Adding upstream version 18.2.2.upstream/18.2.2

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

1 files changed, 1294 insertions, 0 deletions

diff --git a/src/rocksdb/env/fs_posix.cc b/src/rocksdb/env/fs_posix.cc
new file mode 100644
index 000000000..e179a421d
--- /dev/null
+++ b/src/rocksdb/env/fs_posix.cc
@@ -0,0 +1,1294 @@
+//  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
+
+#if !defined(OS_WIN)
+
+#include <dirent.h>
+#ifndef ROCKSDB_NO_DYNAMIC_EXTENSION
+#include <dlfcn.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#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/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/composite_env_wrapper.h"
+#include "env/io_posix.h"
+#include "monitoring/iostats_context_imp.h"
+#include "monitoring/thread_status_updater.h"
+#include "port/lang.h"
+#include "port/port.h"
+#include "rocksdb/options.h"
+#include "rocksdb/slice.h"
+#include "rocksdb/utilities/object_registry.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
+
+extern "C" bool RocksDbIOUringEnable() __attribute__((__weak__));
+
+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
+// Only used for error message.
+struct LockHoldingInfo {
+  int64_t acquire_time;
+  uint64_t acquiring_thread;
+};
+static std::map<std::string, LockHoldingInfo> locked_files;
+static port::Mutex mutex_locked_files;
+
+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_ = /*invalid*/ -1;
+  std::string filename;
+
+  void Clear() {
+    fd_ = -1;
+    filename.clear();
+  }
+
+  virtual ~PosixFileLock() override {
+    // Check for destruction without UnlockFile
+    assert(fd_ == -1);
+  }
+};
+
+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;
+  }
+#else
+  (void)options;
+#endif
+  return flags;
+}
+
+class PosixFileSystem : public FileSystem {
+ public:
+  PosixFileSystem();
+
+  static const char* kClassName() { return "PosixFileSystem"; }
+  const char* Name() const override { return kClassName(); }
+  const char* NickName() const override { return kDefaultName(); }
+
+  ~PosixFileSystem() override {}
+  bool IsInstanceOf(const std::string& name) const override {
+    if (name == "posix") {
+      return true;
+    } else {
+      return FileSystem::IsInstanceOf(name);
+    }
+  }
+
+  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;
+      TEST_SYNC_POINT_CALLBACK("NewSequentialFile: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 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, GetLogicalBlockSizeForReadIfNeeded(options, fname, 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 = IOStatus::OK();
+    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) {
+      s = IOError("While open a file for random read", fname, errno);
+      return s;
+    }
+    SetFD_CLOEXEC(fd, &options);
+
+    if (options.use_mmap_reads) {
+      // 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 {
+        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, GetLogicalBlockSizeForReadIfNeeded(options, fname, fd),
+          options
+#if defined(ROCKSDB_IOURING_PRESENT)
+          ,
+          !IsIOUringEnabled() ? nullptr : 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) {
+      MaybeForceDisableMmap(fd);
+    }
+    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, GetLogicalBlockSizeForWriteIfNeeded(options, 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,
+                                GetLogicalBlockSizeForWriteIfNeeded(
+                                    no_mmap_writes_options, 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) {
+      MaybeForceDisableMmap(fd);
+    }
+    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, GetLogicalBlockSizeForWriteIfNeeded(options, 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,
+                                GetLogicalBlockSizeForWriteIfNeeded(
+                                    no_mmap_writes_options, 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, name));
+    }
+    return IOStatus::OK();
+  }
+
+  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(" + std::to_string(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);
+      }
+    }
+
+    // reset errno before calling readdir()
+    errno = 0;
+    struct dirent* entry;
+
+    while ((entry = readdir(d)) != nullptr) {
+      // filter out '.' and '..' directory entries
+      // which appear only on some platforms
+      const bool ignore =
+          entry->d_type == DT_DIR &&
+          (strcmp(entry->d_name, ".") == 0 ||
+           strcmp(entry->d_name, "..") == 0
+#ifndef ASSERT_STATUS_CHECKED
+           // In case of ASSERT_STATUS_CHECKED, GetChildren support older
+           // version of API for debugging purpose.
+           || opts.do_not_recurse
+#endif
+          );
+      if (!ignore) {
+        result->push_back(entry->d_name);
+      }
+      errno = 0;  // reset errno if readdir() success
+    }
+
+    // always attempt to close the dir
+    const auto pre_close_errno = errno;  // errno may be modified by closedir
+    const int close_result = closedir(d);
+
+    if (pre_close_errno != 0) {
+      // error occurred during readdir
+      return IOError("While readdir", dir, pre_close_errno);
+    }
+
+    if (close_result != 0) {
+      // error occurred during closedir
+      return IOError("While closedir", dir, errno);
+    }
+
+    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 {
+    if (mkdir(name.c_str(), 0755) != 0) {
+      return IOError("While mkdir", name, errno);
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus CreateDirIfMissing(const std::string& name,
+                              const IOOptions& /*opts*/,
+                              IODebugContext* /*dbg*/) override {
+    if (mkdir(name.c_str(), 0755) != 0) {
+      if (errno != EEXIST) {
+        return IOError("While mkdir if missing", name, errno);
+      } else if (!DirExists(name)) {  // Check that name is actually a
+                                      // directory.
+        // Message is taken from mkdir
+        return IOStatus::IOError("`" + name +
+                                 "' exists but is not a directory");
+      }
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus DeleteDir(const std::string& name, const IOOptions& /*opts*/,
+                     IODebugContext* /*dbg*/) override {
+    if (rmdir(name.c_str()) != 0) {
+      return IOError("file rmdir", name, errno);
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus GetFileSize(const std::string& fname, const IOOptions& /*opts*/,
+                       uint64_t* size, IODebugContext* /*dbg*/) override {
+    struct stat sbuf;
+    if (stat(fname.c_str(), &sbuf) != 0) {
+      *size = 0;
+      return IOError("while stat a file for size", fname, errno);
+    } else {
+      *size = sbuf.st_size;
+    }
+    return IOStatus::OK();
+  }
+
+  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 {
+    if (rename(src.c_str(), target.c_str()) != 0) {
+      return IOError("While renaming a file to " + target, src, errno);
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus LinkFile(const std::string& src, const std::string& target,
+                    const IOOptions& /*opts*/,
+                    IODebugContext* /*dbg*/) override {
+    if (link(src.c_str(), target.c_str()) != 0) {
+      if (errno == EXDEV || errno == ENOTSUP) {
+        return IOStatus::NotSupported(errno == EXDEV
+                                          ? "No cross FS links allowed"
+                                          : "Links not supported by FS");
+      }
+      return IOError("while link file to " + target, src, errno);
+    }
+    return IOStatus::OK();
+  }
+
+  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;
+
+    LockHoldingInfo lhi;
+    int64_t current_time = 0;
+    // Ignore status code as the time is only used for error message.
+    SystemClock::Default()
+        ->GetCurrentTime(&current_time)
+        .PermitUncheckedError();
+    lhi.acquire_time = current_time;
+    lhi.acquiring_thread = Env::Default()->GetThreadID();
+
+    mutex_locked_files.Lock();
+    // If it already exists in the locked_files set, then it is already locked,
+    // and fail this lock attempt. Otherwise, insert it into locked_files.
+    // 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
+    const auto it_success = locked_files.insert({fname, lhi});
+    if (it_success.second == false) {
+      LockHoldingInfo prev_info = it_success.first->second;
+      mutex_locked_files.Unlock();
+      errno = ENOLCK;
+      // Note that the thread ID printed is the same one as the one in
+      // posix logger, but posix logger prints it hex format.
+      return IOError("lock hold by current process, acquire time " +
+                         std::to_string(prev_info.acquire_time) +
+                         " acquiring thread " +
+                         std::to_string(prev_info.acquiring_thread),
+                     fname, errno);
+    }
+
+    IOStatus result = IOStatus::OK();
+    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) {
+      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;
+    }
+    if (!result.ok()) {
+      // If there is an error in locking, then remove the pathname from
+      // locked_files. (If we got this far, it did not exist in locked_files
+      // before this call.)
+      locked_files.erase(fname);
+    }
+
+    mutex_locked_files.Unlock();
+    return result;
+  }
+
+  IOStatus UnlockFile(FileLock* lock, const IOOptions& /*opts*/,
+                      IODebugContext* /*dbg*/) override {
+    PosixFileLock* my_lock = reinterpret_cast<PosixFileLock*>(lock);
+    IOStatus result;
+    mutex_locked_files.Lock();
+    // If we are unlocking, then verify that we had locked it earlier,
+    // it should already exist in locked_files. Remove it from locked_files.
+    if (locked_files.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_);
+    my_lock->Clear();
+    delete my_lock;
+    mutex_locked_files.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[4096];
+    char* ret = getcwd(the_path, 4096);
+    if (ret == nullptr) {
+      return IOStatus::IOError(errnoStr(errno).c_str());
+    }
+
+    *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;
+      return CreateDirIfMissing(*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);
+    }
+
+    // sbuf.bfree is total free space available to root
+    // sbuf.bavail is total free space available to unprivileged user
+    //  sbuf.bavail <= sbuf.bfree ... pick correct based upon effective user id
+    if (geteuid()) {
+      // non-zero user is unprivileged, or -1 if error.  take more conservative
+      // size
+      *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bavail);
+    } else {
+      // root user can access all disk space
+      *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bfree);
+    }
+    return IOStatus::OK();
+  }
+
+  IOStatus IsDirectory(const std::string& path, const IOOptions& /*opts*/,
+                       bool* is_dir, IODebugContext* /*dbg*/) override {
+    // First open
+    int fd = -1;
+    int flags = cloexec_flags(O_RDONLY, nullptr);
+    {
+      IOSTATS_TIMER_GUARD(open_nanos);
+      fd = open(path.c_str(), flags);
+    }
+    if (fd < 0) {
+      return IOError("While open for IsDirectory()", path, errno);
+    }
+    IOStatus io_s;
+    struct stat sbuf;
+    if (fstat(fd, &sbuf) < 0) {
+      io_s = IOError("While doing stat for IsDirectory()", path, errno);
+    }
+    close(fd);
+    if (io_s.ok() && nullptr != is_dir) {
+      *is_dir = S_ISDIR(sbuf.st_mode);
+    }
+    return io_s;
+  }
+
+  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;
+  }
+#ifdef OS_LINUX
+  Status RegisterDbPaths(const std::vector<std::string>& paths) override {
+    return logical_block_size_cache_.RefAndCacheLogicalBlockSize(paths);
+  }
+  Status UnregisterDbPaths(const std::vector<std::string>& paths) override {
+    logical_block_size_cache_.UnrefAndTryRemoveCachedLogicalBlockSize(paths);
+    return Status::OK();
+  }
+#endif
+ private:
+  bool forceMmapOff_ = false;  // 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(int fd) {
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+    struct statfs s;
+    if (fstatfs(fd, &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)fd;
+    return false;
+#endif
+  }
+
+  void MaybeForceDisableMmap(int fd) {
+    static std::once_flag s_check_disk_for_mmap_once;
+    assert(this == FileSystem::Default().get());
+    std::call_once(
+        s_check_disk_for_mmap_once,
+        [this](int fdesc) {
+          // this will be executed once in the program's lifetime.
+          // do not use mmapWrite on non ext-3/xfs/tmpfs systems.
+          if (!SupportsFastAllocate(fdesc)) {
+            forceMmapOff_ = true;
+          }
+        },
+        fd);
+  }
+
+#ifdef ROCKSDB_IOURING_PRESENT
+  bool IsIOUringEnabled() {
+    if (RocksDbIOUringEnable && RocksDbIOUringEnable()) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+#endif  // ROCKSDB_IOURING_PRESENT
+
+  // EXPERIMENTAL
+  //
+  // TODO akankshamahajan:
+  // 1. Update Poll API to take into account min_completions
+  // and returns if number of handles in io_handles (any order) completed is
+  // equal to atleast min_completions.
+  // 2. Currently in case of direct_io, Read API is called because of which call
+  // to Poll API fails as it expects IOHandle to be populated.
+  virtual IOStatus Poll(std::vector<void*>& io_handles,
+                        size_t /*min_completions*/) override {
+#if defined(ROCKSDB_IOURING_PRESENT)
+    // io_uring_queue_init.
+    struct io_uring* iu = nullptr;
+    if (thread_local_io_urings_) {
+      iu = static_cast<struct io_uring*>(thread_local_io_urings_->Get());
+    }
+
+    // Init failed, platform doesn't support io_uring.
+    if (iu == nullptr) {
+      return IOStatus::NotSupported("Poll");
+    }
+
+    for (size_t i = 0; i < io_handles.size(); i++) {
+      // The request has been completed in earlier runs.
+      if ((static_cast<Posix_IOHandle*>(io_handles[i]))->is_finished) {
+        continue;
+      }
+      // Loop until IO for io_handles[i] is completed.
+      while (true) {
+        // io_uring_wait_cqe.
+        struct io_uring_cqe* cqe = nullptr;
+        ssize_t ret = io_uring_wait_cqe(iu, &cqe);
+        if (ret) {
+          // abort as it shouldn't be in indeterminate state and there is no
+          // good way currently to handle this error.
+          abort();
+        }
+
+        // Step 3: Populate the request.
+        assert(cqe != nullptr);
+        Posix_IOHandle* posix_handle =
+            static_cast<Posix_IOHandle*>(io_uring_cqe_get_data(cqe));
+        assert(posix_handle->iu == iu);
+        if (posix_handle->iu != iu) {
+          return IOStatus::IOError("");
+        }
+        // Reset cqe data to catch any stray reuse of it
+        static_cast<struct io_uring_cqe*>(cqe)->user_data = 0xd5d5d5d5d5d5d5d5;
+
+        FSReadRequest req;
+        req.scratch = posix_handle->scratch;
+        req.offset = posix_handle->offset;
+        req.len = posix_handle->len;
+
+        size_t finished_len = 0;
+        size_t bytes_read = 0;
+        bool read_again = false;
+        UpdateResult(cqe, "", req.len, posix_handle->iov.iov_len,
+                     true /*async_read*/, posix_handle->use_direct_io,
+                     posix_handle->alignment, finished_len, &req, bytes_read,
+                     read_again);
+        posix_handle->is_finished = true;
+        io_uring_cqe_seen(iu, cqe);
+        posix_handle->cb(req, posix_handle->cb_arg);
+
+        (void)finished_len;
+        (void)bytes_read;
+        (void)read_again;
+
+        if (static_cast<Posix_IOHandle*>(io_handles[i]) == posix_handle) {
+          break;
+        }
+      }
+    }
+    return IOStatus::OK();
+#else
+    (void)io_handles;
+    return IOStatus::NotSupported("Poll");
+#endif
+  }
+
+  virtual IOStatus AbortIO(std::vector<void*>& io_handles) override {
+#if defined(ROCKSDB_IOURING_PRESENT)
+    // io_uring_queue_init.
+    struct io_uring* iu = nullptr;
+    if (thread_local_io_urings_) {
+      iu = static_cast<struct io_uring*>(thread_local_io_urings_->Get());
+    }
+
+    // Init failed, platform doesn't support io_uring.
+    // If Poll is not supported then it didn't submit any request and it should
+    // return OK.
+    if (iu == nullptr) {
+      return IOStatus::OK();
+    }
+
+    for (size_t i = 0; i < io_handles.size(); i++) {
+      Posix_IOHandle* posix_handle =
+          static_cast<Posix_IOHandle*>(io_handles[i]);
+      if (posix_handle->is_finished == true) {
+        continue;
+      }
+      assert(posix_handle->iu == iu);
+      if (posix_handle->iu != iu) {
+        return IOStatus::IOError("");
+      }
+
+      // Prepare the cancel request.
+      struct io_uring_sqe* sqe;
+      sqe = io_uring_get_sqe(iu);
+
+      // In order to cancel the request, sqe->addr of cancel request should
+      // match with the read request submitted which is posix_handle->iov.
+      io_uring_prep_cancel(sqe, &posix_handle->iov, 0);
+      // Sets sqe->user_data to posix_handle.
+      io_uring_sqe_set_data(sqe, posix_handle);
+
+      // submit the request.
+      ssize_t ret = io_uring_submit(iu);
+      if (ret < 0) {
+        fprintf(stderr, "io_uring_submit error: %ld\n", long(ret));
+        return IOStatus::IOError("io_uring_submit() requested but returned " +
+                                 std::to_string(ret));
+      }
+    }
+
+    // After submitting the requests, wait for the requests.
+    for (size_t i = 0; i < io_handles.size(); i++) {
+      if ((static_cast<Posix_IOHandle*>(io_handles[i]))->is_finished) {
+        continue;
+      }
+
+      while (true) {
+        struct io_uring_cqe* cqe = nullptr;
+        ssize_t ret = io_uring_wait_cqe(iu, &cqe);
+        if (ret) {
+          // abort as it shouldn't be in indeterminate state and there is no
+          // good way currently to handle this error.
+          abort();
+        }
+        assert(cqe != nullptr);
+
+        // Returns cqe->user_data.
+        Posix_IOHandle* posix_handle =
+            static_cast<Posix_IOHandle*>(io_uring_cqe_get_data(cqe));
+        assert(posix_handle->iu == iu);
+        if (posix_handle->iu != iu) {
+          return IOStatus::IOError("");
+        }
+        posix_handle->req_count++;
+
+        // Reset cqe data to catch any stray reuse of it
+        static_cast<struct io_uring_cqe*>(cqe)->user_data = 0xd5d5d5d5d5d5d5d5;
+        io_uring_cqe_seen(iu, cqe);
+
+        // - If the request is cancelled successfully, the original request is
+        //   completed with -ECANCELED and the cancel request is completed with
+        //   a result of 0.
+        // - If the request was already running, the original may or
+        //   may not complete in error. The cancel request will complete with
+        //  -EALREADY for that case.
+        // - And finally, if the request to cancel wasn't
+        //   found, the cancel request is completed with -ENOENT.
+        //
+        // Every handle has to wait for 2 requests completion: original one and
+        // the cancel request which is tracked by PosixHandle::req_count.
+        if (posix_handle->req_count == 2 &&
+            static_cast<Posix_IOHandle*>(io_handles[i]) == posix_handle) {
+          posix_handle->is_finished = true;
+          FSReadRequest req;
+          req.status = IOStatus::Aborted();
+          posix_handle->cb(req, posix_handle->cb_arg);
+
+          break;
+        }
+      }
+    }
+    return IOStatus::OK();
+#else
+    // If Poll is not supported then it didn't submit any request and it should
+    // return OK.
+    (void)io_handles;
+    return IOStatus::OK();
+#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_;
+
+#ifdef OS_LINUX
+  static LogicalBlockSizeCache logical_block_size_cache_;
+#endif
+  static size_t GetLogicalBlockSize(const std::string& fname, int fd);
+  // In non-direct IO mode, this directly returns kDefaultPageSize.
+  // Otherwise call GetLogicalBlockSize.
+  static size_t GetLogicalBlockSizeForReadIfNeeded(const EnvOptions& options,
+                                                   const std::string& fname,
+                                                   int fd);
+  static size_t GetLogicalBlockSizeForWriteIfNeeded(const EnvOptions& options,
+                                                    const std::string& fname,
+                                                    int fd);
+};
+
+#ifdef OS_LINUX
+LogicalBlockSizeCache PosixFileSystem::logical_block_size_cache_;
+#endif
+
+size_t PosixFileSystem::GetLogicalBlockSize(const std::string& fname, int fd) {
+#ifdef OS_LINUX
+  return logical_block_size_cache_.GetLogicalBlockSize(fname, fd);
+#else
+  (void)fname;
+  return PosixHelper::GetLogicalBlockSizeOfFd(fd);
+#endif
+}
+
+size_t PosixFileSystem::GetLogicalBlockSizeForReadIfNeeded(
+    const EnvOptions& options, const std::string& fname, int fd) {
+  return options.use_direct_reads
+             ? PosixFileSystem::GetLogicalBlockSize(fname, fd)
+             : kDefaultPageSize;
+}
+
+size_t PosixFileSystem::GetLogicalBlockSizeForWriteIfNeeded(
+    const EnvOptions& options, const std::string& fname, int fd) {
+  return options.use_direct_writes
+             ? PosixFileSystem::GetLogicalBlockSize(fname, fd)
+             : kDefaultPageSize;
+}
+
+PosixFileSystem::PosixFileSystem()
+    : 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_AVOID_DESTRUCTION(std::shared_ptr<FileSystem>, instance)
+  (std::make_shared<PosixFileSystem>());
+  return instance;
+}
+
+#ifndef ROCKSDB_LITE
+static FactoryFunc<FileSystem> posix_filesystem_reg =
+    ObjectLibrary::Default()->AddFactory<FileSystem>(
+        ObjectLibrary::PatternEntry("posix").AddSeparator("://", false),
+        [](const std::string& /* uri */, std::unique_ptr<FileSystem>* f,
+           std::string* /* errmsg */) {
+          f->reset(new PosixFileSystem());
+          return f->get();
+        });
+#endif
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif