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

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

4 files changed, 1679 insertions, 0 deletions

diff --git a/src/blk/kernel/KernelDevice.cc b/src/blk/kernel/KernelDevice.cc
new file mode 100644
index 000000000..d93279965
--- /dev/null
+++ b/src/blk/kernel/KernelDevice.cc
@@ -0,0 +1,1235 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2014 Red Hat
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#include <limits>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/file.h>
+
+#include "KernelDevice.h"
+#include "include/intarith.h"
+#include "include/types.h"
+#include "include/compat.h"
+#include "include/stringify.h"
+#include "common/blkdev.h"
+#include "common/errno.h"
+#if defined(__FreeBSD__)
+#include "bsm/audit_errno.h"
+#endif
+#include "common/debug.h"
+#include "common/numa.h"
+
+#include "global/global_context.h"
+#include "io_uring.h"
+
+#define dout_context cct
+#define dout_subsys ceph_subsys_bdev
+#undef dout_prefix
+#define dout_prefix *_dout << "bdev(" << this << " " << path << ") "
+
+using std::list;
+using std::map;
+using std::string;
+using std::vector;
+
+using ceph::bufferlist;
+using ceph::bufferptr;
+using ceph::make_timespan;
+using ceph::mono_clock;
+using ceph::operator <<;
+
+KernelDevice::KernelDevice(CephContext* cct, aio_callback_t cb, void *cbpriv, aio_callback_t d_cb, void *d_cbpriv)
+  : BlockDevice(cct, cb, cbpriv),
+    aio(false), dio(false),
+    discard_callback(d_cb),
+    discard_callback_priv(d_cbpriv),
+    aio_stop(false),
+    discard_started(false),
+    discard_stop(false),
+    aio_thread(this),
+    discard_thread(this),
+    injecting_crash(0)
+{
+  fd_directs.resize(WRITE_LIFE_MAX, -1);
+  fd_buffereds.resize(WRITE_LIFE_MAX, -1);
+
+  bool use_ioring = cct->_conf.get_val<bool>("bdev_ioring");
+  unsigned int iodepth = cct->_conf->bdev_aio_max_queue_depth;
+
+  if (use_ioring && ioring_queue_t::supported()) {
+    bool use_ioring_hipri = cct->_conf.get_val<bool>("bdev_ioring_hipri");
+    bool use_ioring_sqthread_poll = cct->_conf.get_val<bool>("bdev_ioring_sqthread_poll");
+    io_queue = std::make_unique<ioring_queue_t>(iodepth, use_ioring_hipri, use_ioring_sqthread_poll);
+  } else {
+    static bool once;
+    if (use_ioring && !once) {
+      derr << "WARNING: io_uring API is not supported! Fallback to libaio!"
+           << dendl;
+      once = true;
+    }
+    io_queue = std::make_unique<aio_queue_t>(iodepth);
+  }
+}
+
+int KernelDevice::_lock()
+{
+  dout(10) << __func__ << " " << fd_directs[WRITE_LIFE_NOT_SET] << dendl;
+  // When the block changes, systemd-udevd will open the block,
+  // read some information and close it. Then a failure occurs here.
+  // So we need to try again here.
+  int fd = fd_directs[WRITE_LIFE_NOT_SET];
+  uint64_t nr_tries = 0;
+  for (;;) {
+    struct flock fl = { F_WRLCK,
+                        SEEK_SET };
+    int r = ::fcntl(fd, F_OFD_SETLK, &fl);
+    if (r < 0) {
+      if (errno == EINVAL) {
+        r = ::flock(fd, LOCK_EX | LOCK_NB);
+      }
+    }
+    if (r == 0) {
+      return 0;
+    }
+    if (errno != EAGAIN) {
+      return -errno;
+    }
+    dout(1) << __func__ << " flock busy on " << path << dendl;
+    if (const uint64_t max_retry =
+	cct->_conf.get_val<uint64_t>("bdev_flock_retry");
+        max_retry > 0 && nr_tries++ == max_retry) {
+      return -EAGAIN;
+    }
+    double retry_interval =
+      cct->_conf.get_val<double>("bdev_flock_retry_interval");
+    std::this_thread::sleep_for(ceph::make_timespan(retry_interval));
+  }
+}
+
+int KernelDevice::open(const string& p)
+{
+  path = p;
+  int r = 0, i = 0;
+  dout(1) << __func__ << " path " << path << dendl;
+
+  for (i = 0; i < WRITE_LIFE_MAX; i++) {
+    int fd = ::open(path.c_str(), O_RDWR | O_DIRECT);
+    if (fd  < 0) {
+      r = -errno;
+      break;
+    }
+    fd_directs[i] = fd;
+
+    fd  = ::open(path.c_str(), O_RDWR | O_CLOEXEC);
+    if (fd  < 0) {
+      r = -errno;
+      break;
+    }
+    fd_buffereds[i] = fd;
+  }
+
+  if (i != WRITE_LIFE_MAX) {
+    derr << __func__ << " open got: " << cpp_strerror(r) << dendl;
+    goto out_fail;
+  }
+
+#if defined(F_SET_FILE_RW_HINT)
+  for (i = WRITE_LIFE_NONE; i < WRITE_LIFE_MAX; i++) {
+    if (fcntl(fd_directs[i], F_SET_FILE_RW_HINT, &i) < 0) {
+      r = -errno;
+      break;
+    }
+    if (fcntl(fd_buffereds[i], F_SET_FILE_RW_HINT, &i) < 0) {
+      r = -errno;
+      break;
+    }
+  }
+  if (i != WRITE_LIFE_MAX) {
+    enable_wrt = false;
+    dout(0) << "ioctl(F_SET_FILE_RW_HINT) on " << path << " failed: " << cpp_strerror(r) << dendl;
+  }
+#endif
+
+  dio = true;
+  aio = cct->_conf->bdev_aio;
+  if (!aio) {
+    ceph_abort_msg("non-aio not supported");
+  }
+
+  // disable readahead as it will wreak havoc on our mix of
+  // directio/aio and buffered io.
+  r = posix_fadvise(fd_buffereds[WRITE_LIFE_NOT_SET], 0, 0, POSIX_FADV_RANDOM);
+  if (r) {
+    r = -r;
+    derr << __func__ << " posix_fadvise got: " << cpp_strerror(r) << dendl;
+    goto out_fail;
+  }
+
+  if (lock_exclusive) {
+    r = _lock();
+    if (r < 0) {
+      derr << __func__ << " failed to lock " << path << ": " << cpp_strerror(r)
+	   << dendl;
+      goto out_fail;
+    }
+  }
+
+  struct stat st;
+  r = ::fstat(fd_directs[WRITE_LIFE_NOT_SET], &st);
+  if (r < 0) {
+    r = -errno;
+    derr << __func__ << " fstat got " << cpp_strerror(r) << dendl;
+    goto out_fail;
+  }
+
+  // Operate as though the block size is 4 KB.  The backing file
+  // blksize doesn't strictly matter except that some file systems may
+  // require a read/modify/write if we write something smaller than
+  // it.
+  block_size = cct->_conf->bdev_block_size;
+  if (block_size != (unsigned)st.st_blksize) {
+    dout(1) << __func__ << " backing device/file reports st_blksize "
+	    << st.st_blksize << ", using bdev_block_size "
+	    << block_size << " anyway" << dendl;
+  }
+
+
+  {
+    BlkDev blkdev_direct(fd_directs[WRITE_LIFE_NOT_SET]);
+    BlkDev blkdev_buffered(fd_buffereds[WRITE_LIFE_NOT_SET]);
+
+    if (S_ISBLK(st.st_mode)) {
+      int64_t s;
+      r = blkdev_direct.get_size(&s);
+      if (r < 0) {
+	goto out_fail;
+      }
+      size = s;
+    } else {
+      size = st.st_size;
+    }
+
+    char partition[PATH_MAX], devname[PATH_MAX];
+    if ((r = blkdev_buffered.partition(partition, PATH_MAX)) ||
+	(r = blkdev_buffered.wholedisk(devname, PATH_MAX))) {
+      derr << "unable to get device name for " << path << ": "
+	<< cpp_strerror(r) << dendl;
+      rotational = true;
+    } else {
+      dout(20) << __func__ << " devname " << devname << dendl;
+      rotational = blkdev_buffered.is_rotational();
+      support_discard = blkdev_buffered.support_discard();
+      this->devname = devname;
+      _detect_vdo();
+    }
+  }
+
+  r = _aio_start();
+  if (r < 0) {
+    goto out_fail;
+  }
+  _discard_start();
+
+  // round size down to an even block
+  size &= ~(block_size - 1);
+
+  dout(1) << __func__
+	  << " size " << size
+	  << " (0x" << std::hex << size << std::dec << ", "
+	  << byte_u_t(size) << ")"
+	  << " block_size " << block_size
+	  << " (" << byte_u_t(block_size) << ")"
+	  << " " << (rotational ? "rotational" : "non-rotational")
+      << " discard " << (support_discard ? "supported" : "not supported")
+	  << dendl;
+  return 0;
+
+out_fail:
+  for (i = 0; i < WRITE_LIFE_MAX; i++) {
+    if (fd_directs[i] >= 0) {
+      VOID_TEMP_FAILURE_RETRY(::close(fd_directs[i]));
+      fd_directs[i] = -1;
+    } else {
+      break;
+    }
+    if (fd_buffereds[i] >= 0) {
+      VOID_TEMP_FAILURE_RETRY(::close(fd_buffereds[i]));
+      fd_buffereds[i] = -1;
+    } else {
+      break;
+    }
+  }
+  return r;
+}
+
+int KernelDevice::get_devices(std::set<std::string> *ls) const
+{
+  if (devname.empty()) {
+    return 0;
+  }
+  get_raw_devices(devname, ls);
+  return 0;
+}
+
+void KernelDevice::close()
+{
+  dout(1) << __func__ << dendl;
+  _aio_stop();
+  _discard_stop();
+
+  if (vdo_fd >= 0) {
+    VOID_TEMP_FAILURE_RETRY(::close(vdo_fd));
+    vdo_fd = -1;
+  }
+
+  for (int i = 0; i < WRITE_LIFE_MAX; i++) {
+    assert(fd_directs[i] >= 0);
+    VOID_TEMP_FAILURE_RETRY(::close(fd_directs[i]));
+    fd_directs[i] = -1;
+
+    assert(fd_buffereds[i] >= 0);
+    VOID_TEMP_FAILURE_RETRY(::close(fd_buffereds[i]));
+    fd_buffereds[i] = -1;
+  }
+  path.clear();
+}
+
+int KernelDevice::collect_metadata(const string& prefix, map<string,string> *pm) const
+{
+  (*pm)[prefix + "support_discard"] = stringify((int)(bool)support_discard);
+  (*pm)[prefix + "rotational"] = stringify((int)(bool)rotational);
+  (*pm)[prefix + "size"] = stringify(get_size());
+  (*pm)[prefix + "block_size"] = stringify(get_block_size());
+  (*pm)[prefix + "driver"] = "KernelDevice";
+  if (rotational) {
+    (*pm)[prefix + "type"] = "hdd";
+  } else {
+    (*pm)[prefix + "type"] = "ssd";
+  }
+  if (vdo_fd >= 0) {
+    (*pm)[prefix + "vdo"] = "true";
+    uint64_t total, avail;
+    get_vdo_utilization(vdo_fd, &total, &avail);
+    (*pm)[prefix + "vdo_physical_size"] = stringify(total);
+  }
+
+  {
+    string res_names;
+    std::set<std::string> devnames;
+    if (get_devices(&devnames) == 0) {
+      for (auto& dev : devnames) {
+	if (!res_names.empty()) {
+	  res_names += ",";
+	}
+	res_names += dev;
+      }
+      if (res_names.size()) {
+	(*pm)[prefix + "devices"] = res_names;
+      }
+    }
+  }
+
+  struct stat st;
+  int r = ::fstat(fd_buffereds[WRITE_LIFE_NOT_SET], &st);
+  if (r < 0)
+    return -errno;
+  if (S_ISBLK(st.st_mode)) {
+    (*pm)[prefix + "access_mode"] = "blk";
+
+    char buffer[1024] = {0};
+    BlkDev blkdev{fd_buffereds[WRITE_LIFE_NOT_SET]};
+    if (r = blkdev.partition(buffer, sizeof(buffer)); r) {
+      (*pm)[prefix + "partition_path"] = "unknown";
+    } else {
+      (*pm)[prefix + "partition_path"] = buffer;
+    }
+    buffer[0] = '\0';
+    if (r = blkdev.partition(buffer, sizeof(buffer)); r) {
+      (*pm)[prefix + "dev_node"] = "unknown";
+    } else {
+      (*pm)[prefix + "dev_node"] = buffer;
+    }
+    if (!r) {
+      return 0;
+    }
+    buffer[0] = '\0';
+    blkdev.model(buffer, sizeof(buffer));
+    (*pm)[prefix + "model"] = buffer;
+
+    buffer[0] = '\0';
+    blkdev.dev(buffer, sizeof(buffer));
+    (*pm)[prefix + "dev"] = buffer;
+
+    // nvme exposes a serial number
+    buffer[0] = '\0';
+    blkdev.serial(buffer, sizeof(buffer));
+    (*pm)[prefix + "serial"] = buffer;
+
+    // numa
+    int node;
+    r = blkdev.get_numa_node(&node);
+    if (r >= 0) {
+      (*pm)[prefix + "numa_node"] = stringify(node);
+    }
+  } else {
+    (*pm)[prefix + "access_mode"] = "file";
+    (*pm)[prefix + "path"] = path;
+  }
+  return 0;
+}
+
+void KernelDevice::_detect_vdo()
+{
+  vdo_fd = get_vdo_stats_handle(devname.c_str(), &vdo_name);
+  if (vdo_fd >= 0) {
+    dout(1) << __func__ << " VDO volume " << vdo_name
+	    << " maps to " << devname << dendl;
+  } else {
+    dout(20) << __func__ << " no VDO volume maps to " << devname << dendl;
+  }
+  return;
+}
+
+bool KernelDevice::get_thin_utilization(uint64_t *total, uint64_t *avail) const
+{
+  if (vdo_fd < 0) {
+    return false;
+  }
+  return get_vdo_utilization(vdo_fd, total, avail);
+}
+
+int KernelDevice::choose_fd(bool buffered, int write_hint) const
+{
+  assert(write_hint >= WRITE_LIFE_NOT_SET && write_hint < WRITE_LIFE_MAX);
+  if (!enable_wrt)
+    write_hint = WRITE_LIFE_NOT_SET;
+  return buffered ? fd_buffereds[write_hint] : fd_directs[write_hint];
+}
+
+int KernelDevice::flush()
+{
+  // protect flush with a mutex.  note that we are not really protecting
+  // data here.  instead, we're ensuring that if any flush() caller
+  // sees that io_since_flush is true, they block any racing callers
+  // until the flush is observed.  that allows racing threads to be
+  // calling flush while still ensuring that *any* of them that got an
+  // aio completion notification will not return before that aio is
+  // stable on disk: whichever thread sees the flag first will block
+  // followers until the aio is stable.
+  std::lock_guard l(flush_mutex);
+
+  bool expect = true;
+  if (!io_since_flush.compare_exchange_strong(expect, false)) {
+    dout(10) << __func__ << " no-op (no ios since last flush), flag is "
+	     << (int)io_since_flush.load() << dendl;
+    return 0;
+  }
+
+  dout(10) << __func__ << " start" << dendl;
+  if (cct->_conf->bdev_inject_crash) {
+    ++injecting_crash;
+    // sleep for a moment to give other threads a chance to submit or
+    // wait on io that races with a flush.
+    derr << __func__ << " injecting crash. first we sleep..." << dendl;
+    sleep(cct->_conf->bdev_inject_crash_flush_delay);
+    derr << __func__ << " and now we die" << dendl;
+    cct->_log->flush();
+    _exit(1);
+  }
+  utime_t start = ceph_clock_now();
+  int r = ::fdatasync(fd_directs[WRITE_LIFE_NOT_SET]);
+  utime_t end = ceph_clock_now();
+  utime_t dur = end - start;
+  if (r < 0) {
+    r = -errno;
+    derr << __func__ << " fdatasync got: " << cpp_strerror(r) << dendl;
+    ceph_abort();
+  }
+  dout(5) << __func__ << " in " << dur << dendl;;
+  return r;
+}
+
+int KernelDevice::_aio_start()
+{
+  if (aio) {
+    dout(10) << __func__ << dendl;
+    int r = io_queue->init(fd_directs);
+    if (r < 0) {
+      if (r == -EAGAIN) {
+	derr << __func__ << " io_setup(2) failed with EAGAIN; "
+	     << "try increasing /proc/sys/fs/aio-max-nr" << dendl;
+      } else {
+	derr << __func__ << " io_setup(2) failed: " << cpp_strerror(r) << dendl;
+      }
+      return r;
+    }
+    aio_thread.create("bstore_aio");
+  }
+  return 0;
+}
+
+void KernelDevice::_aio_stop()
+{
+  if (aio) {
+    dout(10) << __func__ << dendl;
+    aio_stop = true;
+    aio_thread.join();
+    aio_stop = false;
+    io_queue->shutdown();
+  }
+}
+
+int KernelDevice::_discard_start()
+{
+    discard_thread.create("bstore_discard");
+    return 0;
+}
+
+void KernelDevice::_discard_stop()
+{
+  dout(10) << __func__ << dendl;
+  {
+    std::unique_lock l(discard_lock);
+    while (!discard_started) {
+      discard_cond.wait(l);
+    }
+    discard_stop = true;
+    discard_cond.notify_all();
+  }
+  discard_thread.join();
+  {
+    std::lock_guard l(discard_lock);
+    discard_stop = false;
+  }
+  dout(10) << __func__ << " stopped" << dendl;
+}
+
+void KernelDevice::discard_drain()
+{
+  dout(10) << __func__ << dendl;
+  std::unique_lock l(discard_lock);
+  while (!discard_queued.empty() || discard_running) {
+    discard_cond.wait(l);
+  }
+}
+
+static bool is_expected_ioerr(const int r)
+{
+  // https://lxr.missinglinkelectronics.com/linux+v4.15/block/blk-core.c#L135
+  return (r == -EOPNOTSUPP || r == -ETIMEDOUT || r == -ENOSPC ||
+	  r == -ENOLINK || r == -EREMOTEIO  || r == -EAGAIN || r == -EIO ||
+	  r == -ENODATA || r == -EILSEQ || r == -ENOMEM ||
+#if defined(__linux__)
+	  r == -EREMCHG || r == -EBADE
+#elif defined(__FreeBSD__)
+	  r == - BSM_ERRNO_EREMCHG || r == -BSM_ERRNO_EBADE
+#endif
+	  );
+}
+
+void KernelDevice::_aio_thread()
+{
+  dout(10) << __func__ << " start" << dendl;
+  int inject_crash_count = 0;
+  while (!aio_stop) {
+    dout(40) << __func__ << " polling" << dendl;
+    int max = cct->_conf->bdev_aio_reap_max;
+    aio_t *aio[max];
+    int r = io_queue->get_next_completed(cct->_conf->bdev_aio_poll_ms,
+					 aio, max);
+    if (r < 0) {
+      derr << __func__ << " got " << cpp_strerror(r) << dendl;
+      ceph_abort_msg("got unexpected error from io_getevents");
+    }
+    if (r > 0) {
+      dout(30) << __func__ << " got " << r << " completed aios" << dendl;
+      for (int i = 0; i < r; ++i) {
+	IOContext *ioc = static_cast<IOContext*>(aio[i]->priv);
+	_aio_log_finish(ioc, aio[i]->offset, aio[i]->length);
+	if (aio[i]->queue_item.is_linked()) {
+	  std::lock_guard l(debug_queue_lock);
+	  debug_aio_unlink(*aio[i]);
+	}
+
+	// set flag indicating new ios have completed.  we do this *before*
+	// any completion or notifications so that any user flush() that
+	// follows the observed io completion will include this io.  Note
+	// that an earlier, racing flush() could observe and clear this
+	// flag, but that also ensures that the IO will be stable before the
+	// later flush() occurs.
+	io_since_flush.store(true);
+
+	long r = aio[i]->get_return_value();
+        if (r < 0) {
+          derr << __func__ << " got r=" << r << " (" << cpp_strerror(r) << ")"
+	       << dendl;
+          if (ioc->allow_eio && is_expected_ioerr(r)) {
+            derr << __func__ << " translating the error to EIO for upper layer"
+		 << dendl;
+            ioc->set_return_value(-EIO);
+          } else {
+	    if (is_expected_ioerr(r)) {
+	      note_io_error_event(
+		devname.c_str(),
+		path.c_str(),
+		r,
+#if defined(HAVE_POSIXAIO)
+                aio[i]->aio.aiocb.aio_lio_opcode,
+#else
+                aio[i]->iocb.aio_lio_opcode,
+#endif
+		aio[i]->offset,
+		aio[i]->length);
+	      ceph_abort_msg(
+		"Unexpected IO error. "
+		"This may suggest a hardware issue. "
+		"Please check your kernel log!");
+	    }
+	    ceph_abort_msg(
+	      "Unexpected IO error. "
+	      "This may suggest HW issue. Please check your dmesg!");
+          }
+        } else if (aio[i]->length != (uint64_t)r) {
+          derr << "aio to 0x" << std::hex << aio[i]->offset
+	       << "~" << aio[i]->length << std::dec
+               << " but returned: " << r << dendl;
+          ceph_abort_msg("unexpected aio return value: does not match length");
+        }
+
+        dout(10) << __func__ << " finished aio " << aio[i] << " r " << r
+                 << " ioc " << ioc
+                 << " with " << (ioc->num_running.load() - 1)
+                 << " aios left" << dendl;
+
+	// NOTE: once num_running and we either call the callback or
+	// call aio_wake we cannot touch ioc or aio[] as the caller
+	// may free it.
+	if (ioc->priv) {
+	  if (--ioc->num_running == 0) {
+	    aio_callback(aio_callback_priv, ioc->priv);
+	  }
+	} else {
+          ioc->try_aio_wake();
+	}
+      }
+    }
+    if (cct->_conf->bdev_debug_aio) {
+      utime_t now = ceph_clock_now();
+      std::lock_guard l(debug_queue_lock);
+      if (debug_oldest) {
+	if (debug_stall_since == utime_t()) {
+	  debug_stall_since = now;
+	} else {
+	  if (cct->_conf->bdev_debug_aio_suicide_timeout) {
+            utime_t cutoff = now;
+	    cutoff -= cct->_conf->bdev_debug_aio_suicide_timeout;
+	    if (debug_stall_since < cutoff) {
+	      derr << __func__ << " stalled aio " << debug_oldest
+		   << " since " << debug_stall_since << ", timeout is "
+		   << cct->_conf->bdev_debug_aio_suicide_timeout
+		   << "s, suicide" << dendl;
+	      ceph_abort_msg("stalled aio... buggy kernel or bad device?");
+	    }
+	  }
+	}
+      }
+    }
+    reap_ioc();
+    if (cct->_conf->bdev_inject_crash) {
+      ++inject_crash_count;
+      if (inject_crash_count * cct->_conf->bdev_aio_poll_ms / 1000 >
+	  cct->_conf->bdev_inject_crash + cct->_conf->bdev_inject_crash_flush_delay) {
+	derr << __func__ << " bdev_inject_crash trigger from aio thread"
+	     << dendl;
+	cct->_log->flush();
+	_exit(1);
+      }
+    }
+  }
+  reap_ioc();
+  dout(10) << __func__ << " end" << dendl;
+}
+
+void KernelDevice::_discard_thread()
+{
+  std::unique_lock l(discard_lock);
+  ceph_assert(!discard_started);
+  discard_started = true;
+  discard_cond.notify_all();
+  while (true) {
+    ceph_assert(discard_finishing.empty());
+    if (discard_queued.empty()) {
+      if (discard_stop)
+	break;
+      dout(20) << __func__ << " sleep" << dendl;
+      discard_cond.notify_all(); // for the thread trying to drain...
+      discard_cond.wait(l);
+      dout(20) << __func__ << " wake" << dendl;
+    } else {
+      discard_finishing.swap(discard_queued);
+      discard_running = true;
+      l.unlock();
+      dout(20) << __func__ << " finishing" << dendl;
+      for (auto p = discard_finishing.begin();p != discard_finishing.end(); ++p) {
+	discard(p.get_start(), p.get_len());
+      }
+
+      discard_callback(discard_callback_priv, static_cast<void*>(&discard_finishing));
+      discard_finishing.clear();
+      l.lock();
+      discard_running = false;
+    }
+  }
+  dout(10) << __func__ << " finish" << dendl;
+  discard_started = false;
+}
+
+int KernelDevice::queue_discard(interval_set<uint64_t> &to_release)
+{
+  if (!support_discard)
+    return -1;
+
+  if (to_release.empty())
+    return 0;
+
+  std::lock_guard l(discard_lock);
+  discard_queued.insert(to_release);
+  discard_cond.notify_all();
+  return 0;
+}
+
+void KernelDevice::_aio_log_start(
+  IOContext *ioc,
+  uint64_t offset,
+  uint64_t length)
+{
+  dout(20) << __func__ << " 0x" << std::hex << offset << "~" << length
+	   << std::dec << dendl;
+  if (cct->_conf->bdev_debug_inflight_ios) {
+    std::lock_guard l(debug_lock);
+    if (debug_inflight.intersects(offset, length)) {
+      derr << __func__ << " inflight overlap of 0x"
+	   << std::hex
+	   << offset << "~" << length << std::dec
+	   << " with " << debug_inflight << dendl;
+      ceph_abort();
+    }
+    debug_inflight.insert(offset, length);
+  }
+}
+
+void KernelDevice::debug_aio_link(aio_t& aio)
+{
+  if (debug_queue.empty()) {
+    debug_oldest = &aio;
+  }
+  debug_queue.push_back(aio);
+}
+
+void KernelDevice::debug_aio_unlink(aio_t& aio)
+{
+  if (aio.queue_item.is_linked()) {
+    debug_queue.erase(debug_queue.iterator_to(aio));
+    if (debug_oldest == &aio) {
+      auto age = cct->_conf->bdev_debug_aio_log_age;
+      if (age && debug_stall_since != utime_t()) {
+        utime_t cutoff = ceph_clock_now();
+	cutoff -= age;
+	if (debug_stall_since < cutoff) {
+	  derr << __func__ << " stalled aio " << debug_oldest
+		<< " since " << debug_stall_since << ", timeout is "
+		<< age
+		<< "s" << dendl;
+	}
+      }
+
+      if (debug_queue.empty()) {
+	debug_oldest = nullptr;
+      } else {
+	debug_oldest = &debug_queue.front();
+      }
+      debug_stall_since = utime_t();
+    }
+  }
+}
+
+void KernelDevice::_aio_log_finish(
+  IOContext *ioc,
+  uint64_t offset,
+  uint64_t length)
+{
+  dout(20) << __func__ << " " << aio << " 0x"
+	   << std::hex << offset << "~" << length << std::dec << dendl;
+  if (cct->_conf->bdev_debug_inflight_ios) {
+    std::lock_guard l(debug_lock);
+    debug_inflight.erase(offset, length);
+  }
+}
+
+void KernelDevice::aio_submit(IOContext *ioc)
+{
+  dout(20) << __func__ << " ioc " << ioc
+	   << " pending " << ioc->num_pending.load()
+	   << " running " << ioc->num_running.load()
+	   << dendl;
+
+  if (ioc->num_pending.load() == 0) {
+    return;
+  }
+
+  // move these aside, and get our end iterator position now, as the
+  // aios might complete as soon as they are submitted and queue more
+  // wal aio's.
+  list<aio_t>::iterator e = ioc->running_aios.begin();
+  ioc->running_aios.splice(e, ioc->pending_aios);
+
+  int pending = ioc->num_pending.load();
+  ioc->num_running += pending;
+  ioc->num_pending -= pending;
+  ceph_assert(ioc->num_pending.load() == 0);  // we should be only thread doing this
+  ceph_assert(ioc->pending_aios.size() == 0);
+
+  if (cct->_conf->bdev_debug_aio) {
+    list<aio_t>::iterator p = ioc->running_aios.begin();
+    while (p != e) {
+      dout(30) << __func__ << " " << *p << dendl;
+      std::lock_guard l(debug_queue_lock);
+      debug_aio_link(*p++);
+    }
+  }
+
+  void *priv = static_cast<void*>(ioc);
+  int r, retries = 0;
+  // num of pending aios should not overflow when passed to submit_batch()
+  assert(pending <= std::numeric_limits<uint16_t>::max());
+  r = io_queue->submit_batch(ioc->running_aios.begin(), e,
+			     pending, priv, &retries);
+
+  if (retries)
+    derr << __func__ << " retries " << retries << dendl;
+  if (r < 0) {
+    derr << " aio submit got " << cpp_strerror(r) << dendl;
+    ceph_assert(r == 0);
+  }
+}
+
+int KernelDevice::_sync_write(uint64_t off, bufferlist &bl, bool buffered, int write_hint)
+{
+  uint64_t len = bl.length();
+  dout(5) << __func__ << " 0x" << std::hex << off << "~" << len
+	  << std::dec << (buffered ? " (buffered)" : " (direct)") << dendl;
+  if (cct->_conf->bdev_inject_crash &&
+      rand() % cct->_conf->bdev_inject_crash == 0) {
+    derr << __func__ << " bdev_inject_crash: dropping io 0x" << std::hex
+	 << off << "~" << len << std::dec << dendl;
+    ++injecting_crash;
+    return 0;
+  }
+  vector<iovec> iov;
+  bl.prepare_iov(&iov);
+
+  auto left = len;
+  auto o = off;
+  size_t idx = 0;
+  do {
+    auto r = ::pwritev(choose_fd(buffered, write_hint),
+      &iov[idx], iov.size() - idx, o);
+
+    if (r < 0) {
+      r = -errno;
+      derr << __func__ << " pwritev error: " << cpp_strerror(r) << dendl;
+      return r;
+    }
+    o += r;
+    left -= r;
+    if (left) {
+      // skip fully processed IOVs
+      while (idx < iov.size() && (size_t)r >= iov[idx].iov_len) {
+        r -= iov[idx++].iov_len;
+      }
+      // update partially processed one if any
+      if (r) {
+        ceph_assert(idx < iov.size());
+        ceph_assert((size_t)r < iov[idx].iov_len);
+        iov[idx].iov_base = static_cast<char*>(iov[idx].iov_base) + r;
+        iov[idx].iov_len -= r;
+        r = 0;
+      }
+      ceph_assert(r == 0);
+    }
+  } while (left);
+
+#ifdef HAVE_SYNC_FILE_RANGE
+  if (buffered) {
+    // initiate IO and wait till it completes
+    auto r = ::sync_file_range(fd_buffereds[WRITE_LIFE_NOT_SET], off, len, SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER|SYNC_FILE_RANGE_WAIT_BEFORE);
+    if (r < 0) {
+      r = -errno;
+      derr << __func__ << " sync_file_range error: " << cpp_strerror(r) << dendl;
+      return r;
+    }
+  }
+#endif
+
+  io_since_flush.store(true);
+
+  return 0;
+}
+
+int KernelDevice::write(
+  uint64_t off,
+  bufferlist &bl,
+  bool buffered,
+  int write_hint)
+{
+  uint64_t len = bl.length();
+  dout(20) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+	   << (buffered ? " (buffered)" : " (direct)")
+	   << dendl;
+  ceph_assert(is_valid_io(off, len));
+  if (cct->_conf->objectstore_blackhole) {
+    lderr(cct) << __func__ << " objectstore_blackhole=true, throwing out IO"
+	       << dendl;
+    return 0;
+  }
+
+  if ((!buffered || bl.get_num_buffers() >= IOV_MAX) &&
+      bl.rebuild_aligned_size_and_memory(block_size, block_size, IOV_MAX)) {
+    dout(20) << __func__ << " rebuilding buffer to be aligned" << dendl;
+  }
+  dout(40) << "data: ";
+  bl.hexdump(*_dout);
+  *_dout << dendl;
+
+  return _sync_write(off, bl, buffered, write_hint);
+}
+
+int KernelDevice::aio_write(
+  uint64_t off,
+  bufferlist &bl,
+  IOContext *ioc,
+  bool buffered,
+  int write_hint)
+{
+  uint64_t len = bl.length();
+  dout(20) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+	   << (buffered ? " (buffered)" : " (direct)")
+	   << dendl;
+  ceph_assert(is_valid_io(off, len));
+  if (cct->_conf->objectstore_blackhole) {
+    lderr(cct) << __func__ << " objectstore_blackhole=true, throwing out IO"
+	       << dendl;
+    return 0;
+  }
+
+  if ((!buffered || bl.get_num_buffers() >= IOV_MAX) &&
+      bl.rebuild_aligned_size_and_memory(block_size, block_size, IOV_MAX)) {
+    dout(20) << __func__ << " rebuilding buffer to be aligned" << dendl;
+  }
+  dout(40) << "data: ";
+  bl.hexdump(*_dout);
+  *_dout << dendl;
+
+  _aio_log_start(ioc, off, len);
+
+#ifdef HAVE_LIBAIO
+  if (aio && dio && !buffered) {
+    if (cct->_conf->bdev_inject_crash &&
+	rand() % cct->_conf->bdev_inject_crash == 0) {
+      derr << __func__ << " bdev_inject_crash: dropping io 0x" << std::hex
+	   << off << "~" << len << std::dec
+	   << dendl;
+      // generate a real io so that aio_wait behaves properly, but make it
+      // a read instead of write, and toss the result.
+      ioc->pending_aios.push_back(aio_t(ioc, choose_fd(false, write_hint)));
+      ++ioc->num_pending;
+      auto& aio = ioc->pending_aios.back();
+      bufferptr p = ceph::buffer::create_small_page_aligned(len);
+      aio.bl.append(std::move(p));
+      aio.bl.prepare_iov(&aio.iov);
+      aio.preadv(off, len);
+      ++injecting_crash;
+    } else {
+      if (bl.length() <= RW_IO_MAX) {
+	// fast path (non-huge write)
+	ioc->pending_aios.push_back(aio_t(ioc, choose_fd(false, write_hint)));
+	++ioc->num_pending;
+	auto& aio = ioc->pending_aios.back();
+	bl.prepare_iov(&aio.iov);
+	aio.bl.claim_append(bl);
+	aio.pwritev(off, len);
+	dout(30) << aio << dendl;
+	dout(5) << __func__ << " 0x" << std::hex << off << "~" << len
+		<< std::dec << " aio " << &aio << dendl;
+      } else {
+	// write in RW_IO_MAX-sized chunks
+	uint64_t prev_len = 0;
+	while (prev_len < bl.length()) {
+	  bufferlist tmp;
+	  if (prev_len + RW_IO_MAX < bl.length()) {
+	    tmp.substr_of(bl, prev_len, RW_IO_MAX);
+	  } else {
+	    tmp.substr_of(bl, prev_len, bl.length() - prev_len);
+	  }
+	  auto len = tmp.length();
+	  ioc->pending_aios.push_back(aio_t(ioc, choose_fd(false, write_hint)));
+	  ++ioc->num_pending;
+	  auto& aio = ioc->pending_aios.back();
+	  tmp.prepare_iov(&aio.iov);
+	  aio.bl.claim_append(tmp);
+	  aio.pwritev(off + prev_len, len);
+	  dout(30) << aio << dendl;
+	  dout(5) << __func__ << " 0x" << std::hex << off + prev_len
+		  << "~" << len
+		  << std::dec << " aio " << &aio << " (piece)" << dendl;
+	  prev_len += len;
+	}
+      }
+    }
+  } else
+#endif
+  {
+    int r = _sync_write(off, bl, buffered, write_hint);
+    _aio_log_finish(ioc, off, len);
+    if (r < 0)
+      return r;
+  }
+  return 0;
+}
+
+int KernelDevice::discard(uint64_t offset, uint64_t len)
+{
+  int r = 0;
+  if (cct->_conf->objectstore_blackhole) {
+    lderr(cct) << __func__ << " objectstore_blackhole=true, throwing out IO"
+	       << dendl;
+    return 0;
+  }
+  if (support_discard) {
+      dout(10) << __func__
+	       << " 0x" << std::hex << offset << "~" << len << std::dec
+	       << dendl;
+
+      r = BlkDev{fd_directs[WRITE_LIFE_NOT_SET]}.discard((int64_t)offset, (int64_t)len);
+  }
+  return r;
+}
+
+int KernelDevice::read(uint64_t off, uint64_t len, bufferlist *pbl,
+		      IOContext *ioc,
+		      bool buffered)
+{
+  dout(5) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+	  << (buffered ? " (buffered)" : " (direct)")
+	  << dendl;
+  ceph_assert(is_valid_io(off, len));
+
+  _aio_log_start(ioc, off, len);
+
+  auto start1 = mono_clock::now();
+
+  auto p = ceph::buffer::ptr_node::create(ceph::buffer::create_small_page_aligned(len));
+  int r = ::pread(buffered ? fd_buffereds[WRITE_LIFE_NOT_SET] : fd_directs[WRITE_LIFE_NOT_SET],
+		  p->c_str(), len, off);
+  auto age = cct->_conf->bdev_debug_aio_log_age;
+  if (mono_clock::now() - start1 >= make_timespan(age)) {
+    derr << __func__ << " stalled read "
+         << " 0x" << std::hex << off << "~" << len << std::dec
+         << (buffered ? " (buffered)" : " (direct)")
+	 << " since " << start1 << ", timeout is "
+	 << age
+	 << "s" << dendl;
+  }
+
+  if (r < 0) {
+    if (ioc->allow_eio && is_expected_ioerr(r)) {
+      r = -EIO;
+    } else {
+      r = -errno;
+    }
+    goto out;
+  }
+  ceph_assert((uint64_t)r == len);
+  pbl->push_back(std::move(p));
+
+  dout(40) << "data: ";
+  pbl->hexdump(*_dout);
+  *_dout << dendl;
+
+ out:
+  _aio_log_finish(ioc, off, len);
+  return r < 0 ? r : 0;
+}
+
+int KernelDevice::aio_read(
+  uint64_t off,
+  uint64_t len,
+  bufferlist *pbl,
+  IOContext *ioc)
+{
+  dout(5) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+	  << dendl;
+
+  int r = 0;
+#ifdef HAVE_LIBAIO
+  if (aio && dio) {
+    ceph_assert(is_valid_io(off, len));
+    _aio_log_start(ioc, off, len);
+    ioc->pending_aios.push_back(aio_t(ioc, fd_directs[WRITE_LIFE_NOT_SET]));
+    ++ioc->num_pending;
+    aio_t& aio = ioc->pending_aios.back();
+    bufferptr p = ceph::buffer::create_small_page_aligned(len);
+    aio.bl.append(std::move(p));
+    aio.bl.prepare_iov(&aio.iov);
+    aio.preadv(off, len);
+    dout(30) << aio << dendl;
+    pbl->append(aio.bl);
+    dout(5) << __func__ << " 0x" << std::hex << off << "~" << len
+	    << std::dec << " aio " << &aio << dendl;
+  } else
+#endif
+  {
+    r = read(off, len, pbl, ioc, false);
+  }
+
+  return r;
+}
+
+int KernelDevice::direct_read_unaligned(uint64_t off, uint64_t len, char *buf)
+{
+  uint64_t aligned_off = p2align(off, block_size);
+  uint64_t aligned_len = p2roundup(off+len, block_size) - aligned_off;
+  bufferptr p = ceph::buffer::create_small_page_aligned(aligned_len);
+  int r = 0;
+
+  auto start1 = mono_clock::now();
+  r = ::pread(fd_directs[WRITE_LIFE_NOT_SET], p.c_str(), aligned_len, aligned_off);
+  auto age = cct->_conf->bdev_debug_aio_log_age;
+  if (mono_clock::now() - start1 >= make_timespan(age)) {
+    derr << __func__ << " stalled read "
+         << " 0x" << std::hex << off << "~" << len << std::dec
+	 << " since " << start1 << ", timeout is "
+	 << age
+	 << "s" << dendl;
+  }
+
+  if (r < 0) {
+    r = -errno;
+    derr << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+      << " error: " << cpp_strerror(r) << dendl;
+    goto out;
+  }
+  ceph_assert((uint64_t)r == aligned_len);
+  memcpy(buf, p.c_str() + (off - aligned_off), len);
+
+  dout(40) << __func__ << " data: ";
+  bufferlist bl;
+  bl.append(buf, len);
+  bl.hexdump(*_dout);
+  *_dout << dendl;
+
+ out:
+  return r < 0 ? r : 0;
+}
+
+int KernelDevice::read_random(uint64_t off, uint64_t len, char *buf,
+                       bool buffered)
+{
+  dout(5) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+          << "buffered " << buffered
+	  << dendl;
+  ceph_assert(len > 0);
+  ceph_assert(off < size);
+  ceph_assert(off + len <= size);
+  int r = 0;
+  auto age = cct->_conf->bdev_debug_aio_log_age;
+
+  //if it's direct io and unaligned, we have to use a internal buffer
+  if (!buffered && ((off % block_size != 0)
+                    || (len % block_size != 0)
+                    || (uintptr_t(buf) % CEPH_PAGE_SIZE != 0)))
+    return direct_read_unaligned(off, len, buf);
+
+  auto start1 = mono_clock::now();
+  if (buffered) {
+    //buffered read
+    auto off0 = off;
+    char *t = buf;
+    uint64_t left = len;
+    while (left > 0) {
+      r = ::pread(fd_buffereds[WRITE_LIFE_NOT_SET], t, left, off);
+      if (r < 0) {
+	r = -errno;
+        derr << __func__ << " 0x" << std::hex << off << "~" << left
+          << std::dec << " error: " << cpp_strerror(r) << dendl;
+	goto out;
+      }
+      off += r;
+      t += r;
+      left -= r;
+    }
+    if (mono_clock::now() - start1 >= make_timespan(age)) {
+      derr << __func__ << " stalled read "
+	   << " 0x" << std::hex << off0 << "~" << len << std::dec
+           << " (buffered) since " << start1 << ", timeout is "
+	   << age
+	   << "s" << dendl;
+    }
+  } else {
+    //direct and aligned read
+    r = ::pread(fd_directs[WRITE_LIFE_NOT_SET], buf, len, off);
+    if (mono_clock::now() - start1 >= make_timespan(age)) {
+      derr << __func__ << " stalled read "
+	   << " 0x" << std::hex << off << "~" << len << std::dec
+           << " (direct) since " << start1 << ", timeout is "
+	   << age
+	   << "s" << dendl;
+    }
+    if (r < 0) {
+      r = -errno;
+      derr << __func__ << " direct_aligned_read" << " 0x" << std::hex
+	   << off << "~" << std::left << std::dec << " error: " << cpp_strerror(r)
+        << dendl;
+      goto out;
+    }
+    ceph_assert((uint64_t)r == len);
+  }
+
+  dout(40) << __func__ << " data: ";
+  bufferlist bl;
+  bl.append(buf, len);
+  bl.hexdump(*_dout);
+  *_dout << dendl;
+
+ out:
+  return r < 0 ? r : 0;
+}
+
+int KernelDevice::invalidate_cache(uint64_t off, uint64_t len)
+{
+  dout(5) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+	  << dendl;
+  ceph_assert(off % block_size == 0);
+  ceph_assert(len % block_size == 0);
+  int r = posix_fadvise(fd_buffereds[WRITE_LIFE_NOT_SET], off, len, POSIX_FADV_DONTNEED);
+  if (r) {
+    r = -r;
+    derr << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
+	 << " error: " << cpp_strerror(r) << dendl;
+  }
+  return r;
+}
diff --git a/src/blk/kernel/KernelDevice.h b/src/blk/kernel/KernelDevice.h
new file mode 100644
index 000000000..7ac9b1e7e
--- /dev/null
+++ b/src/blk/kernel/KernelDevice.h
@@ -0,0 +1,150 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2014 Red Hat
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#ifndef CEPH_BLK_KERNELDEVICE_H
+#define CEPH_BLK_KERNELDEVICE_H
+
+#include <atomic>
+
+#include "include/types.h"
+#include "include/interval_set.h"
+#include "common/Thread.h"
+#include "include/utime.h"
+
+#include "aio/aio.h"
+#include "BlockDevice.h"
+
+#define RW_IO_MAX (INT_MAX & CEPH_PAGE_MASK)
+
+
+class KernelDevice : public BlockDevice {
+  std::vector<int> fd_directs, fd_buffereds;
+  bool enable_wrt = true;
+  std::string path;
+  bool aio, dio;
+
+  int vdo_fd = -1;      ///< fd for vdo sysfs directory
+  std::string vdo_name;
+
+  std::string devname;  ///< kernel dev name (/sys/block/$devname), if any
+
+  ceph::mutex debug_lock = ceph::make_mutex("KernelDevice::debug_lock");
+  interval_set<uint64_t> debug_inflight;
+
+  std::atomic<bool> io_since_flush = {false};
+  ceph::mutex flush_mutex = ceph::make_mutex("KernelDevice::flush_mutex");
+
+  std::unique_ptr<io_queue_t> io_queue;
+  aio_callback_t discard_callback;
+  void *discard_callback_priv;
+  bool aio_stop;
+  bool discard_started;
+  bool discard_stop;
+
+  ceph::mutex discard_lock = ceph::make_mutex("KernelDevice::discard_lock");
+  ceph::condition_variable discard_cond;
+  bool discard_running = false;
+  interval_set<uint64_t> discard_queued;
+  interval_set<uint64_t> discard_finishing;
+
+  struct AioCompletionThread : public Thread {
+    KernelDevice *bdev;
+    explicit AioCompletionThread(KernelDevice *b) : bdev(b) {}
+    void *entry() override {
+      bdev->_aio_thread();
+      return NULL;
+    }
+  } aio_thread;
+
+  struct DiscardThread : public Thread {
+    KernelDevice *bdev;
+    explicit DiscardThread(KernelDevice *b) : bdev(b) {}
+    void *entry() override {
+      bdev->_discard_thread();
+      return NULL;
+    }
+  } discard_thread;
+
+  std::atomic_int injecting_crash;
+
+  void _aio_thread();
+  void _discard_thread();
+  int queue_discard(interval_set<uint64_t> &to_release) override;
+
+  int _aio_start();
+  void _aio_stop();
+
+  int _discard_start();
+  void _discard_stop();
+
+  void _aio_log_start(IOContext *ioc, uint64_t offset, uint64_t length);
+  void _aio_log_finish(IOContext *ioc, uint64_t offset, uint64_t length);
+
+  int _sync_write(uint64_t off, ceph::buffer::list& bl, bool buffered, int write_hint);
+
+  int _lock();
+
+  int direct_read_unaligned(uint64_t off, uint64_t len, char *buf);
+
+  // stalled aio debugging
+  aio_list_t debug_queue;
+  ceph::mutex debug_queue_lock = ceph::make_mutex("KernelDevice::debug_queue_lock");
+  aio_t *debug_oldest = nullptr;
+  utime_t debug_stall_since;
+  void debug_aio_link(aio_t& aio);
+  void debug_aio_unlink(aio_t& aio);
+
+  void _detect_vdo();
+  int choose_fd(bool buffered, int write_hint) const;
+
+public:
+  KernelDevice(CephContext* cct, aio_callback_t cb, void *cbpriv, aio_callback_t d_cb, void *d_cbpriv);
+
+  void aio_submit(IOContext *ioc) override;
+  void discard_drain() override;
+
+  int collect_metadata(const std::string& prefix, std::map<std::string,std::string> *pm) const override;
+  int get_devname(std::string *s) const override {
+    if (devname.empty()) {
+      return -ENOENT;
+    }
+    *s = devname;
+    return 0;
+  }
+  int get_devices(std::set<std::string> *ls) const override;
+
+  bool get_thin_utilization(uint64_t *total, uint64_t *avail) const override;
+
+  int read(uint64_t off, uint64_t len, ceph::buffer::list *pbl,
+	   IOContext *ioc,
+	   bool buffered) override;
+  int aio_read(uint64_t off, uint64_t len, ceph::buffer::list *pbl,
+	       IOContext *ioc) override;
+  int read_random(uint64_t off, uint64_t len, char *buf, bool buffered) override;
+
+  int write(uint64_t off, ceph::buffer::list& bl, bool buffered, int write_hint = WRITE_LIFE_NOT_SET) override;
+  int aio_write(uint64_t off, ceph::buffer::list& bl,
+		IOContext *ioc,
+		bool buffered,
+		int write_hint = WRITE_LIFE_NOT_SET) override;
+  int flush() override;
+  int discard(uint64_t offset, uint64_t len) override;
+
+  // for managing buffered readers/writers
+  int invalidate_cache(uint64_t off, uint64_t len) override;
+  int open(const std::string& path) override;
+  void close() override;
+};
+
+#endif
diff --git a/src/blk/kernel/io_uring.cc b/src/blk/kernel/io_uring.cc
new file mode 100644
index 000000000..17bd35bb4
--- /dev/null
+++ b/src/blk/kernel/io_uring.cc
@@ -0,0 +1,261 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "io_uring.h"
+
+#if defined(HAVE_LIBURING)
+
+#include "liburing.h"
+#include <sys/epoll.h>
+
+struct ioring_data {
+  struct io_uring io_uring;
+  pthread_mutex_t cq_mutex;
+  pthread_mutex_t sq_mutex;
+  int epoll_fd = -1;
+  std::map<int, int> fixed_fds_map;
+};
+
+static int ioring_get_cqe(struct ioring_data *d, unsigned int max,
+			  struct aio_t **paio)
+{
+  struct io_uring *ring = &d->io_uring;
+  struct io_uring_cqe *cqe;
+
+  unsigned nr = 0;
+  unsigned head;
+  io_uring_for_each_cqe(ring, head, cqe) {
+    struct aio_t *io = (struct aio_t *)(uintptr_t) io_uring_cqe_get_data(cqe);
+    io->rval = cqe->res;
+
+    paio[nr++] = io;
+
+    if (nr == max)
+      break;
+  }
+  io_uring_cq_advance(ring, nr);
+
+  return nr;
+}
+
+static int find_fixed_fd(struct ioring_data *d, int real_fd)
+{
+  auto it = d->fixed_fds_map.find(real_fd);
+  if (it == d->fixed_fds_map.end())
+    return -1;
+
+  return it->second;
+}
+
+static void init_sqe(struct ioring_data *d, struct io_uring_sqe *sqe,
+		     struct aio_t *io)
+{
+  int fixed_fd = find_fixed_fd(d, io->fd);
+
+  ceph_assert(fixed_fd != -1);
+
+  if (io->iocb.aio_lio_opcode == IO_CMD_PWRITEV)
+    io_uring_prep_writev(sqe, fixed_fd, &io->iov[0],
+			 io->iov.size(), io->offset);
+  else if (io->iocb.aio_lio_opcode == IO_CMD_PREADV)
+    io_uring_prep_readv(sqe, fixed_fd, &io->iov[0],
+			io->iov.size(), io->offset);
+  else
+    ceph_assert(0);
+
+  io_uring_sqe_set_data(sqe, io);
+  io_uring_sqe_set_flags(sqe, IOSQE_FIXED_FILE);
+}
+
+static int ioring_queue(struct ioring_data *d, void *priv,
+			list<aio_t>::iterator beg, list<aio_t>::iterator end)
+{
+  struct io_uring *ring = &d->io_uring;
+  struct aio_t *io = nullptr;
+
+  ceph_assert(beg != end);
+
+  do {
+    struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
+    if (!sqe)
+      break;
+
+    io = &*beg;
+    io->priv = priv;
+
+    init_sqe(d, sqe, io);
+
+  } while (++beg != end);
+
+  if (!io)
+    /* Queue is full, go and reap something first */
+    return 0;
+
+  return io_uring_submit(ring);
+}
+
+static void build_fixed_fds_map(struct ioring_data *d,
+				std::vector<int> &fds)
+{
+  int fixed_fd = 0;
+  for (int real_fd : fds) {
+    d->fixed_fds_map[real_fd] = fixed_fd++;
+  }
+}
+
+ioring_queue_t::ioring_queue_t(unsigned iodepth_, bool hipri_, bool sq_thread_) :
+  d(make_unique<ioring_data>()),
+  iodepth(iodepth_),
+  hipri(hipri_),
+  sq_thread(sq_thread_)
+{
+}
+
+ioring_queue_t::~ioring_queue_t()
+{
+}
+
+int ioring_queue_t::init(std::vector<int> &fds)
+{
+  unsigned flags = 0;
+
+  pthread_mutex_init(&d->cq_mutex, NULL);
+  pthread_mutex_init(&d->sq_mutex, NULL);
+
+  if (hipri)
+    flags |= IORING_SETUP_IOPOLL;
+  if (sq_thread)
+    flags |= IORING_SETUP_SQPOLL;
+
+  int ret = io_uring_queue_init(iodepth, &d->io_uring, flags);
+  if (ret < 0)
+    return ret;
+
+  ret = io_uring_register_files(&d->io_uring,
+			  &fds[0], fds.size());
+  if (ret < 0) {
+    ret = -errno;
+    goto close_ring_fd;
+  }
+
+  build_fixed_fds_map(d.get(), fds);
+
+  d->epoll_fd = epoll_create1(0);
+  if (d->epoll_fd < 0) {
+    ret = -errno;
+    goto close_ring_fd;
+  }
+
+  struct epoll_event ev;
+  ev.events = EPOLLIN;
+  ret = epoll_ctl(d->epoll_fd, EPOLL_CTL_ADD, d->io_uring.ring_fd, &ev);
+  if (ret < 0) {
+    ret = -errno;
+    goto close_epoll_fd;
+  }
+
+  return 0;
+
+close_epoll_fd:
+  close(d->epoll_fd);
+close_ring_fd:
+  io_uring_queue_exit(&d->io_uring);
+
+  return ret;
+}
+
+void ioring_queue_t::shutdown()
+{
+  d->fixed_fds_map.clear();
+  close(d->epoll_fd);
+  d->epoll_fd = -1;
+  io_uring_queue_exit(&d->io_uring);
+}
+
+int ioring_queue_t::submit_batch(aio_iter beg, aio_iter end,
+                                 uint16_t aios_size, void *priv,
+                                 int *retries)
+{
+  (void)aios_size;
+  (void)retries;
+
+  pthread_mutex_lock(&d->sq_mutex);
+  int rc = ioring_queue(d.get(), priv, beg, end);
+  pthread_mutex_unlock(&d->sq_mutex);
+
+  return rc;
+}
+
+int ioring_queue_t::get_next_completed(int timeout_ms, aio_t **paio, int max)
+{
+get_cqe:
+  pthread_mutex_lock(&d->cq_mutex);
+  int events = ioring_get_cqe(d.get(), max, paio);
+  pthread_mutex_unlock(&d->cq_mutex);
+
+  if (events == 0) {
+    struct epoll_event ev;
+    int ret = TEMP_FAILURE_RETRY(epoll_wait(d->epoll_fd, &ev, 1, timeout_ms));
+    if (ret < 0)
+      events = -errno;
+    else if (ret > 0)
+      /* Time to reap */
+      goto get_cqe;
+  }
+
+  return events;
+}
+
+bool ioring_queue_t::supported()
+{
+  struct io_uring ring;
+  int ret = io_uring_queue_init(16, &ring, 0);
+  if (ret) {
+    return false;
+  }
+  io_uring_queue_exit(&ring);
+  return true;
+}
+
+#else // #if defined(HAVE_LIBURING)
+
+struct ioring_data {};
+
+ioring_queue_t::ioring_queue_t(unsigned iodepth_, bool hipri_, bool sq_thread_)
+{
+  ceph_assert(0);
+}
+
+ioring_queue_t::~ioring_queue_t()
+{
+  ceph_assert(0);
+}
+
+int ioring_queue_t::init(std::vector<int> &fds)
+{
+  ceph_assert(0);
+}
+
+void ioring_queue_t::shutdown()
+{
+  ceph_assert(0);
+}
+
+int ioring_queue_t::submit_batch(aio_iter beg, aio_iter end,
+                                 uint16_t aios_size, void *priv,
+                                 int *retries)
+{
+  ceph_assert(0);
+}
+
+int ioring_queue_t::get_next_completed(int timeout_ms, aio_t **paio, int max)
+{
+  ceph_assert(0);
+}
+
+bool ioring_queue_t::supported()
+{
+  return false;
+}
+
+#endif // #if defined(HAVE_LIBURING)
diff --git a/src/blk/kernel/io_uring.h b/src/blk/kernel/io_uring.h
new file mode 100644
index 000000000..e7d0acde0
--- /dev/null
+++ b/src/blk/kernel/io_uring.h
@@ -0,0 +1,33 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include "acconfig.h"
+
+#include "include/types.h"
+#include "aio/aio.h"
+
+struct ioring_data;
+
+struct ioring_queue_t final : public io_queue_t {
+  std::unique_ptr<ioring_data> d;
+  unsigned iodepth = 0;
+  bool hipri = false;
+  bool sq_thread = false;
+
+  typedef std::list<aio_t>::iterator aio_iter;
+
+  // Returns true if arch is x86-64 and kernel supports io_uring
+  static bool supported();
+
+  ioring_queue_t(unsigned iodepth_, bool hipri_, bool sq_thread_);
+  ~ioring_queue_t() final;
+
+  int init(std::vector<int> &fds) final;
+  void shutdown() final;
+
+  int submit_batch(aio_iter begin, aio_iter end, uint16_t aios_size,
+                   void *priv, int *retries) final;
+  int get_next_completed(int timeout_ms, aio_t **paio, int max) final;
+};