));
+  ASSERT_EQ(nullptr, library.get());
+  Status status = env_->LoadLibrary("rocksdb", "/tmp:./", &library);
+  if (status.ok()) {
+    ASSERT_NE(nullptr, library.get());
+    ASSERT_OK(env_->LoadLibrary(library->Name(), "", &library));
+  }
+  char buff[1024];
+  std::string cwd = getcwd(buff, sizeof(buff));
+
+  status = env_->LoadLibrary("rocksdb", "/tmp:" + cwd, &library);
+  if (status.ok()) {
+    ASSERT_NE(nullptr, library.get());
+    ASSERT_OK(env_->LoadLibrary(library->Name(), "", &library));
+  }
+}
+#endif  // !OS_WIN && !ROCKSDB_NO_DYNAMIC_EXTENSION
+
+TEST_P(EnvPosixTestWithParam, UnSchedule) {
+  std::atomic<bool> called(false);
+  env_->SetBackgroundThreads(1, Env::LOW);
+
+  /* Block the low priority queue */
+  test::SleepingBackgroundTask sleeping_task, sleeping_task1;
+  env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &sleeping_task,
+                 Env::Priority::LOW);
+
+  /* Schedule another task */
+  env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &sleeping_task1,
+                 Env::Priority::LOW, &sleeping_task1);
+
+  /* Remove it with a different tag  */
+  ASSERT_EQ(0, env_->UnSchedule(&called, Env::Priority::LOW));
+
+  /* Remove it from the queue with the right tag */
+  ASSERT_EQ(1, env_->UnSchedule(&sleeping_task1, Env::Priority::LOW));
+
+  // Unblock background thread
+  sleeping_task.WakeUp();
+
+  /* Schedule another task */
+  env_->Schedule(&SetBool, &called);
+  for (int i = 0; i < kDelayMicros; i++) {
+    if (called.load()) {
+      break;
+    }
+    Env::Default()->SleepForMicroseconds(1);
+  }
+  ASSERT_TRUE(called.load());
+
+  ASSERT_TRUE(!sleeping_task.IsSleeping() && !sleeping_task1.IsSleeping());
+  WaitThreadPoolsEmpty();
+}
+
+// This tests assumes that the last scheduled
+// task will run last. In fact, in the allotted
+// sleeping time nothing may actually run or they may
+// run in any order. The purpose of the test is unclear.
+#ifndef OS_WIN
+TEST_P(EnvPosixTestWithParam, RunMany) {
+  std::atomic<int> last_id(0);
+
+  struct CB {
+    std::atomic<int>* last_id_ptr;  // Pointer to shared slot
+    int id;                         // Order# for the execution of this callback
+
+    CB(std::atomic<int>* p, int i) : last_id_ptr(p), id(i) {}
+
+    static void Run(void* v) {
+      CB* cb = reinterpret_cast<CB*>(v);
+      int cur = cb->last_id_ptr->load();
+      ASSERT_EQ(cb->id - 1, cur);
+      cb->last_id_ptr->store(cb->id);
+    }
+  };
+
+  // Schedule in different order than start time
+  CB cb1(&last_id, 1);
+  CB cb2(&last_id, 2);
+  CB cb3(&last_id, 3);
+  CB cb4(&last_id, 4);
+  env_->Schedule(&CB::Run, &cb1);
+  env_->Schedule(&CB::Run, &cb2);
+  env_->Schedule(&CB::Run, &cb3);
+  env_->Schedule(&CB::Run, &cb4);
+
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  int cur = last_id.load(std::memory_order_acquire);
+  ASSERT_EQ(4, cur);
+  WaitThreadPoolsEmpty();
+}
+#endif
+
+struct State {
+  port::Mutex mu;
+  int val;
+  int num_running;
+};
+
+static void ThreadBody(void* arg) {
+  State* s = reinterpret_cast<State*>(arg);
+  s->mu.Lock();
+  s->val += 1;
+  s->num_running -= 1;
+  s->mu.Unlock();
+}
+
+TEST_P(EnvPosixTestWithParam, StartThread) {
+  State state;
+  state.val = 0;
+  state.num_running = 3;
+  for (int i = 0; i < 3; i++) {
+    env_->StartThread(&ThreadBody, &state);
+  }
+  while (true) {
+    state.mu.Lock();
+    int num = state.num_running;
+    state.mu.Unlock();
+    if (num == 0) {
+      break;
+    }
+    Env::Default()->SleepForMicroseconds(kDelayMicros);
+  }
+  ASSERT_EQ(state.val, 3);
+  WaitThreadPoolsEmpty();
+}
+
+TEST_P(EnvPosixTestWithParam, TwoPools) {
+  // Data structures to signal tasks to run.
+  port::Mutex mutex;
+  port::CondVar cv(&mutex);
+  bool should_start = false;
+
+  class CB {
+   public:
+    CB(const std::string& pool_name, int pool_size, port::Mutex* trigger_mu,
+       port::CondVar* trigger_cv, bool* _should_start)
+        : mu_(),
+          num_running_(0),
+          num_finished_(0),
+          pool_size_(pool_size),
+          pool_name_(pool_name),
+          trigger_mu_(trigger_mu),
+          trigger_cv_(trigger_cv),
+          should_start_(_should_start) {}
+
+    static void Run(void* v) {
+      CB* cb = reinterpret_cast<CB*>(v);
+      cb->Run();
+    }
+
+    void Run() {
+      {
+        MutexLock l(&mu_);
+        num_running_++;
+        // make sure we don't have more than pool_size_ jobs running.
+        ASSERT_LE(num_running_, pool_size_.load());
+      }
+
+      {
+        MutexLock l(trigger_mu_);
+        while (!(*should_start_)) {
+          trigger_cv_->Wait();
+        }
+      }
+
+      {
+        MutexLock l(&mu_);
+        num_running_--;
+        num_finished_++;
+      }
+    }
+
+    int NumFinished() {
+      MutexLock l(&mu_);
+      return num_finished_;
+    }
+
+    void Reset(int pool_size) {
+      pool_size_.store(pool_size);
+      num_finished_ = 0;
+    }
+
+   private:
+    port::Mutex mu_;
+    int num_running_;
+    int num_finished_;
+    std::atomic<int> pool_size_;
+    std::string pool_name_;
+    port::Mutex* trigger_mu_;
+    port::CondVar* trigger_cv_;
+    bool* should_start_;
+  };
+
+  const int kLowPoolSize = 2;
+  const int kHighPoolSize = 4;
+  const int kJobs = 8;
+
+  CB low_pool_job("low", kLowPoolSize, &mutex, &cv, &should_start);
+  CB high_pool_job("high", kHighPoolSize, &mutex, &cv, &should_start);
+
+  env_->SetBackgroundThreads(kLowPoolSize);
+  env_->SetBackgroundThreads(kHighPoolSize, Env::Priority::HIGH);
+
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::LOW));
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+
+  // schedule same number of jobs in each pool
+  for (int i = 0; i < kJobs; i++) {
+    env_->Schedule(&CB::Run, &low_pool_job);
+    env_->Schedule(&CB::Run, &high_pool_job, Env::Priority::HIGH);
+  }
+  // Wait a short while for the jobs to be dispatched.
+  int sleep_count = 0;
+  while ((unsigned int)(kJobs - kLowPoolSize) !=
+             env_->GetThreadPoolQueueLen(Env::Priority::LOW) ||
+         (unsigned int)(kJobs - kHighPoolSize) !=
+             env_->GetThreadPoolQueueLen(Env::Priority::HIGH)) {
+    env_->SleepForMicroseconds(kDelayMicros);
+    if (++sleep_count > 100) {
+      break;
+    }
+  }
+
+  ASSERT_EQ((unsigned int)(kJobs - kLowPoolSize),
+            env_->GetThreadPoolQueueLen());
+  ASSERT_EQ((unsigned int)(kJobs - kLowPoolSize),
+            env_->GetThreadPoolQueueLen(Env::Priority::LOW));
+  ASSERT_EQ((unsigned int)(kJobs - kHighPoolSize),
+            env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+
+  // Trigger jobs to run.
+  {
+    MutexLock l(&mutex);
+    should_start = true;
+    cv.SignalAll();
+  }
+
+  // wait for all jobs to finish
+  while (low_pool_job.NumFinished() < kJobs ||
+         high_pool_job.NumFinished() < kJobs) {
+    env_->SleepForMicroseconds(kDelayMicros);
+  }
+
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::LOW));
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+
+  // Hold jobs to schedule;
+  should_start = false;
+
+  // call IncBackgroundThreadsIfNeeded to two pools. One increasing and
+  // the other decreasing
+  env_->IncBackgroundThreadsIfNeeded(kLowPoolSize - 1, Env::Priority::LOW);
+  env_->IncBackgroundThreadsIfNeeded(kHighPoolSize + 1, Env::Priority::HIGH);
+  high_pool_job.Reset(kHighPoolSize + 1);
+  low_pool_job.Reset(kLowPoolSize);
+
+  // schedule same number of jobs in each pool
+  for (int i = 0; i < kJobs; i++) {
+    env_->Schedule(&CB::Run, &low_pool_job);
+    env_->Schedule(&CB::Run, &high_pool_job, Env::Priority::HIGH);
+  }
+  // Wait a short while for the jobs to be dispatched.
+  sleep_count = 0;
+  while ((unsigned int)(kJobs - kLowPoolSize) !=
+             env_->GetThreadPoolQueueLen(Env::Priority::LOW) ||
+         (unsigned int)(kJobs - (kHighPoolSize + 1)) !=
+             env_->GetThreadPoolQueueLen(Env::Priority::HIGH)) {
+    env_->SleepForMicroseconds(kDelayMicros);
+    if (++sleep_count > 100) {
+      break;
+    }
+  }
+  ASSERT_EQ((unsigned int)(kJobs - kLowPoolSize),
+            env_->GetThreadPoolQueueLen());
+  ASSERT_EQ((unsigned int)(kJobs - kLowPoolSize),
+            env_->GetThreadPoolQueueLen(Env::Priority::LOW));
+  ASSERT_EQ((unsigned int)(kJobs - (kHighPoolSize + 1)),
+            env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+
+  // Trigger jobs to run.
+  {
+    MutexLock l(&mutex);
+    should_start = true;
+    cv.SignalAll();
+  }
+
+  // wait for all jobs to finish
+  while (low_pool_job.NumFinished() < kJobs ||
+         high_pool_job.NumFinished() < kJobs) {
+    env_->SleepForMicroseconds(kDelayMicros);
+  }
+
+  env_->SetBackgroundThreads(kHighPoolSize, Env::Priority::HIGH);
+  WaitThreadPoolsEmpty();
+}
+
+TEST_P(EnvPosixTestWithParam, DecreaseNumBgThreads) {
+  constexpr int kWaitMicros = 60000000; // 1min
+
+  std::vector<test::SleepingBackgroundTask> tasks(10);
+
+  // Set number of thread to 1 first.
+  env_->SetBackgroundThreads(1, Env::Priority::HIGH);
+
+  // Schedule 3 tasks. 0 running; Task 1, 2 waiting.
+  for (size_t i = 0; i < 3; i++) {
+    env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &tasks[i],
+                   Env::Priority::HIGH);
+  }
+  ASSERT_FALSE(tasks[0].TimedWaitUntilSleeping(kWaitMicros));
+  ASSERT_EQ(2U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[0].IsSleeping());
+  ASSERT_TRUE(!tasks[1].IsSleeping());
+  ASSERT_TRUE(!tasks[2].IsSleeping());
+
+  // Increase to 2 threads. Task 0, 1 running; 2 waiting
+  env_->SetBackgroundThreads(2, Env::Priority::HIGH);
+  ASSERT_FALSE(tasks[1].TimedWaitUntilSleeping(kWaitMicros));
+  ASSERT_EQ(1U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[0].IsSleeping());
+  ASSERT_TRUE(tasks[1].IsSleeping());
+  ASSERT_TRUE(!tasks[2].IsSleeping());
+
+  // Shrink back to 1 thread. Still task 0, 1 running, 2 waiting
+  env_->SetBackgroundThreads(1, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_EQ(1U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[0].IsSleeping());
+  ASSERT_TRUE(tasks[1].IsSleeping());
+  ASSERT_TRUE(!tasks[2].IsSleeping());
+
+  // The last task finishes. Task 0 running, 2 waiting.
+  tasks[1].WakeUp();
+  ASSERT_FALSE(tasks[1].TimedWaitUntilDone(kWaitMicros));
+  ASSERT_EQ(1U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[0].IsSleeping());
+  ASSERT_TRUE(!tasks[1].IsSleeping());
+  ASSERT_TRUE(!tasks[2].IsSleeping());
+
+  // Increase to 5 threads. Task 0 and 2 running.
+  env_->SetBackgroundThreads(5, Env::Priority::HIGH);
+  ASSERT_FALSE(tasks[2].TimedWaitUntilSleeping(kWaitMicros));
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[0].IsSleeping());
+  ASSERT_TRUE(!tasks[1].IsSleeping());
+  ASSERT_TRUE(tasks[2].IsSleeping());
+
+  // Change number of threads a couple of times while there is no sufficient
+  // tasks.
+  env_->SetBackgroundThreads(7, Env::Priority::HIGH);
+  tasks[2].WakeUp();
+  ASSERT_FALSE(tasks[2].TimedWaitUntilDone(kWaitMicros));
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  env_->SetBackgroundThreads(3, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  env_->SetBackgroundThreads(4, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  env_->SetBackgroundThreads(5, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  env_->SetBackgroundThreads(4, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+
+  Env::Default()->SleepForMicroseconds(kDelayMicros * 50);
+
+  // Enqueue 5 more tasks. Thread pool size now is 4.
+  // Task 0, 3, 4, 5 running;6, 7 waiting.
+  for (size_t i = 3; i < 8; i++) {
+    env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &tasks[i],
+                   Env::Priority::HIGH);
+  }
+  for (size_t i = 3; i <= 5; i++) {
+    ASSERT_FALSE(tasks[i].TimedWaitUntilSleeping(kWaitMicros));
+  }
+  ASSERT_EQ(2U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[0].IsSleeping());
+  ASSERT_TRUE(!tasks[1].IsSleeping());
+  ASSERT_TRUE(!tasks[2].IsSleeping());
+  ASSERT_TRUE(tasks[3].IsSleeping());
+  ASSERT_TRUE(tasks[4].IsSleeping());
+  ASSERT_TRUE(tasks[5].IsSleeping());
+  ASSERT_TRUE(!tasks[6].IsSleeping());
+  ASSERT_TRUE(!tasks[7].IsSleeping());
+
+  // Wake up task 0, 3 and 4. Task 5, 6, 7 running.
+  tasks[0].WakeUp();
+  tasks[3].WakeUp();
+  tasks[4].WakeUp();
+
+  for (size_t i = 5; i < 8; i++) {
+    ASSERT_FALSE(tasks[i].TimedWaitUntilSleeping(kWaitMicros));
+  }
+  ASSERT_EQ(0U, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  for (size_t i = 5; i < 8; i++) {
+    ASSERT_TRUE(tasks[i].IsSleeping());
+  }
+
+  // Shrink back to 1 thread. Still task 5, 6, 7 running
+  env_->SetBackgroundThreads(1, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_TRUE(tasks[5].IsSleeping());
+  ASSERT_TRUE(tasks[6].IsSleeping());
+  ASSERT_TRUE(tasks[7].IsSleeping());
+
+  // Wake up task  6. Task 5, 7 running
+  tasks[6].WakeUp();
+  ASSERT_FALSE(tasks[6].TimedWaitUntilDone(kWaitMicros));
+  ASSERT_TRUE(tasks[5].IsSleeping());
+  ASSERT_TRUE(!tasks[6].IsSleeping());
+  ASSERT_TRUE(tasks[7].IsSleeping());
+
+  // Wake up threads 7. Task 5 running
+  tasks[7].WakeUp();
+  ASSERT_FALSE(tasks[7].TimedWaitUntilDone(kWaitMicros));
+  ASSERT_TRUE(!tasks[7].IsSleeping());
+
+  // Enqueue thread 8 and 9. Task 5 running; one of 8, 9 might be running.
+  env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &tasks[8],
+                 Env::Priority::HIGH);
+  env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &tasks[9],
+                 Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_GT(env_->GetThreadPoolQueueLen(Env::Priority::HIGH), (unsigned int)0);
+  ASSERT_TRUE(!tasks[8].IsSleeping() || !tasks[9].IsSleeping());
+
+  // Increase to 4 threads. Task 5, 8, 9 running.
+  env_->SetBackgroundThreads(4, Env::Priority::HIGH);
+  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  ASSERT_EQ((unsigned int)0, env_->GetThreadPoolQueueLen(Env::Priority::HIGH));
+  ASSERT_TRUE(tasks[8].IsSleeping());
+  ASSERT_TRUE(tasks[9].IsSleeping());
+
+  // Shrink to 1 thread
+  env_->SetBackgroundThreads(1, Env::Priority::HIGH);
+
+  // Wake up thread 9.
+  tasks[9].WakeUp();
+  ASSERT_FALSE(tasks[9].TimedWaitUntilDone(kWaitMicros));
+  ASSERT_TRUE(!tasks[9].IsSleeping());
+  ASSERT_TRUE(tasks[8].IsSleeping());
+
+  // Wake up thread 8
+  tasks[8].WakeUp();
+  ASSERT_FALSE(tasks[8].TimedWaitUntilDone(kWaitMicros));
+  ASSERT_TRUE(!tasks[8].IsSleeping());
+
+  // Wake up the last thread
+  tasks[5].WakeUp();
+  ASSERT_FALSE(tasks[5].TimedWaitUntilDone(kWaitMicros));
+  WaitThreadPoolsEmpty();
+}
+
+#if (defined OS_LINUX || defined OS_WIN)
+// Travis doesn't support fallocate or getting unique ID from files for whatever
+// reason.
+#ifndef TRAVIS
+
+namespace {
+bool IsSingleVarint(const std::string& s) {
+  Slice slice(s);
+
+  uint64_t v;
+  if (!GetVarint64(&slice, &v)) {
+    return false;
+  }
+
+  return slice.size() == 0;
+}
+
+bool IsUniqueIDValid(const std::string& s) {
+  return !s.empty() && !IsSingleVarint(s);
+}
+
+const size_t MAX_ID_SIZE = 100;
+char temp_id[MAX_ID_SIZE];
+
+
+}  // namespace
+
+// Determine whether we can use the FS_IOC_GETVERSION ioctl
+// on a file in directory DIR.  Create a temporary file therein,
+// try to apply the ioctl (save that result), cleanup and
+// return the result.  Return true if it is supported, and
+// false if anything fails.
+// Note that this function "knows" that dir has just been created
+// and is empty, so we create a simply-named test file: "f".
+bool ioctl_support__FS_IOC_GETVERSION(const std::string& dir) {
+#ifdef OS_WIN
+  return true;
+#else
+  const std::string file = dir + "/f";
+  int fd;
+  do {
+    fd = open(file.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
+  } while (fd < 0 && errno == EINTR);
+  long int version;
+  bool ok = (fd >= 0 && ioctl(fd, FS_IOC_GETVERSION, &version) >= 0);
+
+  close(fd);
+  unlink(file.c_str());
+
+  return ok;
+#endif
+}
+
+// To ensure that Env::GetUniqueId-related tests work correctly, the files
+// should be stored in regular storage like "hard disk" or "flash device",
+// and not on a tmpfs file system (like /dev/shm and /tmp on some systems).
+// Otherwise we cannot get the correct id.
+//
+// This function serves as the replacement for test::TmpDir(), which may be
+// customized to be on a file system that doesn't work with GetUniqueId().
+
+class IoctlFriendlyTmpdir {
+ public:
+  explicit IoctlFriendlyTmpdir() {
+    char dir_buf[100];
+
+    const char *fmt = "%s/rocksdb.XXXXXX";
+    const char *tmp = getenv("TEST_IOCTL_FRIENDLY_TMPDIR");
+
+#ifdef OS_WIN
+#define rmdir _rmdir
+    if(tmp == nullptr) {
+      tmp = getenv("TMP");
+    }
+
+    snprintf(dir_buf, sizeof dir_buf, fmt, tmp);
+    auto result = _mktemp(dir_buf);
+    assert(result != nullptr);
+    BOOL ret = CreateDirectory(dir_buf, NULL);
+    assert(ret == TRUE);
+    dir_ = dir_buf;
+#else
+    std::list<std::string> candidate_dir_list = {"/var/tmp", "/tmp"};
+
+    // If $TEST_IOCTL_FRIENDLY_TMPDIR/rocksdb.XXXXXX fits, use
+    // $TEST_IOCTL_FRIENDLY_TMPDIR; subtract 2 for the "%s", and
+    // add 1 for the trailing NUL byte.
+    if (tmp && strlen(tmp) + strlen(fmt) - 2 + 1 <= sizeof dir_buf) {
+      // use $TEST_IOCTL_FRIENDLY_TMPDIR value
+      candidate_dir_list.push_front(tmp);
+    }
+
+    for (const std::string& d : candidate_dir_list) {
+      snprintf(dir_buf, sizeof dir_buf, fmt, d.c_str());
+      if (mkdtemp(dir_buf)) {
+        if (ioctl_support__FS_IOC_GETVERSION(dir_buf)) {
+          dir_ = dir_buf;
+          return;
+        } else {
+          // Diagnose ioctl-related failure only if this is the
+          // directory specified via that envvar.
+          if (tmp && tmp == d) {
+            fprintf(stderr, "TEST_IOCTL_FRIENDLY_TMPDIR-specified directory is "
+                    "not suitable: %s\n", d.c_str());
+          }
+          rmdir(dir_buf);  // ignore failure
+        }
+      } else {
+        // mkdtemp failed: diagnose it, but don't give up.
+        fprintf(stderr, "mkdtemp(%s/...) failed: %s\n", d.c_str(),
+                strerror(errno));
+      }
+    }
+
+    fprintf(stderr, "failed to find an ioctl-friendly temporary directory;"
+            " specify one via the TEST_IOCTL_FRIENDLY_TMPDIR envvar\n");
+    std::abort();
+#endif
+}
+
+  ~IoctlFriendlyTmpdir() {
+    rmdir(dir_.c_str());
+  }
+
+  const std::string& name() const {
+    return dir_;
+  }
+
+ private:
+  std::string dir_;
+};
+
+#ifndef ROCKSDB_LITE
+TEST_F(EnvPosixTest, PositionedAppend) {
+  std::unique_ptr<WritableFile> writable_file;
+  EnvOptions options;
+  options.use_direct_writes = true;
+  options.use_mmap_writes = false;
+  IoctlFriendlyTmpdir ift;
+  ASSERT_OK(env_->NewWritableFile(ift.name() + "/f", &writable_file, options));
+  const size_t kBlockSize = 4096;
+  const size_t kDataSize = kPageSize;
+  // Write a page worth of 'a'
+  auto data_ptr = NewAligned(kDataSize, 'a');
+  Slice data_a(data_ptr.get(), kDataSize);
+  ASSERT_OK(writable_file->PositionedAppend(data_a, 0U));
+  // Write a page worth of 'b' right after the first sector
+  data_ptr = NewAligned(kDataSize, 'b');
+  Slice data_b(data_ptr.get(), kDataSize);
+  ASSERT_OK(writable_file->PositionedAppend(data_b, kBlockSize));
+  ASSERT_OK(writable_file->Close());
+  // The file now has 1 sector worth of a followed by a page worth of b
+
+  // Verify the above
+  std::unique_ptr<SequentialFile> seq_file;
+  ASSERT_OK(env_->NewSequentialFile(ift.name() + "/f", &seq_file, options));
+  size_t scratch_len = kPageSize * 2;
+  std::unique_ptr<char[]> scratch(new char[scratch_len]);
+  Slice result;
+  ASSERT_OK(seq_file->Read(scratch_len, &result, scratch.get()));
+  ASSERT_EQ(kPageSize + kBlockSize, result.size());
+  ASSERT_EQ('a', result[kBlockSize - 1]);
+  ASSERT_EQ('b', result[kBlockSize]);
+}
+#endif  // !ROCKSDB_LITE
+
+// `GetUniqueId()` temporarily returns zero on Windows. `BlockBasedTable` can
+// handle a return value of zero but this test case cannot.
+#ifndef OS_WIN
+TEST_P(EnvPosixTestWithParam, RandomAccessUniqueID) {
+  // Create file.
+  if (env_ == Env::Default()) {
+    EnvOptions soptions;
+    soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+    IoctlFriendlyTmpdir ift;
+    std::string fname = ift.name() + "/testfile";
+    std::unique_ptr<WritableFile> wfile;
+    ASSERT_OK(env_->NewWritableFile(fname, &wfile, soptions));
+
+    std::unique_ptr<RandomAccessFile> file;
+
+    // Get Unique ID
+    ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+    size_t id_size = file->GetUniqueId(temp_id, MAX_ID_SIZE);
+    ASSERT_TRUE(id_size > 0);
+    std::string unique_id1(temp_id, id_size);
+    ASSERT_TRUE(IsUniqueIDValid(unique_id1));
+
+    // Get Unique ID again
+    ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+    id_size = file->GetUniqueId(temp_id, MAX_ID_SIZE);
+    ASSERT_TRUE(id_size > 0);
+    std::string unique_id2(temp_id, id_size);
+    ASSERT_TRUE(IsUniqueIDValid(unique_id2));
+
+    // Get Unique ID again after waiting some time.
+    env_->SleepForMicroseconds(1000000);
+    ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+    id_size = file->GetUniqueId(temp_id, MAX_ID_SIZE);
+    ASSERT_TRUE(id_size > 0);
+    std::string unique_id3(temp_id, id_size);
+    ASSERT_TRUE(IsUniqueIDValid(unique_id3));
+
+    // Check IDs are the same.
+    ASSERT_EQ(unique_id1, unique_id2);
+    ASSERT_EQ(unique_id2, unique_id3);
+
+    // Delete the file
+    env_->DeleteFile(fname);
+  }
+}
+#endif  // !defined(OS_WIN)
+
+// only works in linux platforms
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+TEST_P(EnvPosixTestWithParam, AllocateTest) {
+  if (env_ == Env::Default()) {
+    IoctlFriendlyTmpdir ift;
+    std::string fname = ift.name() + "/preallocate_testfile";
+
+    // Try fallocate in a file to see whether the target file system supports
+    // it.
+    // Skip the test if fallocate is not supported.
+    std::string fname_test_fallocate = ift.name() + "/preallocate_testfile_2";
+    int fd = -1;
+    do {
+      fd = open(fname_test_fallocate.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
+    } while (fd < 0 && errno == EINTR);
+    ASSERT_GT(fd, 0);
+
+    int alloc_status = fallocate(fd, 0, 0, 1);
+
+    int err_number = 0;
+    if (alloc_status != 0) {
+      err_number = errno;
+      fprintf(stderr, "Warning: fallocate() fails, %s\n", strerror(err_number));
+    }
+    close(fd);
+    ASSERT_OK(env_->DeleteFile(fname_test_fallocate));
+    if (alloc_status != 0 && err_number == EOPNOTSUPP) {
+      // The filesystem containing the file does not support fallocate
+      return;
+    }
+
+    EnvOptions soptions;
+    soptions.use_mmap_writes = false;
+    soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+    std::unique_ptr<WritableFile> wfile;
+    ASSERT_OK(env_->NewWritableFile(fname, &wfile, soptions));
+
+    // allocate 100 MB
+    size_t kPreallocateSize = 100 * 1024 * 1024;
+    size_t kBlockSize = 512;
+    size_t kDataSize = 1024 * 1024;
+    auto data_ptr = NewAligned(kDataSize, 'A');
+    Slice data(data_ptr.get(), kDataSize);
+    wfile->SetPreallocationBlockSize(kPreallocateSize);
+    wfile->PrepareWrite(wfile->GetFileSize(), kDataSize);
+    ASSERT_OK(wfile->Append(data));
+    ASSERT_OK(wfile->Flush());
+
+    struct stat f_stat;
+    ASSERT_EQ(stat(fname.c_str(), &f_stat), 0);
+    ASSERT_EQ((unsigned int)kDataSize, f_stat.st_size);
+    // verify that blocks are preallocated
+    // Note here that we don't check the exact number of blocks preallocated --
+    // we only require that number of allocated blocks is at least what we
+    // expect.
+    // It looks like some FS give us more blocks that we asked for. That's fine.
+    // It might be worth investigating further.
+    ASSERT_LE((unsigned int)(kPreallocateSize / kBlockSize), f_stat.st_blocks);
+
+    // close the file, should deallocate the blocks
+    wfile.reset();
+
+    stat(fname.c_str(), &f_stat);
+    ASSERT_EQ((unsigned int)kDataSize, f_stat.st_size);
+    // verify that preallocated blocks were deallocated on file close
+    // Because the FS might give us more blocks, we add a full page to the size
+    // and expect the number of blocks to be less or equal to that.
+    ASSERT_GE((f_stat.st_size + kPageSize + kBlockSize - 1) / kBlockSize,
+              (unsigned int)f_stat.st_blocks);
+  }
+}
+#endif  // ROCKSDB_FALLOCATE_PRESENT
+
+// Returns true if any of the strings in ss are the prefix of another string.
+bool HasPrefix(const std::unordered_set<std::string>& ss) {
+  for (const std::string& s: ss) {
+    if (s.empty()) {
+      return true;
+    }
+    for (size_t i = 1; i < s.size(); ++i) {
+      if (ss.count(s.substr(0, i)) != 0) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+// `GetUniqueId()` temporarily returns zero on Windows. `BlockBasedTable` can
+// handle a return value of zero but this test case cannot.
+#ifndef OS_WIN
+TEST_P(EnvPosixTestWithParam, RandomAccessUniqueIDConcurrent) {
+  if (env_ == Env::Default()) {
+    // Check whether a bunch of concurrently existing files have unique IDs.
+    EnvOptions soptions;
+    soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+
+    // Create the files
+    IoctlFriendlyTmpdir ift;
+    std::vector<std::string> fnames;
+    for (int i = 0; i < 1000; ++i) {
+      fnames.push_back(ift.name() + "/" + "testfile" + ToString(i));
+
+      // Create file.
+      std::unique_ptr<WritableFile> wfile;
+      ASSERT_OK(env_->NewWritableFile(fnames[i], &wfile, soptions));
+    }
+
+    // Collect and check whether the IDs are unique.
+    std::unordered_set<std::string> ids;
+    for (const std::string fname : fnames) {
+      std::unique_ptr<RandomAccessFile> file;
+      std::string unique_id;
+      ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+      size_t id_size = file->GetUniqueId(temp_id, MAX_ID_SIZE);
+      ASSERT_TRUE(id_size > 0);
+      unique_id = std::string(temp_id, id_size);
+      ASSERT_TRUE(IsUniqueIDValid(unique_id));
+
+      ASSERT_TRUE(ids.count(unique_id) == 0);
+      ids.insert(unique_id);
+    }
+
+    // Delete the files
+    for (const std::string fname : fnames) {
+      ASSERT_OK(env_->DeleteFile(fname));
+    }
+
+    ASSERT_TRUE(!HasPrefix(ids));
+  }
+}
+
+TEST_P(EnvPosixTestWithParam, RandomAccessUniqueIDDeletes) {
+  if (env_ == Env::Default()) {
+    EnvOptions soptions;
+    soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+
+    IoctlFriendlyTmpdir ift;
+    std::string fname = ift.name() + "/" + "testfile";
+
+    // Check that after file is deleted we don't get same ID again in a new
+    // file.
+    std::unordered_set<std::string> ids;
+    for (int i = 0; i < 1000; ++i) {
+      // Create file.
+      {
+        std::unique_ptr<WritableFile> wfile;
+        ASSERT_OK(env_->NewWritableFile(fname, &wfile, soptions));
+      }
+
+      // Get Unique ID
+      std::string unique_id;
+      {
+        std::unique_ptr<RandomAccessFile> file;
+        ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+        size_t id_size = file->GetUniqueId(temp_id, MAX_ID_SIZE);
+        ASSERT_TRUE(id_size > 0);
+        unique_id = std::string(temp_id, id_size);
+      }
+
+      ASSERT_TRUE(IsUniqueIDValid(unique_id));
+      ASSERT_TRUE(ids.count(unique_id) == 0);
+      ids.insert(unique_id);
+
+      // Delete the file
+      ASSERT_OK(env_->DeleteFile(fname));
+    }
+
+    ASSERT_TRUE(!HasPrefix(ids));
+  }
+}
+#endif  // !defined(OS_WIN)
+
+TEST_P(EnvPosixTestWithParam, MultiRead) {
+  EnvOptions soptions;
+  soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+  std::string fname = test::PerThreadDBPath(env_, "testfile");
+
+  const size_t kSectorSize = 4096;
+  const size_t kNumSectors = 8;
+
+  // Create file.
+  {
+    std::unique_ptr<WritableFile> wfile;
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && \
+    !defined(OS_AIX)
+    if (soptions.use_direct_writes) {
+      soptions.use_direct_writes = false;
+    }
+#endif
+    ASSERT_OK(env_->NewWritableFile(fname, &wfile, soptions));
+    for (size_t i = 0; i < kNumSectors; ++i) {
+      auto data = NewAligned(kSectorSize * 8, static_cast<char>(i + 1));
+      Slice slice(data.get(), kSectorSize);
+      ASSERT_OK(wfile->Append(slice));
+    }
+    ASSERT_OK(wfile->Close());
+  }
+
+  // More attempts to simulate more partial result sequences.
+  for (uint32_t attempt = 0; attempt < 20; attempt++) {
+    // Random Read
+    Random rnd(301 + attempt);
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->SetCallBack(
+        "PosixRandomAccessFile::MultiRead:io_uring_result", [&](void* arg) {
+          if (attempt > 0) {
+            // No failure in the first attempt.
+            size_t& bytes_read = *static_cast<size_t*>(arg);
+            if (rnd.OneIn(4)) {
+              bytes_read = 0;
+            } else if (rnd.OneIn(3)) {
+              bytes_read = static_cast<size_t>(
+                  rnd.Uniform(static_cast<int>(bytes_read)));
+            }
+          }
+        });
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+
+    std::unique_ptr<RandomAccessFile> file;
+    std::vector<ReadRequest> reqs(3);
+    std::vector<std::unique_ptr<char, Deleter>> data;
+    uint64_t offset = 0;
+    for (size_t i = 0; i < reqs.size(); ++i) {
+      reqs[i].offset = offset;
+      offset += 2 * kSectorSize;
+      reqs[i].len = kSectorSize;
+      data.emplace_back(NewAligned(kSectorSize, 0));
+      reqs[i].scratch = data.back().get();
+    }
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && \
+    !defined(OS_AIX)
+    if (soptions.use_direct_reads) {
+      soptions.use_direct_reads = false;
+    }
+#endif
+    ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+    ASSERT_OK(file->MultiRead(reqs.data(), reqs.size()));
+    for (size_t i = 0; i < reqs.size(); ++i) {
+      auto buf = NewAligned(kSectorSize * 8, static_cast<char>(i * 2 + 1));
+      ASSERT_OK(reqs[i].status);
+      ASSERT_EQ(memcmp(reqs[i].scratch, buf.get(), kSectorSize), 0);
+    }
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->DisableProcessing();
+  }
+}
+
+// Only works in linux platforms
+#ifdef OS_WIN
+TEST_P(EnvPosixTestWithParam, DISABLED_InvalidateCache) {
+#else
+TEST_P(EnvPosixTestWithParam, InvalidateCache) {
+#endif
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+  EnvOptions soptions;
+  soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+  std::string fname = test::PerThreadDBPath(env_, "testfile");
+
+  const size_t kSectorSize = 512;
+  auto data = NewAligned(kSectorSize, 0);
+  Slice slice(data.get(), kSectorSize);
+
+  // Create file.
+  {
+    std::unique_ptr<WritableFile> wfile;
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && !defined(OS_AIX)
+      if (soptions.use_direct_writes) {
+        soptions.use_direct_writes = false;
+      }
+#endif
+      ASSERT_OK(env_->NewWritableFile(fname, &wfile, soptions));
+      ASSERT_OK(wfile->Append(slice));
+      ASSERT_OK(wfile->InvalidateCache(0, 0));
+      ASSERT_OK(wfile->Close());
+  }
+
+    // Random Read
+    {
+      std::unique_ptr<RandomAccessFile> file;
+      auto scratch = NewAligned(kSectorSize, 0);
+      Slice result;
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && !defined(OS_AIX)
+      if (soptions.use_direct_reads) {
+        soptions.use_direct_reads = false;
+      }
+#endif
+      ASSERT_OK(env_->NewRandomAccessFile(fname, &file, soptions));
+      ASSERT_OK(file->Read(0, kSectorSize, &result, scratch.get()));
+      ASSERT_EQ(memcmp(scratch.get(), data.get(), kSectorSize), 0);
+      ASSERT_OK(file->InvalidateCache(0, 11));
+      ASSERT_OK(file->InvalidateCache(0, 0));
+    }
+
+    // Sequential Read
+    {
+      std::unique_ptr<SequentialFile> file;
+      auto scratch = NewAligned(kSectorSize, 0);
+      Slice result;
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && !defined(OS_AIX)
+      if (soptions.use_direct_reads) {
+        soptions.use_direct_reads = false;
+      }
+#endif
+      ASSERT_OK(env_->NewSequentialFile(fname, &file, soptions));
+      if (file->use_direct_io()) {
+        ASSERT_OK(file->PositionedRead(0, kSectorSize, &result, scratch.get()));
+      } else {
+        ASSERT_OK(file->Read(kSectorSize, &result, scratch.get()));
+      }
+      ASSERT_EQ(memcmp(scratch.get(), data.get(), kSectorSize), 0);
+      ASSERT_OK(file->InvalidateCache(0, 11));
+      ASSERT_OK(file->InvalidateCache(0, 0));
+    }
+    // Delete the file
+    ASSERT_OK(env_->DeleteFile(fname));
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->ClearTrace();
+}
+#endif  // not TRAVIS
+#endif  // OS_LINUX || OS_WIN
+
+class TestLogger : public Logger {
+ public:
+  using Logger::Logv;
+  void Logv(const char* format, va_list ap) override {
+    log_count++;
+
+    char new_format[550];
+    std::fill_n(new_format, sizeof(new_format), '2');
+    {
+      va_list backup_ap;
+      va_copy(backup_ap, ap);
+      int n = vsnprintf(new_format, sizeof(new_format) - 1, format, backup_ap);
+      // 48 bytes for extra information + bytes allocated
+
+// When we have n == -1 there is not a terminating zero expected
+#ifdef OS_WIN
+      if (n < 0) {
+        char_0_count++;
+      }
+#endif
+
+      if (new_format[0] == '[') {
+        // "[DEBUG] "
+        ASSERT_TRUE(n <= 56 + (512 - static_cast<int>(sizeof(struct timeval))));
+      } else {
+        ASSERT_TRUE(n <= 48 + (512 - static_cast<int>(sizeof(struct timeval))));
+      }
+      va_end(backup_ap);
+    }
+
+    for (size_t i = 0; i < sizeof(new_format); i++) {
+      if (new_format[i] == 'x') {
+        char_x_count++;
+      } else if (new_format[i] == '\0') {
+        char_0_count++;
+      }
+    }
+  }
+  int log_count;
+  int char_x_count;
+  int char_0_count;
+};
+
+TEST_P(EnvPosixTestWithParam, LogBufferTest) {
+  TestLogger test_logger;
+  test_logger.SetInfoLogLevel(InfoLogLevel::INFO_LEVEL);
+  test_logger.log_count = 0;
+  test_logger.char_x_count = 0;
+  test_logger.char_0_count = 0;
+  LogBuffer log_buffer(InfoLogLevel::INFO_LEVEL, &test_logger);
+  LogBuffer log_buffer_debug(DEBUG_LEVEL, &test_logger);
+
+  char bytes200[200];
+  std::fill_n(bytes200, sizeof(bytes200), '1');
+  bytes200[sizeof(bytes200) - 1] = '\0';
+  char bytes600[600];
+  std::fill_n(bytes600, sizeof(bytes600), '1');
+  bytes600[sizeof(bytes600) - 1] = '\0';
+  char bytes9000[9000];
+  std::fill_n(bytes9000, sizeof(bytes9000), '1');
+  bytes9000[sizeof(bytes9000) - 1] = '\0';
+
+  ROCKS_LOG_BUFFER(&log_buffer, "x%sx", bytes200);
+  ROCKS_LOG_BUFFER(&log_buffer, "x%sx", bytes600);
+  ROCKS_LOG_BUFFER(&log_buffer, "x%sx%sx%sx", bytes200, bytes200, bytes200);
+  ROCKS_LOG_BUFFER(&log_buffer, "x%sx%sx", bytes200, bytes600);
+  ROCKS_LOG_BUFFER(&log_buffer, "x%sx%sx", bytes600, bytes9000);
+
+  ROCKS_LOG_BUFFER(&log_buffer_debug, "x%sx", bytes200);
+  test_logger.SetInfoLogLevel(DEBUG_LEVEL);
+  ROCKS_LOG_BUFFER(&log_buffer_debug, "x%sx%sx%sx", bytes600, bytes9000,
+                   bytes200);
+
+  ASSERT_EQ(0, test_logger.log_count);
+  log_buffer.FlushBufferToLog();
+  log_buffer_debug.FlushBufferToLog();
+  ASSERT_EQ(6, test_logger.log_count);
+  ASSERT_EQ(6, test_logger.char_0_count);
+  ASSERT_EQ(10, test_logger.char_x_count);
+}
+
+class TestLogger2 : public Logger {
+ public:
+  explicit TestLogger2(size_t max_log_size) : max_log_size_(max_log_size) {}
+  using Logger::Logv;
+  void Logv(const char* format, va_list ap) override {
+    char new_format[2000];
+    std::fill_n(new_format, sizeof(new_format), '2');
+    {
+      va_list backup_ap;
+      va_copy(backup_ap, ap);
+      int n = vsnprintf(new_format, sizeof(new_format) - 1, format, backup_ap);
+      // 48 bytes for extra information + bytes allocated
+      ASSERT_TRUE(
+          n <= 48 + static_cast<int>(max_log_size_ - sizeof(struct timeval)));
+      ASSERT_TRUE(n > static_cast<int>(max_log_size_ - sizeof(struct timeval)));
+      va_end(backup_ap);
+    }
+  }
+  size_t max_log_size_;
+};
+
+TEST_P(EnvPosixTestWithParam, LogBufferMaxSizeTest) {
+  char bytes9000[9000];
+  std::fill_n(bytes9000, sizeof(bytes9000), '1');
+  bytes9000[sizeof(bytes9000) - 1] = '\0';
+
+  for (size_t max_log_size = 256; max_log_size <= 1024;
+       max_log_size += 1024 - 256) {
+    TestLogger2 test_logger(max_log_size);
+    test_logger.SetInfoLogLevel(InfoLogLevel::INFO_LEVEL);
+    LogBuffer log_buffer(InfoLogLevel::INFO_LEVEL, &test_logger);
+    ROCKS_LOG_BUFFER_MAX_SZ(&log_buffer, max_log_size, "%s", bytes9000);
+    log_buffer.FlushBufferToLog();
+  }
+}
+
+TEST_P(EnvPosixTestWithParam, Preallocation) {
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+  const std::string src = test::PerThreadDBPath(env_, "testfile");
+  std::unique_ptr<WritableFile> srcfile;
+  EnvOptions soptions;
+  soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && !defined(OS_AIX) && !defined(OS_OPENBSD) && !defined(OS_FREEBSD)
+    if (soptions.use_direct_writes) {
+      ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->SetCallBack(
+          "NewWritableFile:O_DIRECT", [&](void* arg) {
+            int* val = static_cast<int*>(arg);
+            *val &= ~O_DIRECT;
+          });
+    }
+#endif
+    ASSERT_OK(env_->NewWritableFile(src, &srcfile, soptions));
+    srcfile->SetPreallocationBlockSize(1024 * 1024);
+
+    // No writes should mean no preallocation
+    size_t block_size, last_allocated_block;
+    srcfile->GetPreallocationStatus(&block_size, &last_allocated_block);
+    ASSERT_EQ(last_allocated_block, 0UL);
+
+    // Small write should preallocate one block
+    size_t kStrSize = 4096;
+    auto data = NewAligned(kStrSize, 'A');
+    Slice str(data.get(), kStrSize);
+    srcfile->PrepareWrite(srcfile->GetFileSize(), kStrSize);
+    srcfile->Append(str);
+    srcfile->GetPreallocationStatus(&block_size, &last_allocated_block);
+    ASSERT_EQ(last_allocated_block, 1UL);
+
+    // Write an entire preallocation block, make sure we increased by two.
+    {
+      auto buf_ptr = NewAligned(block_size, ' ');
+      Slice buf(buf_ptr.get(), block_size);
+      srcfile->PrepareWrite(srcfile->GetFileSize(), block_size);
+      srcfile->Append(buf);
+      srcfile->GetPreallocationStatus(&block_size, &last_allocated_block);
+      ASSERT_EQ(last_allocated_block, 2UL);
+    }
+
+    // Write five more blocks at once, ensure we're where we need to be.
+    {
+      auto buf_ptr = NewAligned(block_size * 5, ' ');
+      Slice buf = Slice(buf_ptr.get(), block_size * 5);
+      srcfile->PrepareWrite(srcfile->GetFileSize(), buf.size());
+      srcfile->Append(buf);
+      srcfile->GetPreallocationStatus(&block_size, &last_allocated_block);
+      ASSERT_EQ(last_allocated_block, 7UL);
+    }
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->ClearTrace();
+}
+
+// Test that the two ways to get children file attributes (in bulk or
+// individually) behave consistently.
+TEST_P(EnvPosixTestWithParam, ConsistentChildrenAttributes) {
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+  EnvOptions soptions;
+  soptions.use_direct_reads = soptions.use_direct_writes = direct_io_;
+  const int kNumChildren = 10;
+
+  std::string data;
+  for (int i = 0; i < kNumChildren; ++i) {
+    const std::string path =
+        test::TmpDir(env_) + "/" + "testfile_" + std::to_string(i);
+    std::unique_ptr<WritableFile> file;
+#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_SOLARIS) && !defined(OS_AIX) && !defined(OS_OPENBSD) && !defined(OS_FREEBSD)
+      if (soptions.use_direct_writes) {
+        ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->SetCallBack(
+            "NewWritableFile:O_DIRECT", [&](void* arg) {
+              int* val = static_cast<int*>(arg);
+              *val &= ~O_DIRECT;
+            });
+      }
+#endif
+      ASSERT_OK(env_->NewWritableFile(path, &file, soptions));
+      auto buf_ptr = NewAligned(data.size(), 'T');
+      Slice buf(buf_ptr.get(), data.size());
+      file->Append(buf);
+      data.append(std::string(4096, 'T'));
+  }
+
+    std::vector<Env::FileAttributes> file_attrs;
+    ASSERT_OK(env_->GetChildrenFileAttributes(test::TmpDir(env_), &file_attrs));
+    for (int i = 0; i < kNumChildren; ++i) {
+      const std::string name = "testfile_" + std::to_string(i);
+      const std::string path = test::TmpDir(env_) + "/" + name;
+
+      auto file_attrs_iter = std::find_if(
+          file_attrs.begin(), file_attrs.end(),
+          [&name](const Env::FileAttributes& fm) { return fm.name == name; });
+      ASSERT_TRUE(file_attrs_iter != file_attrs.end());
+      uint64_t size;
+      ASSERT_OK(env_->GetFileSize(path, &size));
+      ASSERT_EQ(size, 4096 * i);
+      ASSERT_EQ(size, file_attrs_iter->size_bytes);
+    }
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->ClearTrace();
+}
+
+// Test that all WritableFileWrapper forwards all calls to WritableFile.
+TEST_P(EnvPosixTestWithParam, WritableFileWrapper) {
+  class Base : public WritableFile {
+   public:
+    mutable int *step_;
+
+    void inc(int x) const {
+      EXPECT_EQ(x, (*step_)++);
+    }
+
+    explicit Base(int* step) : step_(step) {
+      inc(0);
+    }
+
+    Status Append(const Slice& /*data*/) override {
+      inc(1);
+      return Status::OK();
+    }
+
+    Status PositionedAppend(const Slice& /*data*/,
+                            uint64_t /*offset*/) override {
+      inc(2);
+      return Status::OK();
+    }
+
+    Status Truncate(uint64_t /*size*/) override {
+      inc(3);
+      return Status::OK();
+    }
+
+    Status Close() override {
+      inc(4);
+      return Status::OK();
+    }
+
+    Status Flush() override {
+      inc(5);
+      return Status::OK();
+    }
+
+    Status Sync() override {
+      inc(6);
+      return Status::OK();
+    }
+
+    Status Fsync() override {
+      inc(7);
+      return Status::OK();
+    }
+
+    bool IsSyncThreadSafe() const override {
+      inc(8);
+      return true;
+    }
+
+    bool use_direct_io() const override {
+      inc(9);
+      return true;
+    }
+
+    size_t GetRequiredBufferAlignment() const override {
+      inc(10);
+      return 0;
+    }
+
+    void SetIOPriority(Env::IOPriority /*pri*/) override { inc(11); }
+
+    Env::IOPriority GetIOPriority() override {
+      inc(12);
+      return Env::IOPriority::IO_LOW;
+    }
+
+    void SetWriteLifeTimeHint(Env::WriteLifeTimeHint /*hint*/) override {
+      inc(13);
+    }
+
+    Env::WriteLifeTimeHint GetWriteLifeTimeHint() override {
+      inc(14);
+      return Env::WriteLifeTimeHint::WLTH_NOT_SET;
+    }
+
+    uint64_t GetFileSize() override {
+      inc(15);
+      return 0;
+    }
+
+    void SetPreallocationBlockSize(size_t /*size*/) override { inc(16); }
+
+    void GetPreallocationStatus(size_t* /*block_size*/,
+                                size_t* /*last_allocated_block*/) override {
+      inc(17);
+    }
+
+    size_t GetUniqueId(char* /*id*/, size_t /*max_size*/) const override {
+      inc(18);
+      return 0;
+    }
+
+    Status InvalidateCache(size_t /*offset*/, size_t /*length*/) override {
+      inc(19);
+      return Status::OK();
+    }
+
+    Status RangeSync(uint64_t /*offset*/, uint64_t /*nbytes*/) override {
+      inc(20);
+      return Status::OK();
+    }
+
+    void PrepareWrite(size_t /*offset*/, size_t /*len*/) override { inc(21); }
+
+    Status Allocate(uint64_t /*offset*/, uint64_t /*len*/) override {
+      inc(22);
+      return Status::OK();
+    }
+
+   public:
+    ~Base() override { inc(23); }
+  };
+
+  class Wrapper : public WritableFileWrapper {
+   public:
+    explicit Wrapper(WritableFile* target) : WritableFileWrapper(target) {}
+  };
+
+  int step = 0;
+
+  {
+    Base b(&step);
+    Wrapper w(&b);
+    w.Append(Slice());
+    w.PositionedAppend(Slice(), 0);
+    w.Truncate(0);
+    w.Close();
+    w.Flush();
+    w.Sync();
+    w.Fsync();
+    w.IsSyncThreadSafe();
+    w.use_direct_io();
+    w.GetRequiredBufferAlignment();
+    w.SetIOPriority(Env::IOPriority::IO_HIGH);
+    w.GetIOPriority();
+    w.SetWriteLifeTimeHint(Env::WriteLifeTimeHint::WLTH_NOT_SET);
+    w.GetWriteLifeTimeHint();
+    w.GetFileSize();
+    w.SetPreallocationBlockSize(0);
+    w.GetPreallocationStatus(nullptr, nullptr);
+    w.GetUniqueId(nullptr, 0);
+    w.InvalidateCache(0, 0);
+    w.RangeSync(0, 0);
+    w.PrepareWrite(0, 0);
+    w.Allocate(0, 0);
+  }
+
+  EXPECT_EQ(24, step);
+}
+
+TEST_P(EnvPosixTestWithParam, PosixRandomRWFile) {
+  const std::string path = test::PerThreadDBPath(env_, "random_rw_file");
+
+  env_->DeleteFile(path);
+
+  std::unique_ptr<RandomRWFile> file;
+
+  // Cannot open non-existing file.
+  ASSERT_NOK(env_->NewRandomRWFile(path, &file, EnvOptions()));
+
+  // Create the file using WriteableFile
+  {
+    std::unique_ptr<WritableFile> wf;
+    ASSERT_OK(env_->NewWritableFile(path, &wf, EnvOptions()));
+  }
+
+  ASSERT_OK(env_->NewRandomRWFile(path, &file, EnvOptions()));
+
+  char buf[10000];
+  Slice read_res;
+
+  ASSERT_OK(file->Write(0, "ABCD"));
+  ASSERT_OK(file->Read(0, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ABCD");
+
+  ASSERT_OK(file->Write(2, "XXXX"));
+  ASSERT_OK(file->Read(0, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ABXXXX");
+
+  ASSERT_OK(file->Write(10, "ZZZ"));
+  ASSERT_OK(file->Read(10, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ZZZ");
+
+  ASSERT_OK(file->Write(11, "Y"));
+  ASSERT_OK(file->Read(10, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ZYZ");
+
+  ASSERT_OK(file->Write(200, "FFFFF"));
+  ASSERT_OK(file->Read(200, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "FFFFF");
+
+  ASSERT_OK(file->Write(205, "XXXX"));
+  ASSERT_OK(file->Read(200, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "FFFFFXXXX");
+
+  ASSERT_OK(file->Write(5, "QQQQ"));
+  ASSERT_OK(file->Read(0, 9, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ABXXXQQQQ");
+
+  ASSERT_OK(file->Read(2, 4, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "XXXQ");
+
+  // Close file and reopen it
+  file->Close();
+  ASSERT_OK(env_->NewRandomRWFile(path, &file, EnvOptions()));
+
+  ASSERT_OK(file->Read(0, 9, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ABXXXQQQQ");
+
+  ASSERT_OK(file->Read(10, 3, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ZYZ");
+
+  ASSERT_OK(file->Read(200, 9, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "FFFFFXXXX");
+
+  ASSERT_OK(file->Write(4, "TTTTTTTTTTTTTTTT"));
+  ASSERT_OK(file->Read(0, 10, &read_res, buf));
+  ASSERT_EQ(read_res.ToString(), "ABXXTTTTTT");
+
+  // Clean up
+  env_->DeleteFile(path);
+}
+
+class RandomRWFileWithMirrorString {
+ public:
+  explicit RandomRWFileWithMirrorString(RandomRWFile* _file) : file_(_file) {}
+
+  void Write(size_t offset, const std::string& data) {
+    // Write to mirror string
+    StringWrite(offset, data);
+
+    // Write to file
+    Status s = file_->Write(offset, data);
+    ASSERT_OK(s) << s.ToString();
+  }
+
+  void Read(size_t offset = 0, size_t n = 1000000) {
+    Slice str_res(nullptr, 0);
+    if (offset < file_mirror_.size()) {
+      size_t str_res_sz = std::min(file_mirror_.size() - offset, n);
+      str_res = Slice(file_mirror_.data() + offset, str_res_sz);
+      StopSliceAtNull(&str_res);
+    }
+
+    Slice file_res;
+    Status s = file_->Read(offset, n, &file_res, buf_);
+    ASSERT_OK(s) << s.ToString();
+    StopSliceAtNull(&file_res);
+
+    ASSERT_EQ(str_res.ToString(), file_res.ToString()) << offset << " " << n;
+  }
+
+  void SetFile(RandomRWFile* _file) { file_ = _file; }
+
+ private:
+  void StringWrite(size_t offset, const std::string& src) {
+    if (offset + src.size() > file_mirror_.size()) {
+      file_mirror_.resize(offset + src.size(), '\0');
+    }
+
+    char* pos = const_cast<char*>(file_mirror_.data() + offset);
+    memcpy(pos, src.data(), src.size());
+  }
+
+  void StopSliceAtNull(Slice* slc) {
+    for (size_t i = 0; i < slc->size(); i++) {
+      if ((*slc)[i] == '\0') {
+        *slc = Slice(slc->data(), i);
+        break;
+      }
+    }
+  }
+
+  char buf_[10000];
+  RandomRWFile* file_;
+  std::string file_mirror_;
+};
+
+TEST_P(EnvPosixTestWithParam, PosixRandomRWFileRandomized) {
+  const std::string path = test::PerThreadDBPath(env_, "random_rw_file_rand");
+  env_->DeleteFile(path);
+
+  std::unique_ptr<RandomRWFile> file;
+
+#ifdef OS_LINUX
+  // Cannot open non-existing file.
+  ASSERT_NOK(env_->NewRandomRWFile(path, &file, EnvOptions()));
+#endif
+
+  // Create the file using WriteableFile
+  {
+    std::unique_ptr<WritableFile> wf;
+    ASSERT_OK(env_->NewWritableFile(path, &wf, EnvOptions()));
+  }
+
+  ASSERT_OK(env_->NewRandomRWFile(path, &file, EnvOptions()));
+  RandomRWFileWithMirrorString file_with_mirror(file.get());
+
+  Random rnd(301);
+  std::string buf;
+  for (int i = 0; i < 10000; i++) {
+    // Genrate random data
+    test::RandomString(&rnd, 10, &buf);
+
+    // Pick random offset for write
+    size_t write_off = rnd.Next() % 1000;
+    file_with_mirror.Write(write_off, buf);
+
+    // Pick random offset for read
+    size_t read_off = rnd.Next() % 1000;
+    size_t read_sz = rnd.Next() % 20;
+    file_with_mirror.Read(read_off, read_sz);
+
+    if (i % 500 == 0) {
+      // Reopen the file every 500 iters
+      ASSERT_OK(env_->NewRandomRWFile(path, &file, EnvOptions()));
+      file_with_mirror.SetFile(file.get());
+    }
+  }
+
+  // clean up
+  env_->DeleteFile(path);
+}
+
+class TestEnv : public EnvWrapper {
+  public:
+    explicit TestEnv() : EnvWrapper(Env::Default()),
+                close_count(0) { }
+
+  class TestLogger : public Logger {
+   public:
+    using Logger::Logv;
+    TestLogger(TestEnv* env_ptr) : Logger() { env = env_ptr; }
+    ~TestLogger() override {
+      if (!closed_) {
+        CloseHelper();
+      }
+    }
+    void Logv(const char* /*format*/, va_list /*ap*/) override{};
+
+   protected:
+    Status CloseImpl() override { return CloseHelper(); }
+
+   private:
+    Status CloseHelper() {
+      env->CloseCountInc();;
+      return Status::OK();
+    }
+    TestEnv* env;
+  };
+
+  void CloseCountInc() { close_count++; }
+
+  int GetCloseCount() { return close_count; }
+
+  Status NewLogger(const std::string& /*fname*/,
+                   std::shared_ptr<Logger>* result) override {
+    result->reset(new TestLogger(this));
+    return Status::OK();
+  }
+
+ private:
+  int close_count;
+};
+
+class EnvTest : public testing::Test {};
+
+TEST_F(EnvTest, Close) {
+  TestEnv* env = new TestEnv();
+  std::shared_ptr<Logger> logger;
+  Status s;
+
+  s = env->NewLogger("", &logger);
+  ASSERT_EQ(s, Status::OK());
+  logger.get()->Close();
+  ASSERT_EQ(env->GetCloseCount(), 1);
+  // Call Close() again. CloseHelper() should not be called again
+  logger.get()->Close();
+  ASSERT_EQ(env->GetCloseCount(), 1);
+  logger.reset();
+  ASSERT_EQ(env->GetCloseCount(), 1);
+
+  s = env->NewLogger("", &logger);
+  ASSERT_EQ(s, Status::OK());
+  logger.reset();
+  ASSERT_EQ(env->GetCloseCount(), 2);
+
+  delete env;
+}
+
+INSTANTIATE_TEST_CASE_P(DefaultEnvWithoutDirectIO, EnvPosixTestWithParam,
+                        ::testing::Values(std::pair<Env*, bool>(Env::Default(),
+                                                                false)));
+#if !defined(ROCKSDB_LITE)
+INSTANTIATE_TEST_CASE_P(DefaultEnvWithDirectIO, EnvPosixTestWithParam,
+                        ::testing::Values(std::pair<Env*, bool>(Env::Default(),
+                                                                true)));
+#endif  // !defined(ROCKSDB_LITE)
+
+#if !defined(ROCKSDB_LITE) && !defined(OS_WIN)
+static std::unique_ptr<Env> chroot_env(
+    NewChrootEnv(Env::Default(), test::TmpDir(Env::Default())));
+INSTANTIATE_TEST_CASE_P(
+    ChrootEnvWithoutDirectIO, EnvPosixTestWithParam,
+    ::testing::Values(std::pair<Env*, bool>(chroot_env.get(), false)));
+INSTANTIATE_TEST_CASE_P(
+    ChrootEnvWithDirectIO, EnvPosixTestWithParam,
+    ::testing::Values(std::pair<Env*, bool>(chroot_env.get(), true)));
+#endif  // !defined(ROCKSDB_LITE) && !defined(OS_WIN)
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/env/file_system.cc b/src/rocksdb/env/file_system.cc
new file mode 100644
index 000000000..646e6e3d1
--- /dev/null
+++ b/src/rocksdb/env/file_system.cc
@@ -0,0 +1,110 @@
+// Copyright (c) 2019-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#include "env/composite_env_wrapper.h"
+#include "rocksdb/file_system.h"
+#include "options/db_options.h"
+#include "rocksdb/utilities/object_registry.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+FileSystem::FileSystem() {}
+
+FileSystem::~FileSystem() {}
+
+Status FileSystem::Load(const std::string& value,
+                        std::shared_ptr<FileSystem>* result) {
+  Status s;
+#ifndef ROCKSDB_LITE
+  s = ObjectRegistry::NewInstance()->NewSharedObject<FileSystem>(value, result);
+#else
+  (void)result;
+  s = Status::NotSupported("Cannot load FileSystem in LITE mode: ", value);
+#endif
+  return s;
+}
+
+FileOptions FileSystem::OptimizeForLogRead(
+              const FileOptions& file_options) const {
+  FileOptions optimized_file_options(file_options);
+  optimized_file_options.use_direct_reads = false;
+  return optimized_file_options;
+}
+
+FileOptions FileSystem::OptimizeForManifestRead(
+    const FileOptions& file_options) const {
+  FileOptions optimized_file_options(file_options);
+  optimized_file_options.use_direct_reads = false;
+  return optimized_file_options;
+}
+
+FileOptions FileSystem::OptimizeForLogWrite(const FileOptions& file_options,
+                                           const DBOptions& db_options) const {
+  FileOptions optimized_file_options(file_options);
+  optimized_file_options.bytes_per_sync = db_options.wal_bytes_per_sync;
+  optimized_file_options.writable_file_max_buffer_size =
+      db_options.writable_file_max_buffer_size;
+  return optimized_file_options;
+}
+
+FileOptions FileSystem::OptimizeForManifestWrite(
+    const FileOptions& file_options) const {
+  return file_options;
+}
+
+FileOptions FileSystem::OptimizeForCompactionTableWrite(
+    const FileOptions& file_options,
+    const ImmutableDBOptions& db_options) const {
+  FileOptions optimized_file_options(file_options);
+  optimized_file_options.use_direct_writes =
+      db_options.use_direct_io_for_flush_and_compaction;
+  return optimized_file_options;
+}
+
+FileOptions FileSystem::OptimizeForCompactionTableRead(
+    const FileOptions& file_options,
+    const ImmutableDBOptions& db_options) const {
+  FileOptions optimized_file_options(file_options);
+  optimized_file_options.use_direct_reads = db_options.use_direct_reads;
+  return optimized_file_options;
+}
+
+Status ReadFileToString(FileSystem* fs, const std::string& fname,
+                        std::string* data) {
+  FileOptions soptions;
+  data->clear();
+  std::unique_ptr<FSSequentialFile> file;
+  Status s = fs->NewSequentialFile(fname, soptions, &file, nullptr);
+  if (!s.ok()) {
+    return s;
+  }
+  static const int kBufferSize = 8192;
+  char* space = new char[kBufferSize];
+  while (true) {
+    Slice fragment;
+    s = file->Read(kBufferSize, IOOptions(), &fragment, space,
+                   nullptr);
+    if (!s.ok()) {
+      break;
+    }
+    data->append(fragment.data(), fragment.size());
+    if (fragment.empty()) {
+      break;
+    }
+  }
+  delete[] space;
+  return s;
+}
+
+#ifdef OS_WIN
+std::shared_ptr<FileSystem> FileSystem::Default() {
+  static LegacyFileSystemWrapper default_fs(Env::Default());
+  static std::shared_ptr<LegacyFileSystemWrapper> default_fs_ptr(
+      &default_fs, [](LegacyFileSystemWrapper*) {});
+  return default_fs_ptr;
+}
+#endif
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/fs_posix.cc b/src/rocksdb/env/fs_posix.cc
new file mode 100644
index 000000000..0f1a41ac2
--- /dev/null
+++ b/src/rocksdb/env/fs_posix.cc
@@ -0,0 +1,913 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors
+#include <dirent.h>
+#ifndef ROCKSDB_NO_DYNAMIC_EXTENSION
+#include <dlfcn.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+
+#if defined(OS_LINUX)
+#include <linux/fs.h>
+#endif
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#if defined(OS_LINUX) || defined(OS_SOLARIS) || defined(OS_ANDROID)
+#include <sys/statfs.h>
+#include <sys/syscall.h>
+#include <sys/sysmacros.h>
+#endif
+#include <sys/statvfs.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#include <algorithm>
+// Get nano time includes
+#if defined(OS_LINUX) || defined(OS_FREEBSD)
+#elif defined(__MACH__)
+#include <Availability.h>
+#include <mach/clock.h>
+#include <mach/mach.h>
+#else
+#include <chrono>
+#endif
+#include <deque>
+#include <set>
+#include <vector>
+
+#include "env/io_posix.h"
+#include "logging/logging.h"
+#include "logging/posix_logger.h"
+#include "monitoring/iostats_context_imp.h"
+#include "monitoring/thread_status_updater.h"
+#include "port/port.h"
+#include "rocksdb/options.h"
+#include "rocksdb/slice.h"
+#include "test_util/sync_point.h"
+#include "util/coding.h"
+#include "util/compression_context_cache.h"
+#include "util/random.h"
+#include "util/string_util.h"
+#include "util/thread_local.h"
+#include "util/threadpool_imp.h"
+
+#if !defined(TMPFS_MAGIC)
+#define TMPFS_MAGIC 0x01021994
+#endif
+#if !defined(XFS_SUPER_MAGIC)
+#define XFS_SUPER_MAGIC 0x58465342
+#endif
+#if !defined(EXT4_SUPER_MAGIC)
+#define EXT4_SUPER_MAGIC 0xEF53
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+namespace {
+
+inline mode_t GetDBFileMode(bool allow_non_owner_access) {
+  return allow_non_owner_access ? 0644 : 0600;
+}
+
+// list of pathnames that are locked
+static std::set<std::string> lockedFiles;
+static port::Mutex mutex_lockedFiles;
+
+static int LockOrUnlock(int fd, bool lock) {
+  errno = 0;
+  struct flock f;
+  memset(&f, 0, sizeof(f));
+  f.l_type = (lock ? F_WRLCK : F_UNLCK);
+  f.l_whence = SEEK_SET;
+  f.l_start = 0;
+  f.l_len = 0;  // Lock/unlock entire file
+  int value = fcntl(fd, F_SETLK, &f);
+
+  return value;
+}
+
+class PosixFileLock : public FileLock {
+ public:
+  int fd_;
+  std::string filename;
+};
+
+int cloexec_flags(int flags, const EnvOptions* options) {
+  // If the system supports opening the file with cloexec enabled,
+  // do so, as this avoids a race condition if a db is opened around
+  // the same time that a child process is forked
+#ifdef O_CLOEXEC
+  if (options == nullptr || options->set_fd_cloexec) {
+    flags |= O_CLOEXEC;
+  }
+#endif
+  return flags;
+}
+
+class PosixFileSystem : public FileSystem {
+ public:
+  PosixFileSystem();
+
+  const char* Name() const override { return "Posix File System"; }
+
+  ~PosixFileSystem() override {}
+
+  void SetFD_CLOEXEC(int fd, const EnvOptions* options) {
+    if ((options == nullptr || options->set_fd_cloexec) && fd > 0) {
+      fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
+    }
+  }
+
+  IOStatus NewSequentialFile(const std::string& fname,
+                             const FileOptions& options,
+                             std::unique_ptr<FSSequentialFile>* result,
+                             IODebugContext* /*dbg*/) override {
+    result->reset();
+    int fd = -1;
+    int flags = cloexec_flags(O_RDONLY, &options);
+    FILE* file = nullptr;
+
+    if (options.use_direct_reads && !options.use_mmap_reads) {
+#ifdef ROCKSDB_LITE
+      return IOStatus::IOError(fname,
+                               "Direct I/O not supported in RocksDB lite");
+#endif  // !ROCKSDB_LITE
+#if !defined(OS_MACOSX) && !defined(OS_OPENBSD) && !defined(OS_SOLARIS)
+      flags |= O_DIRECT;
+#endif
+    }
+
+    do {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(fname.c_str(), flags, GetDBFileMode(allow_non_owner_access_));
+    } while (fd < 0 && errno == EINTR);
+    if (fd < 0) {
+      return IOError("While opening a file for sequentially reading", fname,
+                     errno);
+    }
+
+    SetFD_CLOEXEC(fd, &options);
+
+    if (options.use_direct_reads && !options.use_mmap_reads) {
+#ifdef OS_MACOSX
+      if (fcntl(fd, F_NOCACHE, 1) == -1) {
+        close(fd);
+        return IOError("While fcntl NoCache", fname, errno);
+      }
+#endif
+    } else {
+      do {
+        IOSTATS_TIMER_GUARD(open_nanos);
+        file = fdopen(fd, "r");
+      } while (file == nullptr && errno == EINTR);
+      if (file == nullptr) {
+        close(fd);
+        return IOError("While opening file for sequentially read", fname,
+                       errno);
+      }
+    }
+    result->reset(new PosixSequentialFile(fname, file, fd, options));
+    return IOStatus::OK();
+  }
+
+  IOStatus NewRandomAccessFile(const std::string& fname,
+                               const FileOptions& options,
+                               std::unique_ptr<FSRandomAccessFile>* result,
+                               IODebugContext* /*dbg*/) override {
+    result->reset();
+    IOStatus s;
+    int fd;
+    int flags = cloexec_flags(O_RDONLY, &options);
+
+    if (options.use_direct_reads && !options.use_mmap_reads) {
+#ifdef ROCKSDB_LITE
+      return IOStatus::IOError(fname,
+                               "Direct I/O not supported in RocksDB lite");
+#endif  // !ROCKSDB_LITE
+#if !defined(OS_MACOSX) && !defined(OS_OPENBSD) && !defined(OS_SOLARIS)
+      flags |= O_DIRECT;
+      TEST_SYNC_POINT_CALLBACK("NewRandomAccessFile:O_DIRECT", &flags);
+#endif
+    }
+
+    do {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(fname.c_str(), flags, GetDBFileMode(allow_non_owner_access_));
+    } while (fd < 0 && errno == EINTR);
+    if (fd < 0) {
+      return IOError("While open a file for random read", fname, errno);
+    }
+    SetFD_CLOEXEC(fd, &options);
+
+    if (options.use_mmap_reads && sizeof(void*) >= 8) {
+      // Use of mmap for random reads has been removed because it
+      // kills performance when storage is fast.
+      // Use mmap when virtual address-space is plentiful.
+      uint64_t size;
+      IOOptions opts;
+      s = GetFileSize(fname, opts, &size, nullptr);
+      if (s.ok()) {
+        void* base = mmap(nullptr, size, PROT_READ, MAP_SHARED, fd, 0);
+        if (base != MAP_FAILED) {
+          result->reset(
+              new PosixMmapReadableFile(fd, fname, base, size, options));
+        } else {
+          s = IOError("while mmap file for read", fname, errno);
+          close(fd);
+        }
+      }
+    } else {
+      if (options.use_direct_reads && !options.use_mmap_reads) {
+#ifdef OS_MACOSX
+        if (fcntl(fd, F_NOCACHE, 1) == -1) {
+          close(fd);
+          return IOError("while fcntl NoCache", fname, errno);
+        }
+#endif
+      }
+      result->reset(new PosixRandomAccessFile(fname, fd, options
+#if defined(ROCKSDB_IOURING_PRESENT)
+                                              ,
+                                              thread_local_io_urings_.get()
+#endif
+                                                  ));
+    }
+    return s;
+  }
+
+  virtual IOStatus OpenWritableFile(const std::string& fname,
+                                    const FileOptions& options,
+                                    bool reopen,
+                                    std::unique_ptr<FSWritableFile>* result,
+                                    IODebugContext* /*dbg*/) {
+    result->reset();
+    IOStatus s;
+    int fd = -1;
+    int flags = (reopen) ? (O_CREAT | O_APPEND) : (O_CREAT | O_TRUNC);
+    // Direct IO mode with O_DIRECT flag or F_NOCAHCE (MAC OSX)
+    if (options.use_direct_writes && !options.use_mmap_writes) {
+      // Note: we should avoid O_APPEND here due to ta the following bug:
+      // POSIX requires that opening a file with the O_APPEND flag should
+      // have no affect on the location at which pwrite() writes data.
+      // However, on Linux, if a file is opened with O_APPEND, pwrite()
+      // appends data to the end of the file, regardless of the value of
+      // offset.
+      // More info here: https://linux.die.net/man/2/pwrite
+#ifdef ROCKSDB_LITE
+      return IOStatus::IOError(fname,
+                               "Direct I/O not supported in RocksDB lite");
+#endif  // ROCKSDB_LITE
+      flags |= O_WRONLY;
+#if !defined(OS_MACOSX) && !defined(OS_OPENBSD) && !defined(OS_SOLARIS)
+      flags |= O_DIRECT;
+#endif
+      TEST_SYNC_POINT_CALLBACK("NewWritableFile:O_DIRECT", &flags);
+    } else if (options.use_mmap_writes) {
+      // non-direct I/O
+      flags |= O_RDWR;
+    } else {
+      flags |= O_WRONLY;
+    }
+
+    flags = cloexec_flags(flags, &options);
+
+    do {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(fname.c_str(), flags, GetDBFileMode(allow_non_owner_access_));
+    } while (fd < 0 && errno == EINTR);
+
+    if (fd < 0) {
+      s = IOError("While open a file for appending", fname, errno);
+      return s;
+    }
+    SetFD_CLOEXEC(fd, &options);
+
+    if (options.use_mmap_writes) {
+      if (!checkedDiskForMmap_) {
+        // this will be executed once in the program's lifetime.
+        // do not use mmapWrite on non ext-3/xfs/tmpfs systems.
+        if (!SupportsFastAllocate(fname)) {
+          forceMmapOff_ = true;
+        }
+        checkedDiskForMmap_ = true;
+      }
+    }
+    if (options.use_mmap_writes && !forceMmapOff_) {
+      result->reset(new PosixMmapFile(fname, fd, page_size_, options));
+    } else if (options.use_direct_writes && !options.use_mmap_writes) {
+#ifdef OS_MACOSX
+      if (fcntl(fd, F_NOCACHE, 1) == -1) {
+        close(fd);
+        s = IOError("While fcntl NoCache an opened file for appending", fname,
+                    errno);
+        return s;
+      }
+#elif defined(OS_SOLARIS)
+      if (directio(fd, DIRECTIO_ON) == -1) {
+        if (errno != ENOTTY) {  // ZFS filesystems don't support DIRECTIO_ON
+          close(fd);
+          s = IOError("While calling directio()", fname, errno);
+          return s;
+        }
+      }
+#endif
+      result->reset(new PosixWritableFile(fname, fd, options));
+    } else {
+      // disable mmap writes
+      EnvOptions no_mmap_writes_options = options;
+      no_mmap_writes_options.use_mmap_writes = false;
+      result->reset(new PosixWritableFile(fname, fd, no_mmap_writes_options));
+    }
+    return s;
+  }
+
+  IOStatus NewWritableFile(const std::string& fname, const FileOptions& options,
+                           std::unique_ptr<FSWritableFile>* result,
+                           IODebugContext* dbg) override {
+    return OpenWritableFile(fname, options, false, result, dbg);
+  }
+
+  IOStatus ReopenWritableFile(const std::string& fname,
+                              const FileOptions& options,
+                              std::unique_ptr<FSWritableFile>* result,
+                              IODebugContext* dbg) override {
+    return OpenWritableFile(fname, options, true, result, dbg);
+  }
+
+  IOStatus ReuseWritableFile(const std::string& fname,
+                             const std::string& old_fname,
+                             const FileOptions& options,
+                             std::unique_ptr<FSWritableFile>* result,
+                             IODebugContext* /*dbg*/) override {
+    result->reset();
+    IOStatus s;
+    int fd = -1;
+
+    int flags = 0;
+    // Direct IO mode with O_DIRECT flag or F_NOCAHCE (MAC OSX)
+    if (options.use_direct_writes && !options.use_mmap_writes) {
+#ifdef ROCKSDB_LITE
+      return IOStatus::IOError(fname,
+                               "Direct I/O not supported in RocksDB lite");
+#endif  // !ROCKSDB_LITE
+      flags |= O_WRONLY;
+#if !defined(OS_MACOSX) && !defined(OS_OPENBSD) && !defined(OS_SOLARIS)
+      flags |= O_DIRECT;
+#endif
+      TEST_SYNC_POINT_CALLBACK("NewWritableFile:O_DIRECT", &flags);
+    } else if (options.use_mmap_writes) {
+      // mmap needs O_RDWR mode
+      flags |= O_RDWR;
+    } else {
+      flags |= O_WRONLY;
+    }
+
+    flags = cloexec_flags(flags, &options);
+
+    do {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(old_fname.c_str(), flags,
+                GetDBFileMode(allow_non_owner_access_));
+    } while (fd < 0 && errno == EINTR);
+    if (fd < 0) {
+      s = IOError("while reopen file for write", fname, errno);
+      return s;
+    }
+
+    SetFD_CLOEXEC(fd, &options);
+    // rename into place
+    if (rename(old_fname.c_str(), fname.c_str()) != 0) {
+      s = IOError("while rename file to " + fname, old_fname, errno);
+      close(fd);
+      return s;
+    }
+
+    if (options.use_mmap_writes) {
+      if (!checkedDiskForMmap_) {
+        // this will be executed once in the program's lifetime.
+        // do not use mmapWrite on non ext-3/xfs/tmpfs systems.
+        if (!SupportsFastAllocate(fname)) {
+          forceMmapOff_ = true;
+        }
+        checkedDiskForMmap_ = true;
+      }
+    }
+    if (options.use_mmap_writes && !forceMmapOff_) {
+      result->reset(new PosixMmapFile(fname, fd, page_size_, options));
+    } else if (options.use_direct_writes && !options.use_mmap_writes) {
+#ifdef OS_MACOSX
+      if (fcntl(fd, F_NOCACHE, 1) == -1) {
+        close(fd);
+        s = IOError("while fcntl NoCache for reopened file for append", fname,
+                    errno);
+        return s;
+      }
+#elif defined(OS_SOLARIS)
+      if (directio(fd, DIRECTIO_ON) == -1) {
+        if (errno != ENOTTY) {  // ZFS filesystems don't support DIRECTIO_ON
+          close(fd);
+          s = IOError("while calling directio()", fname, errno);
+          return s;
+        }
+      }
+#endif
+      result->reset(new PosixWritableFile(fname, fd, options));
+    } else {
+      // disable mmap writes
+      FileOptions no_mmap_writes_options = options;
+      no_mmap_writes_options.use_mmap_writes = false;
+      result->reset(new PosixWritableFile(fname, fd, no_mmap_writes_options));
+    }
+    return s;
+  }
+
+  IOStatus NewRandomRWFile(const std::string& fname, const FileOptions& options,
+                           std::unique_ptr<FSRandomRWFile>* result,
+                           IODebugContext* /*dbg*/) override {
+    int fd = -1;
+    int flags = cloexec_flags(O_RDWR, &options);
+
+    while (fd < 0) {
+      IOSTATS_TIMER_GUARD(open_nanos);
+
+      fd = open(fname.c_str(), flags, GetDBFileMode(allow_non_owner_access_));
+      if (fd < 0) {
+        // Error while opening the file
+        if (errno == EINTR) {
+          continue;
+        }
+        return IOError("While open file for random read/write", fname, errno);
+      }
+    }
+
+    SetFD_CLOEXEC(fd, &options);
+    result->reset(new PosixRandomRWFile(fname, fd, options));
+    return IOStatus::OK();
+  }
+
+  IOStatus NewMemoryMappedFileBuffer(
+      const std::string& fname,
+      std::unique_ptr<MemoryMappedFileBuffer>* result) override {
+    int fd = -1;
+    IOStatus status;
+    int flags = cloexec_flags(O_RDWR, nullptr);
+
+    while (fd < 0) {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(fname.c_str(), flags, 0644);
+      if (fd < 0) {
+        // Error while opening the file
+        if (errno == EINTR) {
+          continue;
+        }
+        status =
+            IOError("While open file for raw mmap buffer access", fname, errno);
+        break;
+      }
+    }
+    uint64_t size;
+    if (status.ok()) {
+      IOOptions opts;
+      status = GetFileSize(fname, opts, &size, nullptr);
+    }
+    void* base = nullptr;
+    if (status.ok()) {
+      base = mmap(nullptr, static_cast<size_t>(size), PROT_READ | PROT_WRITE,
+                  MAP_SHARED, fd, 0);
+      if (base == MAP_FAILED) {
+        status = IOError("while mmap file for read", fname, errno);
+      }
+    }
+    if (status.ok()) {
+      result->reset(
+          new PosixMemoryMappedFileBuffer(base, static_cast<size_t>(size)));
+    }
+    if (fd >= 0) {
+      // don't need to keep it open after mmap has been called
+      close(fd);
+    }
+    return status;
+  }
+
+  IOStatus NewDirectory(const std::string& name, const IOOptions& /*opts*/,
+                        std::unique_ptr<FSDirectory>* result,
+                        IODebugContext* /*dbg*/) override {
+    result->reset();
+    int fd;
+    int flags = cloexec_flags(0, nullptr);
+    {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(name.c_str(), flags);
+    }
+    if (fd < 0) {
+      return IOError("While open directory", name, errno);
+    } else {
+      result->reset(new PosixDirectory(fd));
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus NewLogger(const std::string& /*fname*/, const IOOptions& /*opts*/,
+                     std::shared_ptr<ROCKSDB_NAMESPACE::Logger>* /*ptr*/,
+                     IODebugContext* /*dbg*/) override {
+    return IOStatus::NotSupported();
+  }
+
+  IOStatus FileExists(const std::string& fname, const IOOptions& /*opts*/,
+                      IODebugContext* /*dbg*/) override {
+    int result = access(fname.c_str(), F_OK);
+
+    if (result == 0) {
+      return IOStatus::OK();
+    }
+
+    int err = errno;
+    switch (err) {
+      case EACCES:
+      case ELOOP:
+      case ENAMETOOLONG:
+      case ENOENT:
+      case ENOTDIR:
+        return IOStatus::NotFound();
+      default:
+        assert(err == EIO || err == ENOMEM);
+        return IOStatus::IOError("Unexpected error(" + ToString(err) +
+                                 ") accessing file `" + fname + "' ");
+    }
+  }
+
+  IOStatus GetChildren(const std::string& dir, const IOOptions& /*opts*/,
+                       std::vector<std::string>* result,
+                       IODebugContext* /*dbg*/) override {
+    result->clear();
+    DIR* d = opendir(dir.c_str());
+    if (d == nullptr) {
+      switch (errno) {
+        case EACCES:
+        case ENOENT:
+        case ENOTDIR:
+          return IOStatus::NotFound();
+        default:
+          return IOError("While opendir", dir, errno);
+      }
+    }
+    struct dirent* entry;
+    while ((entry = readdir(d)) != nullptr) {
+      result->push_back(entry->d_name);
+    }
+    closedir(d);
+    return IOStatus::OK();
+  }
+
+  IOStatus DeleteFile(const std::string& fname, const IOOptions& /*opts*/,
+                      IODebugContext* /*dbg*/) override {
+    IOStatus result;
+    if (unlink(fname.c_str()) != 0) {
+      result = IOError("while unlink() file", fname, errno);
+    }
+    return result;
+  }
+
+  IOStatus CreateDir(const std::string& name, const IOOptions& /*opts*/,
+                     IODebugContext* /*dbg*/) override {
+    IOStatus result;
+    if (mkdir(name.c_str(), 0755) != 0) {
+      result = IOError("While mkdir", name, errno);
+    }
+    return result;
+  }
+
+  IOStatus CreateDirIfMissing(const std::string& name,
+                              const IOOptions& /*opts*/,
+                              IODebugContext* /*dbg*/) override {
+    IOStatus result;
+    if (mkdir(name.c_str(), 0755) != 0) {
+      if (errno != EEXIST) {
+        result = IOError("While mkdir if missing", name, errno);
+      } else if (!DirExists(name)) {  // Check that name is actually a
+                                      // directory.
+        // Message is taken from mkdir
+        result =
+            IOStatus::IOError("`" + name + "' exists but is not a directory");
+      }
+    }
+    return result;
+  }
+
+  IOStatus DeleteDir(const std::string& name, const IOOptions& /*opts*/,
+                     IODebugContext* /*dbg*/) override {
+    IOStatus result;
+    if (rmdir(name.c_str()) != 0) {
+      result = IOError("file rmdir", name, errno);
+    }
+    return result;
+  }
+
+  IOStatus GetFileSize(const std::string& fname, const IOOptions& /*opts*/,
+                       uint64_t* size, IODebugContext* /*dbg*/) override {
+    IOStatus s;
+    struct stat sbuf;
+    if (stat(fname.c_str(), &sbuf) != 0) {
+      *size = 0;
+      s = IOError("while stat a file for size", fname, errno);
+    } else {
+      *size = sbuf.st_size;
+    }
+    return s;
+  }
+
+  IOStatus GetFileModificationTime(const std::string& fname,
+                                   const IOOptions& /*opts*/,
+                                   uint64_t* file_mtime,
+                                   IODebugContext* /*dbg*/) override {
+    struct stat s;
+    if (stat(fname.c_str(), &s) != 0) {
+      return IOError("while stat a file for modification time", fname, errno);
+    }
+    *file_mtime = static_cast<uint64_t>(s.st_mtime);
+    return IOStatus::OK();
+  }
+
+  IOStatus RenameFile(const std::string& src, const std::string& target,
+                      const IOOptions& /*opts*/,
+                      IODebugContext* /*dbg*/) override {
+    IOStatus result;
+    if (rename(src.c_str(), target.c_str()) != 0) {
+      result = IOError("While renaming a file to " + target, src, errno);
+    }
+    return result;
+  }
+
+  IOStatus LinkFile(const std::string& src, const std::string& target,
+                    const IOOptions& /*opts*/,
+                    IODebugContext* /*dbg*/) override {
+    IOStatus result;
+    if (link(src.c_str(), target.c_str()) != 0) {
+      if (errno == EXDEV) {
+        return IOStatus::NotSupported("No cross FS links allowed");
+      }
+      result = IOError("while link file to " + target, src, errno);
+    }
+    return result;
+  }
+
+  IOStatus NumFileLinks(const std::string& fname, const IOOptions& /*opts*/,
+                        uint64_t* count, IODebugContext* /*dbg*/) override {
+    struct stat s;
+    if (stat(fname.c_str(), &s) != 0) {
+      return IOError("while stat a file for num file links", fname, errno);
+    }
+    *count = static_cast<uint64_t>(s.st_nlink);
+    return IOStatus::OK();
+  }
+
+  IOStatus AreFilesSame(const std::string& first, const std::string& second,
+                        const IOOptions& /*opts*/, bool* res,
+                        IODebugContext* /*dbg*/) override {
+    struct stat statbuf[2];
+    if (stat(first.c_str(), &statbuf[0]) != 0) {
+      return IOError("stat file", first, errno);
+    }
+    if (stat(second.c_str(), &statbuf[1]) != 0) {
+      return IOError("stat file", second, errno);
+    }
+
+    if (major(statbuf[0].st_dev) != major(statbuf[1].st_dev) ||
+        minor(statbuf[0].st_dev) != minor(statbuf[1].st_dev) ||
+        statbuf[0].st_ino != statbuf[1].st_ino) {
+      *res = false;
+    } else {
+      *res = true;
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus LockFile(const std::string& fname, const IOOptions& /*opts*/,
+                    FileLock** lock, IODebugContext* /*dbg*/) override {
+    *lock = nullptr;
+    IOStatus result;
+
+    mutex_lockedFiles.Lock();
+    // If it already exists in the lockedFiles set, then it is already locked,
+    // and fail this lock attempt. Otherwise, insert it into lockedFiles.
+    // This check is needed because fcntl() does not detect lock conflict
+    // if the fcntl is issued by the same thread that earlier acquired
+    // this lock.
+    // We must do this check *before* opening the file:
+    // Otherwise, we will open a new file descriptor. Locks are associated with
+    // a process, not a file descriptor and when *any* file descriptor is
+    // closed, all locks the process holds for that *file* are released
+    if (lockedFiles.insert(fname).second == false) {
+      mutex_lockedFiles.Unlock();
+      errno = ENOLCK;
+      return IOError("lock ", fname, errno);
+    }
+
+    int fd;
+    int flags = cloexec_flags(O_RDWR | O_CREAT, nullptr);
+
+    {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(fname.c_str(), flags, 0644);
+    }
+    if (fd < 0) {
+      result = IOError("while open a file for lock", fname, errno);
+    } else if (LockOrUnlock(fd, true) == -1) {
+      // if there is an error in locking, then remove the pathname from
+      // lockedfiles
+      lockedFiles.erase(fname);
+      result = IOError("While lock file", fname, errno);
+      close(fd);
+    } else {
+      SetFD_CLOEXEC(fd, nullptr);
+      PosixFileLock* my_lock = new PosixFileLock;
+      my_lock->fd_ = fd;
+      my_lock->filename = fname;
+      *lock = my_lock;
+    }
+
+    mutex_lockedFiles.Unlock();
+    return result;
+  }
+
+  IOStatus UnlockFile(FileLock* lock, const IOOptions& /*opts*/,
+                      IODebugContext* /*dbg*/) override {
+    PosixFileLock* my_lock = reinterpret_cast<PosixFileLock*>(lock);
+    IOStatus result;
+    mutex_lockedFiles.Lock();
+    // If we are unlocking, then verify that we had locked it earlier,
+    // it should already exist in lockedFiles. Remove it from lockedFiles.
+    if (lockedFiles.erase(my_lock->filename) != 1) {
+      errno = ENOLCK;
+      result = IOError("unlock", my_lock->filename, errno);
+    } else if (LockOrUnlock(my_lock->fd_, false) == -1) {
+      result = IOError("unlock", my_lock->filename, errno);
+    }
+    close(my_lock->fd_);
+    delete my_lock;
+    mutex_lockedFiles.Unlock();
+    return result;
+  }
+
+  IOStatus GetAbsolutePath(const std::string& db_path,
+                           const IOOptions& /*opts*/, std::string* output_path,
+                           IODebugContext* /*dbg*/) override {
+    if (!db_path.empty() && db_path[0] == '/') {
+      *output_path = db_path;
+      return IOStatus::OK();
+    }
+
+    char the_path[256];
+    char* ret = getcwd(the_path, 256);
+    if (ret == nullptr) {
+      return IOStatus::IOError(strerror(errno));
+    }
+
+    *output_path = ret;
+    return IOStatus::OK();
+  }
+
+  IOStatus GetTestDirectory(const IOOptions& /*opts*/, std::string* result,
+                            IODebugContext* /*dbg*/) override {
+    const char* env = getenv("TEST_TMPDIR");
+    if (env && env[0] != '\0') {
+      *result = env;
+    } else {
+      char buf[100];
+      snprintf(buf, sizeof(buf), "/tmp/rocksdbtest-%d", int(geteuid()));
+      *result = buf;
+    }
+    // Directory may already exist
+    {
+      IOOptions opts;
+      CreateDir(*result, opts, nullptr);
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus GetFreeSpace(const std::string& fname, const IOOptions& /*opts*/,
+                        uint64_t* free_space,
+                        IODebugContext* /*dbg*/) override {
+    struct statvfs sbuf;
+
+    if (statvfs(fname.c_str(), &sbuf) < 0) {
+      return IOError("While doing statvfs", fname, errno);
+    }
+
+    *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bfree);
+    return IOStatus::OK();
+  }
+
+  FileOptions OptimizeForLogWrite(const FileOptions& file_options,
+                                 const DBOptions& db_options) const override {
+    FileOptions optimized = file_options;
+    optimized.use_mmap_writes = false;
+    optimized.use_direct_writes = false;
+    optimized.bytes_per_sync = db_options.wal_bytes_per_sync;
+    // TODO(icanadi) it's faster if fallocate_with_keep_size is false, but it
+    // breaks TransactionLogIteratorStallAtLastRecord unit test. Fix the unit
+    // test and make this false
+    optimized.fallocate_with_keep_size = true;
+    optimized.writable_file_max_buffer_size =
+        db_options.writable_file_max_buffer_size;
+    return optimized;
+  }
+
+  FileOptions OptimizeForManifestWrite(
+      const FileOptions& file_options) const override {
+    FileOptions optimized = file_options;
+    optimized.use_mmap_writes = false;
+    optimized.use_direct_writes = false;
+    optimized.fallocate_with_keep_size = true;
+    return optimized;
+  }
+
+ private:
+  bool checkedDiskForMmap_;
+  bool forceMmapOff_;  // do we override Env options?
+
+  // Returns true iff the named directory exists and is a directory.
+  virtual bool DirExists(const std::string& dname) {
+    struct stat statbuf;
+    if (stat(dname.c_str(), &statbuf) == 0) {
+      return S_ISDIR(statbuf.st_mode);
+    }
+    return false;  // stat() failed return false
+  }
+
+  bool SupportsFastAllocate(const std::string& path) {
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+    struct statfs s;
+    if (statfs(path.c_str(), &s)) {
+      return false;
+    }
+    switch (s.f_type) {
+      case EXT4_SUPER_MAGIC:
+        return true;
+      case XFS_SUPER_MAGIC:
+        return true;
+      case TMPFS_MAGIC:
+        return true;
+      default:
+        return false;
+    }
+#else
+    (void)path;
+    return false;
+#endif
+  }
+
+#if defined(ROCKSDB_IOURING_PRESENT)
+  // io_uring instance
+  std::unique_ptr<ThreadLocalPtr> thread_local_io_urings_;
+#endif
+
+  size_t page_size_;
+
+  // If true, allow non owner read access for db files. Otherwise, non-owner
+  //  has no access to db files.
+  bool allow_non_owner_access_;
+};
+
+PosixFileSystem::PosixFileSystem()
+    : checkedDiskForMmap_(false),
+      forceMmapOff_(false),
+      page_size_(getpagesize()),
+      allow_non_owner_access_(true) {
+#if defined(ROCKSDB_IOURING_PRESENT)
+  // Test whether IOUring is supported, and if it does, create a managing
+  // object for thread local point so that in the future thread-local
+  // io_uring can be created.
+  struct io_uring* new_io_uring = CreateIOUring();
+  if (new_io_uring != nullptr) {
+    thread_local_io_urings_.reset(new ThreadLocalPtr(DeleteIOUring));
+    delete new_io_uring;
+  }
+#endif
+}
+
+}  // namespace
+
+//
+// Default Posix FileSystem
+//
+std::shared_ptr<FileSystem> FileSystem::Default() {
+  static PosixFileSystem default_fs;
+  static std::shared_ptr<PosixFileSystem> default_fs_ptr(
+      &default_fs, [](PosixFileSystem*) {});
+  return default_fs_ptr;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/io_posix.cc b/src/rocksdb/env/io_posix.cc
new file mode 100644
index 000000000..a2bbab38d
--- /dev/null
+++ b/src/rocksdb/env/io_posix.cc
@@ -0,0 +1,1352 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifdef ROCKSDB_LIB_IO_POSIX
+#include "env/io_posix.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <algorithm>
+#if defined(OS_LINUX)
+#include <linux/fs.h>
+#ifndef FALLOC_FL_KEEP_SIZE
+#include <linux/falloc.h>
+#endif
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#ifdef OS_LINUX
+#include <sys/statfs.h>
+#include <sys/syscall.h>
+#include <sys/sysmacros.h>
+#endif
+#include "monitoring/iostats_context_imp.h"
+#include "port/port.h"
+#include "rocksdb/slice.h"
+#include "test_util/sync_point.h"
+#include "util/autovector.h"
+#include "util/coding.h"
+#include "util/string_util.h"
+
+#if defined(OS_LINUX) && !defined(F_SET_RW_HINT)
+#define F_LINUX_SPECIFIC_BASE 1024
+#define F_SET_RW_HINT (F_LINUX_SPECIFIC_BASE + 12)
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+// A wrapper for fadvise, if the platform doesn't support fadvise,
+// it will simply return 0.
+int Fadvise(int fd, off_t offset, size_t len, int advice) {
+#ifdef OS_LINUX
+  return posix_fadvise(fd, offset, len, advice);
+#else
+  (void)fd;
+  (void)offset;
+  (void)len;
+  (void)advice;
+  return 0;  // simply do nothing.
+#endif
+}
+
+namespace {
+
+// On MacOS (and probably *BSD), the posix write and pwrite calls do not support
+// buffers larger than 2^31-1 bytes. These two wrappers fix this issue by
+// cutting the buffer in 1GB chunks. We use this chunk size to be sure to keep
+// the writes aligned.
+
+bool PosixWrite(int fd, const char* buf, size_t nbyte) {
+  const size_t kLimit1Gb = 1UL << 30;
+
+  const char* src = buf;
+  size_t left = nbyte;
+
+  while (left != 0) {
+    size_t bytes_to_write = std::min(left, kLimit1Gb);
+
+    ssize_t done = write(fd, src, bytes_to_write);
+    if (done < 0) {
+      if (errno == EINTR) {
+        continue;
+      }
+      return false;
+    }
+    left -= done;
+    src += done;
+  }
+  return true;
+}
+
+bool PosixPositionedWrite(int fd, const char* buf, size_t nbyte, off_t offset) {
+  const size_t kLimit1Gb = 1UL << 30;
+
+  const char* src = buf;
+  size_t left = nbyte;
+
+  while (left != 0) {
+    size_t bytes_to_write = std::min(left, kLimit1Gb);
+
+    ssize_t done = pwrite(fd, src, bytes_to_write, offset);
+    if (done < 0) {
+      if (errno == EINTR) {
+        continue;
+      }
+      return false;
+    }
+    left -= done;
+    offset += done;
+    src += done;
+  }
+
+  return true;
+}
+
+size_t GetLogicalBufferSize(int __attribute__((__unused__)) fd) {
+#ifdef OS_LINUX
+  struct stat buf;
+  int result = fstat(fd, &buf);
+  if (result == -1) {
+    return kDefaultPageSize;
+  }
+  if (major(buf.st_dev) == 0) {
+    // Unnamed devices (e.g. non-device mounts), reserved as null device number.
+    // These don't have an entry in /sys/dev/block/. Return a sensible default.
+    return kDefaultPageSize;
+  }
+
+  // Reading queue/logical_block_size does not require special permissions.
+  const int kBufferSize = 100;
+  char path[kBufferSize];
+  char real_path[PATH_MAX + 1];
+  snprintf(path, kBufferSize, "/sys/dev/block/%u:%u", major(buf.st_dev),
+           minor(buf.st_dev));
+  if (realpath(path, real_path) == nullptr) {
+    return kDefaultPageSize;
+  }
+  std::string device_dir(real_path);
+  if (!device_dir.empty() && device_dir.back() == '/') {
+    device_dir.pop_back();
+  }
+  // NOTE: sda3 and nvme0n1p1 do not have a `queue/` subdir, only the parent sda
+  // and nvme0n1 have it.
+  // $ ls -al '/sys/dev/block/8:3'
+  // lrwxrwxrwx. 1 root root 0 Jun 26 01:38 /sys/dev/block/8:3 ->
+  // ../../block/sda/sda3
+  // $ ls -al '/sys/dev/block/259:4'
+  // lrwxrwxrwx 1 root root 0 Jan 31 16:04 /sys/dev/block/259:4 ->
+  // ../../devices/pci0000:17/0000:17:00.0/0000:18:00.0/nvme/nvme0/nvme0n1/nvme0n1p1
+  size_t parent_end = device_dir.rfind('/', device_dir.length() - 1);
+  if (parent_end == std::string::npos) {
+    return kDefaultPageSize;
+  }
+  size_t parent_begin = device_dir.rfind('/', parent_end - 1);
+  if (parent_begin == std::string::npos) {
+    return kDefaultPageSize;
+  }
+  std::string parent =
+      device_dir.substr(parent_begin + 1, parent_end - parent_begin - 1);
+  std::string child = device_dir.substr(parent_end + 1, std::string::npos);
+  if (parent != "block" &&
+      (child.compare(0, 4, "nvme") || child.find('p') != std::string::npos)) {
+    device_dir = device_dir.substr(0, parent_end);
+  }
+  std::string fname = device_dir + "/queue/logical_block_size";
+  FILE* fp;
+  size_t size = 0;
+  fp = fopen(fname.c_str(), "r");
+  if (fp != nullptr) {
+    char* line = nullptr;
+    size_t len = 0;
+    if (getline(&line, &len, fp) != -1) {
+      sscanf(line, "%zu", &size);
+    }
+    free(line);
+    fclose(fp);
+  }
+  if (size != 0 && (size & (size - 1)) == 0) {
+    return size;
+  }
+#endif
+  return kDefaultPageSize;
+}
+
+#ifdef ROCKSDB_RANGESYNC_PRESENT
+
+#if !defined(ZFS_SUPER_MAGIC)
+// The magic number for ZFS was not exposed until recently. It should be fixed
+// forever so we can just copy the magic number here.
+#define ZFS_SUPER_MAGIC 0x2fc12fc1
+#endif
+
+bool IsSyncFileRangeSupported(int fd) {
+  // The approach taken in this function is to build a blacklist of cases where
+  // we know `sync_file_range` definitely will not work properly despite passing
+  // the compile-time check (`ROCKSDB_RANGESYNC_PRESENT`). If we are unsure, or
+  // if any of the checks fail in unexpected ways, we allow `sync_file_range` to
+  // be used. This way should minimize risk of impacting existing use cases.
+  struct statfs buf;
+  int ret = fstatfs(fd, &buf);
+  assert(ret == 0);
+  if (ret == 0 && buf.f_type == ZFS_SUPER_MAGIC) {
+    // Testing on ZFS showed the writeback did not happen asynchronously when
+    // `sync_file_range` was called, even though it returned success. Avoid it
+    // and use `fdatasync` instead to preserve the contract of `bytes_per_sync`,
+    // even though this'll incur extra I/O for metadata.
+    return false;
+  }
+
+  ret = sync_file_range(fd, 0 /* offset */, 0 /* nbytes */, 0 /* flags */);
+  assert(!(ret == -1 && errno != ENOSYS));
+  if (ret == -1 && errno == ENOSYS) {
+    // `sync_file_range` is not implemented on all platforms even if
+    // compile-time checks pass and a supported filesystem is in-use. For
+    // example, using ext4 on WSL (Windows Subsystem for Linux),
+    // `sync_file_range()` returns `ENOSYS`
+    // ("Function not implemented").
+    return false;
+  }
+  // None of the cases on the blacklist matched, so allow `sync_file_range` use.
+  return true;
+}
+
+#undef ZFS_SUPER_MAGIC
+
+#endif  // ROCKSDB_RANGESYNC_PRESENT
+
+}  // anonymous namespace
+
+/*
+ * DirectIOHelper
+ */
+#ifndef NDEBUG
+namespace {
+
+bool IsSectorAligned(const size_t off, size_t sector_size) {
+  return off % sector_size == 0;
+}
+
+bool IsSectorAligned(const void* ptr, size_t sector_size) {
+  return uintptr_t(ptr) % sector_size == 0;
+}
+
+}  // namespace
+#endif
+
+/*
+ * PosixSequentialFile
+ */
+PosixSequentialFile::PosixSequentialFile(const std::string& fname, FILE* file,
+                                         int fd, const EnvOptions& options)
+    : filename_(fname),
+      file_(file),
+      fd_(fd),
+      use_direct_io_(options.use_direct_reads),
+      logical_sector_size_(GetLogicalBufferSize(fd_)) {
+  assert(!options.use_direct_reads || !options.use_mmap_reads);
+}
+
+PosixSequentialFile::~PosixSequentialFile() {
+  if (!use_direct_io()) {
+    assert(file_);
+    fclose(file_);
+  } else {
+    assert(fd_);
+    close(fd_);
+  }
+}
+
+IOStatus PosixSequentialFile::Read(size_t n, const IOOptions& /*opts*/,
+                                   Slice* result, char* scratch,
+                                   IODebugContext* /*dbg*/) {
+  assert(result != nullptr && !use_direct_io());
+  IOStatus s;
+  size_t r = 0;
+  do {
+    r = fread_unlocked(scratch, 1, n, file_);
+  } while (r == 0 && ferror(file_) && errno == EINTR);
+  *result = Slice(scratch, r);
+  if (r < n) {
+    if (feof(file_)) {
+      // We leave status as ok if we hit the end of the file
+      // We also clear the error so that the reads can continue
+      // if a new data is written to the file
+      clearerr(file_);
+    } else {
+      // A partial read with an error: return a non-ok status
+      s = IOError("While reading file sequentially", filename_, errno);
+    }
+  }
+  return s;
+}
+
+IOStatus PosixSequentialFile::PositionedRead(uint64_t offset, size_t n,
+                                             const IOOptions& /*opts*/,
+                                             Slice* result, char* scratch,
+                                             IODebugContext* /*dbg*/) {
+  assert(use_direct_io());
+  assert(IsSectorAligned(offset, GetRequiredBufferAlignment()));
+  assert(IsSectorAligned(n, GetRequiredBufferAlignment()));
+  assert(IsSectorAligned(scratch, GetRequiredBufferAlignment()));
+
+  IOStatus s;
+  ssize_t r = -1;
+  size_t left = n;
+  char* ptr = scratch;
+  while (left > 0) {
+    r = pread(fd_, ptr, left, static_cast<off_t>(offset));
+    if (r <= 0) {
+      if (r == -1 && errno == EINTR) {
+        continue;
+      }
+      break;
+    }
+    ptr += r;
+    offset += r;
+    left -= r;
+    if (r % static_cast<ssize_t>(GetRequiredBufferAlignment()) != 0) {
+      // Bytes reads don't fill sectors. Should only happen at the end
+      // of the file.
+      break;
+    }
+  }
+  if (r < 0) {
+    // An error: return a non-ok status
+    s = IOError(
+        "While pread " + ToString(n) + " bytes from offset " + ToString(offset),
+        filename_, errno);
+  }
+  *result = Slice(scratch, (r < 0) ? 0 : n - left);
+  return s;
+}
+
+IOStatus PosixSequentialFile::Skip(uint64_t n) {
+  if (fseek(file_, static_cast<long int>(n), SEEK_CUR)) {
+    return IOError("While fseek to skip " + ToString(n) + " bytes", filename_,
+                   errno);
+  }
+  return IOStatus::OK();
+}
+
+IOStatus PosixSequentialFile::InvalidateCache(size_t offset, size_t length) {
+#ifndef OS_LINUX
+  (void)offset;
+  (void)length;
+  return IOStatus::OK();
+#else
+  if (!use_direct_io()) {
+    // free OS pages
+    int ret = Fadvise(fd_, offset, length, POSIX_FADV_DONTNEED);
+    if (ret != 0) {
+      return IOError("While fadvise NotNeeded offset " + ToString(offset) +
+                         " len " + ToString(length),
+                     filename_, errno);
+    }
+  }
+  return IOStatus::OK();
+#endif
+}
+
+/*
+ * PosixRandomAccessFile
+ */
+#if defined(OS_LINUX)
+size_t PosixHelper::GetUniqueIdFromFile(int fd, char* id, size_t max_size) {
+  if (max_size < kMaxVarint64Length * 3) {
+    return 0;
+  }
+
+  struct stat buf;
+  int result = fstat(fd, &buf);
+  if (result == -1) {
+    return 0;
+  }
+
+  long version = 0;
+  result = ioctl(fd, FS_IOC_GETVERSION, &version);
+  TEST_SYNC_POINT_CALLBACK("GetUniqueIdFromFile:FS_IOC_GETVERSION", &result);
+  if (result == -1) {
+    return 0;
+  }
+  uint64_t uversion = (uint64_t)version;
+
+  char* rid = id;
+  rid = EncodeVarint64(rid, buf.st_dev);
+  rid = EncodeVarint64(rid, buf.st_ino);
+  rid = EncodeVarint64(rid, uversion);
+  assert(rid >= id);
+  return static_cast<size_t>(rid - id);
+}
+#endif
+
+#if defined(OS_MACOSX) || defined(OS_AIX)
+size_t PosixHelper::GetUniqueIdFromFile(int fd, char* id, size_t max_size) {
+  if (max_size < kMaxVarint64Length * 3) {
+    return 0;
+  }
+
+  struct stat buf;
+  int result = fstat(fd, &buf);
+  if (result == -1) {
+    return 0;
+  }
+
+  char* rid = id;
+  rid = EncodeVarint64(rid, buf.st_dev);
+  rid = EncodeVarint64(rid, buf.st_ino);
+  rid = EncodeVarint64(rid, buf.st_gen);
+  assert(rid >= id);
+  return static_cast<size_t>(rid - id);
+}
+#endif
+/*
+ * PosixRandomAccessFile
+ *
+ * pread() based random-access
+ */
+PosixRandomAccessFile::PosixRandomAccessFile(
+    const std::string& fname, int fd, const EnvOptions& options
+#if defined(ROCKSDB_IOURING_PRESENT)
+    ,
+    ThreadLocalPtr* thread_local_io_urings
+#endif
+    )
+    : filename_(fname),
+      fd_(fd),
+      use_direct_io_(options.use_direct_reads),
+      logical_sector_size_(GetLogicalBufferSize(fd_))
+#if defined(ROCKSDB_IOURING_PRESENT)
+      ,
+      thread_local_io_urings_(thread_local_io_urings)
+#endif
+{
+  assert(!options.use_direct_reads || !options.use_mmap_reads);
+  assert(!options.use_mmap_reads || sizeof(void*) < 8);
+}
+
+PosixRandomAccessFile::~PosixRandomAccessFile() { close(fd_); }
+
+IOStatus PosixRandomAccessFile::Read(uint64_t offset, size_t n,
+                                     const IOOptions& /*opts*/, Slice* result,
+                                     char* scratch,
+                                     IODebugContext* /*dbg*/) const {
+  if (use_direct_io()) {
+    assert(IsSectorAligned(offset, GetRequiredBufferAlignment()));
+    assert(IsSectorAligned(n, GetRequiredBufferAlignment()));
+    assert(IsSectorAligned(scratch, GetRequiredBufferAlignment()));
+  }
+  IOStatus s;
+  ssize_t r = -1;
+  size_t left = n;
+  char* ptr = scratch;
+  while (left > 0) {
+    r = pread(fd_, ptr, left, static_cast<off_t>(offset));
+    if (r <= 0) {
+      if (r == -1 && errno == EINTR) {
+        continue;
+      }
+      break;
+    }
+    ptr += r;
+    offset += r;
+    left -= r;
+    if (use_direct_io() &&
+        r % static_cast<ssize_t>(GetRequiredBufferAlignment()) != 0) {
+      // Bytes reads don't fill sectors. Should only happen at the end
+      // of the file.
+      break;
+    }
+  }
+  if (r < 0) {
+    // An error: return a non-ok status
+    s = IOError(
+        "While pread offset " + ToString(offset) + " len " + ToString(n),
+        filename_, errno);
+  }
+  *result = Slice(scratch, (r < 0) ? 0 : n - left);
+  return s;
+}
+
+IOStatus PosixRandomAccessFile::MultiRead(FSReadRequest* reqs,
+                                          size_t num_reqs,
+                                          const IOOptions& options,
+                                          IODebugContext* dbg) {
+#if defined(ROCKSDB_IOURING_PRESENT)
+  struct io_uring* iu = nullptr;
+  if (thread_local_io_urings_) {
+    iu = static_cast<struct io_uring*>(thread_local_io_urings_->Get());
+    if (iu == nullptr) {
+      iu = CreateIOUring();
+      if (iu != nullptr) {
+        thread_local_io_urings_->Reset(iu);
+      }
+    }
+  }
+
+  // Init failed, platform doesn't support io_uring. Fall back to
+  // serialized reads
+  if (iu == nullptr) {
+    return FSRandomAccessFile::MultiRead(reqs, num_reqs, options, dbg);
+  }
+
+  struct WrappedReadRequest {
+    FSReadRequest* req;
+    struct iovec iov;
+    size_t finished_len;
+    explicit WrappedReadRequest(FSReadRequest* r) : req(r), finished_len(0) {}
+  };
+
+  autovector<WrappedReadRequest, 32> req_wraps;
+  autovector<WrappedReadRequest*, 4> incomplete_rq_list;
+
+  for (size_t i = 0; i < num_reqs; i++) {
+    req_wraps.emplace_back(&reqs[i]);
+  }
+
+  size_t reqs_off = 0;
+  while (num_reqs > reqs_off || !incomplete_rq_list.empty()) {
+    size_t this_reqs = (num_reqs - reqs_off) + incomplete_rq_list.size();
+
+    // If requests exceed depth, split it into batches
+    if (this_reqs > kIoUringDepth) this_reqs = kIoUringDepth;
+
+    assert(incomplete_rq_list.size() <= this_reqs);
+    for (size_t i = 0; i < this_reqs; i++) {
+      WrappedReadRequest* rep_to_submit;
+      if (i < incomplete_rq_list.size()) {
+        rep_to_submit = incomplete_rq_list[i];
+      } else {
+        rep_to_submit = &req_wraps[reqs_off++];
+      }
+      assert(rep_to_submit->req->len > rep_to_submit->finished_len);
+      rep_to_submit->iov.iov_base =
+          rep_to_submit->req->scratch + rep_to_submit->finished_len;
+      rep_to_submit->iov.iov_len =
+          rep_to_submit->req->len - rep_to_submit->finished_len;
+
+      struct io_uring_sqe* sqe;
+      sqe = io_uring_get_sqe(iu);
+      io_uring_prep_readv(
+          sqe, fd_, &rep_to_submit->iov, 1,
+          rep_to_submit->req->offset + rep_to_submit->finished_len);
+      io_uring_sqe_set_data(sqe, rep_to_submit);
+    }
+    incomplete_rq_list.clear();
+
+    ssize_t ret =
+        io_uring_submit_and_wait(iu, static_cast<unsigned int>(this_reqs));
+    if (static_cast<size_t>(ret) != this_reqs) {
+      fprintf(stderr, "ret = %ld this_reqs: %ld\n", (long)ret, (long)this_reqs);
+    }
+    assert(static_cast<size_t>(ret) == this_reqs);
+
+    for (size_t i = 0; i < this_reqs; i++) {
+      struct io_uring_cqe* cqe;
+      WrappedReadRequest* req_wrap;
+
+      // We could use the peek variant here, but this seems safer in terms
+      // of our initial wait not reaping all completions
+      ret = io_uring_wait_cqe(iu, &cqe);
+      assert(!ret);
+
+      req_wrap = static_cast<WrappedReadRequest*>(io_uring_cqe_get_data(cqe));
+      FSReadRequest* req = req_wrap->req;
+      if (cqe->res < 0) {
+        req->result = Slice(req->scratch, 0);
+        req->status = IOError("Req failed", filename_, cqe->res);
+      } else {
+        size_t bytes_read = static_cast<size_t>(cqe->res);
+        TEST_SYNC_POINT_CALLBACK(
+            "PosixRandomAccessFile::MultiRead:io_uring_result", &bytes_read);
+        if (bytes_read == req_wrap->iov.iov_len) {
+          req->result = Slice(req->scratch, req->len);
+          req->status = IOStatus::OK();
+        } else if (bytes_read == 0) {
+          // cqe->res == 0 can means EOF, or can mean partial results. See
+          // comment
+          // https://github.com/facebook/rocksdb/pull/6441#issuecomment-589843435
+          // Fall back to pread in this case.
+          Slice tmp_slice;
+          req->status =
+              Read(req->offset + req_wrap->finished_len,
+                   req->len - req_wrap->finished_len, options, &tmp_slice,
+                   req->scratch + req_wrap->finished_len, dbg);
+          req->result =
+              Slice(req->scratch, req_wrap->finished_len + tmp_slice.size());
+        } else if (bytes_read < req_wrap->iov.iov_len) {
+          assert(bytes_read > 0);
+          assert(bytes_read + req_wrap->finished_len < req->len);
+          req_wrap->finished_len += bytes_read;
+          incomplete_rq_list.push_back(req_wrap);
+        } else {
+          req->result = Slice(req->scratch, 0);
+          req->status = IOError("Req returned more bytes than requested",
+                                filename_, cqe->res);
+        }
+      }
+      io_uring_cqe_seen(iu, cqe);
+    }
+  }
+  return IOStatus::OK();
+#else
+  return FSRandomAccessFile::MultiRead(reqs, num_reqs, options, dbg);
+#endif
+}
+
+IOStatus PosixRandomAccessFile::Prefetch(uint64_t offset, size_t n,
+                                         const IOOptions& /*opts*/,
+                                         IODebugContext* /*dbg*/) {
+  IOStatus s;
+  if (!use_direct_io()) {
+    ssize_t r = 0;
+#ifdef OS_LINUX
+    r = readahead(fd_, offset, n);
+#endif
+#ifdef OS_MACOSX
+    radvisory advice;
+    advice.ra_offset = static_cast<off_t>(offset);
+    advice.ra_count = static_cast<int>(n);
+    r = fcntl(fd_, F_RDADVISE, &advice);
+#endif
+    if (r == -1) {
+      s = IOError("While prefetching offset " + ToString(offset) + " len " +
+                      ToString(n),
+                  filename_, errno);
+    }
+  }
+  return s;
+}
+
+#if defined(OS_LINUX) || defined(OS_MACOSX) || defined(OS_AIX)
+size_t PosixRandomAccessFile::GetUniqueId(char* id, size_t max_size) const {
+  return PosixHelper::GetUniqueIdFromFile(fd_, id, max_size);
+}
+#endif
+
+void PosixRandomAccessFile::Hint(AccessPattern pattern) {
+  if (use_direct_io()) {
+    return;
+  }
+  switch (pattern) {
+    case kNormal:
+      Fadvise(fd_, 0, 0, POSIX_FADV_NORMAL);
+      break;
+    case kRandom:
+      Fadvise(fd_, 0, 0, POSIX_FADV_RANDOM);
+      break;
+    case kSequential:
+      Fadvise(fd_, 0, 0, POSIX_FADV_SEQUENTIAL);
+      break;
+    case kWillNeed:
+      Fadvise(fd_, 0, 0, POSIX_FADV_WILLNEED);
+      break;
+    case kWontNeed:
+      Fadvise(fd_, 0, 0, POSIX_FADV_DONTNEED);
+      break;
+    default:
+      assert(false);
+      break;
+  }
+}
+
+IOStatus PosixRandomAccessFile::InvalidateCache(size_t offset, size_t length) {
+  if (use_direct_io()) {
+    return IOStatus::OK();
+  }
+#ifndef OS_LINUX
+  (void)offset;
+  (void)length;
+  return IOStatus::OK();
+#else
+  // free OS pages
+  int ret = Fadvise(fd_, offset, length, POSIX_FADV_DONTNEED);
+  if (ret == 0) {
+    return IOStatus::OK();
+  }
+  return IOError("While fadvise NotNeeded offset " + ToString(offset) +
+                     " len " + ToString(length),
+                 filename_, errno);
+#endif
+}
+
+/*
+ * PosixMmapReadableFile
+ *
+ * mmap() based random-access
+ */
+// base[0,length-1] contains the mmapped contents of the file.
+PosixMmapReadableFile::PosixMmapReadableFile(const int fd,
+                                             const std::string& fname,
+                                             void* base, size_t length,
+                                             const EnvOptions& options)
+    : fd_(fd), filename_(fname), mmapped_region_(base), length_(length) {
+#ifdef NDEBUG
+  (void)options;
+#endif
+  fd_ = fd_ + 0;  // suppress the warning for used variables
+  assert(options.use_mmap_reads);
+  assert(!options.use_direct_reads);
+}
+
+PosixMmapReadableFile::~PosixMmapReadableFile() {
+  int ret = munmap(mmapped_region_, length_);
+  if (ret != 0) {
+    fprintf(stdout, "failed to munmap %p length %" ROCKSDB_PRIszt " \n",
+            mmapped_region_, length_);
+  }
+  close(fd_);
+}
+
+IOStatus PosixMmapReadableFile::Read(uint64_t offset, size_t n,
+                                     const IOOptions& /*opts*/, Slice* result,
+                                     char* /*scratch*/,
+                                     IODebugContext* /*dbg*/) const {
+  IOStatus s;
+  if (offset > length_) {
+    *result = Slice();
+    return IOError("While mmap read offset " + ToString(offset) +
+                       " larger than file length " + ToString(length_),
+                   filename_, EINVAL);
+  } else if (offset + n > length_) {
+    n = static_cast<size_t>(length_ - offset);
+  }
+  *result = Slice(reinterpret_cast<char*>(mmapped_region_) + offset, n);
+  return s;
+}
+
+IOStatus PosixMmapReadableFile::InvalidateCache(size_t offset, size_t length) {
+#ifndef OS_LINUX
+  (void)offset;
+  (void)length;
+  return IOStatus::OK();
+#else
+  // free OS pages
+  int ret = Fadvise(fd_, offset, length, POSIX_FADV_DONTNEED);
+  if (ret == 0) {
+    return IOStatus::OK();
+  }
+  return IOError("While fadvise not needed. Offset " + ToString(offset) +
+                     " len" + ToString(length),
+                 filename_, errno);
+#endif
+}
+
+/*
+ * PosixMmapFile
+ *
+ * We preallocate up to an extra megabyte and use memcpy to append new
+ * data to the file.  This is safe since we either properly close the
+ * file before reading from it, or for log files, the reading code
+ * knows enough to skip zero suffixes.
+ */
+IOStatus PosixMmapFile::UnmapCurrentRegion() {
+  TEST_KILL_RANDOM("PosixMmapFile::UnmapCurrentRegion:0", rocksdb_kill_odds);
+  if (base_ != nullptr) {
+    int munmap_status = munmap(base_, limit_ - base_);
+    if (munmap_status != 0) {
+      return IOError("While munmap", filename_, munmap_status);
+    }
+    file_offset_ += limit_ - base_;
+    base_ = nullptr;
+    limit_ = nullptr;
+    last_sync_ = nullptr;
+    dst_ = nullptr;
+
+    // Increase the amount we map the next time, but capped at 1MB
+    if (map_size_ < (1 << 20)) {
+      map_size_ *= 2;
+    }
+  }
+  return IOStatus::OK();
+}
+
+IOStatus PosixMmapFile::MapNewRegion() {
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  assert(base_ == nullptr);
+  TEST_KILL_RANDOM("PosixMmapFile::UnmapCurrentRegion:0", rocksdb_kill_odds);
+  // we can't fallocate with FALLOC_FL_KEEP_SIZE here
+  if (allow_fallocate_) {
+    IOSTATS_TIMER_GUARD(allocate_nanos);
+    int alloc_status = fallocate(fd_, 0, file_offset_, map_size_);
+    if (alloc_status != 0) {
+      // fallback to posix_fallocate
+      alloc_status = posix_fallocate(fd_, file_offset_, map_size_);
+    }
+    if (alloc_status != 0) {
+      return IOStatus::IOError("Error allocating space to file : " + filename_ +
+                               "Error : " + strerror(alloc_status));
+    }
+  }
+
+  TEST_KILL_RANDOM("PosixMmapFile::Append:1", rocksdb_kill_odds);
+  void* ptr = mmap(nullptr, map_size_, PROT_READ | PROT_WRITE, MAP_SHARED, fd_,
+                   file_offset_);
+  if (ptr == MAP_FAILED) {
+    return IOStatus::IOError("MMap failed on " + filename_);
+  }
+  TEST_KILL_RANDOM("PosixMmapFile::Append:2", rocksdb_kill_odds);
+
+  base_ = reinterpret_cast<char*>(ptr);
+  limit_ = base_ + map_size_;
+  dst_ = base_;
+  last_sync_ = base_;
+  return IOStatus::OK();
+#else
+  return IOStatus::NotSupported("This platform doesn't support fallocate()");
+#endif
+}
+
+IOStatus PosixMmapFile::Msync() {
+  if (dst_ == last_sync_) {
+    return IOStatus::OK();
+  }
+  // Find the beginnings of the pages that contain the first and last
+  // bytes to be synced.
+  size_t p1 = TruncateToPageBoundary(last_sync_ - base_);
+  size_t p2 = TruncateToPageBoundary(dst_ - base_ - 1);
+  last_sync_ = dst_;
+  TEST_KILL_RANDOM("PosixMmapFile::Msync:0", rocksdb_kill_odds);
+  if (msync(base_ + p1, p2 - p1 + page_size_, MS_SYNC) < 0) {
+    return IOError("While msync", filename_, errno);
+  }
+  return IOStatus::OK();
+}
+
+PosixMmapFile::PosixMmapFile(const std::string& fname, int fd, size_t page_size,
+                             const EnvOptions& options)
+    : filename_(fname),
+      fd_(fd),
+      page_size_(page_size),
+      map_size_(Roundup(65536, page_size)),
+      base_(nullptr),
+      limit_(nullptr),
+      dst_(nullptr),
+      last_sync_(nullptr),
+      file_offset_(0) {
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  allow_fallocate_ = options.allow_fallocate;
+  fallocate_with_keep_size_ = options.fallocate_with_keep_size;
+#else
+  (void)options;
+#endif
+  assert((page_size & (page_size - 1)) == 0);
+  assert(options.use_mmap_writes);
+  assert(!options.use_direct_writes);
+}
+
+PosixMmapFile::~PosixMmapFile() {
+  if (fd_ >= 0) {
+    PosixMmapFile::Close(IOOptions(), nullptr);
+  }
+}
+
+IOStatus PosixMmapFile::Append(const Slice& data, const IOOptions& /*opts*/,
+                               IODebugContext* /*dbg*/) {
+  const char* src = data.data();
+  size_t left = data.size();
+  while (left > 0) {
+    assert(base_ <= dst_);
+    assert(dst_ <= limit_);
+    size_t avail = limit_ - dst_;
+    if (avail == 0) {
+      IOStatus s = UnmapCurrentRegion();
+      if (!s.ok()) {
+        return s;
+      }
+      s = MapNewRegion();
+      if (!s.ok()) {
+        return s;
+      }
+      TEST_KILL_RANDOM("PosixMmapFile::Append:0", rocksdb_kill_odds);
+    }
+
+    size_t n = (left <= avail) ? left : avail;
+    assert(dst_);
+    memcpy(dst_, src, n);
+    dst_ += n;
+    src += n;
+    left -= n;
+  }
+  return IOStatus::OK();
+}
+
+IOStatus PosixMmapFile::Close(const IOOptions& /*opts*/,
+                              IODebugContext* /*dbg*/) {
+  IOStatus s;
+  size_t unused = limit_ - dst_;
+
+  s = UnmapCurrentRegion();
+  if (!s.ok()) {
+    s = IOError("While closing mmapped file", filename_, errno);
+  } else if (unused > 0) {
+    // Trim the extra space at the end of the file
+    if (ftruncate(fd_, file_offset_ - unused) < 0) {
+      s = IOError("While ftruncating mmaped file", filename_, errno);
+    }
+  }
+
+  if (close(fd_) < 0) {
+    if (s.ok()) {
+      s = IOError("While closing mmapped file", filename_, errno);
+    }
+  }
+
+  fd_ = -1;
+  base_ = nullptr;
+  limit_ = nullptr;
+  return s;
+}
+
+IOStatus PosixMmapFile::Flush(const IOOptions& /*opts*/,
+                              IODebugContext* /*dbg*/) {
+  return IOStatus::OK();
+}
+
+IOStatus PosixMmapFile::Sync(const IOOptions& /*opts*/,
+                             IODebugContext* /*dbg*/) {
+  if (fdatasync(fd_) < 0) {
+    return IOError("While fdatasync mmapped file", filename_, errno);
+  }
+
+  return Msync();
+}
+
+/**
+ * Flush data as well as metadata to stable storage.
+ */
+IOStatus PosixMmapFile::Fsync(const IOOptions& /*opts*/,
+                              IODebugContext* /*dbg*/) {
+  if (fsync(fd_) < 0) {
+    return IOError("While fsync mmaped file", filename_, errno);
+  }
+
+  return Msync();
+}
+
+/**
+ * Get the size of valid data in the file. This will not match the
+ * size that is returned from the filesystem because we use mmap
+ * to extend file by map_size every time.
+ */
+uint64_t PosixMmapFile::GetFileSize(const IOOptions& /*opts*/,
+                                    IODebugContext* /*dbg*/) {
+  size_t used = dst_ - base_;
+  return file_offset_ + used;
+}
+
+IOStatus PosixMmapFile::InvalidateCache(size_t offset, size_t length) {
+#ifndef OS_LINUX
+  (void)offset;
+  (void)length;
+  return IOStatus::OK();
+#else
+  // free OS pages
+  int ret = Fadvise(fd_, offset, length, POSIX_FADV_DONTNEED);
+  if (ret == 0) {
+    return IOStatus::OK();
+  }
+  return IOError("While fadvise NotNeeded mmapped file", filename_, errno);
+#endif
+}
+
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+IOStatus PosixMmapFile::Allocate(uint64_t offset, uint64_t len,
+                                 const IOOptions& /*opts*/,
+                                 IODebugContext* /*dbg*/) {
+  assert(offset <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  assert(len <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  TEST_KILL_RANDOM("PosixMmapFile::Allocate:0", rocksdb_kill_odds);
+  int alloc_status = 0;
+  if (allow_fallocate_) {
+    alloc_status =
+        fallocate(fd_, fallocate_with_keep_size_ ? FALLOC_FL_KEEP_SIZE : 0,
+                  static_cast<off_t>(offset), static_cast<off_t>(len));
+  }
+  if (alloc_status == 0) {
+    return IOStatus::OK();
+  } else {
+    return IOError(
+        "While fallocate offset " + ToString(offset) + " len " + ToString(len),
+        filename_, errno);
+  }
+}
+#endif
+
+/*
+ * PosixWritableFile
+ *
+ * Use posix write to write data to a file.
+ */
+PosixWritableFile::PosixWritableFile(const std::string& fname, int fd,
+                                     const EnvOptions& options)
+    : FSWritableFile(options),
+      filename_(fname),
+      use_direct_io_(options.use_direct_writes),
+      fd_(fd),
+      filesize_(0),
+      logical_sector_size_(GetLogicalBufferSize(fd_)) {
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  allow_fallocate_ = options.allow_fallocate;
+  fallocate_with_keep_size_ = options.fallocate_with_keep_size;
+#endif
+#ifdef ROCKSDB_RANGESYNC_PRESENT
+  sync_file_range_supported_ = IsSyncFileRangeSupported(fd_);
+#endif  // ROCKSDB_RANGESYNC_PRESENT
+  assert(!options.use_mmap_writes);
+}
+
+PosixWritableFile::~PosixWritableFile() {
+  if (fd_ >= 0) {
+    PosixWritableFile::Close(IOOptions(), nullptr);
+  }
+}
+
+IOStatus PosixWritableFile::Append(const Slice& data, const IOOptions& /*opts*/,
+                                   IODebugContext* /*dbg*/) {
+  if (use_direct_io()) {
+    assert(IsSectorAligned(data.size(), GetRequiredBufferAlignment()));
+    assert(IsSectorAligned(data.data(), GetRequiredBufferAlignment()));
+  }
+  const char* src = data.data();
+  size_t nbytes = data.size();
+
+  if (!PosixWrite(fd_, src, nbytes)) {
+    return IOError("While appending to file", filename_, errno);
+  }
+
+  filesize_ += nbytes;
+  return IOStatus::OK();
+}
+
+IOStatus PosixWritableFile::PositionedAppend(const Slice& data, uint64_t offset,
+                                             const IOOptions& /*opts*/,
+                                             IODebugContext* /*dbg*/) {
+  if (use_direct_io()) {
+    assert(IsSectorAligned(offset, GetRequiredBufferAlignment()));
+    assert(IsSectorAligned(data.size(), GetRequiredBufferAlignment()));
+    assert(IsSectorAligned(data.data(), GetRequiredBufferAlignment()));
+  }
+  assert(offset <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  const char* src = data.data();
+  size_t nbytes = data.size();
+  if (!PosixPositionedWrite(fd_, src, nbytes, static_cast<off_t>(offset))) {
+    return IOError("While pwrite to file at offset " + ToString(offset),
+                   filename_, errno);
+  }
+  filesize_ = offset + nbytes;
+  return IOStatus::OK();
+}
+
+IOStatus PosixWritableFile::Truncate(uint64_t size, const IOOptions& /*opts*/,
+                                     IODebugContext* /*dbg*/) {
+  IOStatus s;
+  int r = ftruncate(fd_, size);
+  if (r < 0) {
+    s = IOError("While ftruncate file to size " + ToString(size), filename_,
+                errno);
+  } else {
+    filesize_ = size;
+  }
+  return s;
+}
+
+IOStatus PosixWritableFile::Close(const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  IOStatus s;
+
+  size_t block_size;
+  size_t last_allocated_block;
+  GetPreallocationStatus(&block_size, &last_allocated_block);
+  if (last_allocated_block > 0) {
+    // trim the extra space preallocated at the end of the file
+    // NOTE(ljin): we probably don't want to surface failure as an IOError,
+    // but it will be nice to log these errors.
+    int dummy __attribute__((__unused__));
+    dummy = ftruncate(fd_, filesize_);
+#if defined(ROCKSDB_FALLOCATE_PRESENT) && defined(FALLOC_FL_PUNCH_HOLE) && \
+    !defined(TRAVIS)
+    // in some file systems, ftruncate only trims trailing space if the
+    // new file size is smaller than the current size. Calling fallocate
+    // with FALLOC_FL_PUNCH_HOLE flag to explicitly release these unused
+    // blocks. FALLOC_FL_PUNCH_HOLE is supported on at least the following
+    // filesystems:
+    //   XFS (since Linux 2.6.38)
+    //   ext4 (since Linux 3.0)
+    //   Btrfs (since Linux 3.7)
+    //   tmpfs (since Linux 3.5)
+    // We ignore error since failure of this operation does not affect
+    // correctness.
+    // TRAVIS - this code does not work on TRAVIS filesystems.
+    // the FALLOC_FL_KEEP_SIZE option is expected to not change the size
+    // of the file, but it does. Simple strace report will show that.
+    // While we work with Travis-CI team to figure out if this is a
+    // quirk of Docker/AUFS, we will comment this out.
+    struct stat file_stats;
+    int result = fstat(fd_, &file_stats);
+    // After ftruncate, we check whether ftruncate has the correct behavior.
+    // If not, we should hack it with FALLOC_FL_PUNCH_HOLE
+    if (result == 0 &&
+        (file_stats.st_size + file_stats.st_blksize - 1) /
+                file_stats.st_blksize !=
+            file_stats.st_blocks / (file_stats.st_blksize / 512)) {
+      IOSTATS_TIMER_GUARD(allocate_nanos);
+      if (allow_fallocate_) {
+        fallocate(fd_, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, filesize_,
+                  block_size * last_allocated_block - filesize_);
+      }
+    }
+#endif
+  }
+
+  if (close(fd_) < 0) {
+    s = IOError("While closing file after writing", filename_, errno);
+  }
+  fd_ = -1;
+  return s;
+}
+
+// write out the cached data to the OS cache
+IOStatus PosixWritableFile::Flush(const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  return IOStatus::OK();
+}
+
+IOStatus PosixWritableFile::Sync(const IOOptions& /*opts*/,
+                                 IODebugContext* /*dbg*/) {
+  if (fdatasync(fd_) < 0) {
+    return IOError("While fdatasync", filename_, errno);
+  }
+  return IOStatus::OK();
+}
+
+IOStatus PosixWritableFile::Fsync(const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  if (fsync(fd_) < 0) {
+    return IOError("While fsync", filename_, errno);
+  }
+  return IOStatus::OK();
+}
+
+bool PosixWritableFile::IsSyncThreadSafe() const { return true; }
+
+uint64_t PosixWritableFile::GetFileSize(const IOOptions& /*opts*/,
+                                        IODebugContext* /*dbg*/) {
+  return filesize_;
+}
+
+void PosixWritableFile::SetWriteLifeTimeHint(Env::WriteLifeTimeHint hint) {
+#ifdef OS_LINUX
+// Suppress Valgrind "Unimplemented functionality" error.
+#ifndef ROCKSDB_VALGRIND_RUN
+  if (hint == write_hint_) {
+    return;
+  }
+  if (fcntl(fd_, F_SET_RW_HINT, &hint) == 0) {
+    write_hint_ = hint;
+  }
+#else
+  (void)hint;
+#endif  // ROCKSDB_VALGRIND_RUN
+#else
+  (void)hint;
+#endif  // OS_LINUX
+}
+
+IOStatus PosixWritableFile::InvalidateCache(size_t offset, size_t length) {
+  if (use_direct_io()) {
+    return IOStatus::OK();
+  }
+#ifndef OS_LINUX
+  (void)offset;
+  (void)length;
+  return IOStatus::OK();
+#else
+  // free OS pages
+  int ret = Fadvise(fd_, offset, length, POSIX_FADV_DONTNEED);
+  if (ret == 0) {
+    return IOStatus::OK();
+  }
+  return IOError("While fadvise NotNeeded", filename_, errno);
+#endif
+}
+
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+IOStatus PosixWritableFile::Allocate(uint64_t offset, uint64_t len,
+                                     const IOOptions& /*opts*/,
+                                     IODebugContext* /*dbg*/) {
+  assert(offset <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  assert(len <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  TEST_KILL_RANDOM("PosixWritableFile::Allocate:0", rocksdb_kill_odds);
+  IOSTATS_TIMER_GUARD(allocate_nanos);
+  int alloc_status = 0;
+  if (allow_fallocate_) {
+    alloc_status =
+        fallocate(fd_, fallocate_with_keep_size_ ? FALLOC_FL_KEEP_SIZE : 0,
+                  static_cast<off_t>(offset), static_cast<off_t>(len));
+  }
+  if (alloc_status == 0) {
+    return IOStatus::OK();
+  } else {
+    return IOError(
+        "While fallocate offset " + ToString(offset) + " len " + ToString(len),
+        filename_, errno);
+  }
+}
+#endif
+
+IOStatus PosixWritableFile::RangeSync(uint64_t offset, uint64_t nbytes,
+                                      const IOOptions& opts,
+                                      IODebugContext* dbg) {
+#ifdef ROCKSDB_RANGESYNC_PRESENT
+  assert(offset <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  assert(nbytes <= static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
+  if (sync_file_range_supported_) {
+    int ret;
+    if (strict_bytes_per_sync_) {
+      // Specifying `SYNC_FILE_RANGE_WAIT_BEFORE` together with an offset/length
+      // that spans all bytes written so far tells `sync_file_range` to wait for
+      // any outstanding writeback requests to finish before issuing a new one.
+      ret =
+          sync_file_range(fd_, 0, static_cast<off_t>(offset + nbytes),
+                          SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE);
+    } else {
+      ret = sync_file_range(fd_, static_cast<off_t>(offset),
+                            static_cast<off_t>(nbytes), SYNC_FILE_RANGE_WRITE);
+    }
+    if (ret != 0) {
+      return IOError("While sync_file_range returned " + ToString(ret),
+                     filename_, errno);
+    }
+    return IOStatus::OK();
+  }
+#endif  // ROCKSDB_RANGESYNC_PRESENT
+  return FSWritableFile::RangeSync(offset, nbytes, opts, dbg);
+}
+
+#ifdef OS_LINUX
+size_t PosixWritableFile::GetUniqueId(char* id, size_t max_size) const {
+  return PosixHelper::GetUniqueIdFromFile(fd_, id, max_size);
+}
+#endif
+
+/*
+ * PosixRandomRWFile
+ */
+
+PosixRandomRWFile::PosixRandomRWFile(const std::string& fname, int fd,
+                                     const EnvOptions& /*options*/)
+    : filename_(fname), fd_(fd) {}
+
+PosixRandomRWFile::~PosixRandomRWFile() {
+  if (fd_ >= 0) {
+    Close(IOOptions(), nullptr);
+  }
+}
+
+IOStatus PosixRandomRWFile::Write(uint64_t offset, const Slice& data,
+                                  const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  const char* src = data.data();
+  size_t nbytes = data.size();
+  if (!PosixPositionedWrite(fd_, src, nbytes, static_cast<off_t>(offset))) {
+    return IOError(
+        "While write random read/write file at offset " + ToString(offset),
+        filename_, errno);
+  }
+
+  return IOStatus::OK();
+}
+
+IOStatus PosixRandomRWFile::Read(uint64_t offset, size_t n,
+                                 const IOOptions& /*opts*/, Slice* result,
+                                 char* scratch, IODebugContext* /*dbg*/) const {
+  size_t left = n;
+  char* ptr = scratch;
+  while (left > 0) {
+    ssize_t done = pread(fd_, ptr, left, offset);
+    if (done < 0) {
+      // error while reading from file
+      if (errno == EINTR) {
+        // read was interrupted, try again.
+        continue;
+      }
+      return IOError("While reading random read/write file offset " +
+                         ToString(offset) + " len " + ToString(n),
+                     filename_, errno);
+    } else if (done == 0) {
+      // Nothing more to read
+      break;
+    }
+
+    // Read `done` bytes
+    ptr += done;
+    offset += done;
+    left -= done;
+  }
+
+  *result = Slice(scratch, n - left);
+  return IOStatus::OK();
+}
+
+IOStatus PosixRandomRWFile::Flush(const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  return IOStatus::OK();
+}
+
+IOStatus PosixRandomRWFile::Sync(const IOOptions& /*opts*/,
+                                 IODebugContext* /*dbg*/) {
+  if (fdatasync(fd_) < 0) {
+    return IOError("While fdatasync random read/write file", filename_, errno);
+  }
+  return IOStatus::OK();
+}
+
+IOStatus PosixRandomRWFile::Fsync(const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  if (fsync(fd_) < 0) {
+    return IOError("While fsync random read/write file", filename_, errno);
+  }
+  return IOStatus::OK();
+}
+
+IOStatus PosixRandomRWFile::Close(const IOOptions& /*opts*/,
+                                  IODebugContext* /*dbg*/) {
+  if (close(fd_) < 0) {
+    return IOError("While close random read/write file", filename_, errno);
+  }
+  fd_ = -1;
+  return IOStatus::OK();
+}
+
+PosixMemoryMappedFileBuffer::~PosixMemoryMappedFileBuffer() {
+  // TODO should have error handling though not much we can do...
+  munmap(this->base_, length_);
+}
+
+/*
+ * PosixDirectory
+ */
+
+PosixDirectory::~PosixDirectory() { close(fd_); }
+
+IOStatus PosixDirectory::Fsync(const IOOptions& /*opts*/,
+                               IODebugContext* /*dbg*/) {
+#ifndef OS_AIX
+  if (fsync(fd_) == -1) {
+    return IOError("While fsync", "a directory", errno);
+  }
+#endif
+  return IOStatus::OK();
+}
+}  // namespace ROCKSDB_NAMESPACE
+#endif
diff --git a/src/rocksdb/env/io_posix.h b/src/rocksdb/env/io_posix.h
new file mode 100644
index 000000000..535bd99cd
--- /dev/null
+++ b/src/rocksdb/env/io_posix.h
@@ -0,0 +1,326 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+#include <errno.h>
+#if defined(ROCKSDB_IOURING_PRESENT)
+#include <liburing.h>
+#include <sys/uio.h>
+#endif
+#include <unistd.h>
+#include <atomic>
+#include <string>
+#include "rocksdb/env.h"
+#include "util/thread_local.h"
+#include "rocksdb/file_system.h"
+#include "rocksdb/io_status.h"
+
+// For non linux platform, the following macros are used only as place
+// holder.
+#if !(defined OS_LINUX) && !(defined CYGWIN) && !(defined OS_AIX)
+#define POSIX_FADV_NORMAL 0     /* [MC1] no further special treatment */
+#define POSIX_FADV_RANDOM 1     /* [MC1] expect random page refs */
+#define POSIX_FADV_SEQUENTIAL 2 /* [MC1] expect sequential page refs */
+#define POSIX_FADV_WILLNEED 3   /* [MC1] will need these pages */
+#define POSIX_FADV_DONTNEED 4   /* [MC1] dont need these pages */
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+static std::string IOErrorMsg(const std::string& context,
+                              const std::string& file_name) {
+  if (file_name.empty()) {
+    return context;
+  }
+  return context + ": " + file_name;
+}
+
+// file_name can be left empty if it is not unkown.
+static IOStatus IOError(const std::string& context,
+                        const std::string& file_name, int err_number) {
+  switch (err_number) {
+    case ENOSPC: {
+      IOStatus s = IOStatus::NoSpace(IOErrorMsg(context, file_name),
+                                     strerror(err_number));
+      s.SetRetryable(true);
+      return s;
+    }
+  case ESTALE:
+    return IOStatus::IOError(IOStatus::kStaleFile);
+  case ENOENT:
+    return IOStatus::PathNotFound(IOErrorMsg(context, file_name),
+                                  strerror(err_number));
+  default:
+    return IOStatus::IOError(IOErrorMsg(context, file_name),
+                             strerror(err_number));
+  }
+}
+
+class PosixHelper {
+ public:
+  static size_t GetUniqueIdFromFile(int fd, char* id, size_t max_size);
+};
+
+class PosixSequentialFile : public FSSequentialFile {
+ private:
+  std::string filename_;
+  FILE* file_;
+  int fd_;
+  bool use_direct_io_;
+  size_t logical_sector_size_;
+
+ public:
+  PosixSequentialFile(const std::string& fname, FILE* file, int fd,
+                      const EnvOptions& options);
+  virtual ~PosixSequentialFile();
+
+  virtual IOStatus Read(size_t n, const IOOptions& opts, Slice* result,
+                        char* scratch, IODebugContext* dbg) override;
+  virtual IOStatus PositionedRead(uint64_t offset, size_t n,
+                                  const IOOptions& opts, Slice* result,
+                                  char* scratch, IODebugContext* dbg) override;
+  virtual IOStatus Skip(uint64_t n) override;
+  virtual IOStatus InvalidateCache(size_t offset, size_t length) override;
+  virtual bool use_direct_io() const override { return use_direct_io_; }
+  virtual size_t GetRequiredBufferAlignment() const override {
+    return logical_sector_size_;
+  }
+};
+
+#if defined(ROCKSDB_IOURING_PRESENT)
+// io_uring instance queue depth
+const unsigned int kIoUringDepth = 256;
+
+inline void DeleteIOUring(void* p) {
+  struct io_uring* iu = static_cast<struct io_uring*>(p);
+  delete iu;
+}
+
+inline struct io_uring* CreateIOUring() {
+  struct io_uring* new_io_uring = new struct io_uring;
+  int ret = io_uring_queue_init(kIoUringDepth, new_io_uring, 0);
+  if (ret) {
+    delete new_io_uring;
+    new_io_uring = nullptr;
+  }
+  return new_io_uring;
+}
+#endif  // defined(ROCKSDB_IOURING_PRESENT)
+
+class PosixRandomAccessFile : public FSRandomAccessFile {
+ protected:
+  std::string filename_;
+  int fd_;
+  bool use_direct_io_;
+  size_t logical_sector_size_;
+#if defined(ROCKSDB_IOURING_PRESENT)
+  ThreadLocalPtr* thread_local_io_urings_;
+#endif
+
+ public:
+  PosixRandomAccessFile(const std::string& fname, int fd,
+                        const EnvOptions& options
+#if defined(ROCKSDB_IOURING_PRESENT)
+                        ,
+                        ThreadLocalPtr* thread_local_io_urings
+#endif
+  );
+  virtual ~PosixRandomAccessFile();
+
+  virtual IOStatus Read(uint64_t offset, size_t n, const IOOptions& opts,
+                        Slice* result, char* scratch,
+                        IODebugContext* dbg) const override;
+
+  virtual IOStatus MultiRead(FSReadRequest* reqs, size_t num_reqs,
+                             const IOOptions& options,
+                             IODebugContext* dbg) override;
+
+  virtual IOStatus Prefetch(uint64_t offset, size_t n, const IOOptions& opts,
+                            IODebugContext* dbg) override;
+
+#if defined(OS_LINUX) || defined(OS_MACOSX) || defined(OS_AIX)
+  virtual size_t GetUniqueId(char* id, size_t max_size) const override;
+#endif
+  virtual void Hint(AccessPattern pattern) override;
+  virtual IOStatus InvalidateCache(size_t offset, size_t length) override;
+  virtual bool use_direct_io() const override { return use_direct_io_; }
+  virtual size_t GetRequiredBufferAlignment() const override {
+    return logical_sector_size_;
+  }
+};
+
+class PosixWritableFile : public FSWritableFile {
+ protected:
+  const std::string filename_;
+  const bool use_direct_io_;
+  int fd_;
+  uint64_t filesize_;
+  size_t logical_sector_size_;
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  bool allow_fallocate_;
+  bool fallocate_with_keep_size_;
+#endif
+#ifdef ROCKSDB_RANGESYNC_PRESENT
+  // Even if the syscall is present, the filesystem may still not properly
+  // support it, so we need to do a dynamic check too.
+  bool sync_file_range_supported_;
+#endif  // ROCKSDB_RANGESYNC_PRESENT
+
+ public:
+  explicit PosixWritableFile(const std::string& fname, int fd,
+                             const EnvOptions& options);
+  virtual ~PosixWritableFile();
+
+  // Need to implement this so the file is truncated correctly
+  // with direct I/O
+  virtual IOStatus Truncate(uint64_t size, const IOOptions& opts,
+                            IODebugContext* dbg) override;
+  virtual IOStatus Close(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Append(const Slice& data, const IOOptions& opts,
+                          IODebugContext* dbg) override;
+  virtual IOStatus PositionedAppend(const Slice& data, uint64_t offset,
+                                    const IOOptions& opts,
+                                    IODebugContext* dbg) override;
+  virtual IOStatus Flush(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Sync(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Fsync(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual bool IsSyncThreadSafe() const override;
+  virtual bool use_direct_io() const override { return use_direct_io_; }
+  virtual void SetWriteLifeTimeHint(Env::WriteLifeTimeHint hint) override;
+  virtual uint64_t GetFileSize(const IOOptions& opts,
+                               IODebugContext* dbg) override;
+  virtual IOStatus InvalidateCache(size_t offset, size_t length) override;
+  virtual size_t GetRequiredBufferAlignment() const override {
+    return logical_sector_size_;
+  }
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  virtual IOStatus Allocate(uint64_t offset, uint64_t len,
+                            const IOOptions& opts,
+                            IODebugContext* dbg) override;
+#endif
+  virtual IOStatus RangeSync(uint64_t offset, uint64_t nbytes,
+                             const IOOptions& opts,
+                             IODebugContext* dbg) override;
+#ifdef OS_LINUX
+  virtual size_t GetUniqueId(char* id, size_t max_size) const override;
+#endif
+};
+
+// mmap() based random-access
+class PosixMmapReadableFile : public FSRandomAccessFile {
+ private:
+  int fd_;
+  std::string filename_;
+  void* mmapped_region_;
+  size_t length_;
+
+ public:
+  PosixMmapReadableFile(const int fd, const std::string& fname, void* base,
+                        size_t length, const EnvOptions& options);
+  virtual ~PosixMmapReadableFile();
+  virtual IOStatus Read(uint64_t offset, size_t n, const IOOptions& opts,
+                        Slice* result, char* scratch,
+                        IODebugContext* dbg) const override;
+  virtual IOStatus InvalidateCache(size_t offset, size_t length) override;
+};
+
+class PosixMmapFile : public FSWritableFile {
+ private:
+  std::string filename_;
+  int fd_;
+  size_t page_size_;
+  size_t map_size_;       // How much extra memory to map at a time
+  char* base_;            // The mapped region
+  char* limit_;           // Limit of the mapped region
+  char* dst_;             // Where to write next  (in range [base_,limit_])
+  char* last_sync_;       // Where have we synced up to
+  uint64_t file_offset_;  // Offset of base_ in file
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  bool allow_fallocate_;  // If false, fallocate calls are bypassed
+  bool fallocate_with_keep_size_;
+#endif
+
+  // Roundup x to a multiple of y
+  static size_t Roundup(size_t x, size_t y) { return ((x + y - 1) / y) * y; }
+
+  size_t TruncateToPageBoundary(size_t s) {
+    s -= (s & (page_size_ - 1));
+    assert((s % page_size_) == 0);
+    return s;
+  }
+
+  IOStatus MapNewRegion();
+  IOStatus UnmapCurrentRegion();
+  IOStatus Msync();
+
+ public:
+  PosixMmapFile(const std::string& fname, int fd, size_t page_size,
+                const EnvOptions& options);
+  ~PosixMmapFile();
+
+  // Means Close() will properly take care of truncate
+  // and it does not need any additional information
+  virtual IOStatus Truncate(uint64_t /*size*/, const IOOptions& /*opts*/,
+                            IODebugContext* /*dbg*/) override {
+    return IOStatus::OK();
+  }
+  virtual IOStatus Close(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Append(const Slice& data, const IOOptions& opts,
+                          IODebugContext* dbg) override;
+  virtual IOStatus Flush(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Sync(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Fsync(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual uint64_t GetFileSize(const IOOptions& opts,
+                               IODebugContext* dbg) override;
+  virtual IOStatus InvalidateCache(size_t offset, size_t length) override;
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+  virtual IOStatus Allocate(uint64_t offset, uint64_t len,
+                            const IOOptions& opts,
+                            IODebugContext* dbg) override;
+#endif
+};
+
+class PosixRandomRWFile : public FSRandomRWFile {
+ public:
+  explicit PosixRandomRWFile(const std::string& fname, int fd,
+                             const EnvOptions& options);
+  virtual ~PosixRandomRWFile();
+
+  virtual IOStatus Write(uint64_t offset, const Slice& data,
+                         const IOOptions& opts, IODebugContext* dbg) override;
+
+  virtual IOStatus Read(uint64_t offset, size_t n, const IOOptions& opts,
+                        Slice* result, char* scratch,
+                        IODebugContext* dbg) const override;
+
+  virtual IOStatus Flush(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Sync(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Fsync(const IOOptions& opts, IODebugContext* dbg) override;
+  virtual IOStatus Close(const IOOptions& opts, IODebugContext* dbg) override;
+
+ private:
+  const std::string filename_;
+  int fd_;
+};
+
+struct PosixMemoryMappedFileBuffer : public MemoryMappedFileBuffer {
+  PosixMemoryMappedFileBuffer(void* _base, size_t _length)
+      : MemoryMappedFileBuffer(_base, _length) {}
+  virtual ~PosixMemoryMappedFileBuffer();
+};
+
+class PosixDirectory : public FSDirectory {
+ public:
+  explicit PosixDirectory(int fd) : fd_(fd) {}
+  ~PosixDirectory();
+  virtual IOStatus Fsync(const IOOptions& opts, IODebugContext* dbg) override;
+
+ private:
+  int fd_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/mock_env.cc b/src/rocksdb/env/mock_env.cc
new file mode 100644
index 000000000..c246c13e1
--- /dev/null
+++ b/src/rocksdb/env/mock_env.cc
@@ -0,0 +1,774 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "env/mock_env.h"
+#include <algorithm>
+#include <chrono>
+#include "port/sys_time.h"
+#include "util/cast_util.h"
+#include "util/murmurhash.h"
+#include "util/random.h"
+#include "util/rate_limiter.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class MemFile {
+ public:
+  explicit MemFile(Env* env, const std::string& fn, bool _is_lock_file = false)
+      : env_(env),
+        fn_(fn),
+        refs_(0),
+        is_lock_file_(_is_lock_file),
+        locked_(false),
+        size_(0),
+        modified_time_(Now()),
+        rnd_(static_cast<uint32_t>(
+            MurmurHash(fn.data(), static_cast<int>(fn.size()), 0))),
+        fsynced_bytes_(0) {}
+  // No copying allowed.
+  MemFile(const MemFile&) = delete;
+  void operator=(const MemFile&) = delete;
+
+  void Ref() {
+    MutexLock lock(&mutex_);
+    ++refs_;
+  }
+
+  bool is_lock_file() const { return is_lock_file_; }
+
+  bool Lock() {
+    assert(is_lock_file_);
+    MutexLock lock(&mutex_);
+    if (locked_) {
+      return false;
+    } else {
+      locked_ = true;
+      return true;
+    }
+  }
+
+  void Unlock() {
+    assert(is_lock_file_);
+    MutexLock lock(&mutex_);
+    locked_ = false;
+  }
+
+  void Unref() {
+    bool do_delete = false;
+    {
+      MutexLock lock(&mutex_);
+      --refs_;
+      assert(refs_ >= 0);
+      if (refs_ <= 0) {
+        do_delete = true;
+      }
+    }
+
+    if (do_delete) {
+      delete this;
+    }
+  }
+
+  uint64_t Size() const { return size_; }
+
+  void Truncate(size_t size) {
+    MutexLock lock(&mutex_);
+    if (size < size_) {
+      data_.resize(size);
+      size_ = size;
+    }
+  }
+
+  void CorruptBuffer() {
+    if (fsynced_bytes_ >= size_) {
+      return;
+    }
+    uint64_t buffered_bytes = size_ - fsynced_bytes_;
+    uint64_t start =
+        fsynced_bytes_ + rnd_.Uniform(static_cast<int>(buffered_bytes));
+    uint64_t end = std::min(start + 512, size_.load());
+    MutexLock lock(&mutex_);
+    for (uint64_t pos = start; pos < end; ++pos) {
+      data_[static_cast<size_t>(pos)] = static_cast<char>(rnd_.Uniform(256));
+    }
+  }
+
+  Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const {
+    MutexLock lock(&mutex_);
+    const uint64_t available = Size() - std::min(Size(), offset);
+    size_t offset_ = static_cast<size_t>(offset);
+    if (n > available) {
+      n = static_cast<size_t>(available);
+    }
+    if (n == 0) {
+      *result = Slice();
+      return Status::OK();
+    }
+    if (scratch) {
+      memcpy(scratch, &(data_[offset_]), n);
+      *result = Slice(scratch, n);
+    } else {
+      *result = Slice(&(data_[offset_]), n);
+    }
+    return Status::OK();
+  }
+
+  Status Write(uint64_t offset, const Slice& data) {
+    MutexLock lock(&mutex_);
+    size_t offset_ = static_cast<size_t>(offset);
+    if (offset + data.size() > data_.size()) {
+      data_.resize(offset_ + data.size());
+    }
+    data_.replace(offset_, data.size(), data.data(), data.size());
+    size_ = data_.size();
+    modified_time_ = Now();
+    return Status::OK();
+  }
+
+  Status Append(const Slice& data) {
+    MutexLock lock(&mutex_);
+    data_.append(data.data(), data.size());
+    size_ = data_.size();
+    modified_time_ = Now();
+    return Status::OK();
+  }
+
+  Status Fsync() {
+    fsynced_bytes_ = size_.load();
+    return Status::OK();
+  }
+
+  uint64_t ModifiedTime() const { return modified_time_; }
+
+ private:
+  uint64_t Now() {
+    int64_t unix_time = 0;
+    auto s = env_->GetCurrentTime(&unix_time);
+    assert(s.ok());
+    return static_cast<uint64_t>(unix_time);
+  }
+
+  // Private since only Unref() should be used to delete it.
+  ~MemFile() { assert(refs_ == 0); }
+
+  Env* env_;
+  const std::string fn_;
+  mutable port::Mutex mutex_;
+  int refs_;
+  bool is_lock_file_;
+  bool locked_;
+
+  // Data written into this file, all bytes before fsynced_bytes are
+  // persistent.
+  std::string data_;
+  std::atomic<uint64_t> size_;
+  std::atomic<uint64_t> modified_time_;
+
+  Random rnd_;
+  std::atomic<uint64_t> fsynced_bytes_;
+};
+
+namespace {
+
+class MockSequentialFile : public SequentialFile {
+ public:
+  explicit MockSequentialFile(MemFile* file) : file_(file), pos_(0) {
+    file_->Ref();
+  }
+
+  ~MockSequentialFile() override { file_->Unref(); }
+
+  Status Read(size_t n, Slice* result, char* scratch) override {
+    Status s = file_->Read(pos_, n, result, scratch);
+    if (s.ok()) {
+      pos_ += result->size();
+    }
+    return s;
+  }
+
+  Status Skip(uint64_t n) override {
+    if (pos_ > file_->Size()) {
+      return Status::IOError("pos_ > file_->Size()");
+    }
+    const uint64_t available = file_->Size() - pos_;
+    if (n > available) {
+      n = available;
+    }
+    pos_ += static_cast<size_t>(n);
+    return Status::OK();
+  }
+
+ private:
+  MemFile* file_;
+  size_t pos_;
+};
+
+class MockRandomAccessFile : public RandomAccessFile {
+ public:
+  explicit MockRandomAccessFile(MemFile* file) : file_(file) { file_->Ref(); }
+
+  ~MockRandomAccessFile() override { file_->Unref(); }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    return file_->Read(offset, n, result, scratch);
+  }
+
+ private:
+  MemFile* file_;
+};
+
+class MockRandomRWFile : public RandomRWFile {
+ public:
+  explicit MockRandomRWFile(MemFile* file) : file_(file) { file_->Ref(); }
+
+  ~MockRandomRWFile() override { file_->Unref(); }
+
+  Status Write(uint64_t offset, const Slice& data) override {
+    return file_->Write(offset, data);
+  }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    return file_->Read(offset, n, result, scratch);
+  }
+
+  Status Close() override { return file_->Fsync(); }
+
+  Status Flush() override { return Status::OK(); }
+
+  Status Sync() override { return file_->Fsync(); }
+
+ private:
+  MemFile* file_;
+};
+
+class MockWritableFile : public WritableFile {
+ public:
+  MockWritableFile(MemFile* file, RateLimiter* rate_limiter)
+      : file_(file), rate_limiter_(rate_limiter) {
+    file_->Ref();
+  }
+
+  ~MockWritableFile() override { file_->Unref(); }
+
+  Status Append(const Slice& data) override {
+    size_t bytes_written = 0;
+    while (bytes_written < data.size()) {
+      auto bytes = RequestToken(data.size() - bytes_written);
+      Status s = file_->Append(Slice(data.data() + bytes_written, bytes));
+      if (!s.ok()) {
+        return s;
+      }
+      bytes_written += bytes;
+    }
+    return Status::OK();
+  }
+  Status Truncate(uint64_t size) override {
+    file_->Truncate(static_cast<size_t>(size));
+    return Status::OK();
+  }
+  Status Close() override { return file_->Fsync(); }
+
+  Status Flush() override { return Status::OK(); }
+
+  Status Sync() override { return file_->Fsync(); }
+
+  uint64_t GetFileSize() override { return file_->Size(); }
+
+ private:
+  inline size_t RequestToken(size_t bytes) {
+    if (rate_limiter_ && io_priority_ < Env::IO_TOTAL) {
+      bytes = std::min(
+          bytes, static_cast<size_t>(rate_limiter_->GetSingleBurstBytes()));
+      rate_limiter_->Request(bytes, io_priority_);
+    }
+    return bytes;
+  }
+
+  MemFile* file_;
+  RateLimiter* rate_limiter_;
+};
+
+class MockEnvDirectory : public Directory {
+ public:
+  Status Fsync() override { return Status::OK(); }
+};
+
+class MockEnvFileLock : public FileLock {
+ public:
+  explicit MockEnvFileLock(const std::string& fname) : fname_(fname) {}
+
+  std::string FileName() const { return fname_; }
+
+ private:
+  const std::string fname_;
+};
+
+class TestMemLogger : public Logger {
+ private:
+  std::unique_ptr<WritableFile> file_;
+  std::atomic_size_t log_size_;
+  static const uint64_t flush_every_seconds_ = 5;
+  std::atomic_uint_fast64_t last_flush_micros_;
+  Env* env_;
+  std::atomic<bool> flush_pending_;
+
+ public:
+  TestMemLogger(std::unique_ptr<WritableFile> f, Env* env,
+                const InfoLogLevel log_level = InfoLogLevel::ERROR_LEVEL)
+      : Logger(log_level),
+        file_(std::move(f)),
+        log_size_(0),
+        last_flush_micros_(0),
+        env_(env),
+        flush_pending_(false) {}
+  ~TestMemLogger() override {}
+
+  void Flush() override {
+    if (flush_pending_) {
+      flush_pending_ = false;
+    }
+    last_flush_micros_ = env_->NowMicros();
+  }
+
+  using Logger::Logv;
+  void Logv(const char* format, va_list ap) override {
+    // We try twice: the first time with a fixed-size stack allocated buffer,
+    // and the second time with a much larger dynamically allocated buffer.
+    char buffer[500];
+    for (int iter = 0; iter < 2; iter++) {
+      char* base;
+      int bufsize;
+      if (iter == 0) {
+        bufsize = sizeof(buffer);
+        base = buffer;
+      } else {
+        bufsize = 30000;
+        base = new char[bufsize];
+      }
+      char* p = base;
+      char* limit = base + bufsize;
+
+      struct timeval now_tv;
+      gettimeofday(&now_tv, nullptr);
+      const time_t seconds = now_tv.tv_sec;
+      struct tm t;
+      memset(&t, 0, sizeof(t));
+      struct tm* ret __attribute__((__unused__));
+      ret = localtime_r(&seconds, &t);
+      assert(ret);
+      p += snprintf(p, limit - p, "%04d/%02d/%02d-%02d:%02d:%02d.%06d ",
+                    t.tm_year + 1900, t.tm_mon + 1, t.tm_mday, t.tm_hour,
+                    t.tm_min, t.tm_sec, static_cast<int>(now_tv.tv_usec));
+
+      // Print the message
+      if (p < limit) {
+        va_list backup_ap;
+        va_copy(backup_ap, ap);
+        p += vsnprintf(p, limit - p, format, backup_ap);
+        va_end(backup_ap);
+      }
+
+      // Truncate to available space if necessary
+      if (p >= limit) {
+        if (iter == 0) {
+          continue;  // Try again with larger buffer
+        } else {
+          p = limit - 1;
+        }
+      }
+
+      // Add newline if necessary
+      if (p == base || p[-1] != '\n') {
+        *p++ = '\n';
+      }
+
+      assert(p <= limit);
+      const size_t write_size = p - base;
+
+      file_->Append(Slice(base, write_size));
+      flush_pending_ = true;
+      log_size_ += write_size;
+      uint64_t now_micros =
+          static_cast<uint64_t>(now_tv.tv_sec) * 1000000 + now_tv.tv_usec;
+      if (now_micros - last_flush_micros_ >= flush_every_seconds_ * 1000000) {
+        flush_pending_ = false;
+        last_flush_micros_ = now_micros;
+      }
+      if (base != buffer) {
+        delete[] base;
+      }
+      break;
+    }
+  }
+  size_t GetLogFileSize() const override { return log_size_; }
+};
+
+}  // Anonymous namespace
+
+MockEnv::MockEnv(Env* base_env) : EnvWrapper(base_env), fake_sleep_micros_(0) {}
+
+MockEnv::~MockEnv() {
+  for (FileSystem::iterator i = file_map_.begin(); i != file_map_.end(); ++i) {
+    i->second->Unref();
+  }
+}
+
+// Partial implementation of the Env interface.
+Status MockEnv::NewSequentialFile(const std::string& fname,
+                                  std::unique_ptr<SequentialFile>* result,
+                                  const EnvOptions& /*soptions*/) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(fn) == file_map_.end()) {
+    *result = nullptr;
+    return Status::IOError(fn, "File not found");
+  }
+  auto* f = file_map_[fn];
+  if (f->is_lock_file()) {
+    return Status::InvalidArgument(fn, "Cannot open a lock file.");
+  }
+  result->reset(new MockSequentialFile(f));
+  return Status::OK();
+}
+
+Status MockEnv::NewRandomAccessFile(const std::string& fname,
+                                    std::unique_ptr<RandomAccessFile>* result,
+                                    const EnvOptions& /*soptions*/) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(fn) == file_map_.end()) {
+    *result = nullptr;
+    return Status::IOError(fn, "File not found");
+  }
+  auto* f = file_map_[fn];
+  if (f->is_lock_file()) {
+    return Status::InvalidArgument(fn, "Cannot open a lock file.");
+  }
+  result->reset(new MockRandomAccessFile(f));
+  return Status::OK();
+}
+
+Status MockEnv::NewRandomRWFile(const std::string& fname,
+                                std::unique_ptr<RandomRWFile>* result,
+                                const EnvOptions& /*soptions*/) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(fn) == file_map_.end()) {
+    *result = nullptr;
+    return Status::IOError(fn, "File not found");
+  }
+  auto* f = file_map_[fn];
+  if (f->is_lock_file()) {
+    return Status::InvalidArgument(fn, "Cannot open a lock file.");
+  }
+  result->reset(new MockRandomRWFile(f));
+  return Status::OK();
+}
+
+Status MockEnv::ReuseWritableFile(const std::string& fname,
+                                  const std::string& old_fname,
+                                  std::unique_ptr<WritableFile>* result,
+                                  const EnvOptions& options) {
+  auto s = RenameFile(old_fname, fname);
+  if (!s.ok()) {
+    return s;
+  }
+  result->reset();
+  return NewWritableFile(fname, result, options);
+}
+
+Status MockEnv::NewWritableFile(const std::string& fname,
+                                std::unique_ptr<WritableFile>* result,
+                                const EnvOptions& env_options) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(fn) != file_map_.end()) {
+    DeleteFileInternal(fn);
+  }
+  MemFile* file = new MemFile(this, fn, false);
+  file->Ref();
+  file_map_[fn] = file;
+
+  result->reset(new MockWritableFile(file, env_options.rate_limiter));
+  return Status::OK();
+}
+
+Status MockEnv::NewDirectory(const std::string& /*name*/,
+                             std::unique_ptr<Directory>* result) {
+  result->reset(new MockEnvDirectory());
+  return Status::OK();
+}
+
+Status MockEnv::FileExists(const std::string& fname) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(fn) != file_map_.end()) {
+    // File exists
+    return Status::OK();
+  }
+  // Now also check if fn exists as a dir
+  for (const auto& iter : file_map_) {
+    const std::string& filename = iter.first;
+    if (filename.size() >= fn.size() + 1 && filename[fn.size()] == '/' &&
+        Slice(filename).starts_with(Slice(fn))) {
+      return Status::OK();
+    }
+  }
+  return Status::NotFound();
+}
+
+Status MockEnv::GetChildren(const std::string& dir,
+                            std::vector<std::string>* result) {
+  auto d = NormalizePath(dir);
+  bool found_dir = false;
+  {
+    MutexLock lock(&mutex_);
+    result->clear();
+    for (const auto& iter : file_map_) {
+      const std::string& filename = iter.first;
+
+      if (filename == d) {
+        found_dir = true;
+      } else if (filename.size() >= d.size() + 1 && filename[d.size()] == '/' &&
+                 Slice(filename).starts_with(Slice(d))) {
+        found_dir = true;
+        size_t next_slash = filename.find('/', d.size() + 1);
+        if (next_slash != std::string::npos) {
+          result->push_back(
+              filename.substr(d.size() + 1, next_slash - d.size() - 1));
+        } else {
+          result->push_back(filename.substr(d.size() + 1));
+        }
+      }
+    }
+  }
+  result->erase(std::unique(result->begin(), result->end()), result->end());
+  return found_dir ? Status::OK() : Status::NotFound();
+}
+
+void MockEnv::DeleteFileInternal(const std::string& fname) {
+  assert(fname == NormalizePath(fname));
+  const auto& pair = file_map_.find(fname);
+  if (pair != file_map_.end()) {
+    pair->second->Unref();
+    file_map_.erase(fname);
+  }
+}
+
+Status MockEnv::DeleteFile(const std::string& fname) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(fn) == file_map_.end()) {
+    return Status::IOError(fn, "File not found");
+  }
+
+  DeleteFileInternal(fn);
+  return Status::OK();
+}
+
+Status MockEnv::Truncate(const std::string& fname, size_t size) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  auto iter = file_map_.find(fn);
+  if (iter == file_map_.end()) {
+    return Status::IOError(fn, "File not found");
+  }
+  iter->second->Truncate(size);
+  return Status::OK();
+}
+
+Status MockEnv::CreateDir(const std::string& dirname) {
+  auto dn = NormalizePath(dirname);
+  if (file_map_.find(dn) == file_map_.end()) {
+    MemFile* file = new MemFile(this, dn, false);
+    file->Ref();
+    file_map_[dn] = file;
+  } else {
+    return Status::IOError();
+  }
+  return Status::OK();
+}
+
+Status MockEnv::CreateDirIfMissing(const std::string& dirname) {
+  CreateDir(dirname);
+  return Status::OK();
+}
+
+Status MockEnv::DeleteDir(const std::string& dirname) {
+  return DeleteFile(dirname);
+}
+
+Status MockEnv::GetFileSize(const std::string& fname, uint64_t* file_size) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  auto iter = file_map_.find(fn);
+  if (iter == file_map_.end()) {
+    return Status::IOError(fn, "File not found");
+  }
+
+  *file_size = iter->second->Size();
+  return Status::OK();
+}
+
+Status MockEnv::GetFileModificationTime(const std::string& fname,
+                                        uint64_t* time) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  auto iter = file_map_.find(fn);
+  if (iter == file_map_.end()) {
+    return Status::IOError(fn, "File not found");
+  }
+  *time = iter->second->ModifiedTime();
+  return Status::OK();
+}
+
+Status MockEnv::RenameFile(const std::string& src, const std::string& dest) {
+  auto s = NormalizePath(src);
+  auto t = NormalizePath(dest);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(s) == file_map_.end()) {
+    return Status::IOError(s, "File not found");
+  }
+
+  DeleteFileInternal(t);
+  file_map_[t] = file_map_[s];
+  file_map_.erase(s);
+  return Status::OK();
+}
+
+Status MockEnv::LinkFile(const std::string& src, const std::string& dest) {
+  auto s = NormalizePath(src);
+  auto t = NormalizePath(dest);
+  MutexLock lock(&mutex_);
+  if (file_map_.find(s) == file_map_.end()) {
+    return Status::IOError(s, "File not found");
+  }
+
+  DeleteFileInternal(t);
+  file_map_[t] = file_map_[s];
+  file_map_[t]->Ref();  // Otherwise it might get deleted when noone uses s
+  return Status::OK();
+}
+
+Status MockEnv::NewLogger(const std::string& fname,
+                          std::shared_ptr<Logger>* result) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  auto iter = file_map_.find(fn);
+  MemFile* file = nullptr;
+  if (iter == file_map_.end()) {
+    file = new MemFile(this, fn, false);
+    file->Ref();
+    file_map_[fn] = file;
+  } else {
+    file = iter->second;
+  }
+  std::unique_ptr<WritableFile> f(new MockWritableFile(file, nullptr));
+  result->reset(new TestMemLogger(std::move(f), this));
+  return Status::OK();
+}
+
+Status MockEnv::LockFile(const std::string& fname, FileLock** flock) {
+  auto fn = NormalizePath(fname);
+  {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(fn) != file_map_.end()) {
+      if (!file_map_[fn]->is_lock_file()) {
+        return Status::InvalidArgument(fname, "Not a lock file.");
+      }
+      if (!file_map_[fn]->Lock()) {
+        return Status::IOError(fn, "Lock is already held.");
+      }
+    } else {
+      auto* file = new MemFile(this, fn, true);
+      file->Ref();
+      file->Lock();
+      file_map_[fn] = file;
+    }
+  }
+  *flock = new MockEnvFileLock(fn);
+  return Status::OK();
+}
+
+Status MockEnv::UnlockFile(FileLock* flock) {
+  std::string fn =
+      static_cast_with_check<MockEnvFileLock, FileLock>(flock)->FileName();
+  {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(fn) != file_map_.end()) {
+      if (!file_map_[fn]->is_lock_file()) {
+        return Status::InvalidArgument(fn, "Not a lock file.");
+      }
+      file_map_[fn]->Unlock();
+    }
+  }
+  delete flock;
+  return Status::OK();
+}
+
+Status MockEnv::GetTestDirectory(std::string* path) {
+  *path = "/test";
+  return Status::OK();
+}
+
+Status MockEnv::GetCurrentTime(int64_t* unix_time) {
+  auto s = EnvWrapper::GetCurrentTime(unix_time);
+  if (s.ok()) {
+    *unix_time += fake_sleep_micros_.load() / (1000 * 1000);
+  }
+  return s;
+}
+
+uint64_t MockEnv::NowMicros() {
+  return EnvWrapper::NowMicros() + fake_sleep_micros_.load();
+}
+
+uint64_t MockEnv::NowNanos() {
+  return EnvWrapper::NowNanos() + fake_sleep_micros_.load() * 1000;
+}
+
+Status MockEnv::CorruptBuffer(const std::string& fname) {
+  auto fn = NormalizePath(fname);
+  MutexLock lock(&mutex_);
+  auto iter = file_map_.find(fn);
+  if (iter == file_map_.end()) {
+    return Status::IOError(fn, "File not found");
+  }
+  iter->second->CorruptBuffer();
+  return Status::OK();
+}
+
+std::string MockEnv::NormalizePath(const std::string path) {
+  std::string dst;
+  for (auto c : path) {
+    if (!dst.empty() && c == '/' && dst.back() == '/') {
+      continue;
+    }
+    dst.push_back(c);
+  }
+  return dst;
+}
+
+void MockEnv::FakeSleepForMicroseconds(int64_t micros) {
+  fake_sleep_micros_.fetch_add(micros);
+}
+
+#ifndef ROCKSDB_LITE
+// This is to maintain the behavior before swithcing from InMemoryEnv to MockEnv
+Env* NewMemEnv(Env* base_env) { return new MockEnv(base_env); }
+
+#else  // ROCKSDB_LITE
+
+Env* NewMemEnv(Env* /*base_env*/) { return nullptr; }
+
+#endif  // !ROCKSDB_LITE
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/mock_env.h b/src/rocksdb/env/mock_env.h
new file mode 100644
index 000000000..145cae067
--- /dev/null
+++ b/src/rocksdb/env/mock_env.h
@@ -0,0 +1,114 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+
+#include <atomic>
+#include <map>
+#include <string>
+#include <vector>
+#include "rocksdb/env.h"
+#include "rocksdb/status.h"
+#include "port/port.h"
+#include "util/mutexlock.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class MemFile;
+class MockEnv : public EnvWrapper {
+ public:
+  explicit MockEnv(Env* base_env);
+
+  virtual ~MockEnv();
+
+  // Partial implementation of the Env interface.
+  virtual Status NewSequentialFile(const std::string& fname,
+                                   std::unique_ptr<SequentialFile>* result,
+                                   const EnvOptions& soptions) override;
+
+  virtual Status NewRandomAccessFile(const std::string& fname,
+                                     std::unique_ptr<RandomAccessFile>* result,
+                                     const EnvOptions& soptions) override;
+
+  virtual Status NewRandomRWFile(const std::string& fname,
+                                 std::unique_ptr<RandomRWFile>* result,
+                                 const EnvOptions& options) override;
+
+  virtual Status ReuseWritableFile(const std::string& fname,
+                                   const std::string& old_fname,
+                                   std::unique_ptr<WritableFile>* result,
+                                   const EnvOptions& options) override;
+
+  virtual Status NewWritableFile(const std::string& fname,
+                                 std::unique_ptr<WritableFile>* result,
+                                 const EnvOptions& env_options) override;
+
+  virtual Status NewDirectory(const std::string& name,
+                              std::unique_ptr<Directory>* result) override;
+
+  virtual Status FileExists(const std::string& fname) override;
+
+  virtual Status GetChildren(const std::string& dir,
+                             std::vector<std::string>* result) override;
+
+  void DeleteFileInternal(const std::string& fname);
+
+  virtual Status DeleteFile(const std::string& fname) override;
+
+  virtual Status Truncate(const std::string& fname, size_t size) override;
+
+  virtual Status CreateDir(const std::string& dirname) override;
+
+  virtual Status CreateDirIfMissing(const std::string& dirname) override;
+
+  virtual Status DeleteDir(const std::string& dirname) override;
+
+  virtual Status GetFileSize(const std::string& fname,
+                             uint64_t* file_size) override;
+
+  virtual Status GetFileModificationTime(const std::string& fname,
+                                         uint64_t* time) override;
+
+  virtual Status RenameFile(const std::string& src,
+                            const std::string& target) override;
+
+  virtual Status LinkFile(const std::string& src,
+                          const std::string& target) override;
+
+  virtual Status NewLogger(const std::string& fname,
+                           std::shared_ptr<Logger>* result) override;
+
+  virtual Status LockFile(const std::string& fname, FileLock** flock) override;
+
+  virtual Status UnlockFile(FileLock* flock) override;
+
+  virtual Status GetTestDirectory(std::string* path) override;
+
+  // Results of these can be affected by FakeSleepForMicroseconds()
+  virtual Status GetCurrentTime(int64_t* unix_time) override;
+  virtual uint64_t NowMicros() override;
+  virtual uint64_t NowNanos() override;
+
+  Status CorruptBuffer(const std::string& fname);
+
+  // Doesn't really sleep, just affects output of GetCurrentTime(), NowMicros()
+  // and NowNanos()
+  void FakeSleepForMicroseconds(int64_t micros);
+
+ private:
+  std::string NormalizePath(const std::string path);
+
+  // Map from filenames to MemFile objects, representing a simple file system.
+  typedef std::map<std::string, MemFile*> FileSystem;
+  port::Mutex mutex_;
+  FileSystem file_map_;  // Protected by mutex_.
+
+  std::atomic<int64_t> fake_sleep_micros_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/env/mock_env_test.cc b/src/rocksdb/env/mock_env_test.cc
new file mode 100644
index 000000000..7f339540d
--- /dev/null
+++ b/src/rocksdb/env/mock_env_test.cc
@@ -0,0 +1,85 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+
+#include "env/mock_env.h"
+
+#include <memory>
+#include <string>
+
+#include "rocksdb/env.h"
+#include "test_util/testharness.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class MockEnvTest : public testing::Test {
+ public:
+  MockEnv* env_;
+  const EnvOptions soptions_;
+
+  MockEnvTest()
+      : env_(new MockEnv(Env::Default())) {
+  }
+  ~MockEnvTest() override { delete env_; }
+};
+
+TEST_F(MockEnvTest, Corrupt) {
+  const std::string kGood = "this is a good string, synced to disk";
+  const std::string kCorrupted = "this part may be corrupted";
+  const std::string kFileName = "/dir/f";
+  std::unique_ptr<WritableFile> writable_file;
+  ASSERT_OK(env_->NewWritableFile(kFileName, &writable_file, soptions_));
+  ASSERT_OK(writable_file->Append(kGood));
+  ASSERT_TRUE(writable_file->GetFileSize() == kGood.size());
+
+  std::string scratch;
+  scratch.resize(kGood.size() + kCorrupted.size() + 16);
+  Slice result;
+  std::unique_ptr<RandomAccessFile> rand_file;
+  ASSERT_OK(env_->NewRandomAccessFile(kFileName, &rand_file, soptions_));
+  ASSERT_OK(rand_file->Read(0, kGood.size(), &result, &(scratch[0])));
+  ASSERT_EQ(result.compare(kGood), 0);
+
+  // Sync + corrupt => no change
+  ASSERT_OK(writable_file->Fsync());
+  ASSERT_OK(dynamic_cast<MockEnv*>(env_)->CorruptBuffer(kFileName));
+  result.clear();
+  ASSERT_OK(rand_file->Read(0, kGood.size(), &result, &(scratch[0])));
+  ASSERT_EQ(result.compare(kGood), 0);
+
+  // Add new data and corrupt it
+  ASSERT_OK(writable_file->Append(kCorrupted));
+  ASSERT_TRUE(writable_file->GetFileSize() == kGood.size() + kCorrupted.size());
+  result.clear();
+  ASSERT_OK(rand_file->Read(kGood.size(), kCorrupted.size(),
+            &result, &(scratch[0])));
+  ASSERT_EQ(result.compare(kCorrupted), 0);
+  // Corrupted
+  ASSERT_OK(dynamic_cast<MockEnv*>(env_)->CorruptBuffer(kFileName));
+  result.clear();
+  ASSERT_OK(rand_file->Read(kGood.size(), kCorrupted.size(),
+            &result, &(scratch[0])));
+  ASSERT_NE(result.compare(kCorrupted), 0);
+}
+
+TEST_F(MockEnvTest, FakeSleeping) {
+  int64_t now = 0;
+  auto s = env_->GetCurrentTime(&now);
+  ASSERT_OK(s);
+  env_->FakeSleepForMicroseconds(3 * 1000 * 1000);
+  int64_t after_sleep = 0;
+  s = env_->GetCurrentTime(&after_sleep);
+  ASSERT_OK(s);
+  auto delta = after_sleep - now;
+  // this will be true unless test runs for 2 seconds
+  ASSERT_TRUE(delta == 3 || delta == 4);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}