BlueFS.cc

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

#include "BlueFS.h"

#include "common/debug.h"
#include "common/errno.h"
#include "common/perf_counters.h"
#include "BlockDevice.h"
#include "Allocator.h"

#define dout_subsys ceph_subsys_bluefs
#undef dout_prefix
#define dout_prefix *_dout << "bluefs "

BlueFS::BlueFS()
  : bdev(MAX_BDEV),
    ioc(MAX_BDEV),
    block_all(MAX_BDEV),
    block_total(MAX_BDEV, 0)
{
}

BlueFS::~BlueFS()
{
  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(g_ceph_context, "BlueFS",
                        l_bluefs_first, l_bluefs_last);
  b.add_u64_counter(l_bluefs_gift_bytes, "gift_bytes",
		    "Bytes gifted from BlueStore");
  b.add_u64_counter(l_bluefs_reclaim_bytes, "reclaim_bytes",
		    "Bytes reclaimed by BlueStore");
  b.add_u64(l_bluefs_db_total_bytes, "db_total_bytes",
	    "Total bytes (main db device)");
  b.add_u64(l_bluefs_db_free_bytes, "db_free_bytes",
	    "Free bytes (main db device)");
  b.add_u64(l_bluefs_wal_total_bytes, "wal_total_bytes",
	    "Total bytes (wal device)");
  b.add_u64(l_bluefs_wal_free_bytes, "wal_free_bytes",
	    "Free bytes (wal device)");
  b.add_u64(l_bluefs_slow_total_bytes, "slow_total_bytes",
	    "Total bytes (slow device)");
  b.add_u64(l_bluefs_slow_free_bytes, "slow_free_bytes",
	    "Free bytes (slow device)");
  b.add_u64(l_bluefs_num_files, "num_files", "File count");
  b.add_u64(l_bluefs_log_bytes, "log_bytes", "Size of the metadata log");
  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");
  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");
  b.add_u64_counter(l_bluefs_bytes_written_sst, "bytes_written_sst",
		    "Bytes written to SSTs");
  logger = b.create_perf_counters();
  g_ceph_context->get_perfcounters_collection()->add(logger);
}

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

void BlueFS::_update_logger_stats()
{
  // we must be holding the lock
  logger->set(l_bluefs_num_files, file_map.size());
  logger->set(l_bluefs_log_bytes, log_writer->file->fnode.size);

  if (alloc[BDEV_WAL]) {
    logger->set(l_bluefs_wal_total_bytes, block_total[BDEV_WAL]);
    logger->set(l_bluefs_wal_free_bytes, alloc[BDEV_WAL]->get_free());
  }
  if (alloc[BDEV_DB]) {
    logger->set(l_bluefs_db_total_bytes, block_total[BDEV_DB]);
    logger->set(l_bluefs_db_free_bytes, alloc[BDEV_DB]->get_free());
  }
  if (alloc[BDEV_SLOW]) {
    logger->set(l_bluefs_slow_total_bytes, block_total[BDEV_SLOW]);
    logger->set(l_bluefs_slow_free_bytes, alloc[BDEV_SLOW]->get_free());
  }
}

int BlueFS::add_block_device(unsigned id, string path)
{
  dout(10) << __func__ << " bdev " << id << " path " << path << dendl;
  assert(id < bdev.size());
  assert(bdev[id] == NULL);
  BlockDevice *b = BlockDevice::create(path, NULL, NULL);
  int r = b->open(path);
  if (r < 0) {
    delete b;
    return r;
  }
  dout(1) << __func__ << " bdev " << id << " path " << path
	  << " size " << pretty_si_t(b->get_size()) << "B" << dendl;
  bdev[id] = b;
  ioc[id] = new IOContext(NULL);
  return 0;
}

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

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

void BlueFS::add_block_extent(unsigned id, uint64_t offset, uint64_t length)
{
  std::unique_lock<std::mutex> l(lock);
  dout(1) << __func__ << " bdev " << id
          << " 0x" << std::hex << offset << "~" << length << std::dec
	  << dendl;
  assert(id < bdev.size());
  assert(bdev[id]);
  assert(bdev[id]->get_size() >= offset + length);
  block_all[id].insert(offset, length);
  block_total[id] += length;

  if (id < alloc.size() && alloc[id]) {
    log_t.op_alloc_add(id, offset, length);
    int r = _flush_and_sync_log(l);
    assert(r == 0);
    alloc[id]->init_add_free(offset, length);
  }

  if (logger)
    logger->inc(l_bluefs_gift_bytes, length);
  dout(10) << __func__ << " done" << dendl;
}

int BlueFS::reclaim_blocks(unsigned id, uint64_t want,
			   uint64_t *offset, uint32_t *length)
{
  std::unique_lock<std::mutex> l(lock);
  dout(1) << __func__ << " bdev " << id
          << " want 0x" << std::hex << want << std::dec << dendl;
  assert(id < alloc.size());
  assert(alloc[id]);
  int r = alloc[id]->reserve(want);
  assert(r == 0); // caller shouldn't ask for more than they can get

  r = alloc[id]->allocate(want, g_conf->bluefs_alloc_size, 0,
			    offset, length);
  assert(r >= 0);
  if (*length < want)
    alloc[id]->unreserve(want - *length);

  block_all[id].erase(*offset, *length);
  block_total[id] -= *length;
  log_t.op_alloc_rm(id, *offset, *length);
  r = _flush_and_sync_log(l);
  assert(r == 0);

  if (logger)
    logger->inc(l_bluefs_reclaim_bytes, *length);
  dout(1) << __func__ << " bdev " << id << " want 0x" << std::hex << want
	  << " got 0x" << *offset << "~" << *length << std::dec << dendl;
  return 0;
}

uint64_t BlueFS::get_fs_usage()
{
  std::lock_guard<std::mutex> l(lock);
  uint64_t total_bytes = 0;
  for (auto& p : file_map) {
    total_bytes += p.second->fnode.get_allocated();
  }
  return total_bytes;
}

uint64_t BlueFS::get_total(unsigned id)
{
  std::lock_guard<std::mutex> l(lock);
  assert(id < block_all.size());
  return block_total[id];
}

uint64_t BlueFS::get_free(unsigned id)
{
  std::lock_guard<std::mutex> l(lock);
  assert(id < alloc.size());
  return alloc[id]->get_free();
}

void BlueFS::get_usage(vector<pair<uint64_t,uint64_t>> *usage)
{
  std::lock_guard<std::mutex> l(lock);
  usage->resize(bdev.size());
  for (unsigned id = 0; id < bdev.size(); ++id) {
    if (!bdev[id]) {
      (*usage)[id] = make_pair(0, 0);
      continue;
    }
    (*usage)[id].first = alloc[id]->get_free();
    (*usage)[id].second = block_total[id];
    uint64_t used =
      (block_total[id] - (*usage)[id].first) * 100 / block_total[id];
    dout(10) << __func__ << " bdev " << id
	     << " free " << (*usage)[id].first
	     << " (" << pretty_si_t((*usage)[id].first) << "B)"
	     << " / " << (*usage)[id].second
	     << " (" << pretty_si_t((*usage)[id].second) << "B)"
	     << ", used " << used << "%"
	     << dendl;
  }
}

int BlueFS::get_block_extents(unsigned id, interval_set<uint64_t> *extents)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " bdev " << id << dendl;
  if (id >= block_all.size())
    return -EINVAL;
  *extents = block_all[id];
  return 0;
}

int BlueFS::mkfs(uuid_d osd_uuid)
{
  std::unique_lock<std::mutex> l(lock);
  dout(1) << __func__
	  << " osd_uuid " << osd_uuid
	  << dendl;

  _init_alloc();
  _init_logger();

  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 = new File;
  log_file->fnode.ino = 1;
  log_file->fnode.prefer_bdev = BDEV_WAL;
  int r = _allocate(
    log_file->fnode.prefer_bdev,
    g_conf->bluefs_max_log_runway,
    &log_file->fnode.extents);
  assert(r == 0);
  log_writer = _create_writer(log_file);

  // initial txn
  log_t.op_init();
  for (unsigned bdev = 0; bdev < MAX_BDEV; ++bdev) {
    interval_set<uint64_t>& p = block_all[bdev];
    if (p.empty())
      continue;
    for (interval_set<uint64_t>::iterator q = p.begin(); q != p.end(); ++q) {
      dout(20) << __func__ << " op_alloc_add " << bdev << " 0x"
               << std::hex << q.get_start() << "~" << q.get_len() << std::dec
               << dendl;
      log_t.op_alloc_add(bdev, q.get_start(), q.get_len());
    }
  }
  _flush_and_sync_log(l);

  // write supers
  super.log_fnode = log_file->fnode;
  _write_super();
  flush_bdev();

  // clean up
  super = bluefs_super_t();
  _close_writer(log_writer);
  log_writer = NULL;
  block_all.clear();
  block_total.clear();
  _stop_alloc();
  _shutdown_logger();

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

void BlueFS::_init_alloc()
{
  dout(20) << __func__ << dendl;
  alloc.resize(MAX_BDEV);
  for (unsigned id = 0; id < bdev.size(); ++id) {
    if (!bdev[id]) {
      continue;
    }
    assert(bdev[id]->get_size());
    alloc[id] = Allocator::create(g_conf->bluefs_allocator,
                                  bdev[id]->get_size(),
                                  g_conf->bluefs_alloc_size);
    interval_set<uint64_t>& p = block_all[id];
    for (interval_set<uint64_t>::iterator q = p.begin(); q != p.end(); ++q) {
      alloc[id]->init_add_free(q.get_start(), q.get_len());
    }
  }
}

void BlueFS::_stop_alloc()
{
  dout(20) << __func__ << dendl;
  for (auto p : alloc) {
    if (p != nullptr)  {
      p->shutdown();
      delete p;
    }
  }
  alloc.clear();
}

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

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

  block_all.clear();
  block_all.resize(MAX_BDEV);
  block_total.clear();
  block_total.resize(MAX_BDEV, 0);
  _init_alloc();

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

  // init freelist
  for (auto& p : file_map) {
    dout(30) << __func__ << " noting alloc for " << p.second->fnode << dendl;
    for (auto& q : p.second->fnode.extents) {
      alloc[q.bdev]->init_rm_free(q.offset, q.length);
    }
  }

  // set up the log for future writes
  log_writer = _create_writer(_get_file(1));
  assert(log_writer->file->fnode.ino == 1);
  log_writer->pos = log_writer->file->fnode.size;
  dout(10) << __func__ << " log write pos set to 0x"
           << std::hex << log_writer->pos << std::dec
           << dendl;

  _init_logger();
  return 0;

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

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

  sync_metadata();

  _close_writer(log_writer);
  log_writer = NULL;

  _stop_alloc();
  file_map.clear();
  dir_map.clear();
  super = bluefs_super_t();
  log_t.clear();
  _shutdown_logger();
}

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

int BlueFS::_write_super()
{
  // 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;
  assert(bl.length() <= get_super_length());
  bl.append_zero(get_super_length() - bl.length());

  bdev[BDEV_DB]->aio_write(get_super_offset(), bl, ioc[BDEV_DB], false);
  bdev[BDEV_DB]->aio_submit(ioc[BDEV_DB]);
  ioc[BDEV_DB]->aio_wait();
  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[BDEV_DB]->read(get_super_offset(), get_super_length(),
			  &bl, ioc[BDEV_DB], false);
  if (r < 0)
    return r;

  bufferlist::iterator p = bl.begin();
  ::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::_replay(bool noop)
{
  dout(10) << __func__ << (noop ? " NO-OP" : "") << dendl;
  ino_last = 1;  // by the log
  log_seq = 0;

  FileRef log_file;
  if (noop) {
    log_file = new File;
  } else {
    log_file = _get_file(1);
  }
  log_file->fnode = super.log_fnode;
  dout(10) << __func__ << " log_fnode " << super.log_fnode << dendl;

  FileReader *log_reader = new FileReader(
    log_file, g_conf->bluefs_max_prefetch,
    false,  // !random
    true);  // ignore eof
  while (true) {
    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, &log_reader->buf, read_pos, super.block_size,
		    &bl, NULL);
      assert(r == (int)super.block_size);
      read_pos += r;
    }
    uint64_t more = 0;
    uint64_t seq;
    uuid_d uuid;
    {
      bufferlist::iterator p = bl.begin();
      __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) {
      dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
               << ": stop: uuid " << uuid << " != super.uuid " << super.uuid
               << dendl;
      break;
    }
    if (seq != log_seq + 1) {
      dout(10) << __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, &log_reader->buf, 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;
	break;
      }
      assert(r == (int)more);
      bl.claim_append(t);
      read_pos += r;
    }
    bluefs_transaction_t t;
    try {
      bufferlist::iterator p = bl.begin();
      ::decode(t, p);
    }
    catch (buffer::error& e) {
      dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
               << ": stop: failed to decode: " << e.what()
               << dendl;
      delete log_reader;
      return -EIO;
    }
    assert(seq == t.seq);
    dout(10) << __func__ << " 0x" << std::hex << pos << std::dec
             << ": " << t << dendl;

    bufferlist::iterator p = t.op_bl.begin();
    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;
	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;
	  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, &log_reader->buf, 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;
	      assert(0 == "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;
	  assert(next_seq >= log_seq);
	  log_seq = next_seq - 1; // we will increment it below
	}
	break;

      case bluefs_transaction_t::OP_ALLOC_ADD:
        {
	  __u8 id;
	  uint64_t offset, length;
	  ::decode(id, p);
	  ::decode(offset, p);
	  ::decode(length, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_alloc_add " << " " << (int)id
                   << ":0x" << std::hex << offset << "~" << length << std::dec
                   << dendl;
	  if (!noop) {
	    block_all[id].insert(offset, length);
	    block_total[id] += length;
	    alloc[id]->init_add_free(offset, length);
	  }
	}
	break;

      case bluefs_transaction_t::OP_ALLOC_RM:
        {
	  __u8 id;
	  uint64_t offset, length;
	  ::decode(id, p);
	  ::decode(offset, p);
	  ::decode(length, p);
	  dout(20) << __func__ << " 0x" << std::hex << pos << std::dec
                   << ":  op_alloc_rm " << " " << (int)id
                   << ":0x" << std::hex << offset << "~" << length << std::dec
                   << dendl;
	  if (!noop) {
	    block_all[id].erase(offset, length);
	    block_total[id] -= length;
	    alloc[id]->init_rm_free(offset, length);
	  }
	}
	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 (!noop) {
	    FileRef file = _get_file(ino);
	    assert(file->fnode.ino);
	    map<string,DirRef>::iterator q = dir_map.find(dirname);
	    assert(q != dir_map.end());
	    map<string,FileRef>::iterator r = q->second->file_map.find(filename);
	    assert(r == q->second->file_map.end());
	    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 (!noop) {
	    map<string,DirRef>::iterator q = dir_map.find(dirname);
	    assert(q != dir_map.end());
	    map<string,FileRef>::iterator r = q->second->file_map.find(filename);
	    assert(r != q->second->file_map.end());
            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 (!noop) {
	    map<string,DirRef>::iterator q = dir_map.find(dirname);
	    assert(q == dir_map.end());
	    dir_map[dirname] = new 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 (!noop) {
	    map<string,DirRef>::iterator q = dir_map.find(dirname);
	    assert(q != dir_map.end());
	    assert(q->second->file_map.empty());
	    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 (!noop) {
	    FileRef f = _get_file(fnode.ino);
	    f->fnode = fnode;
	    if (fnode.ino > ino_last) {
	      ino_last = fnode.ino;
	    }
	  }
	}
	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 (!noop) {
	    auto p = file_map.find(ino);
	    assert(p != file_map.end());
	    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;
      }
    }
    assert(p.end());

    // we successfully replayed the transaction; bump the seq and log size
    ++log_seq;
    log_file->fnode.size = log_reader->buf.pos;
  }

  dout(10) << __func__ << " log file size was 0x"
           << std::hex << log_file->fnode.size << std::dec << dendl;
  delete log_reader;

  if (!noop) {
    // verify file link counts are all >0
    for (auto& p : 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;
      }
    }
  }

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

BlueFS::FileRef BlueFS::_get_file(uint64_t ino)
{
  auto p = file_map.find(ino);
  if (p == file_map.end()) {
    FileRef f = new File;
    file_map[ino] = f;
    dout(30) << __func__ << " ino " << ino << " = " << f
	     << " (new)" << dendl;
    return f;
  } else {
    dout(30) << __func__ << " ino " << ino << " = " << p->second << dendl;
    return p->second;
  }
}

void BlueFS::_drop_link(FileRef file)
{
  dout(20) << __func__ << " had refs " << file->refs
	   << " on " << file->fnode << dendl;
  assert(file->refs > 0);
  --file->refs;
  if (file->refs == 0) {
    dout(20) << __func__ << " destroying " << file->fnode << dendl;
    assert(file->num_reading.load() == 0);
    log_t.op_file_remove(file->fnode.ino);
    for (auto& r : file->fnode.extents) {
      alloc[r.bdev]->release(r.offset, r.length);
    }
    file_map.erase(file->fnode.ino);
    file->deleted = true;
    if (file->dirty_seq) {
      assert(file->dirty_seq > log_seq_stable);
      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 = 0;
    }
  }
}

int BlueFS::_read_random(
  FileReader *h,         ///< [in] read from here
  uint64_t off,          ///< [in] offset
  size_t len,            ///< [in] this many bytes
  char *out)             ///< [out] optional: or copy it here
{
  dout(10) << __func__ << " h " << h
           << " 0x" << std::hex << off << "~" << len << std::dec
	   << " from " << h->file->fnode << 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;
  }

  int ret = 0;
  while (len > 0) {
    uint64_t x_off = 0;
    vector<bluefs_extent_t>::iterator p = h->file->fnode.seek(off, &x_off);
    uint64_t l = MIN(p->length - x_off, len);
    dout(20) << __func__ << " read buffered 0x"
             << std::hex << x_off << "~" << l << std::dec
             << " of " << *p << dendl;
    int r = bdev[p->bdev]->read_random(p->offset + x_off, l, out,
				       g_conf->bluefs_buffered_io);
    assert(r == 0);
    off += l;
    len -= l;
    ret += l;
    out += l;
  }

  dout(20) << __func__ << " got " << ret << dendl;
  --h->file->num_reading;
  return ret;
}

int BlueFS::_read(
  FileReader *h,         ///< [in] read from here
  FileReaderBuffer *buf, ///< [in] reader state
  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
{
  dout(10) << __func__ << " h " << h
           << " 0x" << std::hex << off << "~" << len << std::dec
	   << " from " << h->file->fnode << 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;
  }
  if (outbl)
    outbl->clear();

  int ret = 0;
  while (len > 0) {
    size_t left;
    if (off < buf->bl_off || off >= buf->get_buf_end()) {
      buf->bl.clear();
      buf->bl_off = off & super.block_mask();
      uint64_t x_off = 0;
      vector<bluefs_extent_t>::iterator p =
	h->file->fnode.seek(buf->bl_off, &x_off);
      uint64_t want = ROUND_UP_TO(len + (off & ~super.block_mask()),
				  super.block_size);
      want = MAX(want, buf->max_prefetch);
      uint64_t l = MIN(p->length - x_off, want);
      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 = bdev[p->bdev]->read(p->offset + x_off, l, &buf->bl, ioc[p->bdev],
				  g_conf->bluefs_buffered_io);
      assert(r == 0);
    }
    left = buf->get_buf_remaining(off);
    dout(20) << __func__ << " left 0x" << std::hex << left
             << " len 0x" << len << std::dec << dendl;

    int r = MIN(len, left);
    if (outbl) {
      bufferlist t;
      t.substr_of(buf->bl, off - buf->bl_off, r);
      outbl->claim_append(t);
    }
    if (out) {
      // NOTE: h->bl is normally a contiguous buffer so c_str() is free.
      memcpy(out, buf->bl.c_str() + off - buf->bl_off, r);
      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;
  assert(!outbl || (int)outbl->length() == ret);
  --h->file->num_reading;
  return ret;
}

void BlueFS::_invalidate_cache(FileRef f, uint64_t offset, uint64_t length)
{
  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;
  vector<bluefs_extent_t>::iterator p = f->fnode.seek(offset, &x_off);
  while (length > 0 && p != f->fnode.extents.end()) {
    uint64_t x_len = 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()
{
  int avg_dir_size = 40;  // fixme
  int avg_file_size = 12;
  uint64_t size = 4096 * 2;
  size += file_map.size() * (1 + sizeof(bluefs_fnode_t));
  for (auto& p : block_all)
    size += p.num_intervals() * (1 + 1 + sizeof(uint64_t) * 2);
  size += dir_map.size() + (1 + avg_dir_size);
  size += file_map.size() * (1 + avg_dir_size + avg_file_size);
  return ROUND_UP_TO(size, super.block_size);
}

void BlueFS::compact_log()
{
  std::unique_lock<std::mutex> l(lock);
  if (g_conf->bluefs_compact_log_sync) {
     _compact_log_sync();
  } else {
    _compact_log_async(l);
  }
}

bool BlueFS::_should_compact_log()
{
  uint64_t current = log_writer->file->fnode.size;
  uint64_t expected = _estimate_log_size();
  float ratio = (float)current / (float)expected;
  dout(10) << __func__ << " current 0x" << std::hex << current
	   << " expected " << expected << std::dec
	   << " ratio " << ratio
	   << (log_flushing ? " (async compaction in progress)" : "")
	   << dendl;
  if (log_flushing ||
      current < g_conf->bluefs_log_compact_min_size ||
      ratio < g_conf->bluefs_log_compact_min_ratio) {
    return false;
  }
  return true;
}

void BlueFS::_compact_log_dump_metadata(bluefs_transaction_t *t)
{
  t->seq = 1;
  t->uuid = super.uuid;
  dout(20) << __func__ << " op_init" << dendl;

  t->op_init();
  for (unsigned bdev = 0; bdev < MAX_BDEV; ++bdev) {
    interval_set<uint64_t>& p = block_all[bdev];
    for (interval_set<uint64_t>::iterator q = p.begin(); q != p.end(); ++q) {
      dout(20) << __func__ << " op_alloc_add " << bdev << " 0x"
               << std::hex << q.get_start() << "~" << q.get_len() << std::dec
               << dendl;
      t->op_alloc_add(bdev, q.get_start(), q.get_len());
    }
  }
  for (auto& p : file_map) {
    if (p.first == 1)
      continue;
    dout(20) << __func__ << " op_file_update " << p.second->fnode << dendl;
    assert(p.first > 1);
    t->op_file_update(p.second->fnode);
  }
  for (auto& p : dir_map) {
    dout(20) << __func__ << " op_dir_create " << p.first << dendl;
    t->op_dir_create(p.first);
    for (auto& q : p.second->file_map) {
      dout(20) << __func__ << " op_dir_link " << p.first << "/" << q.first
	       << " to " << q.second->fnode.ino << dendl;
      t->op_dir_link(p.first, q.first, q.second->fnode.ino);
    }
  }
}

void BlueFS::_compact_log_sync()
{
  dout(10) << __func__ << dendl;
  File *log_file = log_writer->file.get();

  // clear out log (be careful who calls us!!!)
  log_t.clear();

  bluefs_transaction_t t;
  _compact_log_dump_metadata(&t);

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

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

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

  vector<bluefs_extent_t> old_extents;
  old_extents.swap(log_file->fnode.extents);
  while (log_file->fnode.get_allocated() < need) {
    int r = _allocate(log_file->fnode.prefer_bdev,
		      need - log_file->fnode.get_allocated(),
		      &log_file->fnode.extents);
    assert(r == 0);
  }

  _close_writer(log_writer);

  log_file->fnode.size = bl.length();
  log_writer = _create_writer(log_file);
  log_writer->append(bl);
  int r = _flush(log_writer, true);
  assert(r == 0);
  wait_for_aio(log_writer);

  dout(10) << __func__ << " writing super" << dendl;
  super.log_fnode = log_file->fnode;
  ++super.version;
  _write_super();
  flush_bdev();

  dout(10) << __func__ << " release old log extents " << old_extents << dendl;
  for (auto& r : old_extents) {
    alloc[r.bdev]->release(r.offset, r.length);
  }

  logger->inc(l_bluefs_log_compactions);
}

/*
 * 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(std::unique_lock<std::mutex>& l)
{
  dout(10) << __func__ << dendl;
  File *log_file = log_writer->file.get();

  // 1. allocate new log space and jump to it.
  old_log_jump_to = log_file->fnode.get_allocated();
  uint64_t need = old_log_jump_to + g_conf->bluefs_max_log_runway;
  dout(10) << __func__ << " old_log_jump_to 0x" << std::hex << old_log_jump_to
           << " need 0x" << need << std::dec << dendl;
  while (log_file->fnode.get_allocated() < need) {
    int r = _allocate(log_file->fnode.prefer_bdev,
		      g_conf->bluefs_max_log_runway,
		      &log_file->fnode.extents);
    assert(r == 0);
  }
  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);
  log_t.op_jump(log_seq, old_log_jump_to);
  _flush_and_sync_log(l, 0, old_log_jump_to);

  // 2. prepare compacted log
  bluefs_transaction_t t;
  _compact_log_dump_metadata(&t);

  // conservative estimate for final encoded size
  new_log_jump_to = ROUND_UP_TO(t.op_bl.length() + super.block_size * 2,
                                g_conf->bluefs_alloc_size);
  t.op_jump(log_seq, new_log_jump_to);

  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;

  // create a new log [writer]
  new_log = new File;
  new_log->fnode.ino = 0;   // so that _flush_range won't try to log the fnode
  int r = _allocate(BlueFS::BDEV_DB, new_log_jump_to,
                    &new_log->fnode.extents);
  assert(r == 0);
  new_log_writer = _create_writer(new_log);
  new_log_writer->append(bl);

  // 3. flush
  _flush(new_log_writer, true);
  lock.unlock();

  // 4. wait
  dout(10) << __func__ << " waiting for compacted log to sync" << dendl;
  wait_for_aio(new_log_writer);
  flush_bdev();

  // 5. retake lock
  lock.lock();

  // 6. update our log fnode
  // discard first old_log_jump_to extents
  dout(10) << __func__ << " remove 0x" << std::hex << old_log_jump_to << std::dec
	   << " of " << log_file->fnode.extents << dendl;
  uint64_t discarded = 0;
  vector<bluefs_extent_t> old_extents;
  while (discarded < old_log_jump_to) {
    bluefs_extent_t& e = log_file->fnode.extents.front();
    bluefs_extent_t temp = e;
    if (discarded + e.length <= old_log_jump_to) {
      dout(10) << __func__ << " remove old log extent " << e << dendl;
      discarded += e.length;
      log_file->fnode.extents.erase(log_file->fnode.extents.begin());
    } else {
      dout(10) << __func__ << " remove front of old log extent " << e << dendl;
      uint64_t drop = old_log_jump_to - discarded;
      temp.length = drop;
      e.offset += drop;
      e.length -= drop;
      discarded += drop;
      dout(10) << __func__ << "   kept " << e << " removed " << temp << dendl;
    }
    old_extents.push_back(temp);
  }
  new_log->fnode.extents.insert(new_log->fnode.extents.end(),
				log_file->fnode.extents.begin(),
				log_file->fnode.extents.end());

  // clear the extents from old log file, they are added to new log
  log_file->fnode.extents.clear();

  // swap the log files. New log file is the log file now.
  log_file->fnode.extents.swap(new_log->fnode.extents);
  log_writer->pos = log_writer->file->fnode.size =
    log_writer->pos - old_log_jump_to + new_log_jump_to;

  // 7. write the super block to reflect the changes
  dout(10) << __func__ << " writing super" << dendl;
  super.log_fnode = log_file->fnode;
  ++super.version;
  _write_super();

  lock.unlock();
  flush_bdev();
  lock.lock();

  // 8. release old space
  dout(10) << __func__ << " release old log extents " << old_extents << dendl;
  for (auto& r : old_extents) {
    alloc[r.bdev]->release(r.offset, r.length);
  }

  // delete the new log, remove from the dirty files list
  _close_writer(new_log_writer);
  if (new_log->dirty_seq) {
    assert(dirty_files.count(new_log->dirty_seq));
    auto it = dirty_files[new_log->dirty_seq].iterator_to(*new_log);
    dirty_files[new_log->dirty_seq].erase(it);
  }
  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);
}

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);
  }
}

void BlueFS::flush_log()
{
  std::unique_lock<std::mutex> l(lock);
  _flush_and_sync_log(l);
}

int BlueFS::_flush_and_sync_log(std::unique_lock<std::mutex>& l,
				uint64_t want_seq,
				uint64_t jump_to)
{
  while (log_flushing) {
    dout(10) << __func__ << " want_seq " << want_seq
	     << " log is currently flushing, waiting" << dendl;
    log_cond.wait(l);
  }
  if (want_seq && want_seq <= log_seq_stable) {
    dout(10) << __func__ << " want_seq " << want_seq << " <= log_seq_stable "
	     << log_seq_stable << ", done" << dendl;
    return 0;
  }
  if (log_t.empty()) {
    dout(10) << __func__ << " want_seq " << want_seq
	     << " " << log_t << " not dirty, no-op" << dendl;
    return 0;
  }
  uint64_t seq = log_t.seq = ++log_seq;
  assert(want_seq == 0 || want_seq <= seq);
  log_t.uuid = super.uuid;
  dout(10) << __func__ << " " << log_t << dendl;
  assert(!log_t.empty());

  // allocate some more space (before we run out)?
  int64_t runway = log_writer->file->fnode.get_allocated() -
    log_writer->get_effective_write_pos();
  if (runway < (int64_t)g_conf->bluefs_min_log_runway) {
    dout(10) << __func__ << " allocating more log runway (0x"
	     << std::hex << runway << std::dec  << " remaining)" << dendl;
    while (new_log_writer) {
      dout(10) << __func__ << " waiting for async compaction" << dendl;
      log_cond.wait(l);
    }
    int r = _allocate(log_writer->file->fnode.prefer_bdev,
		      g_conf->bluefs_max_log_runway,
		      &log_writer->file->fnode.extents);
    assert(r == 0);
    log_t.op_file_update(log_writer->file->fnode);
  }

  bufferlist bl;
  ::encode(log_t, bl);

  // pad to block boundary
  _pad_bl(bl);
  logger->inc(l_bluefs_logged_bytes, bl.length());

  log_writer->append(bl);

  log_t.clear();
  log_t.seq = 0;  // just so debug output is less confusing
  log_flushing = true;

  flush_bdev();
  int r = _flush(log_writer, true);
  assert(r == 0);

  if (jump_to) {
    dout(10) << __func__ << " jumping log offset from 0x" << std::hex
	     << log_writer->pos << " -> 0x" << jump_to << std::dec << dendl;
    log_writer->pos = jump_to;
    log_writer->file->fnode.size = jump_to;
  }

  // drop lock while we wait for io
  l.unlock();
  wait_for_aio(log_writer);
  flush_bdev();
  l.lock();

  log_flushing = false;
  log_cond.notify_all();

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

    auto p = dirty_files.begin();
    while (p != dirty_files.end()) {
      if (p->first > log_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;
        assert(file->dirty_seq > 0);
        assert(file->dirty_seq <= log_seq_stable);
        dout(20) << __func__ << " cleaned file " << file->fnode << dendl;
        file->dirty_seq = 0;
        p->second.erase(l++);
      }

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

  return 0;
}

int BlueFS::_flush_range(FileWriter *h, uint64_t offset, uint64_t length)
{
  dout(10) << __func__ << " " << h << " pos 0x" << std::hex << h->pos
	   << " 0x" << offset << "~" << length << std::dec
	   << " to " << h->file->fnode << dendl;
  assert(!h->file->deleted);
  assert(h->file->num_readers.load() == 0);

  bool buffered;
  if (h->file->fnode.ino == 1)
    buffered = false;
  else
    buffered = g_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;
  }
  assert(offset <= h->file->fnode.size);

  uint64_t allocated = h->file->fnode.get_allocated();

  // do not bother to dirty the file if we are overwriting
  // previously allocated extents.
  bool must_dirty = false;
  if (allocated < offset + length) {
    // we should never run out of log space here; see the min runway check
    // in _flush_and_sync_log.
    assert(h->file->fnode.ino != 1);
    int r = _allocate(h->file->fnode.prefer_bdev,
		      offset + length - allocated,
		      &h->file->fnode.extents);
    if (r < 0) {
      derr << __func__ << " allocated: 0x" << std::hex << allocated
           << " offset: 0x" << offset << " length: 0x" << length << std::dec
           << dendl;
      return r;
    }
    must_dirty = true;
  }
  if (h->file->fnode.size < offset + length) {
    h->file->fnode.size = offset + length;
    if (h->file->fnode.ino > 1) {
      // 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.
      must_dirty = true;
    }
  }
  if (must_dirty) {
    h->file->fnode.mtime = ceph_clock_now(NULL);
    assert(h->file->fnode.ino >= 1);
    log_t.op_file_update(h->file->fnode);
    if (h->file->dirty_seq == 0) {
      h->file->dirty_seq = log_seq + 1;
      dirty_files[h->file->dirty_seq].push_back(*h->file);
      dout(20) << __func__ << " dirty_seq = " << log_seq + 1
	       << " (was clean)" << dendl;
    } else {
      if (h->file->dirty_seq != log_seq + 1) {
        // need re-dirty, erase from list first
        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 = log_seq + 1;
        dirty_files[h->file->dirty_seq].push_back(*h->file);
        dout(20) << __func__ << " dirty_seq = " << log_seq + 1
                 << " (was " << h->file->dirty_seq << ")" << dendl;
      } else {
        dout(20) << __func__ << " dirty_seq = " << log_seq + 1
                 << " (unchanged, do nothing) " << dendl;
      }
    }
  }
  dout(20) << __func__ << " file now " << h->file->fnode << dendl;

  uint64_t x_off = 0;
  vector<bluefs_extent_t>::iterator p = h->file->fnode.seek(offset, &x_off);
  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();
  bufferlist bl;
  if (partial) {
    dout(20) << __func__ << " using partial tail 0x"
             << std::hex << partial << std::dec << dendl;
    assert(h->tail_block.length() == partial);
    bl.claim_append(h->tail_block);
    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();
      }
    }
  }
  if (length == partial + h->buffer.length()) {
    bl.claim_append(h->buffer);
  } else {
    bufferlist t;
    t.substr_of(h->buffer, 0, length);
    bl.claim_append(t);
    t.substr_of(h->buffer, length, h->buffer.length() - length);
    h->buffer.swap(t);
    dout(20) << " leaving 0x" << std::hex << h->buffer.length() << std::dec
             << " unflushed" << dendl;
  }
  assert(bl.length() == 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;

  h->pos = offset + length;
  h->tail_block.clear();

  uint64_t bloff = 0;
  while (length > 0) {
    uint64_t x_len = MIN(p->length - x_off, length);
    bufferlist t;
    t.substr_of(bl, bloff, x_len);
    unsigned tail = x_len & ~super.block_mask();
    if (tail) {
      dout(20) << __func__ << " caching tail of 0x"
               << std::hex << tail << std::dec
	       << " and padding block with zeros" << dendl;
      h->tail_block.substr_of(bl, bl.length() - tail, tail);
      t.append_zero(super.block_size - tail);
    }
    bdev[p->bdev]->aio_write(p->offset + x_off, t, h->iocv[p->bdev], buffered);
    bloff += x_len;
    length -= x_len;
    ++p;
    x_off = 0;
  }
  for (unsigned i = 0; i < MAX_BDEV; ++i) {
    if (bdev[i]) {
      assert(h->iocv[i]);
      if (h->iocv[i]->has_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;
}

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

int BlueFS::_flush(FileWriter *h, bool force)
{
  uint64_t length = h->buffer.length();
  uint64_t offset = h->pos;
  if (!force &&
      length < g_conf->bluefs_min_flush_size) {
    dout(10) << __func__ << " " << h << " ignoring, length " << length
	     << " < min_flush_size " << g_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;
  assert(h->pos <= h->file->fnode.size);
  return _flush_range(h, offset, length);
}

int BlueFS::_truncate(FileWriter *h, uint64_t offset)
{
  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
  assert(h->file->fnode.ino > 1);

  // truncate off unflushed data?
  if (h->pos < offset &&
      h->pos + h->buffer.length() > offset) {
    bufferlist t;
    dout(20) << __func__ << " tossing out last " << offset - h->pos
	     << " unflushed bytes" << dendl;
    t.substr_of(h->buffer, 0, offset - h->pos);
    h->buffer.swap(t);
    assert(0 == "actually this shouldn't happen");
  }
  if (h->buffer.length()) {
    int r = _flush(h, true);
    if (r < 0)
      return r;
  }
  if (offset == h->file->fnode.size) {
    return 0;  // no-op!
  }
  if (offset > h->file->fnode.size) {
    assert(0 == "truncate up not supported");
  }
  assert(h->file->fnode.size >= offset);
  h->file->fnode.size = offset;
  log_t.op_file_update(h->file->fnode);
  return 0;
}

int BlueFS::_fsync(FileWriter *h, std::unique_lock<std::mutex>& l)
{
  dout(10) << __func__ << " " << h << " " << h->file->fnode << dendl;
  int r = _flush(h, true);
  if (r < 0)
     return r;
  uint64_t old_dirty_seq = h->file->dirty_seq;
  lock.unlock();
  wait_for_aio(h);
  lock.lock();
  if (old_dirty_seq) {
    uint64_t s = log_seq;
    dout(20) << __func__ << " file metadata was dirty (" << old_dirty_seq
	     << ") on " << h->file->fnode << ", flushing log" << dendl;
    _flush_and_sync_log(l, old_dirty_seq);
    assert(h->file->dirty_seq == 0 ||  // cleaned
	   h->file->dirty_seq > s);    // or redirtied by someone else
  }
  return 0;
}

void BlueFS::flush_bdev()
{
  // NOTE: this is safe to call without a lock.
  dout(20) << __func__ << dendl;
  for (auto p : bdev) {
    if (p)
      p->flush();
  }
}

int BlueFS::_allocate(uint8_t id, uint64_t len, vector<bluefs_extent_t> *ev)
{
  dout(10) << __func__ << " len 0x" << std::hex << len << std::dec
           << " from " << (int)id << dendl;
  assert(id < alloc.size());
  uint64_t min_alloc_size = g_conf->bluefs_alloc_size;

  uint64_t left = ROUND_UP_TO(len, min_alloc_size);
  int r = -ENOSPC;
  if (alloc[id]) {
    r = alloc[id]->reserve(left);
  }
  if (r < 0) {
    if (id != BDEV_SLOW) {
      if (bdev[id])
	derr << __func__ << " failed to allocate 0x" << std::hex << left
	     << " on bdev " << (int)id
	     << ", free 0x" << alloc[id]->get_free()
	     << "; fallback to bdev " << (int)id + 1
	     << std::dec << dendl;
      return _allocate(id + 1, len, ev);
    }
    if (bdev[id])
      derr << __func__ << " failed to allocate 0x" << std::hex << left
	   << " on bdev " << (int)id
	   << ", free 0x" << alloc[id]->get_free() << std::dec << dendl;
    else
      derr << __func__ << " failed to allocate 0x" << std::hex << left
	   << " on bdev " << (int)id << ", dne" << std::dec << dendl;
    return r;
  }

  uint64_t hint = 0;
  if (!ev->empty()) {
    hint = ev->back().end();
  }

  int count = 0;
  std::vector<AllocExtent> extents = 
        std::vector<AllocExtent>(left / min_alloc_size);

  r = alloc[id]->alloc_extents(left, min_alloc_size,
                               hint, &extents, &count);
  if (r < 0) {
    assert(0 == "allocate failed... wtf");
    return r;
  }
  for (int i = 0; i < count; i++) {
    bluefs_extent_t e = bluefs_extent_t(id, extents[i].offset, extents[i].length);
    if (!ev->empty() &&
	ev->back().bdev == e.bdev &&
	ev->back().end() == (uint64_t) e.offset) {
      ev->back().length += e.length;
    } else {
      ev->push_back(e);
    }
  }
   
  return 0;
}

int BlueFS::_preallocate(FileRef f, uint64_t off, uint64_t len)
{
  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;
  }
  assert(f->fnode.ino > 1);
  uint64_t allocated = f->fnode.get_allocated();
  if (off + len > allocated) {
    uint64_t want = off + len - allocated;
    int r = _allocate(f->fnode.prefer_bdev, want, &f->fnode.extents);
    if (r < 0)
      return r;
    log_t.op_file_update(f->fnode);
  }
  return 0;
}

void BlueFS::sync_metadata()
{
  std::unique_lock<std::mutex> l(lock);
  if (log_t.empty()) {
    dout(10) << __func__ << " - no pending log events" << dendl;
    return;
  }
  dout(10) << __func__ << dendl;
  utime_t start = ceph_clock_now(NULL);
  for (auto p : alloc) {
    if (p) {
      p->commit_start();
    }
  }
  _flush_and_sync_log(l);
  for (auto p : alloc) {
    if (p) {
      p->commit_finish();
    }
  }

  if (_should_compact_log()) {
    if (g_conf->bluefs_compact_log_sync) {
      _compact_log_sync();
    } else {
      _compact_log_async(l);
    }
  }

  utime_t end = ceph_clock_now(NULL);
  utime_t dur = end - start;
  dout(10) << __func__ << " done in " << dur << dendl;
}

int BlueFS::open_for_write(
  const string& dirname,
  const string& filename,
  FileWriter **h,
  bool overwrite)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  DirRef dir;
  if (p == dir_map.end()) {
    // implicitly create the dir
    dout(20) << __func__ << "  dir " << dirname
	     << " does not exist" << dendl;
    return -ENOENT;
  } else {
    dir = p->second;
  }

  FileRef file;
  bool create = false;
  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 = new File;
    file->fnode.ino = ++ino_last;
    file_map[ino_last] = file;
    dir->file_map[filename] = file;
    ++file->refs;
    create = true;
  } 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;
      file->fnode.size = 0;
      for (auto& p : file->fnode.extents) {
        alloc[p.bdev]->release(p.offset, p.length);
      }
      file->fnode.extents.clear();
    }
  }
  assert(file->fnode.ino > 1);

  file->fnode.mtime = ceph_clock_now(NULL);
  file->fnode.prefer_bdev = 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 (strcmp(dirname.c_str() + dirname.length() - 5, ".slow") == 0) {
      file->fnode.prefer_bdev = BlueFS::BDEV_SLOW;
    } else if (strcmp(dirname.c_str() + dirname.length() - 4, ".wal") == 0) {
      file->fnode.prefer_bdev = BlueFS::BDEV_WAL;
    }
  }
  dout(20) << __func__ << " mapping " << dirname << "/" << filename
	   << " to bdev " << (int)file->fnode.prefer_bdev << dendl;

  log_t.op_file_update(file->fnode);
  if (create)
    log_t.op_dir_link(dirname, filename, file->fnode.ino);

  *h = _create_writer(file);

  if (0 == filename.compare(filename.length() - 4, 4, ".log")) {
    (*h)->writer_type = BlueFS::WRITER_WAL;
    if (logger) {
      logger->inc(l_bluefs_files_written_wal);
    }
  } else if (0 == filename.compare(filename.length() - 4, 4, ".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(NULL);
    } else {
      w->iocv[i] = NULL;
    }
  }
  return w;
}

void BlueFS::_close_writer(FileWriter *h)
{
  dout(10) << __func__ << " " << h << " type " << h->writer_type << dendl;
  for (unsigned i=0; i<MAX_BDEV; ++i) {
    if (bdev[i]) {
      assert(h->iocv[i]);
      h->iocv[i]->aio_wait();
      bdev[i]->queue_reap_ioc(h->iocv[i]);
    }
  }
  delete h;
}

int BlueFS::open_for_read(
  const string& dirname,
  const string& filename,
  FileReader **h,
  bool random)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << "/" << filename
	   << (random ? " (random)":" (sequential)") << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  if (p == 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 : g_conf->bluefs_max_prefetch,
		      random, false);
  dout(10) << __func__ << " h " << *h << " on " << file->fnode << dendl;
  return 0;
}

int BlueFS::rename(
  const string& old_dirname, const string& old_filename,
  const string& new_dirname, const string& new_filename)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << old_dirname << "/" << old_filename
	   << " -> " << new_dirname << "/" << new_filename << dendl;
  map<string,DirRef>::iterator p = dir_map.find(old_dirname);
  if (p == 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 = dir_map.find(new_dirname);
  if (p == 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;
    assert(q->second != file);
    log_t.op_dir_unlink(new_dirname, new_filename);
    _drop_link(q->second);
  }

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

  new_dir->file_map[new_filename] = file;
  old_dir->file_map.erase(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(const string& dirname)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  if (p != dir_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " exists" << dendl;
    return -EEXIST;
  }
  dir_map[dirname] = new Dir;
  log_t.op_dir_create(dirname);
  return 0;
}

int BlueFS::rmdir(const string& dirname)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  if (p == 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;
  }
  dir_map.erase(dirname);
  log_t.op_dir_remove(dirname);
  return 0;
}

bool BlueFS::dir_exists(const string& dirname)
{
  std::lock_guard<std::mutex> l(lock);
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  bool exists = p != dir_map.end();
  dout(10) << __func__ << " " << dirname << " = " << (int)exists << dendl;
  return exists;
}

int BlueFS::stat(const string& dirname, const string& filename,
		 uint64_t *size, utime_t *mtime)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  if (p == 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(const string& dirname, const string& filename,
		      FileLock **plock)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  if (p == 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);
  File *file;
  if (q == dir->file_map.end()) {
    dout(20) << __func__ << " dir " << dirname << " (" << dir
	     << ") file " << filename
	     << " not found, creating" << dendl;
    file = new File;
    file->fnode.ino = ++ino_last;
    file->fnode.mtime = ceph_clock_now(NULL);
    file_map[ino_last] = file;
    dir->file_map[filename] = file;
    ++file->refs;
    log_t.op_file_update(file->fnode);
    log_t.op_dir_link(dirname, filename, file->fnode.ino);
  } else {
    file = q->second.get();
    if (file->locked) {
      dout(10) << __func__ << " already locked" << dendl;
      return -EBUSY;
    }
  }
  file->locked = true;
  *plock = new FileLock(file);
  dout(10) << __func__ << " locked " << file->fnode
	   << " with " << *plock << dendl;
  return 0;
}

int BlueFS::unlock_file(FileLock *fl)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << fl << " on " << fl->file->fnode << dendl;
  assert(fl->file->locked);
  fl->file->locked = false;
  delete fl;
  return 0;
}

int BlueFS::readdir(const string& dirname, vector<string> *ls)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << dendl;
  if (dirname.size() == 0) {
    // list dirs
    ls->reserve(dir_map.size() + 2);
    for (auto& q : dir_map) {
      ls->push_back(q.first);
    }
  } else {
    // list files in dir
    map<string,DirRef>::iterator p = dir_map.find(dirname);
    if (p == 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(const string& dirname, const string& filename)
{
  std::lock_guard<std::mutex> l(lock);
  dout(10) << __func__ << " " << dirname << "/" << filename << dendl;
  map<string,DirRef>::iterator p = dir_map.find(dirname);
  if (p == 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(filename);
  log_t.op_dir_unlink(dirname, filename);
  _drop_link(file);
  return 0;
}