import quincy beta 17.1.0

[ceph.git] / ceph / src / os / bluestore / BlueFS.cc

// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab

#include "boost/algorithm/string.hpp" 
#include "bluestore_common.h"
#include "BlueFS.h"

#include "common/debug.h"
#include "common/errno.h"
#include "common/perf_counters.h"
#include "Allocator.h"
#include "include/ceph_assert.h"
#include "common/admin_socket.h"

#define dout_context cct
#define dout_subsys ceph_subsys_bluefs
#undef dout_prefix
#define dout_prefix *_dout << "bluefs "
using TOPNSPC::common::cmd_getval;

using std::byte;
using std::list;
using std::make_pair;
using std::map;
using std::ostream;
using std::pair;
using std::set;
using std::string;
using std::to_string;
using std::vector;

using ceph::bufferlist;
using ceph::decode;
using ceph::encode;
using ceph::Formatter;


MEMPOOL_DEFINE_OBJECT_FACTORY(BlueFS::File, bluefs_file, bluefs);
MEMPOOL_DEFINE_OBJECT_FACTORY(BlueFS::Dir, bluefs_dir, bluefs);
MEMPOOL_DEFINE_OBJECT_FACTORY(BlueFS::FileWriter, bluefs_file_writer, bluefs_file_writer);
MEMPOOL_DEFINE_OBJECT_FACTORY(BlueFS::FileReaderBuffer,
			      bluefs_file_reader_buffer, bluefs_file_reader);
MEMPOOL_DEFINE_OBJECT_FACTORY(BlueFS::FileReader, bluefs_file_reader, bluefs_file_reader);
MEMPOOL_DEFINE_OBJECT_FACTORY(BlueFS::FileLock, bluefs_file_lock, bluefs);

static void wal_discard_cb(void *priv, void* priv2) {
  BlueFS *bluefs = static_cast<BlueFS*>(priv);
  interval_set<uint64_t> *tmp = static_cast<interval_set<uint64_t>*>(priv2);
  bluefs->handle_discard(BlueFS::BDEV_WAL, *tmp);
}

static void db_discard_cb(void *priv, void* priv2) {
  BlueFS *bluefs = static_cast<BlueFS*>(priv);
  interval_set<uint64_t> *tmp = static_cast<interval_set<uint64_t>*>(priv2);
  bluefs->handle_discard(BlueFS::BDEV_DB, *tmp);
}

static void slow_discard_cb(void *priv, void* priv2) {
  BlueFS *bluefs = static_cast<BlueFS*>(priv);
  interval_set<uint64_t> *tmp = static_cast<interval_set<uint64_t>*>(priv2);
  bluefs->handle_discard(BlueFS::BDEV_SLOW, *tmp);
}

class BlueFS::SocketHook : public AdminSocketHook {
  BlueFS* bluefs;
public:
  static BlueFS::SocketHook* create(BlueFS* bluefs)
  {
    BlueFS::SocketHook* hook = nullptr;
    AdminSocket* admin_socket = bluefs->cct->get_admin_socket();
    if (admin_socket) {
      hook = new BlueFS::SocketHook(bluefs);
      int r = admin_socket->register_command("bluestore bluefs device info "
                                             "name=alloc_size,type=CephInt,req=false",
                                             hook,
                                             "Shows space report for bluefs devices. "
                                             "This also includes an estimation for space "
                                             "available to bluefs at main device. "
                                             "alloc_size, if set, specifies the custom bluefs "
                                             "allocation unit size for the estimation above.");
      if (r != 0) {
        ldout(bluefs->cct, 1) << __func__ << " cannot register SocketHook" << dendl;
        delete hook;
        hook = nullptr;
      } else {
        r = admin_socket->register_command("bluefs stats",
                                           hook,
                                           "Dump internal statistics for bluefs."
                                           "");
        ceph_assert(r == 0);
	r = admin_socket->register_command("bluefs files list", hook,
					   "print files in bluefs");
	ceph_assert(r == 0);
	r = admin_socket->register_command("bluefs debug_inject_read_zeros", hook,
					   "Injects 8K zeros into next BlueFS read. Debug only.");
	ceph_assert(r == 0);
      }
    }
    return hook;
  }

  ~SocketHook() {
    AdminSocket* admin_socket = bluefs->cct->get_admin_socket();
    admin_socket->unregister_commands(this);
  }
private:
  SocketHook(BlueFS* bluefs) :
    bluefs(bluefs) {}
  int call(std::string_view command, const cmdmap_t& cmdmap,
	   Formatter *f,
	   std::ostream& errss,
	   bufferlist& out) override {
    if (command == "bluestore bluefs device info") {
      int64_t alloc_size = 0;
      cmd_getval(cmdmap, "alloc_size", alloc_size);
      if ((alloc_size & (alloc_size - 1)) != 0) {
	errss << "Invalid allocation size:'" << alloc_size << std::endl;
	return -EINVAL;
      }
      if (alloc_size == 0)
	alloc_size = bluefs->cct->_conf->bluefs_shared_alloc_size;
      f->open_object_section("bluefs_device_info");
      for (unsigned dev = BDEV_WAL; dev <= BDEV_SLOW; dev++) {
	if (bluefs->bdev[dev]) {
	  f->open_object_section("dev");
	  f->dump_string("device", bluefs->get_device_name(dev));
	  ceph_assert(bluefs->alloc[dev]);
          auto total = bluefs->get_total(dev);
          auto free = bluefs->get_free(dev);
          auto used = bluefs->get_used(dev);

          f->dump_int("total", total);
          f->dump_int("free", free);
          f->dump_int("bluefs_used", used);
          if (bluefs->is_shared_alloc(dev)) {
            size_t avail = bluefs->probe_alloc_avail(dev, alloc_size);
            f->dump_int("bluefs max available", avail);
          }
          f->close_section();
        }
      }

      f->close_section();
    } else if (command == "bluefs stats") {
      std::stringstream ss;
      bluefs->dump_block_extents(ss);
      bluefs->dump_volume_selector(ss);
      out.append(ss);
    } else if (command == "bluefs files list") {
      const char* devnames[3] = {"wal","db","slow"};
      std::lock_guard l(bluefs->nodes.lock);
      f->open_array_section("files");
      for (auto &d : bluefs->nodes.dir_map) {
        std::string dir = d.first;
        for (auto &r : d.second->file_map) {
          f->open_object_section("file");
          f->dump_string("name", (dir + "/" + r.first).c_str());
          std::vector<size_t> sizes;
          sizes.resize(bluefs->bdev.size());
          for(auto& i : r.second->fnode.extents) {
            sizes[i.bdev] += i.length;
          }
          for (size_t i = 0; i < sizes.size(); i++) {
            if (sizes[i]>0) {
	      if (i < sizeof(devnames) / sizeof(*devnames))
		f->dump_int(devnames[i], sizes[i]);
	      else
		f->dump_int(("dev-"+to_string(i)).c_str(), sizes[i]);
	    }
          }
          f->close_section();
        }
      }
      f->close_section();
      f->flush(out);
    } else if (command == "bluefs debug_inject_read_zeros") {
      bluefs->inject_read_zeros++;
    } else {
      errss << "Invalid command" << std::endl;
      return -ENOSYS;
    }
    return 0;
  }
};

BlueFS::BlueFS(CephContext* cct)
  : cct(cct),
    bdev(MAX_BDEV),
    ioc(MAX_BDEV),
    block_reserved(MAX_BDEV),
    alloc(MAX_BDEV),
    alloc_size(MAX_BDEV, 0)
{
  dirty.pending_release.resize(MAX_BDEV);
  discard_cb[BDEV_WAL] = wal_discard_cb;
  discard_cb[BDEV_DB] = db_discard_cb;
  discard_cb[BDEV_SLOW] = slow_discard_cb;
  asok_hook = SocketHook::create(this);
}

BlueFS::~BlueFS()
{
  delete asok_hook;
  for (auto p : ioc) {
    if (p)
      p->aio_wait();
  }
  for (auto p : bdev) {
    if (p) {
      p->close();
      delete p;
    }
  }
  for (auto p : ioc) {
    delete p;
  }
}

void BlueFS::_init_logger()
{
  PerfCountersBuilder b(cct, "bluefs",
                        l_bluefs_first, l_bluefs_last);
  b.add_u64(l_bluefs_db_total_bytes, "db_total_bytes",
	    "Total bytes (main db device)",
	    "b", PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_db_used_bytes, "db_used_bytes",
	    "Used bytes (main db device)",
	    "u", PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_wal_total_bytes, "wal_total_bytes",
	    "Total bytes (wal device)",
	    "walb", PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_wal_used_bytes, "wal_used_bytes",
	    "Used bytes (wal device)",
	    "walu", PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_slow_total_bytes, "slow_total_bytes",
	    "Total bytes (slow device)",
	    "slob", PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_slow_used_bytes, "slow_used_bytes",
	    "Used bytes (slow device)",
	    "slou", PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_num_files, "num_files", "File count",
	    "f", PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64(l_bluefs_log_bytes, "log_bytes", "Size of the metadata log",
	    "jlen", PerfCountersBuilder::PRIO_INTERESTING, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_log_compactions, "log_compactions",
		    "Compactions of the metadata log");
  b.add_u64_counter(l_bluefs_logged_bytes, "logged_bytes",
		    "Bytes written to the metadata log",
		    "j",
		    PerfCountersBuilder::PRIO_CRITICAL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_files_written_wal, "files_written_wal",
		    "Files written to WAL");
  b.add_u64_counter(l_bluefs_files_written_sst, "files_written_sst",
		    "Files written to SSTs");
  b.add_u64_counter(l_bluefs_bytes_written_wal, "bytes_written_wal",
		    "Bytes written to WAL",
		    "walb",
		    PerfCountersBuilder::PRIO_CRITICAL);
  b.add_u64_counter(l_bluefs_bytes_written_sst, "bytes_written_sst",
		    "Bytes written to SSTs",
		    "sstb",
		    PerfCountersBuilder::PRIO_CRITICAL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_bytes_written_slow, "bytes_written_slow",
		    "Bytes written to WAL/SSTs at slow device",
		    "slwb",
		    PerfCountersBuilder::PRIO_CRITICAL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_max_bytes_wal, "max_bytes_wal",
		    "Maximum bytes allocated from WAL",
		    "mxwb",
		    PerfCountersBuilder::PRIO_INTERESTING,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_max_bytes_db, "max_bytes_db",
		    "Maximum bytes allocated from DB",
		    "mxdb",
		    PerfCountersBuilder::PRIO_INTERESTING,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_max_bytes_slow, "max_bytes_slow",
		    "Maximum bytes allocated from SLOW",
		    "mxwb",
		    PerfCountersBuilder::PRIO_INTERESTING,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_main_alloc_unit, "alloc_unit_main",
		    "Allocation unit size (in bytes) for primary/shared device",
		    "aumb",
		    PerfCountersBuilder::PRIO_CRITICAL,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_db_alloc_unit, "alloc_unit_db",
		    "Allocation unit size (in bytes) for standalone DB device",
		    "audb",
		    PerfCountersBuilder::PRIO_CRITICAL,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_wal_alloc_unit, "alloc_unit_wal",
		    "Allocation unit size (in bytes) for standalone WAL device",
		    "auwb",
		    PerfCountersBuilder::PRIO_CRITICAL,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_random_count, "read_random_count",
		    "random read requests processed",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64_counter(l_bluefs_read_random_bytes, "read_random_bytes",
		    "Bytes requested in random read mode",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_random_disk_count, "read_random_disk_count",
		    "random reads requests going to disk",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64_counter(l_bluefs_read_random_disk_bytes, "read_random_disk_bytes",
		    "Bytes read from disk in random read mode",
		    "rrb",
		    PerfCountersBuilder::PRIO_INTERESTING,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_random_disk_bytes_wal, "read_random_disk_bytes_wal",
		    "random reads requests going to WAL disk",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_random_disk_bytes_db, "read_random_disk_bytes_db",
		    "random reads requests going to DB disk",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_random_disk_bytes_slow, "read_random_disk_bytes_slow",
		    "random reads requests going to main disk",
		    "rrsb",
		    PerfCountersBuilder::PRIO_INTERESTING,
		    unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_random_buffer_count, "read_random_buffer_count",
		    "random read requests processed using prefetch buffer",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64_counter(l_bluefs_read_random_buffer_bytes, "read_random_buffer_bytes",
		    "Bytes read from prefetch buffer in random read mode",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_count, "read_count",
		    "buffered read requests processed",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64_counter(l_bluefs_read_bytes, "read_bytes",
		    "Bytes requested in buffered read mode",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_disk_count, "read_disk_count",
		    "buffered reads requests going to disk",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64_counter(l_bluefs_read_disk_bytes, "read_disk_bytes",
		    "Bytes read in buffered mode from disk",
		    "rb",
		    PerfCountersBuilder::PRIO_INTERESTING, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_disk_bytes_wal, "read_disk_bytes_wal",
		    "reads requests going to WAL disk",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_disk_bytes_db, "read_disk_bytes_db",
		    "reads requests going to DB disk",
		    NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_disk_bytes_slow, "read_disk_bytes_slow",
		    "reads requests going to main disk",
		    "rsb",
		    PerfCountersBuilder::PRIO_INTERESTING, unit_t(UNIT_BYTES));
  b.add_u64_counter(l_bluefs_read_prefetch_count, "read_prefetch_count",
		    "prefetch read requests processed",
		     NULL,
		    PerfCountersBuilder::PRIO_USEFUL);
  b.add_u64_counter(l_bluefs_read_prefetch_bytes, "read_prefetch_bytes",
		    "Bytes requested in prefetch read mode",
		     NULL,
		    PerfCountersBuilder::PRIO_USEFUL, unit_t(UNIT_BYTES));
  b.add_u64(l_bluefs_read_zeros_candidate, "read_zeros_candidate",
	    "How many times bluefs read found page with all 0s");
  b.add_u64(l_bluefs_read_zeros_errors, "read_zeros_errors",
	    "How many times bluefs read found transient page with all 0s");

  logger = b.create_perf_counters();
  cct->get_perfcounters_collection()->add(logger);
}

void BlueFS::_shutdown_logger()
{
  cct->get_perfcounters_collection()->remove(logger);
  delete logger;
}

void BlueFS::_update_logger_stats()
{
  if (alloc[BDEV_WAL]) {
    logger->set(l_bluefs_wal_total_bytes, _get_total(BDEV_WAL));
    logger->set(l_bluefs_wal_used_bytes, _get_used(BDEV_WAL));
  }
  if (alloc[BDEV_DB]) {
    logger->set(l_bluefs_db_total_bytes, _get_total(BDEV_DB));
    logger->set(l_bluefs_db_used_bytes, _get_used(BDEV_DB));
  }
  if (alloc[BDEV_SLOW]) {
    logger->set(l_bluefs_slow_total_bytes, _get_total(BDEV_SLOW));
    logger->set(l_bluefs_slow_used_bytes, _get_used(BDEV_SLOW));
  }
}

int BlueFS::add_block_device(unsigned id, const string& path, bool trim,
                             uint64_t reserved,
                             bluefs_shared_alloc_context_t* _shared_alloc)
{
  dout(10) << __func__ << " bdev " << id << " path " << path << " "
           << reserved << dendl;
  ceph_assert(id < bdev.size());
  ceph_assert(bdev[id] == NULL);
  BlockDevice *b = BlockDevice::create(cct, path, NULL, NULL,
				       discard_cb[id], static_cast<void*>(this));
  block_reserved[id] = reserved;
  if (_shared_alloc) {
    b->set_no_exclusive_lock();
  }
  int r = b->open(path);
  if (r < 0) {
    delete b;
    return r;
  }
  if (trim) {
    b->discard(0, b->get_size());
  }

  dout(1) << __func__ << " bdev " << id << " path " << path
	  << " size " << byte_u_t(b->get_size()) << dendl;
  bdev[id] = b;
  ioc[id] = new IOContext(cct, NULL);
  if (_shared_alloc) {
    ceph_assert(!shared_alloc);
    shared_alloc = _shared_alloc;
    alloc[id] = shared_alloc->a;
    shared_alloc_id = id;
  }
  return 0;
}

bool BlueFS::bdev_support_label(unsigned id)
{
  ceph_assert(id < bdev.size());
  ceph_assert(bdev[id]);
  return bdev[id]->supported_bdev_label();
}

uint64_t BlueFS::get_block_device_size(unsigned id) const
{
  if (id < bdev.size() && bdev[id])
    return bdev[id]->get_size();
  return 0;
}

void BlueFS::handle_discard(unsigned id, interval_set<uint64_t>& to_release)
{
  dout(10) << __func__ << " bdev " << id << dendl;
  ceph_assert(alloc[id]);
  alloc[id]->release(to_release);
  if (is_shared_alloc(id)) {
    shared_alloc->bluefs_used -= to_release.size();
  }
}

uint64_t BlueFS::get_used()
{
  uint64_t used = 0;
  for (unsigned id = 0; id < MAX_BDEV; ++id) {
    used += _get_used(id);
  }
  return used;
}

uint64_t BlueFS::_get_used(unsigned id) const
{
  uint64_t used = 0;
  if (!alloc[id])
     return 0;

  if (is_shared_alloc(id)) {
    used = shared_alloc->bluefs_used;
  } else {
    used = _get_total(id) - alloc[id]->get_free();
  }
  return used;
}

uint64_t BlueFS::get_used(unsigned id)
{
  ceph_assert(id < alloc.size());
  ceph_assert(alloc[id]);
  return _get_used(id);
}

uint64_t BlueFS::_get_total(unsigned id) const
{
  ceph_assert(id < bdev.size());
  ceph_assert(id < block_reserved.size());
  return get_block_device_size(id) - block_reserved[id];
}

uint64_t BlueFS::get_total(unsigned id)
{
  return _get_total(id);
}

uint64_t BlueFS::get_free(unsigned id)
{
  ceph_assert(id < alloc.size());
  return alloc[id]->get_free();
}

void BlueFS::dump_perf_counters(Formatter *f)
{
  f->open_object_section("bluefs_perf_counters");
  logger->dump_formatted(f,0);
  f->close_section();
}

void BlueFS::dump_block_extents(ostream& out)
{
  for (unsigned i = 0; i < MAX_BDEV; ++i) {
    if (!bdev[i]) {
      continue;
    }
    auto total = get_total(i);
    auto free = get_free(i);

    out << i << " : device size 0x" << std::hex << total
        << " : using 0x" << total - free
	<< std::dec << "(" << byte_u_t(total - free) << ")";
    out << "\n";
  }
}

int BlueFS::get_block_extents(unsigned id, interval_set<uint64_t> *extents)
{
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " bdev " << id << dendl;
  ceph_assert(id < alloc.size());
  for (auto& p : nodes.file_map) {
    for (auto& q : p.second->fnode.extents) {
      if (q.bdev == id) {
        extents->insert(q.offset, q.length);
      }
    }
  }
  return 0;
}

int BlueFS::mkfs(uuid_d osd_uuid, const bluefs_layout_t& layout)
{
  dout(1) << __func__
	  << " osd_uuid " << osd_uuid
	  << dendl;

  // set volume selector if not provided before/outside
  if (vselector == nullptr) {
    vselector.reset(
      new OriginalVolumeSelector(
        get_block_device_size(BlueFS::BDEV_WAL) * 95 / 100,
        get_block_device_size(BlueFS::BDEV_DB) * 95 / 100,
        get_block_device_size(BlueFS::BDEV_SLOW) * 95 / 100));
  }

  _init_logger();
  _init_alloc();

  super.version = 1;
  super.block_size = bdev[BDEV_DB]->get_block_size();
  super.osd_uuid = osd_uuid;
  super.uuid.generate_random();
  dout(1) << __func__ << " uuid " << super.uuid << dendl;

  // init log
  FileRef log_file = ceph::make_ref<File>();
  log_file->fnode.ino = 1;
  log_file->vselector_hint = vselector->get_hint_for_log();
  int r = _allocate(
    vselector->select_prefer_bdev(log_file->vselector_hint),
    cct->_conf->bluefs_max_log_runway,
    &log_file->fnode);
  vselector->add_usage(log_file->vselector_hint, log_file->fnode);
  ceph_assert(r == 0);
  log.writer = _create_writer(log_file);

  // initial txn
  ceph_assert(log.seq_live == 1);
  log.t.seq = 1;
  log.t.op_init();
  _flush_and_sync_log_LD();

  // write supers
  super.log_fnode = log_file->fnode;
  super.memorized_layout = layout;
  _write_super(BDEV_DB);
  _flush_bdev();

  // clean up
  super = bluefs_super_t();
  _close_writer(log.writer);
  log.writer = NULL;
  vselector.reset(nullptr);
  _stop_alloc();
  _shutdown_logger();
  if (shared_alloc) {
    ceph_assert(shared_alloc->need_init);
    shared_alloc->need_init = false;
  }

  dout(10) << __func__ << " success" << dendl;
  return 0;
}

void BlueFS::_init_alloc()
{
  dout(20) << __func__ << dendl;

  size_t wal_alloc_size = 0;
  if (bdev[BDEV_WAL]) {
    wal_alloc_size = cct->_conf->bluefs_alloc_size;
    alloc_size[BDEV_WAL] = wal_alloc_size;
  }
  logger->set(l_bluefs_wal_alloc_unit, wal_alloc_size);

  if (bdev[BDEV_SLOW]) {
    alloc_size[BDEV_DB] = cct->_conf->bluefs_alloc_size;
    alloc_size[BDEV_SLOW] = cct->_conf->bluefs_shared_alloc_size;
    logger->set(l_bluefs_db_alloc_unit, cct->_conf->bluefs_alloc_size);
    logger->set(l_bluefs_main_alloc_unit, cct->_conf->bluefs_shared_alloc_size);
  } else {
    alloc_size[BDEV_DB] = cct->_conf->bluefs_shared_alloc_size;
    logger->set(l_bluefs_main_alloc_unit, 0);
    logger->set(l_bluefs_db_alloc_unit, cct->_conf->bluefs_shared_alloc_size);
  }
  // new wal and db devices are never shared
  if (bdev[BDEV_NEWWAL]) {
    alloc_size[BDEV_NEWWAL] = cct->_conf->bluefs_alloc_size;
  }
  if (bdev[BDEV_NEWDB]) {
    alloc_size[BDEV_NEWDB] = cct->_conf->bluefs_alloc_size;
  }

  for (unsigned id = 0; id < bdev.size(); ++id) {
    if (!bdev[id]) {
      continue;
    }
    ceph_assert(bdev[id]->get_size());
    ceph_assert(alloc_size[id]);
    if (is_shared_alloc(id)) {
      dout(1) << __func__ << " shared, id " << id << std::hex
              << ", capacity 0x" << bdev[id]->get_size()
              << ", block size 0x" << alloc_size[id]
              << std::dec << dendl;
    } else {
      std::string name = "bluefs-";
      const char* devnames[] = { "wal","db","slow" };
      if (id <= BDEV_SLOW)
        name += devnames[id];
      else
        name += to_string(uintptr_t(this));
      dout(1) << __func__ << " new, id " << id << std::hex
              << ", allocator name " << name
              << ", allocator type " << cct->_conf->bluefs_allocator
              << ", capacity 0x" << bdev[id]->get_size()
              << ", block size 0x" << alloc_size[id]
              << std::dec << dendl;
      alloc[id] = Allocator::create(cct, cct->_conf->bluefs_allocator,
				    bdev[id]->get_size(),
				    alloc_size[id],
				    0, 0,
				    name);
      alloc[id]->init_add_free(
        block_reserved[id],
        _get_total(id));
    }
  }
}

void BlueFS::_stop_alloc()
{
  dout(20) << __func__ << dendl;
  for (auto p : bdev) {
    if (p)
      p->discard_drain();
  }

  for (size_t i = 0; i < alloc.size(); ++i) {
    if (alloc[i] && !is_shared_alloc(i)) {
      alloc[i]->shutdown();
      delete alloc[i];
      alloc[i] = nullptr;
    }
  }
}

int BlueFS::_read_and_check(uint8_t ndev, uint64_t off, uint64_t len,
			    ceph::buffer::list *pbl, IOContext *ioc, bool buffered)
{
  dout(10) << __func__ << " dev " << int(ndev)
           << ": 0x" << std::hex << off << "~" << len << std::dec
	   << (buffered ? " buffered" : "")
	   << dendl;
  int r;
  bufferlist bl;
  r = _bdev_read(ndev, off, len, &bl, ioc, buffered);
  if (r != 0) {
    return r;
  }
  uint64_t block_size = bdev[ndev]->get_block_size();
  if (inject_read_zeros) {
    if (len >= block_size * 2) {
      derr << __func__ << " injecting error, zeros at "
	   << int(ndev) << ": 0x" << std::hex << (off + len / 2)
	   << "~" << (block_size * 2) << std::dec << dendl;
      //use beginning, replace 8K in the middle with zeros, use tail
      bufferlist temp;
      bl.splice(0, len / 2 - block_size, &temp);
      temp.append(buffer::create(block_size * 2, 0));
      bl.splice(block_size * 2, len / 2 - block_size, &temp);
      bl = temp;
      inject_read_zeros--;
    }
  }
  //make a check if there is a block with all 0
  uint64_t to_check_len = len;
  uint64_t skip = p2nphase(off, block_size);
  if (skip >= to_check_len) {
    return r;
  }
  auto it = bl.begin(skip);
  to_check_len -= skip;
  bool all_zeros = false;
  while (all_zeros == false && to_check_len >= block_size) {
    // checking 0s step
    unsigned block_left = block_size;
    unsigned avail;
    const char* data;
    all_zeros = true;
    while (all_zeros && block_left > 0) {
      avail = it.get_ptr_and_advance(block_left, &data);
      block_left -= avail;
      all_zeros = mem_is_zero(data, avail);
    }
    // skipping step
    while (block_left > 0) {
      avail = it.get_ptr_and_advance(block_left, &data);
      block_left -= avail;
    }
    to_check_len -= block_size;
  }
  if (all_zeros) {
    logger->inc(l_bluefs_read_zeros_candidate, 1);
    bufferlist bl_reread;
    r = _bdev_read(ndev, off, len, &bl_reread, ioc, buffered);
    if (r != 0) {
      return r;
    }
    // check if both read gave the same
    if (!bl.contents_equal(bl_reread)) {
      // report problems to log, but continue, maybe it will be good now...
      derr << __func__ << " initial read of " << int(ndev)
	   << ": 0x" << std::hex << off << "~" << len
	   << std::dec << ": different then re-read " << dendl;
      logger->inc(l_bluefs_read_zeros_errors, 1);
    }
    // use second read will be better if is different
    pbl->append(bl_reread);
  } else {
    pbl->append(bl);
  }
  return r;
}

int BlueFS::_read_random_and_check(
  uint8_t ndev, uint64_t off, uint64_t len, char *buf, bool buffered)
{
  dout(10) << __func__ << " dev " << int(ndev)
           << ": 0x" << std::hex << off << "~" << len << std::dec
	   << (buffered ? " buffered" : "")
	   << dendl;
  int r;
  r = _bdev_read_random(ndev, off, len, buf, buffered);
  if (r != 0) {
    return r;
  }
  uint64_t block_size = bdev[ndev]->get_block_size();
  if (inject_read_zeros) {
    if (len >= block_size * 2) {
      derr << __func__ << " injecting error, zeros at "
	   << int(ndev) << ": 0x" << std::hex << (off + len / 2)
	   << "~" << (block_size * 2) << std::dec << dendl;
      //zero middle 8K
      memset(buf + len / 2 - block_size, 0, block_size * 2);
      inject_read_zeros--;
    }
  }
  //make a check if there is a block with all 0
  uint64_t to_check_len = len;
  const char* data = buf;
  uint64_t skip = p2nphase(off, block_size);
  if (skip >= to_check_len) {
    return r;
  }
  to_check_len -= skip;
  data += skip;

  bool all_zeros = false;
  while (all_zeros == false && to_check_len >= block_size) {
    if (mem_is_zero(data, block_size)) {
      // at least one block is all zeros
      all_zeros = true;
      break;
    }
    data += block_size;
    to_check_len -= block_size;
  }
  if (all_zeros) {
    logger->inc(l_bluefs_read_zeros_candidate, 1);
    std::unique_ptr<char[]> data_reread(new char[len]);
    r = _bdev_read_random(ndev, off, len, &data_reread[0], buffered);
    if (r != 0) {
      return r;
    }
    // check if both read gave the same
    if (memcmp(buf, &data_reread[0], len) != 0) {
      derr << __func__ << " initial read of " << int(ndev)
	   << ": 0x" << std::hex << off << "~" << len
	   << std::dec << ": different then re-read " << dendl;
      logger->inc(l_bluefs_read_zeros_errors, 1);
      // second read is probably better
      memcpy(buf, &data_reread[0], len);
    }
  }
  return r;
}

int BlueFS::_bdev_read(uint8_t ndev, uint64_t off, uint64_t len,
  ceph::buffer::list* pbl, IOContext* ioc, bool buffered)
{
  int cnt = 0;
  switch (ndev) {
    case BDEV_WAL: cnt = l_bluefs_read_disk_bytes_wal; break;
    case BDEV_DB: cnt = l_bluefs_read_disk_bytes_db; break;
    case BDEV_SLOW: cnt = l_bluefs_read_disk_bytes_slow; break;

  }
  if (cnt) {
    logger->inc(cnt, len);
  }
  return bdev[ndev]->read(off, len, pbl, ioc, buffered);
}

int BlueFS::_bdev_read_random(uint8_t ndev, uint64_t off, uint64_t len,
  char* buf, bool buffered)
{
  int cnt = 0;
  switch (ndev) {
    case BDEV_WAL: cnt = l_bluefs_read_random_disk_bytes_wal; break;
    case BDEV_DB: cnt = l_bluefs_read_random_disk_bytes_db; break;
    case BDEV_SLOW: cnt = l_bluefs_read_random_disk_bytes_slow; break;
  }
  if (cnt) {
    logger->inc(cnt, len);
  }
  return bdev[ndev]->read_random(off, len, buf, buffered);
}

int BlueFS::mount()
{
  dout(1) << __func__ << dendl;

  _init_logger();
  int r = _open_super();
  if (r < 0) {
    derr << __func__ << " failed to open super: " << cpp_strerror(r) << dendl;
    goto out;
  }

  // set volume selector if not provided before/outside
  if (vselector == nullptr) {
    vselector.reset(
      new OriginalVolumeSelector(
        get_block_device_size(BlueFS::BDEV_WAL) * 95 / 100,
        get_block_device_size(BlueFS::BDEV_DB) * 95 / 100,
        get_block_device_size(BlueFS::BDEV_SLOW) * 95 / 100));
  }

  _init_alloc();

  r = _replay(false, false);
  if (r < 0) {
    derr << __func__ << " failed to replay log: " << cpp_strerror(r) << dendl;
    _stop_alloc();
    goto out;
  }

  // init freelist
  for (auto& p : nodes.file_map) {
    dout(30) << __func__ << " noting alloc for " << p.second->fnode << dendl;
    for (auto& q : p.second->fnode.extents) {
      bool is_shared = is_shared_alloc(q.bdev);
      ceph_assert(!is_shared || (is_shared && shared_alloc));
      if (is_shared && shared_alloc->need_init && shared_alloc->a) {
        shared_alloc->bluefs_used += q.length;
        alloc[q.bdev]->init_rm_free(q.offset, q.length);
      } else if (!is_shared) {
        alloc[q.bdev]->init_rm_free(q.offset, q.length);
      }
    }
  }
  if (shared_alloc) {
    shared_alloc->need_init = false;
    dout(1) << __func__ << " shared_bdev_used = "
            << shared_alloc->bluefs_used << dendl;
  } else {
    dout(1) << __func__ << " shared bdev not used"
            << dendl;
  }

  // set up the log for future writes
  log.writer = _create_writer(_get_file(1));
  ceph_assert(log.writer->file->fnode.ino == 1);
  log.writer->pos = log.writer->file->fnode.size;
  log.writer->file->fnode.reset_delta();
  dout(10) << __func__ << " log write pos set to 0x"
           << std::hex << log.writer->pos << std::dec
           << dendl;
  // update log size
  logger->set(l_bluefs_log_bytes, log.writer->file->fnode.size);
  return 0;

 out:
  super = bluefs_super_t();
  return r;
}

int BlueFS::maybe_verify_layout(const bluefs_layout_t& layout) const
{
  if (super.memorized_layout) {
    if (layout == *super.memorized_layout) {
      dout(10) << __func__ << " bluefs layout verified positively" << dendl;
    } else {
      derr << __func__ << " memorized layout doesn't fit current one" << dendl;
      return -EIO;
    }
  } else {
    dout(10) << __func__ << " no memorized_layout in bluefs superblock"
             << dendl;
  }

  return 0;
}

void BlueFS::umount(bool avoid_compact)
{
  dout(1) << __func__ << dendl;

  sync_metadata(avoid_compact);
  if (cct->_conf->bluefs_check_volume_selector_on_umount) {
    _check_vselector_LNF();
  }
  _close_writer(log.writer);
  log.writer = NULL;
  log.t.clear();

  vselector.reset(nullptr);
  _stop_alloc();
  nodes.file_map.clear();
  nodes.dir_map.clear();
  super = bluefs_super_t();
  _shutdown_logger();
}

int BlueFS::prepare_new_device(int id, const bluefs_layout_t& layout)
{
  dout(1) << __func__ << dendl;

  if(id == BDEV_NEWDB) {
    int new_log_dev_cur = BDEV_WAL;
    int new_log_dev_next = BDEV_WAL;
    if (!bdev[BDEV_WAL]) {
      new_log_dev_cur = BDEV_NEWDB;
      new_log_dev_next = BDEV_DB;
    }
    _rewrite_log_and_layout_sync_LNF_LD(false,
      BDEV_NEWDB,
      new_log_dev_cur,
      new_log_dev_next,
      RENAME_DB2SLOW,
      layout);
    //}
  } else if(id == BDEV_NEWWAL) {
    _rewrite_log_and_layout_sync_LNF_LD(false,
      BDEV_DB,
      BDEV_NEWWAL,
      BDEV_WAL,
      REMOVE_WAL,
      layout);
  } else {
    assert(false);
  }
  return 0;
}

void BlueFS::collect_metadata(map<string,string> *pm, unsigned skip_bdev_id)
{
  if (skip_bdev_id != BDEV_DB && bdev[BDEV_DB])
    bdev[BDEV_DB]->collect_metadata("bluefs_db_", pm);
  if (bdev[BDEV_WAL])
    bdev[BDEV_WAL]->collect_metadata("bluefs_wal_", pm);
}

void BlueFS::get_devices(set<string> *ls)
{
  for (unsigned i = 0; i < MAX_BDEV; ++i) {
    if (bdev[i]) {
      bdev[i]->get_devices(ls);
    }
  }
}

int BlueFS::fsck()
{
  dout(1) << __func__ << dendl;
  // hrm, i think we check everything on mount...
  return 0;
}

int BlueFS::_write_super(int dev)
{
  // build superblock
  bufferlist bl;
  encode(super, bl);
  uint32_t crc = bl.crc32c(-1);
  encode(crc, bl);
  dout(10) << __func__ << " super block length(encoded): " << bl.length() << dendl;
  dout(10) << __func__ << " superblock " << super.version << dendl;
  dout(10) << __func__ << " log_fnode " << super.log_fnode << dendl;
  ceph_assert_always(bl.length() <= get_super_length());
  bl.append_zero(get_super_length() - bl.length());

  bdev[dev]->write(get_super_offset(), bl, false, WRITE_LIFE_SHORT);
  dout(20) << __func__ << " v " << super.version
           << " crc 0x" << std::hex << crc
           << " offset 0x" << get_super_offset() << std::dec
           << dendl;
  return 0;
}

int BlueFS::_open_super()
{
  dout(10) << __func__ << dendl;

  bufferlist bl;
  uint32_t expected_crc, crc;
  int r;

  // always the second block
  r = _bdev_read(BDEV_DB, get_super_offset(), get_super_length(),
		 &bl, ioc[BDEV_DB], false);
  if (r < 0)
    return r;

  auto p = bl.cbegin();
  decode(super, p);
  {
    bufferlist t;
    t.substr_of(bl, 0, p.get_off());
    crc = t.crc32c(-1);
  }
  decode(expected_crc, p);
  if (crc != expected_crc) {
    derr << __func__ << " bad crc on superblock, expected 0x"
         << std::hex << expected_crc << " != actual 0x" << crc << std::dec
         << dendl;
    return -EIO;
  }
  dout(10) << __func__ << " superblock " << super.version << dendl;
  dout(10) << __func__ << " log_fnode " << super.log_fnode << dendl;
  return 0;
}

int BlueFS::_check_allocations(const bluefs_fnode_t& fnode,
  boost::dynamic_bitset<uint64_t>* used_blocks,
  bool is_alloc, //true when allocating, false when deallocating
  const char* op_name)
{
  auto& fnode_extents = fnode.extents;
  for (auto e : fnode_extents) {
    auto id = e.bdev;
    bool fail = false;
    ceph_assert(id < MAX_BDEV);
    if (int r = _verify_alloc_granularity(id, e.offset, e.length,
					  op_name); r < 0) {
      return r;
    }

    apply_for_bitset_range(e.offset, e.length, alloc_size[id], used_blocks[id],
      [&](uint64_t pos, boost::dynamic_bitset<uint64_t> &bs) {
	if (is_alloc == bs.test(pos)) {
	  fail = true;
	} else {
	  bs.flip(pos);
	}
      }
    );
    if (fail) {
      derr << __func__ << " " << op_name << " invalid extent " << int(e.bdev)
        << ": 0x" << std::hex << e.offset << "~" << e.length << std::dec
	<< (is_alloc == true ?
	    ": duplicate reference, ino " : ": double free, ino ")
	<< fnode.ino << dendl;
      return -EFAULT;
    }
  }
  return 0;
}

int BlueFS::_verify_alloc_granularity(
  __u8 id, uint64_t offset, uint64_t length, const char *op)
{
  if ((offset & (alloc_size[id] - 1)) ||
      (length & (alloc_size[id] - 1))) {
    derr << __func__ << " " << op << " of " << (int)id
	 << ":0x" << std::hex << offset << "~" << length << std::dec
	 << " does not align to alloc_size 0x"
	 << std::hex << alloc_size[id] << std::dec << dendl;
    // be helpful
    auto need = alloc_size[id];
    while (need && ((offset & (need - 1)) ||
		    (length & (need - 1)))) {
      need >>= 1;
    }
    if (need) {
      const char *which;
      if (id == BDEV_SLOW ||
	  (id == BDEV_DB && !bdev[BDEV_SLOW])) {
	which = "bluefs_shared_alloc_size";
      } else {
	which = "bluefs_alloc_size";
      }
      derr << "work-around by setting " << which << " = " << need
	   << " for this OSD" << dendl;
    }
    return -EFAULT;
  }
  return 0;
}

int BlueFS::_replay(bool noop, bool to_stdout)
{
  dout(10) << __func__ << (noop ? " NO-OP" : "") << dendl;
  ino_last = 1;  // by the log
  uint64_t log_seq = 0;

  FileRef log_file;
  log_file = _get_file(1);

  log_file->fnode = super.log_fnode;
  if (!noop) {
    log_file->vselector_hint =
      vselector->get_hint_for_log();
  } else {
    // do not use fnode from superblock in 'noop' mode - log_file's one should
    // be fine and up-to-date
    ceph_assert(log_file->fnode.ino == 1);
    ceph_assert(log_file->fnode.extents.size() != 0);
  }
  dout(10) << __func__ << " log_fnode " << super.log_fnode << dendl;
  if (unlikely(to_stdout)) {
    std::cout << " log_fnode " << super.log_fnode << std::endl;
  } 

  FileReader *log_reader = new FileReader(
    log_file, cct->_conf->bluefs_max_prefetch,
    false,  // !random
    true);  // ignore eof

  bool seen_recs = false;

  boost::dynamic_bitset<uint64_t> used_blocks[MAX_BDEV];

  if (!noop) {
    if (cct->_conf->bluefs_log_replay_check_allocations) {
      for (size_t i = 0; i < MAX_BDEV; ++i) {
	if (alloc_size[i] != 0 && bdev[i] != nullptr) {
	  used_blocks[i].resize(round_up_to(bdev[i]->get_size(), alloc_size[i]) / alloc_size[i]);
	}
      }
      // check initial log layout
      int r = _check_allocations(log_file->fnode,
				 used_blocks, true, "Log from super");
      if (r < 0) {
	return r;
      }
    }
  }
  
  while (true) {
    ceph_assert((log_reader->buf.pos & ~super.block_mask()) == 0);
    uint64_t pos = log_reader->buf.pos;
    uint64_t read_pos = pos;
    bufferlist bl;
    {
      int r = _read(log_reader, read_pos, super.block_size,
		    &bl, NULL);
      if (r != (int)super.block_size && cct->_conf->bluefs_replay_recovery) {
	r += _do_replay_recovery_read(log_reader, pos, read_pos + r, super.block_size - r, &bl);
      }
      assert(r == (int)super.block_size);
      read_pos += r;
    }
    uint64_t more = 0;
    uint64_t seq;
    uuid_d uuid;
    {
      auto p = bl.cbegin();
      __u8 a, b;
      uint32_t len;
      decode(a, p);
      decode(b, p);
      decode(len, p);
      decode(uuid, p);
      decode(seq, p);
      if (len + 6 > bl.length()) {
	more = round_up_to(len + 6 - bl.length(), super.block_size);
      }
    }
    if (uuid != super.uuid) {
      if (seen_recs) {
	dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
		 << ": stop: uuid " << uuid << " != super.uuid " << super.uuid
		 << dendl;
      } else {
	derr << __func__ << " 0x" << std::hex << pos << std::dec
		 << ": stop: uuid " << uuid << " != super.uuid " << super.uuid
		 << ", block dump: \n";
	bufferlist t;
	t.substr_of(bl, 0, super.block_size);
	t.hexdump(*_dout);
	*_dout << dendl;
      }
      break;
    }
    if (seq != log_seq + 1) {
      if (seen_recs) {
	dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
		 << ": stop: seq " << seq << " != expected " << log_seq + 1
		 << dendl;;
      } else {
	derr << __func__ << " 0x" << std::hex << pos << std::dec
	     << ": stop: seq " << seq << " != expected " << log_seq + 1
	     << dendl;;
      }
      break;
    }
    if (more) {
      dout(20) << __func__ << " need 0x" << std::hex << more << std::dec
               << " more bytes" << dendl;
      bufferlist t;
      int r = _read(log_reader, read_pos, more, &t, NULL);
      if (r < (int)more) {
	dout(10) << __func__ << " 0x" << std::hex << pos
                 << ": stop: len is 0x" << bl.length() + more << std::dec
                 << ", which is past eof" << dendl;
	if (cct->_conf->bluefs_replay_recovery) {
	  //try to search for more data
	  r += _do_replay_recovery_read(log_reader, pos, read_pos + r, more - r, &t);
	  if (r < (int)more) {
	    //in normal mode we must read r==more, for recovery it is too strict
	    break;
	  }
	}
      }
      ceph_assert(r == (int)more);
      bl.claim_append(t);
      read_pos += r;
    }
    bluefs_transaction_t t;
    try {
      auto p = bl.cbegin();
      decode(t, p);
      seen_recs = true;
    }
    catch (ceph::buffer::error& e) {
      // Multi-block transactions might be incomplete due to unexpected
      // power off. Hence let's treat that as a regular stop condition.
      if (seen_recs && more) {
        dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
                 << ": stop: failed to decode: " << e.what()
                 << dendl;
      } else {
        derr << __func__ << " 0x" << std::hex << pos << std::dec
             << ": stop: failed to decode: " << e.what()
             << dendl;
        delete log_reader;
        return -EIO;
      }
      break;
    }
    ceph_assert(seq == t.seq);
    dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
             << ": " << t << dendl;
    if (unlikely(to_stdout)) {
      std::cout << " 0x" << std::hex << pos << std::dec
                << ": " << t << std::endl;
    }

    auto p = t.op_bl.cbegin();
    while (!p.end()) {
      __u8 op;
      decode(op, p);
      switch (op) {

      case bluefs_transaction_t::OP_INIT:
	dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                 << ":  op_init" << dendl;
        if (unlikely(to_stdout)) {
          std::cout << " 0x" << std::hex << pos << std::dec
                    << ":  op_init" << std::endl;
        }

	ceph_assert(t.seq == 1);
	break;

      case bluefs_transaction_t::OP_JUMP:
        {
	  uint64_t next_seq;
	  uint64_t offset;
	  decode(next_seq, p);
	  decode(offset, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
		   << ":  op_jump seq " << next_seq
		   << " offset 0x" << std::hex << offset << std::dec << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_jump seq " << next_seq
                      << " offset 0x" << std::hex << offset << std::dec
                      << std::endl;
          }

	  ceph_assert(next_seq > log_seq);
	  log_seq = next_seq - 1; // we will increment it below
	  uint64_t skip = offset - read_pos;
	  if (skip) {
	    bufferlist junk;
	    int r = _read(log_reader, read_pos, skip, &junk,
			  NULL);
	    if (r != (int)skip) {
	      dout(10) << __func__ << " 0x" << std::hex << read_pos
		       << ": stop: failed to skip to " << offset
		       << std::dec << dendl;
	      ceph_abort_msg("problem with op_jump");
	    }
	  }
	}
	break;

      case bluefs_transaction_t::OP_JUMP_SEQ:
        {
	  uint64_t next_seq;
	  decode(next_seq, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_jump_seq " << next_seq << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_jump_seq " << next_seq << std::endl;
          }

	  ceph_assert(next_seq > log_seq);
	  log_seq = next_seq - 1; // we will increment it below
	}
	break;

      case bluefs_transaction_t::OP_ALLOC_ADD:
	// LEGACY, do nothing but read params
        {
          __u8 id;
          uint64_t offset, length;
          decode(id, p);
          decode(offset, p);
          decode(length, p);
        }
	break;

      case bluefs_transaction_t::OP_ALLOC_RM:
	// LEGACY, do nothing but read params
        {
          __u8 id;
          uint64_t offset, length;
          decode(id, p);
          decode(offset, p);
          decode(length, p);
        }
        break;

      case bluefs_transaction_t::OP_DIR_LINK:
        {
	  string dirname, filename;
	  uint64_t ino;
	  decode(dirname, p);
	  decode(filename, p);
	  decode(ino, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_dir_link " << " " << dirname << "/" << filename
                   << " to " << ino
		   << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_dir_link " << " " << dirname << "/" << filename
                      << " to " << ino
                      << std::endl;
          }

	  if (!noop) {
	    FileRef file = _get_file(ino);
	    ceph_assert(file->fnode.ino);
	    map<string,DirRef>::iterator q = nodes.dir_map.find(dirname);
	    ceph_assert(q != nodes.dir_map.end());
	    map<string,FileRef>::iterator r = q->second->file_map.find(filename);
	    ceph_assert(r == q->second->file_map.end());

            vselector->sub_usage(file->vselector_hint, file->fnode);
            file->vselector_hint =
              vselector->get_hint_by_dir(dirname);
            vselector->add_usage(file->vselector_hint, file->fnode);

	    q->second->file_map[filename] = file;
	    ++file->refs;
	  }
	}
	break;

      case bluefs_transaction_t::OP_DIR_UNLINK:
        {
	  string dirname, filename;
	  decode(dirname, p);
	  decode(filename, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_dir_unlink " << " " << dirname << "/" << filename
                   << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_dir_unlink " << " " << dirname << "/" << filename
                      << std::endl;
          }
 
	  if (!noop) {
	    map<string,DirRef>::iterator q = nodes.dir_map.find(dirname);
	    ceph_assert(q != nodes.dir_map.end());
	    map<string,FileRef>::iterator r = q->second->file_map.find(filename);
	    ceph_assert(r != q->second->file_map.end());
            ceph_assert(r->second->refs > 0); 
	    --r->second->refs;
	    q->second->file_map.erase(r);
	  }
	}
	break;

      case bluefs_transaction_t::OP_DIR_CREATE:
        {
	  string dirname;
	  decode(dirname, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_dir_create " << dirname << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_dir_create " << dirname << std::endl;
          }

	  if (!noop) {
	    map<string,DirRef>::iterator q = nodes.dir_map.find(dirname);
	    ceph_assert(q == nodes.dir_map.end());
	    nodes.dir_map[dirname] = ceph::make_ref<Dir>();
	  }
	}
	break;

      case bluefs_transaction_t::OP_DIR_REMOVE:
        {
	  string dirname;
	  decode(dirname, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_dir_remove " << dirname << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_dir_remove " << dirname << std::endl;
          }

	  if (!noop) {
	    map<string,DirRef>::iterator q = nodes.dir_map.find(dirname);
	    ceph_assert(q != nodes.dir_map.end());
	    ceph_assert(q->second->file_map.empty());
	    nodes.dir_map.erase(q);
	  }
	}
	break;

      case bluefs_transaction_t::OP_FILE_UPDATE:
        {
	  bluefs_fnode_t fnode;
	  decode(fnode, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_file_update " << " " << fnode << " " << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_file_update " << " " << fnode << std::endl;
          }
          if (!noop) {
	    FileRef f = _get_file(fnode.ino);
	    if (cct->_conf->bluefs_log_replay_check_allocations) {
              int r = _check_allocations(f->fnode,
		used_blocks, false, "OP_FILE_UPDATE");
              if (r < 0) {
                return r;
              }
            }
            if (fnode.ino != 1) {
              vselector->sub_usage(f->vselector_hint, f->fnode);
            }
            f->fnode = fnode;
            if (fnode.ino != 1) {
              vselector->add_usage(f->vselector_hint, f->fnode);
            }

	    if (fnode.ino > ino_last) {
	      ino_last = fnode.ino;
	    }
            if (cct->_conf->bluefs_log_replay_check_allocations) {
              int r = _check_allocations(f->fnode,
		used_blocks, true, "OP_FILE_UPDATE");
              if (r < 0) {
                return r;
              }
            }
	  } else if (noop && fnode.ino == 1) {
	    FileRef f = _get_file(fnode.ino);
	    f->fnode = fnode;
	  }
        }
	break;
      case bluefs_transaction_t::OP_FILE_UPDATE_INC:
	{
	  bluefs_fnode_delta_t delta;
	  decode(delta, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
	    << ":  op_file_update_inc " << " " << delta << " " << dendl;
	  if (unlikely(to_stdout)) {
	    std::cout << " 0x" << std::hex << pos << std::dec
	      << ":  op_file_update_inc " << " " << delta << std::endl;
	  }
	  if (!noop) {
	    FileRef f = _get_file(delta.ino);
	    bluefs_fnode_t& fnode = f->fnode;
	    if (delta.offset != fnode.allocated) {
	      derr << __func__ << " invalid op_file_update_inc, new extents miss end of file"
		   << " fnode=" << fnode
		   << " delta=" << delta
		   << dendl;
	      ceph_assert(delta.offset == fnode.allocated);
	    }
	    if (cct->_conf->bluefs_log_replay_check_allocations) {
              int r = _check_allocations(fnode,
		used_blocks, false, "OP_FILE_UPDATE_INC");
              if (r < 0) {
                return r;
              }
            }

	    fnode.ino = delta.ino;
	    fnode.mtime = delta.mtime;
	    if (fnode.ino != 1) {
	      vselector->sub_usage(f->vselector_hint, fnode);
	    }
	    fnode.size = delta.size;
	    fnode.claim_extents(delta.extents);
	    dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
		     << ":  op_file_update_inc produced " << " " << fnode << " " << dendl;

	    if (fnode.ino != 1) {
	      vselector->add_usage(f->vselector_hint, fnode);
	    }

	    if (fnode.ino > ino_last) {
	      ino_last = fnode.ino;
	    }
	    if (cct->_conf->bluefs_log_replay_check_allocations) {
              int r = _check_allocations(f->fnode,
		used_blocks, true, "OP_FILE_UPDATE_INC");
              if (r < 0) {
                return r;
              }
	    }
	  } else if (noop && delta.ino == 1) {
	    // we need to track bluefs log, even in noop mode
	    FileRef f = _get_file(1);
	    bluefs_fnode_t& fnode = f->fnode;
	    fnode.ino = delta.ino;
	    fnode.mtime = delta.mtime;
	    fnode.size = delta.size;
	    fnode.claim_extents(delta.extents);
	  }
	}
      break;

      case bluefs_transaction_t::OP_FILE_REMOVE:
        {
	  uint64_t ino;
	  decode(ino, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_file_remove " << ino << dendl;
          if (unlikely(to_stdout)) {
            std::cout << " 0x" << std::hex << pos << std::dec
                      << ":  op_file_remove " << ino << std::endl;
          }

          if (!noop) {
            auto p = nodes.file_map.find(ino);
            ceph_assert(p != nodes.file_map.end());
            vselector->sub_usage(p->second->vselector_hint, p->second->fnode);
            if (cct->_conf->bluefs_log_replay_check_allocations) {
	      int r = _check_allocations(p->second->fnode,
		used_blocks, false, "OP_FILE_REMOVE");
              if (r < 0) {
		return r;
              }
            }
            nodes.file_map.erase(p);
          }
        }
	break;

      default:
	derr << __func__ << " 0x" << std::hex << pos << std::dec
             << ": stop: unrecognized op " << (int)op << dendl;
	delete log_reader;
        return -EIO;
      }
    }
    ceph_assert(p.end());

    // we successfully replayed the transaction; bump the seq and log size
    ++log_seq;
    log_file->fnode.size = log_reader->buf.pos;
  }
  if (!noop) {
    vselector->add_usage(log_file->vselector_hint, log_file->fnode);
    log.seq_live = log_seq + 1;
    dirty.seq_live = log_seq + 1;
    log.t.seq = log.seq_live;
    dirty.seq_stable = log_seq;
  }

  dout(10) << __func__ << " log file size was 0x"
           << std::hex << log_file->fnode.size << std::dec << dendl;
  if (unlikely(to_stdout)) {
    std::cout << " log file size was 0x"
              << std::hex << log_file->fnode.size << std::dec << std::endl;
  }

  delete log_reader;

  if (!noop) {
    // verify file link counts are all >0
    for (auto& p : nodes.file_map) {
      if (p.second->refs == 0 &&
	  p.second->fnode.ino > 1) {
	derr << __func__ << " file with link count 0: " << p.second->fnode
	     << dendl;
	return -EIO;
      }
    }
  }
  // reflect file count in logger
  logger->set(l_bluefs_num_files, nodes.file_map.size());

  dout(10) << __func__ << " done" << dendl;
  return 0;
}

int BlueFS::log_dump()
{
  // only dump log file's content
  ceph_assert(log.writer == nullptr && "cannot log_dump on mounted BlueFS");
  _init_logger();
  int r = _open_super();
  if (r < 0) {
    derr << __func__ << " failed to open super: " << cpp_strerror(r) << dendl;
    return r;
  }
  r = _replay(true, true);
  if (r < 0) {
    derr << __func__ << " failed to replay log: " << cpp_strerror(r) << dendl;
  }
  _shutdown_logger();
  super = bluefs_super_t();
  return r;
}

int BlueFS::device_migrate_to_existing(
  CephContext *cct,
  const set<int>& devs_source,
  int dev_target,
  const bluefs_layout_t& layout)
{
  vector<byte> buf;
  bool buffered = cct->_conf->bluefs_buffered_io;

  dout(10) << __func__ << " devs_source " << devs_source
	   << " dev_target " << dev_target << dendl;
  assert(dev_target < (int)MAX_BDEV);

  int flags = 0;
  flags |= devs_source.count(BDEV_DB) ?
    (REMOVE_DB | RENAME_SLOW2DB) : 0;
  flags |= devs_source.count(BDEV_WAL) ? REMOVE_WAL : 0;
  int dev_target_new = dev_target;

  // Slow device without separate DB one is addressed via BDEV_DB
  // Hence need renaming.
  if ((flags & REMOVE_DB) && dev_target == BDEV_SLOW) {
    dev_target_new = BDEV_DB;
    dout(0) << __func__ << " super to be written to " << dev_target << dendl;
  }

  for (auto& [ino, file_ref] : nodes.file_map) {
    //do not copy log
    if (file_ref->fnode.ino == 1) {
      continue;
    }
    dout(10) << __func__ << " " << ino << " " << file_ref->fnode << dendl;

    auto& fnode_extents = file_ref->fnode.extents;
    vselector->sub_usage(file_ref->vselector_hint, file_ref->fnode);

    bool rewrite = std::any_of(
      fnode_extents.begin(),
      fnode_extents.end(),
      [=](auto& ext) {
	return ext.bdev != dev_target && devs_source.count(ext.bdev);
      });
    if (rewrite) {
      dout(10) << __func__ << "  migrating" << dendl;

      // read entire file
      bufferlist bl;
      for (auto old_ext : fnode_extents) {
	buf.resize(old_ext.length);
	int r = _bdev_read_random(old_ext.bdev,
	  old_ext.offset,
	  old_ext.length,
	  (char*)&buf.at(0),
	  buffered);
	if (r != 0) {
	  derr << __func__ << " failed to read 0x" << std::hex
	       << old_ext.offset << "~" << old_ext.length << std::dec
	       << " from " << (int)dev_target << dendl;
	  return -EIO;
	}
	bl.append((char*)&buf[0], old_ext.length);
      }

      // write entire file
      PExtentVector extents;
      auto l = _allocate_without_fallback(dev_target, bl.length(), &extents);
      if (l < 0) {
	derr << __func__ << " unable to allocate len 0x" << std::hex
	     << bl.length() << std::dec << " from " << (int)dev_target
	     << ": " << cpp_strerror(l) << dendl;
	return -ENOSPC;
      }

      uint64_t off = 0;
      for (auto& i : extents) {
	bufferlist cur;
	uint64_t cur_len = std::min<uint64_t>(i.length, bl.length() - off);
	ceph_assert(cur_len > 0);
	cur.substr_of(bl, off, cur_len);
	int r = bdev[dev_target]->write(i.offset, cur, buffered);
	ceph_assert(r == 0);
	off += cur_len;
      }

      // release old extents
      for (auto old_ext : fnode_extents) {
	PExtentVector to_release;
	to_release.emplace_back(old_ext.offset, old_ext.length);
	alloc[old_ext.bdev]->release(to_release);
        if (is_shared_alloc(old_ext.bdev)) {
          shared_alloc->bluefs_used -= to_release.size();
        }
      }

      // update fnode
      fnode_extents.clear();
      for (auto& i : extents) {
	fnode_extents.emplace_back(dev_target_new, i.offset, i.length);
      }
    } else {
      for (auto& ext : fnode_extents) {
	if (dev_target != dev_target_new && ext.bdev == dev_target) {
	  dout(20) << __func__ << "  " << " ... adjusting extent 0x"
		   << std::hex << ext.offset << std::dec
		   << " bdev " << dev_target << " -> " << dev_target_new
		   << dendl;
	  ext.bdev = dev_target_new;
	}
      }
    }
    vselector->add_usage(file_ref->vselector_hint, file_ref->fnode);
  }
  // new logging device in the current naming scheme
  int new_log_dev_cur = bdev[BDEV_WAL] ?
    BDEV_WAL :
    bdev[BDEV_DB] ? BDEV_DB : BDEV_SLOW;

  // new logging device in new naming scheme
  int new_log_dev_next = new_log_dev_cur;

  if (devs_source.count(new_log_dev_cur)) {
    // SLOW device is addressed via BDEV_DB too hence either WAL or DB
    new_log_dev_next = (flags & REMOVE_WAL) || !bdev[BDEV_WAL] ?
      BDEV_DB :
      BDEV_WAL;

    dout(0) << __func__ << " log moved from " << new_log_dev_cur
      << " to " << new_log_dev_next << dendl;

    new_log_dev_cur =
      (flags & REMOVE_DB) && new_log_dev_next == BDEV_DB ?
        BDEV_SLOW :
        new_log_dev_next;
  }

  _rewrite_log_and_layout_sync_LNF_LD(
    false,
    (flags & REMOVE_DB) ? BDEV_SLOW : BDEV_DB,
    new_log_dev_cur,
    new_log_dev_next,
    flags,
    layout);
  return 0;
}

int BlueFS::device_migrate_to_new(
  CephContext *cct,
  const set<int>& devs_source,
  int dev_target,
  const bluefs_layout_t& layout)
{
  vector<byte> buf;
  bool buffered = cct->_conf->bluefs_buffered_io;

  dout(10) << __func__ << " devs_source " << devs_source
	   << " dev_target " << dev_target << dendl;
  assert(dev_target == (int)BDEV_NEWDB || dev_target == (int)BDEV_NEWWAL);

  int flags = 0;

  flags |= devs_source.count(BDEV_DB) ?
    (!bdev[BDEV_SLOW] ? RENAME_DB2SLOW: REMOVE_DB) :
    0;
  flags |= devs_source.count(BDEV_WAL) ? REMOVE_WAL : 0;
  int dev_target_new = dev_target; //FIXME: remove, makes no sense

  for (auto& p : nodes.file_map) {
    //do not copy log
    if (p.second->fnode.ino == 1) {
      continue;
    }
    dout(10) << __func__ << " " << p.first << " " << p.second->fnode << dendl;

    auto& fnode_extents = p.second->fnode.extents;

    bool rewrite = false;
    for (auto ext_it = fnode_extents.begin();
	 ext_it != p.second->fnode.extents.end();
	 ++ext_it) {
      if (ext_it->bdev != dev_target && devs_source.count(ext_it->bdev)) {
	rewrite = true;
	break;
      }
    }
    if (rewrite) {
      dout(10) << __func__ << "  migrating" << dendl;

      // read entire file
      bufferlist bl;
      for (auto old_ext : fnode_extents) {
	buf.resize(old_ext.length);
	int r = _bdev_read_random(old_ext.bdev,
	  old_ext.offset,
	  old_ext.length,
	  (char*)&buf.at(0),
	  buffered);
	if (r != 0) {
	  derr << __func__ << " failed to read 0x" << std::hex
	       << old_ext.offset << "~" << old_ext.length << std::dec
	       << " from " << (int)dev_target << dendl;
	  return -EIO;
	}
	bl.append((char*)&buf[0], old_ext.length);
      }

      // write entire file
      PExtentVector extents;
      auto l = _allocate_without_fallback(dev_target, bl.length(), &extents);
      if (l < 0) {
	derr << __func__ << " unable to allocate len 0x" << std::hex
	     << bl.length() << std::dec << " from " << (int)dev_target
	     << ": " << cpp_strerror(l) << dendl;
	return -ENOSPC;
      }

      uint64_t off = 0;
      for (auto& i : extents) {
	bufferlist cur;
	uint64_t cur_len = std::min<uint64_t>(i.length, bl.length() - off);
	ceph_assert(cur_len > 0);
	cur.substr_of(bl, off, cur_len);
	int r = bdev[dev_target]->write(i.offset, cur, buffered);
	ceph_assert(r == 0);
	off += cur_len;
      }

      // release old extents
      for (auto old_ext : fnode_extents) {
	PExtentVector to_release;
	to_release.emplace_back(old_ext.offset, old_ext.length);
	alloc[old_ext.bdev]->release(to_release);
        if (is_shared_alloc(old_ext.bdev)) {
          shared_alloc->bluefs_used -= to_release.size();
        }
      }

      // update fnode
      fnode_extents.clear();
      for (auto& i : extents) {
	fnode_extents.emplace_back(dev_target_new, i.offset, i.length);
      }
    }
  }
  // new logging device in the current naming scheme
  int new_log_dev_cur =
    bdev[BDEV_NEWWAL] ?
      BDEV_NEWWAL :
      bdev[BDEV_WAL] && !(flags & REMOVE_WAL) ?
        BDEV_WAL :
	bdev[BDEV_NEWDB] ?
	  BDEV_NEWDB :
	  bdev[BDEV_DB] && !(flags & REMOVE_DB)?
	    BDEV_DB :
	    BDEV_SLOW;

  // new logging device in new naming scheme
  int new_log_dev_next =
    new_log_dev_cur == BDEV_NEWWAL ?
      BDEV_WAL :
      new_log_dev_cur == BDEV_NEWDB ?
	BDEV_DB :
        new_log_dev_cur;

  int super_dev =
    dev_target == BDEV_NEWDB ?
      BDEV_NEWDB :
      bdev[BDEV_DB] ?
        BDEV_DB :
	BDEV_SLOW;

  _rewrite_log_and_layout_sync_LNF_LD(
    false,
    super_dev,
    new_log_dev_cur,
    new_log_dev_next,
    flags,
    layout);
  return 0;
}

BlueFS::FileRef BlueFS::_get_file(uint64_t ino)
{
  auto p = nodes.file_map.find(ino);
  if (p == nodes.file_map.end()) {
    FileRef f = ceph::make_ref<File>();
    nodes.file_map[ino] = f;
    // track files count in logger
    logger->set(l_bluefs_num_files, nodes.file_map.size());
    dout(30) << __func__ << " ino " << ino << " = " << f
	     << " (new)" << dendl;
    return f;
  } else {
    dout(30) << __func__ << " ino " << ino << " = " << p->second << dendl;
    return p->second;
  }
}


/**
To modify fnode both FileWriter::lock and File::lock must be obtained.
The special case is when we modify bluefs log (ino 1) or
we are compacting log (ino 0).

In any case it is enough to hold File::lock to be sure fnode will not be modified.
*/
struct lock_fnode_print {
  BlueFS::FileRef file;
  lock_fnode_print(BlueFS::FileRef file) : file(file) {};
};
std::ostream& operator<<(std::ostream& out, const lock_fnode_print& to_lock) {
  std::lock_guard l(to_lock.file->lock);
  out << to_lock.file->fnode;
  return out;
}

void BlueFS::_drop_link_D(FileRef file)
{
  dout(20) << __func__ << " had refs " << file->refs
	   << " on " << lock_fnode_print(file) << dendl;
  ceph_assert(file->refs > 0);
  ceph_assert(ceph_mutex_is_locked(log.lock));
  ceph_assert(ceph_mutex_is_locked(nodes.lock));

  --file->refs;
  if (file->refs == 0) {
    dout(20) << __func__ << " destroying " << file->fnode << dendl;
    ceph_assert(file->num_reading.load() == 0);
    vselector->sub_usage(file->vselector_hint, file->fnode);
    log.t.op_file_remove(file->fnode.ino);
    nodes.file_map.erase(file->fnode.ino);
    logger->set(l_bluefs_num_files, nodes.file_map.size());
    file->deleted = true;

    std::lock_guard dl(dirty.lock);
    for (auto& r : file->fnode.extents) {
      dirty.pending_release[r.bdev].insert(r.offset, r.length);
    }
    if (file->dirty_seq > dirty.seq_stable) {
      // retract request to serialize changes
      ceph_assert(dirty.files.count(file->dirty_seq));
      auto it = dirty.files[file->dirty_seq].iterator_to(*file);
      dirty.files[file->dirty_seq].erase(it);
      file->dirty_seq = dirty.seq_stable;
    }
  }
}

int64_t BlueFS::_read_random(
  FileReader *h,         ///< [in] read from here
  uint64_t off,          ///< [in] offset
  uint64_t len,          ///< [in] this many bytes
  char *out)             ///< [out] copy it here
{
  auto* buf = &h->buf;

  int64_t ret = 0;
  dout(10) << __func__ << " h " << h
           << " 0x" << std::hex << off << "~" << len << std::dec
	   << " from " << lock_fnode_print(h->file) << dendl;

  ++h->file->num_reading;

  if (!h->ignore_eof &&
      off + len > h->file->fnode.size) {
    if (off > h->file->fnode.size)
      len = 0;
    else
      len = h->file->fnode.size - off;
    dout(20) << __func__ << " reaching (or past) eof, len clipped to 0x"
	     << std::hex << len << std::dec << dendl;
  }
  logger->inc(l_bluefs_read_random_count, 1);
  logger->inc(l_bluefs_read_random_bytes, len);

  std::shared_lock s_lock(h->lock);
  buf->bl.reassign_to_mempool(mempool::mempool_bluefs_file_reader);
  while (len > 0) {
    if (off < buf->bl_off || off >= buf->get_buf_end()) {
      s_lock.unlock();
      uint64_t x_off = 0;
      auto p = h->file->fnode.seek(off, &x_off);
      ceph_assert(p != h->file->fnode.extents.end());
      uint64_t l = std::min(p->length - x_off, len);
      //hard cap to 1GB
      l = std::min(l, uint64_t(1) << 30);
      dout(20) << __func__ << " read random 0x"
	       << std::hex << x_off << "~" << l << std::dec
	       << " of " << *p << dendl;
      int r;
      if (!cct->_conf->bluefs_check_for_zeros) {
	r = _bdev_read_random(p->bdev, p->offset + x_off, l, out,
			      cct->_conf->bluefs_buffered_io);
      } else {
	r = _read_random_and_check(p->bdev, p->offset + x_off, l, out,
			cct->_conf->bluefs_buffered_io);
      }
      ceph_assert(r == 0);
      off += l;
      len -= l;
      ret += l;
      out += l;

      logger->inc(l_bluefs_read_random_disk_count, 1);
      logger->inc(l_bluefs_read_random_disk_bytes, l);
      if (len > 0) {
	s_lock.lock();
      }
    } else {
      auto left = buf->get_buf_remaining(off);
      int64_t r = std::min(len, left);
      logger->inc(l_bluefs_read_random_buffer_count, 1);
      logger->inc(l_bluefs_read_random_buffer_bytes, r);
      dout(20) << __func__ << " left 0x" << std::hex << left
	      << " 0x" << off << "~" << len << std::dec
	      << dendl;

      auto p = buf->bl.begin();
      p.seek(off - buf->bl_off);
      p.copy(r, out);
      out += r;

      dout(30) << __func__ << " result chunk (0x"
	       << std::hex << r << std::dec << " bytes):\n";
      bufferlist t;
      t.substr_of(buf->bl, off - buf->bl_off, r);
      t.hexdump(*_dout);
      *_dout << dendl;

      off += r;
      len -= r;
      ret += r;
      buf->pos += r;
    }
  }
  dout(20) << __func__ << " got " << ret << dendl;
  --h->file->num_reading;
  return ret;
}

int64_t BlueFS::_read(
  FileReader *h,         ///< [in] read from here
  uint64_t off,          ///< [in] offset
  size_t len,            ///< [in] this many bytes
  bufferlist *outbl,     ///< [out] optional: reference the result here
  char *out)             ///< [out] optional: or copy it here
{
  FileReaderBuffer *buf = &(h->buf);

  bool prefetch = !outbl && !out;
  dout(10) << __func__ << " h " << h
           << " 0x" << std::hex << off << "~" << len << std::dec
	   << " from " << lock_fnode_print(h->file)
	   << (prefetch ? " prefetch" : "")
	   << dendl;

  ++h->file->num_reading;

  if (!h->ignore_eof &&
      off + len > h->file->fnode.size) {
    if (off > h->file->fnode.size)
      len = 0;
    else
      len = h->file->fnode.size - off;
    dout(20) << __func__ << " reaching (or past) eof, len clipped to 0x"
	     << std::hex << len << std::dec << dendl;
  }
  logger->inc(l_bluefs_read_count, 1);
  logger->inc(l_bluefs_read_bytes, len);
  if (prefetch) {
    logger->inc(l_bluefs_read_prefetch_count, 1);
    logger->inc(l_bluefs_read_prefetch_bytes, len);
  }

  if (outbl)
    outbl->clear();

  int64_t ret = 0;
  std::shared_lock s_lock(h->lock);
  while (len > 0) {
    size_t left;
    if (off < buf->bl_off || off >= buf->get_buf_end()) {
      s_lock.unlock();
      std::unique_lock u_lock(h->lock);
      buf->bl.reassign_to_mempool(mempool::mempool_bluefs_file_reader);
      if (off < buf->bl_off || off >= buf->get_buf_end()) {
        // if precondition hasn't changed during locking upgrade.
        buf->bl.clear();
        buf->bl_off = off & super.block_mask();
        uint64_t x_off = 0;
        auto p = h->file->fnode.seek(buf->bl_off, &x_off);
	if (p == h->file->fnode.extents.end()) {
	  dout(5) << __func__ << " reading less then required "
		  << ret << "<" << ret + len << dendl;
	  break;
	}

        uint64_t want = round_up_to(len + (off & ~super.block_mask()),
				    super.block_size);
        want = std::max(want, buf->max_prefetch);
        uint64_t l = std::min(p->length - x_off, want);
        //hard cap to 1GB
	l = std::min(l, uint64_t(1) << 30);
        uint64_t eof_offset = round_up_to(h->file->fnode.size, super.block_size);
        if (!h->ignore_eof &&
	    buf->bl_off + l > eof_offset) {
	  l = eof_offset - buf->bl_off;
        }
        dout(20) << __func__ << " fetching 0x"
                 << std::hex << x_off << "~" << l << std::dec
                 << " of " << *p << dendl;
	int r;
	if (!cct->_conf->bluefs_check_for_zeros) {
	  r = _bdev_read(p->bdev, p->offset + x_off, l, &buf->bl, ioc[p->bdev],
			 cct->_conf->bluefs_buffered_io);
	} else {
	  r = _read_and_check(
	    p->bdev, p->offset + x_off, l, &buf->bl, ioc[p->bdev],
	    cct->_conf->bluefs_buffered_io);
	}
	logger->inc(l_bluefs_read_disk_count, 1);
	logger->inc(l_bluefs_read_disk_bytes, l);

        ceph_assert(r == 0);
      }
      u_lock.unlock();
      s_lock.lock();
      // we should recheck if buffer is valid after lock downgrade
      continue; 
    }
    left = buf->get_buf_remaining(off);
    dout(20) << __func__ << " left 0x" << std::hex << left
             << " len 0x" << len << std::dec << dendl;

    int64_t r = std::min(len, left);
    if (outbl) {
      bufferlist t;
      t.substr_of(buf->bl, off - buf->bl_off, r);
      outbl->claim_append(t);
    }
    if (out) {
      auto p = buf->bl.begin();
      p.seek(off - buf->bl_off);
      p.copy(r, out);
      out += r;
    }

    dout(30) << __func__ << " result chunk (0x"
             << std::hex << r << std::dec << " bytes):\n";
    bufferlist t;
    t.substr_of(buf->bl, off - buf->bl_off, r);
    t.hexdump(*_dout);
    *_dout << dendl;

    off += r;
    len -= r;
    ret += r;
    buf->pos += r;
  }

  dout(20) << __func__ << " got " << ret << dendl;
  ceph_assert(!outbl || (int)outbl->length() == ret);
  --h->file->num_reading;
  return ret;
}

void BlueFS::invalidate_cache(FileRef f, uint64_t offset, uint64_t length)
{
  std::lock_guard l(f->lock);
  dout(10) << __func__ << " file " << f->fnode
	   << " 0x" << std::hex << offset << "~" << length << std::dec
           << dendl;
  if (offset & ~super.block_mask()) {
    offset &= super.block_mask();
    length = round_up_to(length, super.block_size);
  }
  uint64_t x_off = 0;
  auto p = f->fnode.seek(offset, &x_off);
  while (length > 0 && p != f->fnode.extents.end()) {
    uint64_t x_len = std::min(p->length - x_off, length);
    bdev[p->bdev]->invalidate_cache(p->offset + x_off, x_len);
    dout(20) << __func__  << " 0x" << std::hex << x_off << "~" << x_len
             << std:: dec << " of " << *p << dendl;
    offset += x_len;
    length -= x_len;
  }
}

uint64_t BlueFS::_estimate_log_size_N()
{
  std::lock_guard nl(nodes.lock);
  int avg_dir_size = 40;  // fixme
  int avg_file_size = 12;
  uint64_t size = 4096 * 2;
  size += nodes.file_map.size() * (1 + sizeof(bluefs_fnode_t));
  size += nodes.dir_map.size() + (1 + avg_dir_size);
  size += nodes.file_map.size() * (1 + avg_dir_size + avg_file_size);
  return round_up_to(size, super.block_size);
}

void BlueFS::compact_log()/*_LNF_LD_NF_D*/
{
  if (!cct->_conf->bluefs_replay_recovery_disable_compact) {
    if (cct->_conf->bluefs_compact_log_sync) {
      _compact_log_sync_LNF_LD();
    } else {
      _compact_log_async_LD_LNF_D();
    }
  }
}

bool BlueFS::_should_start_compact_log_L_N()
{
  if (log_is_compacting.load() == true) {
    // compaction is already running
    return false;
  }
  uint64_t current;
  {
    std::lock_guard ll(log.lock);
    current = log.writer->file->fnode.size;
  }
  uint64_t expected = _estimate_log_size_N();
  float ratio = (float)current / (float)expected;
  dout(10) << __func__ << " current 0x" << std::hex << current
	   << " expected " << expected << std::dec
	   << " ratio " << ratio
	   << dendl;
  if (current < cct->_conf->bluefs_log_compact_min_size ||
      ratio < cct->_conf->bluefs_log_compact_min_ratio) {
    return false;
  }
  return true;
}

void BlueFS::_compact_log_dump_metadata_NF(bluefs_transaction_t *t,
					int flags)
{
  std::lock_guard nl(nodes.lock);

  t->seq = 1;
  t->uuid = super.uuid;
  dout(20) << __func__ << " op_init" << dendl;

  t->op_init();
  for (auto& [ino, file_ref] : nodes.file_map) {
    if (ino == 1)
      continue;
    ceph_assert(ino > 1);
    std::lock_guard fl(file_ref->lock);
    for(auto& e : file_ref->fnode.extents) {
      auto bdev = e.bdev;
      auto bdev_new = bdev;
      ceph_assert(!((flags & REMOVE_WAL) && bdev == BDEV_WAL));
      if ((flags & RENAME_SLOW2DB) && bdev == BDEV_SLOW) {
	bdev_new = BDEV_DB;
      }
      if ((flags & RENAME_DB2SLOW) && bdev == BDEV_DB) {
	bdev_new = BDEV_SLOW;
      }
      if (bdev == BDEV_NEWDB) {
	// REMOVE_DB xor RENAME_DB
	ceph_assert(!(flags & REMOVE_DB) != !(flags & RENAME_DB2SLOW));
	ceph_assert(!(flags & RENAME_SLOW2DB));
	bdev_new = BDEV_DB;
      }
      if (bdev == BDEV_NEWWAL) {
	ceph_assert(flags & REMOVE_WAL);
	bdev_new = BDEV_WAL;
      }
      e.bdev = bdev_new;
    }
    dout(20) << __func__ << " op_file_update " << file_ref->fnode << dendl;
    t->op_file_update(file_ref->fnode);
  }
  for (auto& [path, dir_ref] : nodes.dir_map) {
    dout(20) << __func__ << " op_dir_create " << path << dendl;
    t->op_dir_create(path);
    for (auto& [fname, file_ref] : dir_ref->file_map) {
      dout(20) << __func__ << " op_dir_link " << path << "/" << fname
	       << " to " << file_ref->fnode.ino << dendl;
      t->op_dir_link(path, fname, file_ref->fnode.ino);
    }
  }
}
/* Streams to t files modified before *capture_before_seq* and all dirs */
void BlueFS::_compact_log_async_dump_metadata_NF(bluefs_transaction_t *t,
						 uint64_t capture_before_seq)
{
  std::lock_guard nl(nodes.lock);

  t->seq = 1;
  t->uuid = super.uuid;
  dout(20) << __func__ << " op_init" << dendl;

  t->op_init();
  for (auto& [ino, file_ref] : nodes.file_map) {
    if (ino == 1)
      continue;
    ceph_assert(ino > 1);
    std::lock_guard fl(file_ref->lock);
    if (file_ref->dirty_seq < capture_before_seq) {
      dout(20) << __func__ << " op_file_update " << file_ref->fnode << dendl;
    } else {
      dout(20) << __func__ << " op_file_update just modified, dirty_seq="
	       << file_ref->dirty_seq << " " << file_ref->fnode << dendl;
    }
    t->op_file_update(file_ref->fnode);
  }
  for (auto& [path, dir_ref] : nodes.dir_map) {
    dout(20) << __func__ << " op_dir_create " << path << dendl;
    t->op_dir_create(path);
    for (auto& [fname, file_ref] : dir_ref->file_map) {
      dout(20) << __func__ << " op_dir_link " << path << "/" << fname
	       << " to " << file_ref->fnode.ino << dendl;
      t->op_dir_link(path, fname, file_ref->fnode.ino);
    }
  }
}

void BlueFS::_compact_log_sync_LNF_LD()
{
  dout(10) << __func__ << dendl;
  uint8_t prefer_bdev;
  {
    std::lock_guard ll(log.lock);
    prefer_bdev =
      vselector->select_prefer_bdev(log.writer->file->vselector_hint);
  }
  _rewrite_log_and_layout_sync_LNF_LD(true,
    BDEV_DB,
    prefer_bdev,
    prefer_bdev,
    0,
    super.memorized_layout);
  logger->inc(l_bluefs_log_compactions);
}

void BlueFS::_rewrite_log_and_layout_sync_LNF_LD(bool allocate_with_fallback,
					 int super_dev,
					 int log_dev,
					 int log_dev_new,
					 int flags,
					 std::optional<bluefs_layout_t> layout)
{
  std::lock_guard ll(log.lock);

  File *log_file = log.writer->file.get();

  // log.t.seq is always set to current live seq
  ceph_assert(log.t.seq == log.seq_live);
  // Capturing entire state. Dump anything that has been stored there.
  log.t.clear();
  log.t.seq = log.seq_live;
  // From now on, no changes to log.t are permitted until we finish rewriting log.
  // Can allow dirty to remain dirty - log.seq_live will not change.

  dout(20) << __func__ << " super_dev:" << super_dev
                       << " log_dev:" << log_dev
                       << " log_dev_new:" << log_dev_new
		       << " flags:" << flags
		       << dendl;
  bluefs_transaction_t t;
  _compact_log_dump_metadata_NF(&t, flags);

  dout(20) << __func__ << " op_jump_seq " << log.seq_live << dendl;
  t.op_jump_seq(log.seq_live);

  bufferlist bl;
  encode(t, bl);
  _pad_bl(bl);

  uint64_t need = bl.length() + cct->_conf->bluefs_max_log_runway;
  dout(20) << __func__ << " need " << need << dendl;

  bluefs_fnode_t old_fnode;
  int r;
  vselector->sub_usage(log_file->vselector_hint, log_file->fnode);
  log_file->fnode.swap_extents(old_fnode);
  if (allocate_with_fallback) {
    r = _allocate(log_dev, need, &log_file->fnode);
    ceph_assert(r == 0);
  } else {
    PExtentVector extents;
    r = _allocate_without_fallback(log_dev,
			       need,
			       &extents);
    ceph_assert(r == 0);
    for (auto& p : extents) {
      log_file->fnode.append_extent(
	bluefs_extent_t(log_dev, p.offset, p.length));
    }
  }

  _close_writer(log.writer);

  // we will write it to super
  log_file->fnode.reset_delta();
  log_file->fnode.size = bl.length();

  log.writer = _create_writer(log_file);
  log.writer->append(bl);
  _flush_special(log.writer);
  vselector->add_usage(log_file->vselector_hint, log_file->fnode);
#ifdef HAVE_LIBAIO
  if (!cct->_conf->bluefs_sync_write) {
    list<aio_t> completed_ios;
    _claim_completed_aios(log.writer, &completed_ios);
    _wait_for_aio(log.writer);
    completed_ios.clear();
  }
#endif
  _flush_bdev();

  super.memorized_layout = layout;
  super.log_fnode = log_file->fnode;
  // rename device if needed
  if (log_dev != log_dev_new) {
    dout(10) << __func__ << " renaming log extents to " << log_dev_new << dendl;
    for (auto& p : super.log_fnode.extents) {
      p.bdev = log_dev_new;
    }
  }
  dout(10) << __func__ << " writing super, log fnode: " << super.log_fnode << dendl;

  ++super.version;
  _write_super(super_dev);
  _flush_bdev();

  dout(10) << __func__ << " release old log extents " << old_fnode.extents << dendl;
  std::lock_guard dl(dirty.lock);
  for (auto& r : old_fnode.extents) {
    dirty.pending_release[r.bdev].insert(r.offset, r.length);
  }
}

/*
 * 1. Allocate a new extent to continue the log, and then log an event
 * that jumps the log write position to the new extent.  At this point, the
 * old extent(s) won't be written to, and reflect everything to compact.
 * New events will be written to the new region that we'll keep.
 *
 * 2. While still holding the lock, encode a bufferlist that dumps all of the
 * in-memory fnodes and names.  This will become the new beginning of the
 * log.  The last event will jump to the log continuation extent from #1.
 *
 * 3. Queue a write to a new extent for the new beginnging of the log.
 *
 * 4. Drop lock and wait
 *
 * 5. Retake the lock.
 *
 * 6. Update the log_fnode to splice in the new beginning.
 *
 * 7. Write the new superblock.
 *
 * 8. Release the old log space.  Clean up.
 */

void BlueFS::_compact_log_async_LD_LNF_D() //also locks FW for new_writer
{
  dout(10) << __func__ << dendl;
  // only one compaction allowed at one time
  bool old_is_comp = std::atomic_exchange(&log_is_compacting, true);
  if (old_is_comp) {
    dout(10) << __func__ << " ongoing" <<dendl;
    return;
  }

  log.lock.lock();
  File *log_file = log.writer->file.get();
  FileWriter *new_log_writer = nullptr;
  FileRef new_log = nullptr;
  uint64_t new_log_jump_to = 0;
  uint64_t old_log_jump_to = 0;

  new_log = ceph::make_ref<File>();
  new_log->fnode.ino = 0;   // we use _flush_special to avoid log of the fnode

  // Part 1.
  // Prepare current log for jumping into it.
  // 1. Allocate extent
  // 2. Update op to log
  // 3. Jump op to log
  // During that, no one else can write to log, otherwise we risk jumping backwards.
  // We need to sync log, because we are injecting discontinuity, and writer is not prepared for that.

  //signal _maybe_extend_log that expansion of log is temporary inacceptable
  bool old_forbidden = atomic_exchange(&log_forbidden_to_expand, true);
  ceph_assert(old_forbidden == false);

  vselector->sub_usage(log_file->vselector_hint, log_file->fnode);

  // 1.1 allocate new log space and jump to it.
  old_log_jump_to = log_file->fnode.get_allocated();
  uint64_t runway = log_file->fnode.get_allocated() - log.writer->get_effective_write_pos();
  dout(10) << __func__ << " old_log_jump_to 0x" << std::hex << old_log_jump_to
           << " need 0x" << (old_log_jump_to + cct->_conf->bluefs_max_log_runway) << std::dec << dendl;
  int r = _allocate(vselector->select_prefer_bdev(log_file->vselector_hint),
		    cct->_conf->bluefs_max_log_runway,
                    &log_file->fnode);
  ceph_assert(r == 0);
  //adjust usage as flush below will need it
  vselector->add_usage(log_file->vselector_hint, log_file->fnode);
  dout(10) << __func__ << " log extents " << log_file->fnode.extents << dendl;

  // update the log file change and log a jump to the offset where we want to
  // write the new entries
  log.t.op_file_update(log_file->fnode);
  // jump to new position should mean next seq
  log.t.op_jump(log.seq_live + 1, old_log_jump_to);
  uint64_t seq_now = log.seq_live;
  // we need to flush all bdev because we will be streaming all dirty files to log
  // TODO - think - if _flush_and_sync_log_jump will not add dirty files nor release pending allocations
  // then flush_bdev() will not be necessary
  _flush_bdev();
  _flush_and_sync_log_jump_D(old_log_jump_to, runway);

  // out of jump section

  // 2. prepare compacted log
  bluefs_transaction_t t;
  _compact_log_async_dump_metadata_NF(&t, seq_now);

  // now state is captured to bufferlist
  // log can be used to write to, ops in log will be continuation of captured state
  log.lock.unlock();

  uint64_t max_alloc_size = std::max(alloc_size[BDEV_WAL],
				     std::max(alloc_size[BDEV_DB],
					      alloc_size[BDEV_SLOW]));

  // conservative estimate for final encoded size
  new_log_jump_to = round_up_to(t.op_bl.length() + super.block_size * 2,
                                max_alloc_size);
  //newly constructed log head will jump to what we had before
  t.op_jump(seq_now, new_log_jump_to);

  // allocate
  //FIXME: check if we want DB here?
  r = _allocate(BlueFS::BDEV_DB, new_log_jump_to,
                    &new_log->fnode);
  ceph_assert(r == 0);

  bufferlist bl;
  encode(t, bl);
  _pad_bl(bl);

  dout(10) << __func__ << " new_log_jump_to 0x" << std::hex << new_log_jump_to
	   << std::dec << dendl;

  new_log_writer = _create_writer(new_log);

  new_log_writer->append(bl);
  // 3. flush
  _flush_special(new_log_writer);

  // 4. wait
  _flush_bdev(new_log_writer);
  // 5. update our log fnode
  // we need to append to new_log the extents that were allocated in step 1.1
  // we do it by inverse logic - we drop 'old_log_jump_to' bytes and keep rest
  // todo - maybe improve _allocate so we will give clear set of new allocations
  uint64_t processed = 0;
  mempool::bluefs::vector<bluefs_extent_t> old_extents;
  for (auto& e : log_file->fnode.extents) {
    if (processed + e.length <= old_log_jump_to) {
      // drop whole extent
      dout(10) << __func__ << " remove old log extent " << e << dendl;
      old_extents.push_back(e);
    } else {
      // keep, but how much?
      if (processed < old_log_jump_to) {
	ceph_assert(processed + e.length > old_log_jump_to);
	ceph_assert(old_log_jump_to - processed <= std::numeric_limits<uint32_t>::max());
	uint32_t cut_at = uint32_t(old_log_jump_to - processed);
	// need to cut, first half gets dropped
	bluefs_extent_t retire(e.bdev, e.offset, cut_at);
	old_extents.push_back(retire);
	// second half goes to new log
	bluefs_extent_t keep(e.bdev, e.offset + cut_at, e.length - cut_at);
	new_log->fnode.append_extent(keep);
	dout(10) << __func__ << " kept " << keep << " removed " << retire << dendl;
      } else {
	// take entire extent
	ceph_assert(processed >= old_log_jump_to);
	new_log->fnode.append_extent(e);
	dout(10) << __func__ << " kept " << e << dendl;
      }
    }
    processed += e.length;
  }
  // we will write it to super
  new_log->fnode.reset_delta();

  // 6. write the super block to reflect the changes
  dout(10) << __func__ << " writing super" << dendl;
  new_log->fnode.ino = log_file->fnode.ino;
  new_log->fnode.size = 0;
  new_log->fnode.mtime = ceph_clock_now();
  super.log_fnode = new_log->fnode;
  ++super.version;
  _write_super(BDEV_DB);
  _flush_bdev();

  log.lock.lock();
  // swapping log_file and new_log
  vselector->sub_usage(log_file->vselector_hint, log_file->fnode);

  // clear the extents from old log file, they are added to new log
  log_file->fnode.clear_extents();
  // swap the log files. New log file is the log file now.
  new_log->fnode.swap_extents(log_file->fnode);

  log.writer->pos = log.writer->file->fnode.size =
    log.writer->pos - old_log_jump_to + new_log_jump_to;

  vselector->add_usage(log_file->vselector_hint, log_file->fnode);

  log.lock.unlock();

  old_forbidden = atomic_exchange(&log_forbidden_to_expand, false);
  ceph_assert(old_forbidden == true);
  //to wake up if someone was in need of expanding log
  log_cond.notify_all();

  // 7. release old space
  dout(10) << __func__ << " release old log extents " << old_extents << dendl;
  {
    std::lock_guard dl(dirty.lock);
    for (auto& r : old_extents) {
      dirty.pending_release[r.bdev].insert(r.offset, r.length);
    }
  }

  // delete the new log, remove from the dirty files list
  _close_writer(new_log_writer);
  new_log_writer = nullptr;
  new_log = nullptr;
  log_cond.notify_all();

  dout(10) << __func__ << " log extents " << log_file->fnode.extents << dendl;
  logger->inc(l_bluefs_log_compactions);

  old_is_comp = atomic_exchange(&log_is_compacting, false);
  ceph_assert(old_is_comp);
}

void BlueFS::_pad_bl(bufferlist& bl)
{
  uint64_t partial = bl.length() % super.block_size;
  if (partial) {
    dout(10) << __func__ << " padding with 0x" << std::hex
	     << super.block_size - partial << " zeros" << std::dec << dendl;
    bl.append_zero(super.block_size - partial);
  }
}


// Returns log seq that was live before advance.
uint64_t BlueFS::_log_advance_seq()
{
  ceph_assert(ceph_mutex_is_locked(dirty.lock));
  ceph_assert(ceph_mutex_is_locked(log.lock));
  //acquire new seq
  // this will became seq_stable once we write
  ceph_assert(dirty.seq_stable < dirty.seq_live);
  ceph_assert(log.t.seq == log.seq_live);
  uint64_t seq = log.seq_live;
  log.t.uuid = super.uuid;

  ++dirty.seq_live;
  ++log.seq_live;
  ceph_assert(dirty.seq_live == log.seq_live);
  return seq;
}


// Adds to log.t file modifications mentioned in `dirty.files`.
// Note: some bluefs ops may have already been stored in log.t transaction.
void BlueFS::_consume_dirty(uint64_t seq)
{
  ceph_assert(ceph_mutex_is_locked(dirty.lock));
  ceph_assert(ceph_mutex_is_locked(log.lock));

  // log dirty files
  // we just incremented log_seq. It is now illegal to add to dirty.files[log_seq]
  auto lsi = dirty.files.find(seq);
  if (lsi != dirty.files.end()) {
    dout(20) << __func__ << " " << lsi->second.size() << " dirty.files" << dendl;
    for (auto &f : lsi->second) {
      // fnode here is protected indirectly
      // the only path that adds to dirty.files goes from _fsync()
      // _fsync() is executed under writer lock,
      // and does not exit until syncing log is done
      dout(20) << __func__ << "   op_file_update_inc " << f.fnode << dendl;
      log.t.op_file_update_inc(f.fnode);
    }
  }
}

// Extends log if its free space is smaller then bluefs_min_log_runway.
// Returns space available *BEFORE* adding new space. Signed for additional <0 detection.
int64_t BlueFS::_maybe_extend_log()
{
  ceph_assert(ceph_mutex_is_locked(log.lock));
  // allocate some more space (before we run out)?
  // BTW: this triggers `flush()` in the `page_aligned_appender` of `log.writer`.
  int64_t runway = log.writer->file->fnode.get_allocated() -
    log.writer->get_effective_write_pos();
  if (runway < (int64_t)cct->_conf->bluefs_min_log_runway) {
    dout(10) << __func__ << " allocating more log runway (0x"
	     << std::hex << runway << std::dec  << " remaining)" << dendl;
    /*
     * Usually, when we are low on space in log, we just allocate new extent,
     * put update op(log) to log and we are fine.
     * Problem - it interferes with log compaction:
     * New log produced in compaction will include - as last op - jump into some offset (anchor) of current log.
     * It is assumed that log region (anchor - end) will contain all changes made by bluefs since
     * full state capture into new log.
     * Putting log update into (anchor - end) region is illegal, because any update there must be compatible with
     * both logs, but old log is different then new log.
     *
     * Possible solutions:
     * - stall extending log until we finish compacting and switch log (CURRENT)
     * - re-run compaction with more runway for old log
     * - add OP_FILE_ADDEXT that adds extent; will be compatible with both logs
     */
    if (log_forbidden_to_expand.load() == true) {
      return -EWOULDBLOCK;
    }
    vselector->sub_usage(log.writer->file->vselector_hint, log.writer->file->fnode);
    int r = _allocate(
      vselector->select_prefer_bdev(log.writer->file->vselector_hint),
      cct->_conf->bluefs_max_log_runway,
      &log.writer->file->fnode);
    ceph_assert(r == 0);
    vselector->add_usage(log.writer->file->vselector_hint, log.writer->file->fnode);
    log.t.op_file_update_inc(log.writer->file->fnode);
  }
  return runway;
}

void BlueFS::_flush_and_sync_log_core(int64_t runway)
{
  ceph_assert(ceph_mutex_is_locked(log.lock));
  dout(10) << __func__ << " " << log.t << dendl;

  bufferlist bl;
  bl.reserve(super.block_size);
  encode(log.t, bl);
  // pad to block boundary
  size_t realign = super.block_size - (bl.length() % super.block_size);
  if (realign && realign != super.block_size)
    bl.append_zero(realign);

  logger->inc(l_bluefs_logged_bytes, bl.length());

  if (true) {
    ceph_assert(bl.length() <= runway); // if we write this, we will have an unrecoverable data loss
                                        // transaction will not fit extents before growth -> data loss on _replay
  }

  log.writer->append(bl);

  // prepare log for new transactions
  log.t.clear();
  log.t.seq = log.seq_live;

  uint64_t new_data = _flush_special(log.writer);
  vselector->add_usage(log.writer->file->vselector_hint, new_data);
}

// Clears dirty.files up to (including) seq_stable.
void BlueFS::_clear_dirty_set_stable_D(uint64_t seq)
{
  std::lock_guard dl(dirty.lock);

  // clean dirty files
  if (seq > dirty.seq_stable) {
    dirty.seq_stable = seq;
    dout(20) << __func__ << " seq_stable " << dirty.seq_stable << dendl;

    // undirty all files that were already streamed to log
    auto p = dirty.files.begin();
    while (p != dirty.files.end()) {
      if (p->first > dirty.seq_stable) {
        dout(20) << __func__ << " done cleaning up dirty files" << dendl;
        break;
      }

      auto l = p->second.begin();
      while (l != p->second.end()) {
        File *file = &*l;
        ceph_assert(file->dirty_seq <= dirty.seq_stable);
        dout(20) << __func__ << " cleaned file " << file->fnode.ino << dendl;
        file->dirty_seq = dirty.seq_stable;
        p->second.erase(l++);
      }

      ceph_assert(p->second.empty());
      dirty.files.erase(p++);
    }
  } else {
    dout(20) << __func__ << " seq_stable " << dirty.seq_stable
             << " already >= out seq " << seq
             << ", we lost a race against another log flush, done" << dendl;
  }
}

void BlueFS::_release_pending_allocations(vector<interval_set<uint64_t>>& to_release)
{
  for (unsigned i = 0; i < to_release.size(); ++i) {
    if (!to_release[i].empty()) {
      /* OK, now we have the guarantee alloc[i] won't be null. */
      int r = 0;
      if (cct->_conf->bdev_enable_discard && cct->_conf->bdev_async_discard) {
	r = bdev[i]->queue_discard(to_release[i]);
	if (r == 0)
	  continue;
      } else if (cct->_conf->bdev_enable_discard) {
	for (auto p = to_release[i].begin(); p != to_release[i].end(); ++p) {
	  bdev[i]->discard(p.get_start(), p.get_len());
	}
      }
      alloc[i]->release(to_release[i]);
      if (is_shared_alloc(i)) {
        shared_alloc->bluefs_used -= to_release[i].size();
      }
    }
  }
}

int BlueFS::_flush_and_sync_log_LD(uint64_t want_seq)
{
  int64_t available_runway;
  do {
    log.lock.lock();
    dirty.lock.lock();
    if (want_seq && want_seq <= dirty.seq_stable) {
      dout(10) << __func__ << " want_seq " << want_seq << " <= seq_stable "
	       << dirty.seq_stable << ", done" << dendl;
      dirty.lock.unlock();
      log.lock.unlock();
      return 0;
    }

    available_runway = _maybe_extend_log();
    if (available_runway == -EWOULDBLOCK) {
      // we are in need of adding runway, but we are during log-switch from compaction
      dirty.lock.unlock();
      //instead log.lock.unlock() do move ownership
      std::unique_lock<ceph::mutex> ll(log.lock, std::adopt_lock);
      while (log_forbidden_to_expand.load()) {
	log_cond.wait(ll);
      }
    } else {
      ceph_assert(available_runway >= 0);
    }
  } while (available_runway < 0);
  
  ceph_assert(want_seq == 0 || want_seq <= dirty.seq_live); // illegal to request seq that was not created yet
  uint64_t seq =_log_advance_seq();
  _consume_dirty(seq);
  vector<interval_set<uint64_t>> to_release(dirty.pending_release.size());
  to_release.swap(dirty.pending_release);
  dirty.lock.unlock();

  _flush_and_sync_log_core(available_runway);
  _flush_bdev(log.writer);
  logger->set(l_bluefs_log_bytes, log.writer->file->fnode.size);
  //now log.lock is no longer needed
  log.lock.unlock();

  _clear_dirty_set_stable_D(seq);
  _release_pending_allocations(to_release);

  _update_logger_stats();
  return 0;
}

// Flushes log and immediately adjusts log_writer pos.
int BlueFS::_flush_and_sync_log_jump_D(uint64_t jump_to,
				     int64_t available_runway)
{
  ceph_assert(ceph_mutex_is_locked(log.lock));

  ceph_assert(jump_to);
  // we synchronize writing to log, by lock to log.lock

  dirty.lock.lock();
  uint64_t seq =_log_advance_seq();
  _consume_dirty(seq);
  vector<interval_set<uint64_t>> to_release(dirty.pending_release.size());
  to_release.swap(dirty.pending_release);
  dirty.lock.unlock();
  _flush_and_sync_log_core(available_runway);

  dout(10) << __func__ << " jumping log offset from 0x" << std::hex
	   << log.writer->pos << " -> 0x" << jump_to << std::dec << dendl;
  log.writer->pos = jump_to;
  vselector->sub_usage(log.writer->file->vselector_hint, log.writer->file->fnode.size);
  log.writer->file->fnode.size = jump_to;
  vselector->add_usage(log.writer->file->vselector_hint, log.writer->file->fnode.size);

  _flush_bdev(log.writer);

  _clear_dirty_set_stable_D(seq);
  _release_pending_allocations(to_release);

  logger->set(l_bluefs_log_bytes, log.writer->file->fnode.size);
  _update_logger_stats();
  return 0;
}

ceph::bufferlist BlueFS::FileWriter::flush_buffer(
  CephContext* const cct,
  const bool partial,
  const unsigned length,
  const bluefs_super_t& super)
{
  ceph_assert(ceph_mutex_is_locked(this->lock) || file->fnode.ino <= 1);
  ceph::bufferlist bl;
  if (partial) {
    tail_block.splice(0, tail_block.length(), &bl);
  }
  const auto remaining_len = length - bl.length();
  buffer.splice(0, remaining_len, &bl);
  if (buffer.length()) {
    dout(20) << " leaving 0x" << std::hex << buffer.length() << std::dec
             << " unflushed" << dendl;
  }
  if (const unsigned tail = bl.length() & ~super.block_mask(); tail) {
    const auto padding_len = super.block_size - tail;
    dout(20) << __func__ << " caching tail of 0x"
             << std::hex << tail
             << " and padding block with 0x" << padding_len
             << " buffer.length() " << buffer.length()
             << std::dec << dendl;
    // We need to go through the `buffer_appender` to get a chance to
    // preserve in-memory contiguity and not mess with the alignment.
    // Otherwise a costly rebuild could happen in e.g. `KernelDevice`.
    buffer_appender.append_zero(padding_len);
    buffer.splice(buffer.length() - padding_len, padding_len, &bl);
    // Deep copy the tail here. This allows to avoid costlier copy on
    // bufferlist rebuild in e.g. `KernelDevice` and minimizes number
    // of memory allocations.
    // The alternative approach would be to place the entire tail and
    // padding on a dedicated, 4 KB long memory chunk. This shouldn't
    // trigger the rebuild while still being less expensive.
    buffer_appender.substr_of(bl, bl.length() - padding_len - tail, tail);
    buffer.splice(buffer.length() - tail, tail, &tail_block);
  } else {
    tail_block.clear();
  }
  return bl;
}

int BlueFS::_signal_dirty_to_log_D(FileWriter *h)
{
  ceph_assert(ceph_mutex_is_locked(h->lock));
  std::lock_guard dl(dirty.lock);
  h->file->fnode.mtime = ceph_clock_now();
  ceph_assert(h->file->fnode.ino >= 1);
  if (h->file->dirty_seq <= dirty.seq_stable) {
    h->file->dirty_seq = dirty.seq_live;
    dirty.files[h->file->dirty_seq].push_back(*h->file);
    dout(20) << __func__ << " dirty_seq = " << dirty.seq_live
	     << " (was clean)" << dendl;
  } else {
    if (h->file->dirty_seq != dirty.seq_live) {
      // need re-dirty, erase from list first
      ceph_assert(dirty.files.count(h->file->dirty_seq));
      auto it = dirty.files[h->file->dirty_seq].iterator_to(*h->file);
      dirty.files[h->file->dirty_seq].erase(it);
      h->file->dirty_seq = dirty.seq_live;
      dirty.files[h->file->dirty_seq].push_back(*h->file);
      dout(20) << __func__ << " dirty_seq = " << dirty.seq_live
	       << " (was " << h->file->dirty_seq << ")" << dendl;
    } else {
      dout(20) << __func__ << " dirty_seq = " << dirty.seq_live
	       << " (unchanged, do nothing) " << dendl;
    }
  }
  return 0;
}

void BlueFS::flush_range(FileWriter *h, uint64_t offset, uint64_t length)/*_WF*/
{
  _maybe_check_vselector_LNF();
  std::unique_lock hl(h->lock);
  _flush_range_F(h, offset, length);
}

int BlueFS::_flush_range_F(FileWriter *h, uint64_t offset, uint64_t length)
{
  ceph_assert(ceph_mutex_is_locked(h->lock));
  ceph_assert(h->file->num_readers.load() == 0);
  ceph_assert(h->file->fnode.ino > 1);

  dout(10) << __func__ << " " << h << " pos 0x" << std::hex << h->pos
	   << " 0x" << offset << "~" << length << std::dec
	   << " to " << h->file->fnode << dendl;
  if (h->file->deleted) {
    dout(10) << __func__ << "  deleted, no-op" << dendl;
    return 0;
  }

  bool buffered = cct->_conf->bluefs_buffered_io;

  if (offset + length <= h->pos)
    return 0;
  if (offset < h->pos) {
    length -= h->pos - offset;
    offset = h->pos;
    dout(10) << " still need 0x"
             << std::hex << offset << "~" << length << std::dec
             << dendl;
  }
  std::lock_guard file_lock(h->file->lock);
  ceph_assert(offset <= h->file->fnode.size);

  uint64_t allocated = h->file->fnode.get_allocated();
  vselector->sub_usage(h->file->vselector_hint, h->file->fnode);
  // do not bother to dirty the file if we are overwriting
  // previously allocated extents.
  if (allocated < offset + length) {
    // we should never run out of log space here; see the min runway check
    // in _flush_and_sync_log.
    int r = _allocate(vselector->select_prefer_bdev(h->file->vselector_hint),
		      offset + length - allocated,
		      &h->file->fnode);
    if (r < 0) {
      derr << __func__ << " allocated: 0x" << std::hex << allocated
           << " offset: 0x" << offset << " length: 0x" << length << std::dec
           << dendl;
      vselector->add_usage(h->file->vselector_hint, h->file->fnode); // undo
      ceph_abort_msg("bluefs enospc");
      return r;
    }
    h->file->is_dirty = true;
  }
  if (h->file->fnode.size < offset + length) {
    h->file->fnode.size = offset + length;
    h->file->is_dirty = true;
  }

  dout(20) << __func__ << " file now, unflushed " << h->file->fnode << dendl;
  int res = _flush_data(h, offset, length, buffered);
  vselector->add_usage(h->file->vselector_hint, h->file->fnode);
  return res;
}

int BlueFS::_flush_data(FileWriter *h, uint64_t offset, uint64_t length, bool buffered)
{
  if (h->file->fnode.ino > 1) {
    ceph_assert(ceph_mutex_is_locked(h->lock));
    ceph_assert(ceph_mutex_is_locked(h->file->lock));
  }
  uint64_t x_off = 0;
  auto p = h->file->fnode.seek(offset, &x_off);
  ceph_assert(p != h->file->fnode.extents.end());
  dout(20) << __func__ << " in " << *p << " x_off 0x"
           << std::hex << x_off << std::dec << dendl;

  unsigned partial = x_off & ~super.block_mask();
  if (partial) {
    dout(20) << __func__ << " using partial tail 0x"
             << std::hex << partial << std::dec << dendl;
    x_off -= partial;
    offset -= partial;
    length += partial;
    dout(20) << __func__ << " waiting for previous aio to complete" << dendl;
    for (auto p : h->iocv) {
      if (p) {
	p->aio_wait();
      }
    }
  }

  auto bl = h->flush_buffer(cct, partial, length, super);
  ceph_assert(bl.length() >= length);
  h->pos = offset + length;
  length = bl.length();

  switch (h->writer_type) {
  case WRITER_WAL:
    logger->inc(l_bluefs_bytes_written_wal, length);
    break;
  case WRITER_SST:
    logger->inc(l_bluefs_bytes_written_sst, length);
    break;
  }

  dout(30) << "dump:\n";
  bl.hexdump(*_dout);
  *_dout << dendl;

  uint64_t bloff = 0;
  uint64_t bytes_written_slow = 0;
  while (length > 0) {
    uint64_t x_len = std::min(p->length - x_off, length);
    bufferlist t;
    t.substr_of(bl, bloff, x_len);
    if (cct->_conf->bluefs_sync_write) {
      bdev[p->bdev]->write(p->offset + x_off, t, buffered, h->write_hint);
    } else {
      bdev[p->bdev]->aio_write(p->offset + x_off, t, h->iocv[p->bdev], buffered, h->write_hint);
    }
    h->dirty_devs[p->bdev] = true;
    if (p->bdev == BDEV_SLOW) {
      bytes_written_slow += t.length();
    }

    bloff += x_len;
    length -= x_len;
    ++p;
    x_off = 0;
  }
  if (bytes_written_slow) {
    logger->inc(l_bluefs_bytes_written_slow, bytes_written_slow);
  }
  for (unsigned i = 0; i < MAX_BDEV; ++i) {
    if (bdev[i]) {
      if (h->iocv[i] && h->iocv[i]->has_pending_aios()) {
        bdev[i]->aio_submit(h->iocv[i]);
      }
    }
  }
  dout(20) << __func__ << " h " << h << " pos now 0x"
           << std::hex << h->pos << std::dec << dendl;
  return 0;
}

#ifdef HAVE_LIBAIO
// we need to retire old completed aios so they don't stick around in
// memory indefinitely (along with their bufferlist refs).
void BlueFS::_claim_completed_aios(FileWriter *h, list<aio_t> *ls)
{
  for (auto p : h->iocv) {
    if (p) {
      ls->splice(ls->end(), p->running_aios);
    }
  }
  dout(10) << __func__ << " got " << ls->size() << " aios" << dendl;
}

void BlueFS::_wait_for_aio(FileWriter *h)
{
  // NOTE: this is safe to call without a lock, as long as our reference is
  // stable.
  utime_t start;
  lgeneric_subdout(cct, bluefs, 10) << __func__;
  start = ceph_clock_now();
  *_dout << " " << h << dendl;
  for (auto p : h->iocv) {
    if (p) {
      p->aio_wait();
    }
  }
  dout(10) << __func__ << " " << h << " done in " << (ceph_clock_now() - start) << dendl;
}
#endif

void BlueFS::append_try_flush(FileWriter *h, const char* buf, size_t len)/*_WF_LNF_NF_LD_D*/
{
  bool flushed_sum = false;
  {
    std::unique_lock hl(h->lock);
    size_t max_size = 1ull << 30; // cap to 1GB
    while (len > 0) {
      bool need_flush = true;
      auto l0 = h->get_buffer_length();
      if (l0 < max_size) {
	size_t l = std::min(len, max_size - l0);
	h->append(buf, l);
	buf += l;
	len -= l;
	need_flush = h->get_buffer_length() >= cct->_conf->bluefs_min_flush_size;
      }
      if (need_flush) {
	bool flushed = false;
	int r = _flush_F(h, true, &flushed);
	ceph_assert(r == 0);
	flushed_sum |= flushed;
	// make sure we've made any progress with flush hence the
	// loop doesn't iterate forever
	ceph_assert(h->get_buffer_length() < max_size);
      }
    }
  }
  if (flushed_sum) {
    _maybe_compact_log_LNF_NF_LD_D();
  }
}

void BlueFS::flush(FileWriter *h, bool force)/*_WF_LNF_NF_LD_D*/
{
  bool flushed = false;
  int r;
  {
    std::unique_lock hl(h->lock);
    r = _flush_F(h, force, &flushed);
    ceph_assert(r == 0);
  }
  if (r == 0 && flushed) {
    _maybe_compact_log_LNF_NF_LD_D();
  }
}

int BlueFS::_flush_F(FileWriter *h, bool force, bool *flushed)
{
  ceph_assert(ceph_mutex_is_locked(h->lock));
  uint64_t length = h->get_buffer_length();
  uint64_t offset = h->pos;
  if (flushed) {
    *flushed = false;
  }
  if (!force &&
      length < cct->_conf->bluefs_min_flush_size) {
    dout(10) << __func__ << " " << h << " ignoring, length " << length
	     << " < min_flush_size " << cct->_conf->bluefs_min_flush_size
	     << dendl;
    return 0;
  }
  if (length == 0) {
    dout(10) << __func__ << " " << h << " no dirty data on "
	     << h->file->fnode << dendl;
    return 0;
  }
  dout(10) << __func__ << " " << h << " 0x"
           << std::hex << offset << "~" << length << std::dec
	   << " to " << h->file->fnode << dendl;
  ceph_assert(h->pos <= h->file->fnode.size);
  int r = _flush_range_F(h, offset, length);
  if (flushed) {
    *flushed = true;
  }
  return r;
}

// Flush for bluefs special files.
// Does not add extents to h.
// Does not mark h as dirty.
// we do not need to dirty the log file (or it's compacting
// replacement) when the file size changes because replay is
// smart enough to discover it on its own.
uint64_t BlueFS::_flush_special(FileWriter *h)
{
  ceph_assert(h->file->fnode.ino <= 1);
  uint64_t length = h->get_buffer_length();
  uint64_t offset = h->pos;
  uint64_t new_data = 0;
  ceph_assert(length + offset <= h->file->fnode.get_allocated());
  if (h->file->fnode.size < offset + length) {
    new_data = offset + length - h->file->fnode.size;
    h->file->fnode.size = offset + length;
  }
  _flush_data(h, offset, length, false);
  return new_data;
}

int BlueFS::truncate(FileWriter *h, uint64_t offset)/*_WF_L*/
{
  std::lock_guard hl(h->lock);
  dout(10) << __func__ << " 0x" << std::hex << offset << std::dec
           << " file " << h->file->fnode << dendl;
  if (h->file->deleted) {
    dout(10) << __func__ << "  deleted, no-op" << dendl;
    return 0;
  }

  // we never truncate internal log files
  ceph_assert(h->file->fnode.ino > 1);

  // truncate off unflushed data?
  if (h->pos < offset &&
      h->pos + h->get_buffer_length() > offset) {
    dout(20) << __func__ << " tossing out last " << offset - h->pos
	     << " unflushed bytes" << dendl;
    ceph_abort_msg("actually this shouldn't happen");
  }
  if (h->get_buffer_length()) {
    int r = _flush_F(h, true);
    if (r < 0)
      return r;
  }
  if (offset == h->file->fnode.size) {
    return 0;  // no-op!
  }
  if (offset > h->file->fnode.size) {
    ceph_abort_msg("truncate up not supported");
  }
  ceph_assert(h->file->fnode.size >= offset);
  _flush_bdev(h);

  std::lock_guard ll(log.lock);
  vselector->sub_usage(h->file->vselector_hint, h->file->fnode.size);
  h->file->fnode.size = offset;
  vselector->add_usage(h->file->vselector_hint, h->file->fnode.size);
  log.t.op_file_update_inc(h->file->fnode);
  return 0;
}

int BlueFS::fsync(FileWriter *h)/*_WF_WD_WLD_WLNF_WNF*/
{
  _maybe_check_vselector_LNF();
  std::unique_lock hl(h->lock);
  uint64_t old_dirty_seq = 0;
  {
    dout(10) << __func__ << " " << h << " " << h->file->fnode << dendl;
    int r = _flush_F(h, true);
    if (r < 0)
      return r;
    _flush_bdev(h);
    if (h->file->is_dirty) {
      _signal_dirty_to_log_D(h);
      h->file->is_dirty = false;
    }
    {
      std::lock_guard dl(dirty.lock);
      if (dirty.seq_stable < h->file->dirty_seq) {
	old_dirty_seq = h->file->dirty_seq;
	dout(20) << __func__ << " file metadata was dirty (" << old_dirty_seq
		 << ") on " << h->file->fnode << ", flushing log" << dendl;
      }
    }
  }
  if (old_dirty_seq) {
    _flush_and_sync_log_LD(old_dirty_seq);
  }
  _maybe_compact_log_LNF_NF_LD_D();

  return 0;
}

// be careful - either h->file->lock or log.lock must be taken
void BlueFS::_flush_bdev(FileWriter *h)
{
  if (h->file->fnode.ino > 1) {
    ceph_assert(ceph_mutex_is_locked(h->lock));
  } else if (h->file->fnode.ino == 1) {
    ceph_assert(ceph_mutex_is_locked(log.lock));
  }
  std::array<bool, MAX_BDEV> flush_devs = h->dirty_devs;
  h->dirty_devs.fill(false);
#ifdef HAVE_LIBAIO
  if (!cct->_conf->bluefs_sync_write) {
    list<aio_t> completed_ios;
    _claim_completed_aios(h, &completed_ios);
    _wait_for_aio(h);
    completed_ios.clear();
  }
#endif
  _flush_bdev(flush_devs);
}

void BlueFS::_flush_bdev(std::array<bool, MAX_BDEV>& dirty_bdevs)
{
  // NOTE: this is safe to call without a lock.
  dout(20) << __func__ << dendl;
  for (unsigned i = 0; i < MAX_BDEV; i++) {
    if (dirty_bdevs[i])
      bdev[i]->flush();
  }
}

void BlueFS::_flush_bdev()
{
  // NOTE: this is safe to call without a lock.
  dout(20) << __func__ << dendl;
  for (unsigned i = 0; i < MAX_BDEV; i++) {
    // alloc space from BDEV_SLOW is unexpected.
    // So most cases we don't alloc from BDEV_SLOW and so avoiding flush not-used device.
    if (bdev[i] && (i != BDEV_SLOW || _get_used(i))) {
      bdev[i]->flush();
    }
  }
}

const char* BlueFS::get_device_name(unsigned id)
{
  if (id >= MAX_BDEV) return "BDEV_INV";
  const char* names[] = {"BDEV_WAL", "BDEV_DB", "BDEV_SLOW", "BDEV_NEWWAL", "BDEV_NEWDB"};
  return names[id];
}

int BlueFS::_allocate_without_fallback(uint8_t id, uint64_t len,
		      PExtentVector* extents)
{
  dout(10) << __func__ << " len 0x" << std::hex << len << std::dec
           << " from " << (int)id << dendl;
  assert(id < alloc.size());
  if (!alloc[id]) {
    return -ENOENT;
  }
  extents->reserve(4);  // 4 should be (more than) enough for most allocations
  int64_t need = round_up_to(len, alloc_size[id]);
  int64_t alloc_len = alloc[id]->allocate(need, alloc_size[id], 0, extents);
  if (alloc_len < 0 || alloc_len < need) {
    if (alloc_len > 0) {
      alloc[id]->release(*extents);
    }
    derr << __func__ << " unable to allocate 0x" << std::hex << need
	 << " on bdev " << (int)id
         << ", allocator name " << alloc[id]->get_name()
         << ", allocator type " << alloc[id]->get_type()
         << ", capacity 0x" << alloc[id]->get_capacity()
         << ", block size 0x" << alloc[id]->get_block_size()
         << ", alloc size 0x" << alloc_size[id]
         << ", free 0x" << alloc[id]->get_free()
         << ", fragmentation " << alloc[id]->get_fragmentation()
         << ", allocated 0x" << (alloc_len > 0 ? alloc_len : 0)
	 << std::dec << dendl;
    alloc[id]->dump();
    return -ENOSPC;
  }
  if (is_shared_alloc(id)) {
    shared_alloc->bluefs_used += alloc_len;
  }

  return 0;
}

int BlueFS::_allocate(uint8_t id, uint64_t len,
		      bluefs_fnode_t* node)
{
  dout(10) << __func__ << " len 0x" << std::hex << len << std::dec
           << " from " << (int)id << dendl;
  ceph_assert(id < alloc.size());
  int64_t alloc_len = 0;
  PExtentVector extents;
  uint64_t hint = 0;
  int64_t need = len;
  if (alloc[id]) {
    need = round_up_to(len, alloc_size[id]);
    if (!node->extents.empty() && node->extents.back().bdev == id) {
      hint = node->extents.back().end();
    }   
    extents.reserve(4);  // 4 should be (more than) enough for most allocations
    alloc_len = alloc[id]->allocate(need, alloc_size[id], hint, &extents);
  }
  if (alloc_len < 0 || alloc_len < need) {
    if (alloc[id]) {
      if (alloc_len > 0) {
        alloc[id]->release(extents);
      }
      dout(1) << __func__ << " unable to allocate 0x" << std::hex << need
	      << " on bdev " << (int)id
              << ", allocator name " << alloc[id]->get_name()
              << ", allocator type " << alloc[id]->get_type()
              << ", capacity 0x" << alloc[id]->get_capacity()
              << ", block size 0x" << alloc[id]->get_block_size()
              << ", alloc size 0x" << alloc_size[id]
              << ", free 0x" << alloc[id]->get_free()
              << ", fragmentation " << alloc[id]->get_fragmentation()
              << ", allocated 0x" << (alloc_len > 0 ? alloc_len : 0)
	      << std::dec << dendl;
    } else {
      dout(20) << __func__ << " alloc-id not set on index="<< (int)id << " unable to allocate 0x" << std::hex << need
	       << " on bdev " << (int)id << std::dec << dendl;
    }
    if (id != BDEV_SLOW) {
      dout(20) << __func__ << " fallback to bdev "
	       << (int)id + 1
	       << dendl;
      return _allocate(id + 1, len, node);
    } else {
      derr << __func__ << " allocation failed, needed 0x" << std::hex << need
           << dendl;
    }
    return -ENOSPC;
  } else {
    uint64_t used = _get_used(id);
    if (max_bytes[id] < used) {
      logger->set(max_bytes_pcounters[id], used);
      max_bytes[id] = used;
    }
    if (is_shared_alloc(id)) {
      shared_alloc->bluefs_used += alloc_len;
    }
  }

  for (auto& p : extents) {
    node->append_extent(bluefs_extent_t(id, p.offset, p.length));
  }
   
  return 0;
}

int BlueFS::preallocate(FileRef f, uint64_t off, uint64_t len)/*_LF*/
{
  std::lock_guard ll(log.lock);
  std::lock_guard fl(f->lock);
  dout(10) << __func__ << " file " << f->fnode << " 0x"
	   << std::hex << off << "~" << len << std::dec << dendl;
  if (f->deleted) {
    dout(10) << __func__ << "  deleted, no-op" << dendl;
    return 0;
  }
  ceph_assert(f->fnode.ino > 1);
  uint64_t allocated = f->fnode.get_allocated();
  if (off + len > allocated) {
    uint64_t want = off + len - allocated;

    vselector->sub_usage(f->vselector_hint, f->fnode);
    int r = _allocate(vselector->select_prefer_bdev(f->vselector_hint),
      want,
      &f->fnode);
    vselector->add_usage(f->vselector_hint, f->fnode);
    if (r < 0)
      return r;

    log.t.op_file_update_inc(f->fnode);
  }
  return 0;
}

void BlueFS::sync_metadata(bool avoid_compact)/*_LNF_NF_LD_D*/
{
  bool can_skip_flush;
  {
    std::lock_guard ll(log.lock);
    std::lock_guard dl(dirty.lock);
    can_skip_flush = log.t.empty() && dirty.files.empty();
  }
  if (can_skip_flush) {
    dout(10) << __func__ << " - no pending log events" << dendl;
  } else {
    utime_t start;
    lgeneric_subdout(cct, bluefs, 10) << __func__;
    start = ceph_clock_now();
    *_dout <<  dendl;
    _flush_bdev(); // FIXME?
    _flush_and_sync_log_LD();
    dout(10) << __func__ << " done in " << (ceph_clock_now() - start) << dendl;
  }

  if (!avoid_compact) {
    _maybe_compact_log_LNF_NF_LD_D();
  }
}

void BlueFS::_maybe_compact_log_LNF_NF_LD_D()
{
  if (!cct->_conf->bluefs_replay_recovery_disable_compact &&
      _should_start_compact_log_L_N()) {
    if (cct->_conf->bluefs_compact_log_sync) {
      _compact_log_sync_LNF_LD();
    } else {
      _compact_log_async_LD_LNF_D();
    }
  }
}

int BlueFS::open_for_write(
  std::string_view dirname,
  std::string_view filename,
  FileWriter **h,
  bool overwrite)/*_N_LD*/
{
  _maybe_check_vselector_LNF();
  FileRef file;
  bool create = false;
  bool truncate = false;
  mempool::bluefs::vector<bluefs_extent_t> pending_release_extents;
  {
  std::unique_lock nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  DirRef dir;
  if (p == nodes.dir_map.end()) {
    // implicitly create the dir
    dout(20) << __func__ << "  dir " << dirname
	     << " does not exist" << dendl;
    return -ENOENT;
  } else {
    dir = p->second;
  }

  map<string,FileRef>::iterator q = dir->file_map.find(filename);
  if (q == dir->file_map.end()) {
    if (overwrite) {
      dout(20) << __func__ << " dir " << dirname << " (" << dir
	       << ") file " << filename
	       << " does not exist" << dendl;
      return -ENOENT;
    }
    file = ceph::make_ref<File>();
    file->fnode.ino = ++ino_last;
    nodes.file_map[ino_last] = file;
    dir->file_map[string{filename}] = file;
    ++file->refs;
    create = true;
    logger->set(l_bluefs_num_files, nodes.file_map.size());
  } else {
    // overwrite existing file?
    file = q->second;
    if (overwrite) {
      dout(20) << __func__ << " dir " << dirname << " (" << dir
	       << ") file " << filename
	       << " already exists, overwrite in place" << dendl;
    } else {
      dout(20) << __func__ << " dir " << dirname << " (" << dir
	       << ") file " << filename
	       << " already exists, truncate + overwrite" << dendl;
      vselector->sub_usage(file->vselector_hint, file->fnode);
      file->fnode.size = 0;
      pending_release_extents.swap(file->fnode.extents);
      truncate = true;

      file->fnode.clear_extents();
    }
  }
  ceph_assert(file->fnode.ino > 1);

  file->fnode.mtime = ceph_clock_now();
  file->vselector_hint = vselector->get_hint_by_dir(dirname);
  if (create || truncate) {
    vselector->add_usage(file->vselector_hint, file->fnode); // update file count
  }

  dout(20) << __func__ << " mapping " << dirname << "/" << filename
	   << " vsel_hint " << file->vselector_hint
	   << dendl;
  }
  {
    std::lock_guard ll(log.lock);
    log.t.op_file_update(file->fnode);
    if (create)
      log.t.op_dir_link(dirname, filename, file->fnode.ino);

    std::lock_guard dl(dirty.lock);
    for (auto& p : pending_release_extents) {
      dirty.pending_release[p.bdev].insert(p.offset, p.length);
    }
  }
  *h = _create_writer(file);

  if (boost::algorithm::ends_with(filename, ".log")) {
    (*h)->writer_type = BlueFS::WRITER_WAL;
    if (logger && !overwrite) {
      logger->inc(l_bluefs_files_written_wal);
    }
  } else if (boost::algorithm::ends_with(filename, ".sst")) {
    (*h)->writer_type = BlueFS::WRITER_SST;
    if (logger) {
      logger->inc(l_bluefs_files_written_sst);
    }
  }

  dout(10) << __func__ << " h " << *h << " on " << file->fnode << dendl;
  return 0;
}

BlueFS::FileWriter *BlueFS::_create_writer(FileRef f)
{
  FileWriter *w = new FileWriter(f);
  for (unsigned i = 0; i < MAX_BDEV; ++i) {
    if (bdev[i]) {
      w->iocv[i] = new IOContext(cct, NULL);
    }
  }
  return w;
}

void BlueFS::_drain_writer(FileWriter *h)
{
  dout(10) << __func__ << " " << h << " type " << h->writer_type << dendl;
  //h->buffer.reassign_to_mempool(mempool::mempool_bluefs_file_writer);
  for (unsigned i=0; i<MAX_BDEV; ++i) {
    if (bdev[i]) {
      if (h->iocv[i]) {
	h->iocv[i]->aio_wait();
	delete h->iocv[i];
      }
    }
  }
  // sanity
  if (h->file->fnode.size >= (1ull << 30)) {
    dout(10) << __func__ << " file is unexpectedly large:" << h->file->fnode << dendl;
  }
}

void BlueFS::_close_writer(FileWriter *h)
{
  _drain_writer(h);
  delete h;
}
void BlueFS::close_writer(FileWriter *h)
{
  {
    std::lock_guard l(h->lock);
    _drain_writer(h);
  }
  delete h;
}

uint64_t BlueFS::debug_get_dirty_seq(FileWriter *h)
{
  std::lock_guard l(h->lock);
  return h->file->dirty_seq;
}

bool BlueFS::debug_get_is_dev_dirty(FileWriter *h, uint8_t dev)
{
  std::lock_guard l(h->lock);
  return h->dirty_devs[dev];
}

int BlueFS::open_for_read(
  std::string_view dirname,
  std::string_view filename,
  FileReader **h,
  bool random)/*_N*/
{
  _maybe_check_vselector_LNF();
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << "/" << filename
	   << (random ? " (random)":" (sequential)") << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " not found" << dendl;
    return -ENOENT;
  }
  DirRef dir = p->second;

  map<string,FileRef>::iterator q = dir->file_map.find(filename);
  if (q == dir->file_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " (" << dir
	     << ") file " << filename
	     << " not found" << dendl;
    return -ENOENT;
  }
  File *file = q->second.get();

  *h = new FileReader(file, random ? 4096 : cct->_conf->bluefs_max_prefetch,
		      random, false);
  dout(10) << __func__ << " h " << *h << " on " << file->fnode << dendl;
  return 0;
}

int BlueFS::rename(
  std::string_view old_dirname, std::string_view old_filename,
  std::string_view new_dirname, std::string_view new_filename)/*_LND*/
{
  std::lock_guard ll(log.lock);
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << old_dirname << "/" << old_filename
	   << " -> " << new_dirname << "/" << new_filename << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(old_dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << old_dirname << " not found" << dendl;
    return -ENOENT;
  }
  DirRef old_dir = p->second;
  map<string,FileRef>::iterator q = old_dir->file_map.find(old_filename);
  if (q == old_dir->file_map.end()) {
    dout(20) << __func__ << " dir " << old_dirname << " (" << old_dir
	     << ") file " << old_filename
	     << " not found" << dendl;
    return -ENOENT;
  }
  FileRef file = q->second;

  p = nodes.dir_map.find(new_dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << new_dirname << " not found" << dendl;
    return -ENOENT;
  }
  DirRef new_dir = p->second;
  q = new_dir->file_map.find(new_filename);
  if (q != new_dir->file_map.end()) {
    dout(20) << __func__ << " dir " << new_dirname << " (" << old_dir
	     << ") file " << new_filename
	     << " already exists, unlinking" << dendl;
    ceph_assert(q->second != file);
    log.t.op_dir_unlink(new_dirname, new_filename);
    _drop_link_D(q->second);
  }

  dout(10) << __func__ << " " << new_dirname << "/" << new_filename << " "
	   << " " << file->fnode << dendl;

  new_dir->file_map[string{new_filename}] = file;
  old_dir->file_map.erase(string{old_filename});

  log.t.op_dir_link(new_dirname, new_filename, file->fnode.ino);
  log.t.op_dir_unlink(old_dirname, old_filename);
  return 0;
}

int BlueFS::mkdir(std::string_view dirname)/*_LN*/
{
  std::lock_guard ll(log.lock);
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  if (p != nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " exists" << dendl;
    return -EEXIST;
  }
  nodes.dir_map[string{dirname}] = ceph::make_ref<Dir>();
  log.t.op_dir_create(dirname);
  return 0;
}

int BlueFS::rmdir(std::string_view dirname)/*_LN*/
{
  std::lock_guard ll(log.lock);
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << dendl;
  auto p = nodes.dir_map.find(dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " does not exist" << dendl;
    return -ENOENT;
  }
  DirRef dir = p->second;
  if (!dir->file_map.empty()) {
    dout(20) << __func__ << " dir " << dirname << " not empty" << dendl;
    return -ENOTEMPTY;
  }
  nodes.dir_map.erase(string{dirname});
  log.t.op_dir_remove(dirname);
  return 0;
}

bool BlueFS::dir_exists(std::string_view dirname)/*_N*/
{
  std::lock_guard nl(nodes.lock);
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  bool exists = p != nodes.dir_map.end();
  dout(10) << __func__ << " " << dirname << " = " << (int)exists << dendl;
  return exists;
}

int BlueFS::stat(std::string_view dirname, std::string_view filename,
		 uint64_t *size, utime_t *mtime)/*_N*/
{
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " not found" << dendl;
    return -ENOENT;
  }
  DirRef dir = p->second;
  map<string,FileRef>::iterator q = dir->file_map.find(filename);
  if (q == dir->file_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " (" << dir
	     << ") file " << filename
	     << " not found" << dendl;
    return -ENOENT;
  }
  File *file = q->second.get();
  dout(10) << __func__ << " " << dirname << "/" << filename
	   << " " << file->fnode << dendl;
  if (size)
    *size = file->fnode.size;
  if (mtime)
    *mtime = file->fnode.mtime;
  return 0;
}

int BlueFS::lock_file(std::string_view dirname, std::string_view filename,
		      FileLock **plock)/*_LN*/
{
  std::lock_guard ll(log.lock);
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " not found" << dendl;
    return -ENOENT;
  }
  DirRef dir = p->second;
  auto q = dir->file_map.find(filename);
  FileRef file;
  if (q == dir->file_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " (" << dir
	     << ") file " << filename
	     << " not found, creating" << dendl;
    file = ceph::make_ref<File>();
    file->fnode.ino = ++ino_last;
    file->fnode.mtime = ceph_clock_now();
    nodes.file_map[ino_last] = file;
    dir->file_map[string{filename}] = file;
    logger->set(l_bluefs_num_files, nodes.file_map.size());
    ++file->refs;
    log.t.op_file_update(file->fnode);
    log.t.op_dir_link(dirname, filename, file->fnode.ino);
  } else {
    file = q->second;
    if (file->locked) {
      dout(10) << __func__ << " already locked" << dendl;
      return -ENOLCK;
    }
  }
  file->locked = true;
  *plock = new FileLock(file);
  dout(10) << __func__ << " locked " << file->fnode
	   << " with " << *plock << dendl;
  return 0;
}

int BlueFS::unlock_file(FileLock *fl)/*_N*/
{
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << fl << " on " << fl->file->fnode << dendl;
  ceph_assert(fl->file->locked);
  fl->file->locked = false;
  delete fl;
  return 0;
}

int BlueFS::readdir(std::string_view dirname, vector<string> *ls)/*_N*/
{
  // dirname may contain a trailing /
  if (!dirname.empty() && dirname.back() == '/') {
    dirname.remove_suffix(1);
  }
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << dendl;
  if (dirname.empty()) {
    // list dirs
    ls->reserve(nodes.dir_map.size() + 2);
    for (auto& q : nodes.dir_map) {
      ls->push_back(q.first);
    }
  } else {
    // list files in dir
    map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
    if (p == nodes.dir_map.end()) {
      dout(20) << __func__ << " dir " << dirname << " not found" << dendl;
      return -ENOENT;
    }
    DirRef dir = p->second;
    ls->reserve(dir->file_map.size() + 2);
    for (auto& q : dir->file_map) {
      ls->push_back(q.first);
    }
  }
  ls->push_back(".");
  ls->push_back("..");
  return 0;
}

int BlueFS::unlink(std::string_view dirname, std::string_view filename)/*_LND*/
{
  std::lock_guard ll(log.lock);
  std::lock_guard nl(nodes.lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = nodes.dir_map.find(dirname);
  if (p == nodes.dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " not found" << dendl;
    return -ENOENT;
  }
  DirRef dir = p->second;
  map<string,FileRef>::iterator q = dir->file_map.find(filename);
  if (q == dir->file_map.end()) {
    dout(20) << __func__ << " file " << dirname << "/" << filename
	     << " not found" << dendl;
    return -ENOENT;
  }
  FileRef file = q->second;
  if (file->locked) {
    dout(20) << __func__ << " file " << dirname << "/" << filename
             << " is locked" << dendl;
    return -EBUSY;
  }
  dir->file_map.erase(string{filename});
  log.t.op_dir_unlink(dirname, filename);
  _drop_link_D(file);
  return 0;
}

bool BlueFS::wal_is_rotational()
{
  if (bdev[BDEV_WAL]) {
    return bdev[BDEV_WAL]->is_rotational();
  } else if (bdev[BDEV_DB]) {
    return bdev[BDEV_DB]->is_rotational();
  }
  return bdev[BDEV_SLOW]->is_rotational();
}

/*
  Algorithm.
  do_replay_recovery_read is used when bluefs log abruptly ends, but it seems that more data should be there.
  Idea is to search disk for definiton of extents that will be accompanied with bluefs log in future,
  and try if using it will produce healthy bluefs transaction.
  We encode already known bluefs log extents and search disk for these bytes.
  When we find it, we decode following bytes as extent.
  We read that whole extent and then check if merged with existing log part gives a proper bluefs transaction.
 */
int BlueFS::_do_replay_recovery_read(FileReader *log_reader,
				    size_t replay_pos,
				    size_t read_offset,
				    size_t read_len,
				    bufferlist* bl) {
  dout(1) << __func__ << " replay_pos=0x" << std::hex << replay_pos <<
    " needs 0x" << read_offset << "~" << read_len << std::dec << dendl;

  bluefs_fnode_t& log_fnode = log_reader->file->fnode;
  bufferlist bin_extents;
  ::encode(log_fnode.extents, bin_extents);
  dout(2) << __func__ << " log file encoded extents length = " << bin_extents.length() << dendl;

  // cannot process if too small to effectively search
  ceph_assert(bin_extents.length() >= 32);
  bufferlist last_32;
  last_32.substr_of(bin_extents, bin_extents.length() - 32, 32);

  //read fixed part from replay_pos to end of bluefs_log extents
  bufferlist fixed;
  uint64_t e_off = 0;
  auto e = log_fnode.seek(replay_pos, &e_off);
  ceph_assert(e != log_fnode.extents.end());
  int r = _bdev_read(e->bdev, e->offset + e_off, e->length - e_off, &fixed, ioc[e->bdev],
		     cct->_conf->bluefs_buffered_io);
  ceph_assert(r == 0);
  //capture dev of last good extent
  uint8_t last_e_dev = e->bdev;
  uint64_t last_e_off = e->offset;
  ++e;
  while (e != log_fnode.extents.end()) {
    r = _bdev_read(e->bdev, e->offset, e->length, &fixed, ioc[e->bdev],
		   cct->_conf->bluefs_buffered_io);
    ceph_assert(r == 0);
    last_e_dev = e->bdev;
    ++e;
  }
  ceph_assert(replay_pos + fixed.length() == read_offset);

  dout(2) << __func__ << " valid data in log = " << fixed.length() << dendl;

  struct compare {
    bool operator()(const bluefs_extent_t& a, const bluefs_extent_t& b) const {
      if (a.bdev < b.bdev) return true;
      if (a.offset < b.offset) return true;
      return a.length < b.length;
    }
  };
  std::set<bluefs_extent_t, compare> extents_rejected;
  for (int dcnt = 0; dcnt < 3; dcnt++) {
    uint8_t dev = (last_e_dev + dcnt) % MAX_BDEV;
    if (bdev[dev] == nullptr) continue;
    dout(2) << __func__ << " processing " << get_device_name(dev) << dendl;
    interval_set<uint64_t> disk_regions;
    disk_regions.insert(0, bdev[dev]->get_size());
    for (auto f : nodes.file_map) {
      auto& e = f.second->fnode.extents;
      for (auto& p : e) {
	if (p.bdev == dev) {
	  disk_regions.erase(p.offset, p.length);
	}
      }
    }
    size_t disk_regions_count = disk_regions.num_intervals();
    dout(5) << __func__ << " " << disk_regions_count << " regions to scan on " << get_device_name(dev) << dendl;

    auto reg = disk_regions.lower_bound(last_e_off);
    //for all except first, start from beginning
    last_e_off = 0;
    if (reg == disk_regions.end()) {
      reg = disk_regions.begin();
    }
    const uint64_t chunk_size = 4 * 1024 * 1024;
    const uint64_t page_size = 4096;
    const uint64_t max_extent_size = 16;
    uint64_t overlay_size = last_32.length() + max_extent_size;
    for (size_t i = 0; i < disk_regions_count; reg++, i++) {
      if (reg == disk_regions.end()) {
	reg = disk_regions.begin();
      }
      uint64_t pos = reg.get_start();
      uint64_t len = reg.get_len();

      std::unique_ptr<char[]> raw_data_p{new char[page_size + chunk_size]};
      char* raw_data = raw_data_p.get();
      memset(raw_data, 0, page_size);

      while (len > last_32.length()) {
	uint64_t chunk_len = len > chunk_size ? chunk_size : len;
	dout(5) << __func__ << " read "
		<< get_device_name(dev) << ":0x" << std::hex << pos << "+" << chunk_len
		<< std::dec << dendl;
	r = _bdev_read_random(dev, pos, chunk_len,
	  raw_data + page_size, cct->_conf->bluefs_buffered_io);
	ceph_assert(r == 0);

	//search for fixed_last_32
	char* chunk_b = raw_data + page_size;
	char* chunk_e = chunk_b + chunk_len;

	char* search_b = chunk_b - overlay_size;
	char* search_e = chunk_e;

	for (char* sp = search_b; ; sp += last_32.length()) {
	  sp = (char*)memmem(sp, search_e - sp, last_32.c_str(), last_32.length());
	  if (sp == nullptr) {
	    break;
	  }

	  char* n = sp + last_32.length();
	  dout(5) << __func__ << " checking location 0x" << std::hex << pos + (n - chunk_b) << std::dec << dendl;
	  bufferlist test;
	  test.append(n, std::min<size_t>(max_extent_size, chunk_e - n));
	  bluefs_extent_t ne;
	  try {
	    bufferlist::const_iterator p = test.begin();
	    ::decode(ne, p);
	  } catch (buffer::error& e) {
	    continue;
	  }
	  if (extents_rejected.count(ne) != 0) {
	    dout(5) << __func__ << " extent " << ne << " already refected" <<dendl;
	    continue;
	  }
	  //insert as rejected already. if we succeed, it wouldn't make difference.
	  extents_rejected.insert(ne);

	  if (ne.bdev >= MAX_BDEV ||
	      bdev[ne.bdev] == nullptr ||
	      ne.length > 16 * 1024 * 1024 ||
	      (ne.length & 4095) != 0 ||
	      ne.offset + ne.length > bdev[ne.bdev]->get_size() ||
	      (ne.offset & 4095) != 0) {
	    dout(5) << __func__ << " refusing extent " << ne << dendl;
	    continue;
	  }
	  dout(5) << __func__ << " checking extent " << ne << dendl;

	  //read candidate extent - whole
	  bufferlist candidate;
	  candidate.append(fixed);
	  r = _bdev_read(ne.bdev, ne.offset, ne.length, &candidate, ioc[ne.bdev],
			 cct->_conf->bluefs_buffered_io);
	  ceph_assert(r == 0);

	  //check if transaction & crc is ok
	  bluefs_transaction_t t;
	  try {
	    bufferlist::const_iterator p = candidate.begin();
	    ::decode(t, p);
	  }
	  catch (buffer::error& e) {
	    dout(5) << __func__ << " failed match" << dendl;
	    continue;
	  }

	  //success, it seems a probable candidate
	  uint64_t l = std::min<uint64_t>(ne.length, read_len);
	  //trim to required size
	  bufferlist requested_read;
	  requested_read.substr_of(candidate, fixed.length(), l);
	  bl->append(requested_read);
	  dout(5) << __func__ << " successful extension of log " << l << "/" << read_len << dendl;
	  log_fnode.append_extent(ne);
	  log_fnode.recalc_allocated();
	  log_reader->buf.pos += l;
	  return l;
	}
	//save overlay for next search
	memcpy(search_b, chunk_e - overlay_size, overlay_size);
	pos += chunk_len;
	len -= chunk_len;
      }
    }
  }
  return 0;
}

void BlueFS::_check_vselector_LNF() {
  BlueFSVolumeSelector* vs = vselector->clone_empty();
  if (!vs) {
    return;
  }
  std::lock_guard ll(log.lock);
  std::lock_guard nl(nodes.lock);
  // Checking vselector is under log, nodes and file(s) locks,
  // so any modification of vselector must be under at least one of those locks.
  for (auto& f : nodes.file_map) {
    f.second->lock.lock();
    vs->add_usage(f.second->vselector_hint, f.second->fnode);
  }
  bool res = vselector->compare(vs);
  if (!res) {
    dout(0) << "Current:";
    vselector->dump(*_dout);
    *_dout << dendl;
    dout(0) << "Expected:";
    vs->dump(*_dout);
    *_dout << dendl;
  }
  ceph_assert(res);
  for (auto& f : nodes.file_map) {
    f.second->lock.unlock();
  }
  delete vs;
}

size_t BlueFS::probe_alloc_avail(int dev, uint64_t alloc_size)
{
  size_t total = 0;
  auto iterated_allocation = [&](size_t off, size_t len) {
    //only count in size that is alloc_size aligned
    size_t dist_to_alignment;
    size_t offset_in_block = off & (alloc_size - 1);
    if (offset_in_block == 0)
      dist_to_alignment = 0;
    else
      dist_to_alignment = alloc_size - offset_in_block;
    if (dist_to_alignment >= len)
      return;
    len -= dist_to_alignment;
    total += p2align(len, alloc_size);
  };
  if (alloc[dev]) {
    alloc[dev]->dump(iterated_allocation);
  }
  return total;
}
// ===============================================
// OriginalVolumeSelector

void* OriginalVolumeSelector::get_hint_for_log() const {
  return reinterpret_cast<void*>(BlueFS::BDEV_WAL);
}
void* OriginalVolumeSelector::get_hint_by_dir(std::string_view dirname) const {
  uint8_t res = BlueFS::BDEV_DB;
  if (dirname.length() > 5) {
    // the "db.slow" and "db.wal" directory names are hard-coded at
    // match up with bluestore.  the slow device is always the second
    // one (when a dedicated block.db device is present and used at
    // bdev 0).  the wal device is always last.
    if (boost::algorithm::ends_with(dirname, ".slow") && slow_total) {
      res = BlueFS::BDEV_SLOW;
    } else if (boost::algorithm::ends_with(dirname, ".wal") && wal_total) {
      res = BlueFS::BDEV_WAL;
    }
  }
  return reinterpret_cast<void*>(res);
}

uint8_t OriginalVolumeSelector::select_prefer_bdev(void* hint)
{
  return (uint8_t)(reinterpret_cast<uint64_t>(hint));
}

void OriginalVolumeSelector::get_paths(const std::string& base, paths& res) const
{
  res.emplace_back(base, db_total);
  res.emplace_back(base + ".slow",
    slow_total ? slow_total : db_total); // use fake non-zero value if needed to
                                         // avoid RocksDB complains
}

#undef dout_prefix
#define dout_prefix *_dout << "OriginalVolumeSelector: "

void OriginalVolumeSelector::dump(ostream& sout) {
  sout<< "wal_total:" << wal_total
    << ", db_total:" << db_total
    << ", slow_total:" << slow_total
    << std::endl;
}

// ===============================================
// FitToFastVolumeSelector

void FitToFastVolumeSelector::get_paths(const std::string& base, paths& res) const {
  res.emplace_back(base, 1);  // size of the last db_path has no effect
}