bump version to 12.0.3-pve3

[ceph.git] / ceph / src / librbd / ImageCtx.cc

// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
#include <errno.h>
#include <boost/assign/list_of.hpp>
#include <stddef.h>

#include "common/ceph_context.h"
#include "common/dout.h"
#include "common/errno.h"
#include "common/perf_counters.h"
#include "common/WorkQueue.h"
#include "common/Timer.h"

#include "librbd/AsyncOperation.h"
#include "librbd/AsyncRequest.h"
#include "librbd/ExclusiveLock.h"
#include "librbd/internal.h"
#include "librbd/ImageCtx.h"
#include "librbd/ImageState.h"
#include "librbd/ImageWatcher.h"
#include "librbd/Journal.h"
#include "librbd/LibrbdAdminSocketHook.h"
#include "librbd/ObjectMap.h"
#include "librbd/Operations.h"
#include "librbd/operation/ResizeRequest.h"
#include "librbd/Utils.h"
#include "librbd/LibrbdWriteback.h"
#include "librbd/exclusive_lock/AutomaticPolicy.h"
#include "librbd/exclusive_lock/StandardPolicy.h"
#include "librbd/io/AioCompletion.h"
#include "librbd/io/ImageRequestWQ.h"
#include "librbd/journal/StandardPolicy.h"

#include "osdc/Striper.h"
#include <boost/bind.hpp>

#define dout_subsys ceph_subsys_rbd
#undef dout_prefix
#define dout_prefix *_dout << "librbd::ImageCtx: "

using std::map;
using std::pair;
using std::set;
using std::string;
using std::vector;

using ceph::bufferlist;
using librados::snap_t;
using librados::IoCtx;

namespace librbd {

namespace {

class ThreadPoolSingleton : public ThreadPool {
public:
  ContextWQ *op_work_queue;

  explicit ThreadPoolSingleton(CephContext *cct)
    : ThreadPool(cct, "librbd::thread_pool", "tp_librbd", 1,
                 "rbd_op_threads"),
      op_work_queue(new ContextWQ("librbd::op_work_queue",
                                  cct->_conf->rbd_op_thread_timeout,
                                  this)) {
    start();
  }
  ~ThreadPoolSingleton() override {
    op_work_queue->drain();
    delete op_work_queue;

    stop();
  }
};

class SafeTimerSingleton : public SafeTimer {
public:
  Mutex lock;

  explicit SafeTimerSingleton(CephContext *cct)
      : SafeTimer(cct, lock, true),
        lock("librbd::Journal::SafeTimerSingleton::lock") {
    init();
  }
  ~SafeTimerSingleton() {
    Mutex::Locker locker(lock);
    shutdown();
  }
};

struct C_FlushCache : public Context {
  ImageCtx *image_ctx;
  Context *on_safe;

  C_FlushCache(ImageCtx *_image_ctx, Context *_on_safe)
    : image_ctx(_image_ctx), on_safe(_on_safe) {
  }
  void finish(int r) override {
    // successful cache flush indicates all IO is now safe
    image_ctx->flush_cache(on_safe);
  }
};

struct C_ShutDownCache : public Context {
  ImageCtx *image_ctx;
  Context *on_finish;

  C_ShutDownCache(ImageCtx *_image_ctx, Context *_on_finish)
    : image_ctx(_image_ctx), on_finish(_on_finish) {
  }
  void finish(int r) override {
    image_ctx->object_cacher->stop();
    on_finish->complete(r);
  }
};

struct C_InvalidateCache : public Context {
  ImageCtx *image_ctx;
  bool purge_on_error;
  bool reentrant_safe;
  Context *on_finish;

  C_InvalidateCache(ImageCtx *_image_ctx, bool _purge_on_error,
                    bool _reentrant_safe, Context *_on_finish)
    : image_ctx(_image_ctx), purge_on_error(_purge_on_error),
      reentrant_safe(_reentrant_safe), on_finish(_on_finish) {
  }
  void finish(int r) override {
    assert(image_ctx->cache_lock.is_locked());
    CephContext *cct = image_ctx->cct;

    if (r == -EBLACKLISTED) {
      lderr(cct) << "Blacklisted during flush!  Purging cache..." << dendl;
      image_ctx->object_cacher->purge_set(image_ctx->object_set);
    } else if (r != 0 && purge_on_error) {
      lderr(cct) << "invalidate cache encountered error "
                 << cpp_strerror(r) << " !Purging cache..." << dendl;
      image_ctx->object_cacher->purge_set(image_ctx->object_set);
    } else if (r != 0) {
      lderr(cct) << "flush_cache returned " << r << dendl;
    }

    loff_t unclean = image_ctx->object_cacher->release_set(
      image_ctx->object_set);
    if (unclean == 0) {
      r = 0;
    } else {
      lderr(cct) << "could not release all objects from cache: "
                 << unclean << " bytes remain" << dendl;
      if (r == 0) {
        r = -EBUSY;
      }
    }

    if (reentrant_safe) {
      on_finish->complete(r);
    } else {
      image_ctx->op_work_queue->queue(on_finish, r);
    }
  }

};

} // anonymous namespace

  const string ImageCtx::METADATA_CONF_PREFIX = "conf_";

  ImageCtx::ImageCtx(const string &image_name, const string &image_id,
		     const char *snap, IoCtx& p, bool ro)
    : cct((CephContext*)p.cct()),
      perfcounter(NULL),
      snap_id(CEPH_NOSNAP),
      snap_exists(true),
      read_only(ro),
      flush_encountered(false),
      exclusive_locked(false),
      name(image_name),
      image_watcher(NULL),
      journal(NULL),
      owner_lock(util::unique_lock_name("librbd::ImageCtx::owner_lock", this)),
      md_lock(util::unique_lock_name("librbd::ImageCtx::md_lock", this)),
      cache_lock(util::unique_lock_name("librbd::ImageCtx::cache_lock", this)),
      snap_lock(util::unique_lock_name("librbd::ImageCtx::snap_lock", this)),
      parent_lock(util::unique_lock_name("librbd::ImageCtx::parent_lock", this)),
      object_map_lock(util::unique_lock_name("librbd::ImageCtx::object_map_lock", this)),
      async_ops_lock(util::unique_lock_name("librbd::ImageCtx::async_ops_lock", this)),
      copyup_list_lock(util::unique_lock_name("librbd::ImageCtx::copyup_list_lock", this)),
      completed_reqs_lock(util::unique_lock_name("librbd::ImageCtx::completed_reqs_lock", this)),
      extra_read_flags(0),
      old_format(true),
      order(0), size(0), features(0),
      format_string(NULL),
      id(image_id), parent(NULL),
      stripe_unit(0), stripe_count(0), flags(0),
      object_cacher(NULL), writeback_handler(NULL), object_set(NULL),
      readahead(),
      total_bytes_read(0),
      state(new ImageState<>(this)),
      operations(new Operations<>(*this)),
      exclusive_lock(nullptr), object_map(nullptr),
      io_work_queue(nullptr), op_work_queue(nullptr),
      asok_hook(nullptr)
  {
    md_ctx.dup(p);
    data_ctx.dup(p);
    if (snap)
      snap_name = snap;

    memset(&header, 0, sizeof(header));

    ThreadPool *thread_pool;
    get_thread_pool_instance(cct, &thread_pool, &op_work_queue);
    io_work_queue = new io::ImageRequestWQ(
      this, "librbd::io_work_queue", cct->_conf->rbd_op_thread_timeout,
      thread_pool);

    if (cct->_conf->rbd_auto_exclusive_lock_until_manual_request) {
      exclusive_lock_policy = new exclusive_lock::AutomaticPolicy(this);
    } else {
      exclusive_lock_policy = new exclusive_lock::StandardPolicy(this);
    }
    journal_policy = new journal::StandardPolicy<ImageCtx>(this);
  }

  ImageCtx::~ImageCtx() {
    assert(image_watcher == NULL);
    assert(exclusive_lock == NULL);
    assert(object_map == NULL);
    assert(journal == NULL);
    assert(asok_hook == NULL);

    if (perfcounter) {
      perf_stop();
    }
    if (object_cacher) {
      delete object_cacher;
      object_cacher = NULL;
    }
    if (writeback_handler) {
      delete writeback_handler;
      writeback_handler = NULL;
    }
    if (object_set) {
      delete object_set;
      object_set = NULL;
    }
    delete[] format_string;

    md_ctx.aio_flush();
    data_ctx.aio_flush();
    io_work_queue->drain();

    delete journal_policy;
    delete exclusive_lock_policy;
    delete io_work_queue;
    delete operations;
    delete state;
  }

  void ImageCtx::init() {
    assert(!header_oid.empty());
    assert(old_format || !id.empty());

    asok_hook = new LibrbdAdminSocketHook(this);

    string pname = string("librbd-") + id + string("-") +
      data_ctx.get_pool_name() + string("-") + name;
    if (!snap_name.empty()) {
      pname += "-";
      pname += snap_name;
    }

    perf_start(pname);

    if (cache) {
      Mutex::Locker l(cache_lock);
      ldout(cct, 20) << "enabling caching..." << dendl;
      writeback_handler = new LibrbdWriteback(this, cache_lock);

      uint64_t init_max_dirty = cache_max_dirty;
      if (cache_writethrough_until_flush)
	init_max_dirty = 0;
      ldout(cct, 20) << "Initial cache settings:"
		     << " size=" << cache_size
		     << " num_objects=" << 10
		     << " max_dirty=" << init_max_dirty
		     << " target_dirty=" << cache_target_dirty
		     << " max_dirty_age="
		     << cache_max_dirty_age << dendl;

      object_cacher = new ObjectCacher(cct, pname, *writeback_handler, cache_lock,
				       NULL, NULL,
				       cache_size,
				       10,  /* reset this in init */
				       init_max_dirty,
				       cache_target_dirty,
				       cache_max_dirty_age,
				       cache_block_writes_upfront);

      // size object cache appropriately
      uint64_t obj = cache_max_dirty_object;
      if (!obj) {
	obj = MIN(2000, MAX(10, cache_size / 100 / sizeof(ObjectCacher::Object)));
      }
      ldout(cct, 10) << " cache bytes " << cache_size
	<< " -> about " << obj << " objects" << dendl;
      object_cacher->set_max_objects(obj);

      object_set = new ObjectCacher::ObjectSet(NULL, data_ctx.get_id(), 0);
      object_set->return_enoent = true;
      object_cacher->start();
    }

    readahead.set_trigger_requests(readahead_trigger_requests);
    readahead.set_max_readahead_size(readahead_max_bytes);
  }

  void ImageCtx::shutdown() {
    delete image_watcher;
    image_watcher = nullptr;

    delete asok_hook;
    asok_hook = nullptr;
  }

  void ImageCtx::init_layout()
  {
    if (stripe_unit == 0 || stripe_count == 0) {
      stripe_unit = 1ull << order;
      stripe_count = 1;
    }

    vector<uint64_t> alignments;
    alignments.push_back(stripe_count << order); // object set (in file striping terminology)
    alignments.push_back(stripe_unit * stripe_count); // stripe
    alignments.push_back(stripe_unit); // stripe unit
    readahead.set_alignments(alignments);

    layout = file_layout_t();
    layout.stripe_unit = stripe_unit;
    layout.stripe_count = stripe_count;
    layout.object_size = 1ull << order;
    layout.pool_id = data_ctx.get_id();  // FIXME: pool id overflow?

    delete[] format_string;
    size_t len = object_prefix.length() + 16;
    format_string = new char[len];
    if (old_format) {
      snprintf(format_string, len, "%s.%%012llx", object_prefix.c_str());
    } else {
      snprintf(format_string, len, "%s.%%016llx", object_prefix.c_str());
    }

    ldout(cct, 10) << "init_layout stripe_unit " << stripe_unit
		   << " stripe_count " << stripe_count
		   << " object_size " << layout.object_size
		   << " prefix " << object_prefix
		   << " format " << format_string
		   << dendl;
  }

  void ImageCtx::perf_start(string name) {
    PerfCountersBuilder plb(cct, name, l_librbd_first, l_librbd_last);

    plb.add_u64_counter(l_librbd_rd, "rd", "Reads");
    plb.add_u64_counter(l_librbd_rd_bytes, "rd_bytes", "Data size in reads");
    plb.add_time_avg(l_librbd_rd_latency, "rd_latency", "Latency of reads");
    plb.add_u64_counter(l_librbd_wr, "wr", "Writes");
    plb.add_u64_counter(l_librbd_wr_bytes, "wr_bytes", "Written data");
    plb.add_time_avg(l_librbd_wr_latency, "wr_latency", "Write latency");
    plb.add_u64_counter(l_librbd_discard, "discard", "Discards");
    plb.add_u64_counter(l_librbd_discard_bytes, "discard_bytes", "Discarded data");
    plb.add_time_avg(l_librbd_discard_latency, "discard_latency", "Discard latency");
    plb.add_u64_counter(l_librbd_flush, "flush", "Flushes");
    plb.add_u64_counter(l_librbd_aio_flush, "aio_flush", "Async flushes");
    plb.add_time_avg(l_librbd_aio_flush_latency, "aio_flush_latency", "Latency of async flushes");
    plb.add_u64_counter(l_librbd_ws, "ws", "WriteSames");
    plb.add_u64_counter(l_librbd_ws_bytes, "ws_bytes", "WriteSame data");
    plb.add_time_avg(l_librbd_ws_latency, "ws_latency", "WriteSame latency");
    plb.add_u64_counter(l_librbd_snap_create, "snap_create", "Snap creations");
    plb.add_u64_counter(l_librbd_snap_remove, "snap_remove", "Snap removals");
    plb.add_u64_counter(l_librbd_snap_rollback, "snap_rollback", "Snap rollbacks");
    plb.add_u64_counter(l_librbd_snap_rename, "snap_rename", "Snap rename");
    plb.add_u64_counter(l_librbd_notify, "notify", "Updated header notifications");
    plb.add_u64_counter(l_librbd_resize, "resize", "Resizes");
    plb.add_u64_counter(l_librbd_readahead, "readahead", "Read ahead");
    plb.add_u64_counter(l_librbd_readahead_bytes, "readahead_bytes", "Data size in read ahead");
    plb.add_u64_counter(l_librbd_invalidate_cache, "invalidate_cache", "Cache invalidates");

    perfcounter = plb.create_perf_counters();
    cct->get_perfcounters_collection()->add(perfcounter);
  }

  void ImageCtx::perf_stop() {
    assert(perfcounter);
    cct->get_perfcounters_collection()->remove(perfcounter);
    delete perfcounter;
  }

  void ImageCtx::set_read_flag(unsigned flag) {
    extra_read_flags |= flag;
  }

  int ImageCtx::get_read_flags(snap_t snap_id) {
    int flags = librados::OPERATION_NOFLAG | extra_read_flags;
    if (snap_id == LIBRADOS_SNAP_HEAD)
      return flags;

    if (balance_snap_reads)
      flags |= librados::OPERATION_BALANCE_READS;
    else if (localize_snap_reads)
      flags |= librados::OPERATION_LOCALIZE_READS;
    return flags;
  }

  int ImageCtx::snap_set(cls::rbd::SnapshotNamespace in_snap_namespace,
			 string in_snap_name)
  {
    assert(snap_lock.is_wlocked());
    snap_t in_snap_id = get_snap_id(in_snap_namespace, in_snap_name);
    if (in_snap_id != CEPH_NOSNAP) {
      snap_id = in_snap_id;
      snap_namespace = in_snap_namespace;
      snap_name = in_snap_name;
      snap_exists = true;
      data_ctx.snap_set_read(snap_id);
      return 0;
    }
    return -ENOENT;
  }

  void ImageCtx::snap_unset()
  {
    assert(snap_lock.is_wlocked());
    snap_id = CEPH_NOSNAP;
    snap_namespace = {};
    snap_name = "";
    snap_exists = true;
    data_ctx.snap_set_read(snap_id);
  }

  snap_t ImageCtx::get_snap_id(cls::rbd::SnapshotNamespace in_snap_namespace,
			       string in_snap_name) const
  {
    assert(snap_lock.is_locked());
    auto it = snap_ids.find({in_snap_namespace, in_snap_name});
    if (it != snap_ids.end())
      return it->second;
    return CEPH_NOSNAP;
  }

  const SnapInfo* ImageCtx::get_snap_info(snap_t in_snap_id) const
  {
    assert(snap_lock.is_locked());
    map<snap_t, SnapInfo>::const_iterator it =
      snap_info.find(in_snap_id);
    if (it != snap_info.end())
      return &it->second;
    return NULL;
  }

  int ImageCtx::get_snap_name(snap_t in_snap_id,
			      string *out_snap_name) const
  {
    assert(snap_lock.is_locked());
    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info) {
      *out_snap_name = info->name;
      return 0;
    }
    return -ENOENT;
  }

  int ImageCtx::get_snap_namespace(snap_t in_snap_id,
				   cls::rbd::SnapshotNamespace *out_snap_namespace) const
  {
    assert(snap_lock.is_locked());
    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info) {
      *out_snap_namespace = info->snap_namespace;
      return 0;
    }
    return -ENOENT;
  }

  int ImageCtx::get_parent_spec(snap_t in_snap_id,
				ParentSpec *out_pspec) const
  {
    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info) {
      *out_pspec = info->parent.spec;
      return 0;
    }
    return -ENOENT;
  }

  uint64_t ImageCtx::get_current_size() const
  {
    assert(snap_lock.is_locked());
    return size;
  }

  uint64_t ImageCtx::get_object_size() const
  {
    return 1ull << order;
  }

  string ImageCtx::get_object_name(uint64_t num) const {
    char buf[object_prefix.length() + 32];
    snprintf(buf, sizeof(buf), format_string, num);
    return string(buf);
  }

  uint64_t ImageCtx::get_stripe_unit() const
  {
    return stripe_unit;
  }

  uint64_t ImageCtx::get_stripe_count() const
  {
    return stripe_count;
  }

  uint64_t ImageCtx::get_stripe_period() const
  {
    return stripe_count * (1ull << order);
  }

  int ImageCtx::is_snap_protected(snap_t in_snap_id,
				  bool *is_protected) const
  {
    assert(snap_lock.is_locked());
    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info) {
      *is_protected =
	(info->protection_status == RBD_PROTECTION_STATUS_PROTECTED);
      return 0;
    }
    return -ENOENT;
  }

  int ImageCtx::is_snap_unprotected(snap_t in_snap_id,
				    bool *is_unprotected) const
  {
    assert(snap_lock.is_locked());
    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info) {
      *is_unprotected =
	(info->protection_status == RBD_PROTECTION_STATUS_UNPROTECTED);
      return 0;
    }
    return -ENOENT;
  }

  void ImageCtx::add_snap(cls::rbd::SnapshotNamespace in_snap_namespace,
			  string in_snap_name,
			  snap_t id, uint64_t in_size,
			  const ParentInfo &parent, uint8_t protection_status,
                          uint64_t flags, utime_t timestamp)
  {
    assert(snap_lock.is_wlocked());
    snaps.push_back(id);
    SnapInfo info(in_snap_name, in_snap_namespace,
		  in_size, parent, protection_status, flags, timestamp);
    snap_info.insert({id, info});
    snap_ids.insert({{in_snap_namespace, in_snap_name}, id});
  }

  void ImageCtx::rm_snap(cls::rbd::SnapshotNamespace in_snap_namespace,
			 string in_snap_name,
			 snap_t id)
  {
    assert(snap_lock.is_wlocked());
    snaps.erase(std::remove(snaps.begin(), snaps.end(), id), snaps.end());
    snap_info.erase(id);
    snap_ids.erase({in_snap_namespace, in_snap_name});
  }

  uint64_t ImageCtx::get_image_size(snap_t in_snap_id) const
  {
    assert(snap_lock.is_locked());
    if (in_snap_id == CEPH_NOSNAP) {
      if (!resize_reqs.empty() &&
          resize_reqs.front()->shrinking()) {
        return resize_reqs.front()->get_image_size();
      }
      return size;
    }

    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info) {
      return info->size;
    }
    return 0;
  }

  uint64_t ImageCtx::get_object_count(snap_t in_snap_id) const {
    assert(snap_lock.is_locked());
    uint64_t image_size = get_image_size(in_snap_id);
    return Striper::get_num_objects(layout, image_size);
  }

  bool ImageCtx::test_features(uint64_t features) const
  {
    RWLock::RLocker l(snap_lock);
    return test_features(features, snap_lock);
  }

  bool ImageCtx::test_features(uint64_t in_features,
                               const RWLock &in_snap_lock) const
  {
    assert(snap_lock.is_locked());
    return ((features & in_features) == in_features);
  }

  int ImageCtx::get_flags(librados::snap_t _snap_id, uint64_t *_flags) const
  {
    assert(snap_lock.is_locked());
    if (_snap_id == CEPH_NOSNAP) {
      *_flags = flags;
      return 0;
    }
    const SnapInfo *info = get_snap_info(_snap_id);
    if (info) {
      *_flags = info->flags;
      return 0;
    }
    return -ENOENT;
  }

  bool ImageCtx::test_flags(uint64_t flags) const
  {
    RWLock::RLocker l(snap_lock);
    return test_flags(flags, snap_lock);
  }

  bool ImageCtx::test_flags(uint64_t flags, const RWLock &in_snap_lock) const
  {
    assert(snap_lock.is_locked());
    uint64_t snap_flags;
    get_flags(snap_id, &snap_flags);
    return ((snap_flags & flags) == flags);
  }

  int ImageCtx::update_flags(snap_t in_snap_id, uint64_t flag, bool enabled)
  {
    assert(snap_lock.is_wlocked());
    uint64_t *_flags;
    if (in_snap_id == CEPH_NOSNAP) {
      _flags = &flags;
    } else {
      map<snap_t, SnapInfo>::iterator it = snap_info.find(in_snap_id);
      if (it == snap_info.end()) {
        return -ENOENT;
      }
      _flags = &it->second.flags;
    }

    if (enabled) {
      (*_flags) |= flag;
    } else {
      (*_flags) &= ~flag;
    }
    return 0;
  }

  const ParentInfo* ImageCtx::get_parent_info(snap_t in_snap_id) const
  {
    assert(snap_lock.is_locked());
    assert(parent_lock.is_locked());
    if (in_snap_id == CEPH_NOSNAP)
      return &parent_md;
    const SnapInfo *info = get_snap_info(in_snap_id);
    if (info)
      return &info->parent;
    return NULL;
  }

  int64_t ImageCtx::get_parent_pool_id(snap_t in_snap_id) const
  {
    const ParentInfo *info = get_parent_info(in_snap_id);
    if (info)
      return info->spec.pool_id;
    return -1;
  }

  string ImageCtx::get_parent_image_id(snap_t in_snap_id) const
  {
    const ParentInfo *info = get_parent_info(in_snap_id);
    if (info)
      return info->spec.image_id;
    return "";
  }

  uint64_t ImageCtx::get_parent_snap_id(snap_t in_snap_id) const
  {
    const ParentInfo *info = get_parent_info(in_snap_id);
    if (info)
      return info->spec.snap_id;
    return CEPH_NOSNAP;
  }

  int ImageCtx::get_parent_overlap(snap_t in_snap_id, uint64_t *overlap) const
  {
    assert(snap_lock.is_locked());
    const ParentInfo *info = get_parent_info(in_snap_id);
    if (info) {
      *overlap = info->overlap;
      return 0;
    }
    return -ENOENT;
  }

  void ImageCtx::aio_read_from_cache(object_t o, uint64_t object_no,
				     bufferlist *bl, size_t len,
				     uint64_t off, Context *onfinish,
				     int fadvise_flags) {
    snap_lock.get_read();
    ObjectCacher::OSDRead *rd = object_cacher->prepare_read(snap_id, bl, fadvise_flags);
    snap_lock.put_read();
    ObjectExtent extent(o, object_no, off, len, 0);
    extent.oloc.pool = data_ctx.get_id();
    extent.buffer_extents.push_back(make_pair(0, len));
    rd->extents.push_back(extent);
    cache_lock.Lock();
    int r = object_cacher->readx(rd, object_set, onfinish);
    cache_lock.Unlock();
    if (r != 0)
      onfinish->complete(r);
  }

  void ImageCtx::write_to_cache(object_t o, const bufferlist& bl, size_t len,
				uint64_t off, Context *onfinish,
				int fadvise_flags, uint64_t journal_tid) {
    snap_lock.get_read();
    ObjectCacher::OSDWrite *wr = object_cacher->prepare_write(
      snapc, bl, ceph::real_time::min(), fadvise_flags, journal_tid);
    snap_lock.put_read();
    ObjectExtent extent(o, 0, off, len, 0);
    extent.oloc.pool = data_ctx.get_id();
    // XXX: nspace is always default, io_ctx_impl field private
    //extent.oloc.nspace = data_ctx.io_ctx_impl->oloc.nspace;
    extent.buffer_extents.push_back(make_pair(0, len));
    wr->extents.push_back(extent);
    {
      Mutex::Locker l(cache_lock);
      object_cacher->writex(wr, object_set, onfinish);
    }
  }

  void ImageCtx::user_flushed() {
    if (object_cacher && cache_writethrough_until_flush) {
      md_lock.get_read();
      bool flushed_before = flush_encountered;
      md_lock.put_read();

      uint64_t max_dirty = cache_max_dirty;
      if (!flushed_before && max_dirty > 0) {
	md_lock.get_write();
	flush_encountered = true;
	md_lock.put_write();

	ldout(cct, 10) << "saw first user flush, enabling writeback" << dendl;
	Mutex::Locker l(cache_lock);
	object_cacher->set_max_dirty(max_dirty);
      }
    }
  }

  void ImageCtx::flush_cache(Context *onfinish) {
    cache_lock.Lock();
    object_cacher->flush_set(object_set, onfinish);
    cache_lock.Unlock();
  }

  void ImageCtx::shut_down_cache(Context *on_finish) {
    if (object_cacher == NULL) {
      on_finish->complete(0);
      return;
    }

    cache_lock.Lock();
    object_cacher->release_set(object_set);
    cache_lock.Unlock();

    C_ShutDownCache *shut_down = new C_ShutDownCache(this, on_finish);
    flush_cache(new C_InvalidateCache(this, true, false, shut_down));
  }

  int ImageCtx::invalidate_cache(bool purge_on_error) {
    flush_async_operations();
    if (object_cacher == NULL) {
      return 0;
    }

    cache_lock.Lock();
    object_cacher->release_set(object_set);
    cache_lock.Unlock();

    C_SaferCond ctx;
    flush_cache(new C_InvalidateCache(this, purge_on_error, true, &ctx));

    int result = ctx.wait();
    return result;
  }

  void ImageCtx::invalidate_cache(bool purge_on_error, Context *on_finish) {
    if (object_cacher == NULL) {
      op_work_queue->queue(on_finish, 0);
      return;
    }

    cache_lock.Lock();
    object_cacher->release_set(object_set);
    cache_lock.Unlock();

    flush_cache(new C_InvalidateCache(this, purge_on_error, false, on_finish));
  }

  void ImageCtx::clear_nonexistence_cache() {
    assert(cache_lock.is_locked());
    if (!object_cacher)
      return;
    object_cacher->clear_nonexistence(object_set);
  }

  bool ImageCtx::is_cache_empty() {
    Mutex::Locker locker(cache_lock);
    return object_cacher->set_is_empty(object_set);
  }

  void ImageCtx::register_watch(Context *on_finish) {
    assert(image_watcher == NULL);
    image_watcher = new ImageWatcher<>(*this);
    image_watcher->register_watch(on_finish);
  }

  uint64_t ImageCtx::prune_parent_extents(vector<pair<uint64_t,uint64_t> >& objectx,
					  uint64_t overlap)
  {
    // drop extents completely beyond the overlap
    while (!objectx.empty() && objectx.back().first >= overlap)
      objectx.pop_back();

    // trim final overlapping extent
    if (!objectx.empty() && objectx.back().first + objectx.back().second > overlap)
      objectx.back().second = overlap - objectx.back().first;

    uint64_t len = 0;
    for (vector<pair<uint64_t,uint64_t> >::iterator p = objectx.begin();
	 p != objectx.end();
	 ++p)
      len += p->second;
    ldout(cct, 10) << "prune_parent_extents image overlap " << overlap
		   << ", object overlap " << len
		   << " from image extents " << objectx << dendl;
    return len;
  }

  void ImageCtx::flush_async_operations() {
    C_SaferCond ctx;
    flush_async_operations(&ctx);
    ctx.wait();
  }

  void ImageCtx::flush_async_operations(Context *on_finish) {
    {
      Mutex::Locker l(async_ops_lock);
      if (!async_ops.empty()) {
        ldout(cct, 20) << "flush async operations: " << on_finish << " "
                       << "count=" << async_ops.size() << dendl;
        async_ops.front()->add_flush_context(on_finish);
        return;
      }
    }
    on_finish->complete(0);
  }

  int ImageCtx::flush() {
    C_SaferCond cond_ctx;
    flush(&cond_ctx);
    return cond_ctx.wait();
  }

  void ImageCtx::flush(Context *on_safe) {
    // ensure no locks are held when flush is complete
    on_safe = util::create_async_context_callback(*this, on_safe);

    if (object_cacher != NULL) {
      // flush cache after completing all in-flight AIO ops
      on_safe = new C_FlushCache(this, on_safe);
    }
    flush_async_operations(on_safe);
  }

  void ImageCtx::cancel_async_requests() {
    C_SaferCond ctx;
    cancel_async_requests(&ctx);
    ctx.wait();
  }

  void ImageCtx::cancel_async_requests(Context *on_finish) {
    {
      Mutex::Locker async_ops_locker(async_ops_lock);
      if (!async_requests.empty()) {
        ldout(cct, 10) << "canceling async requests: count="
                       << async_requests.size() << dendl;
        for (auto req : async_requests) {
          ldout(cct, 10) << "canceling async request: " << req << dendl;
          req->cancel();
        }
        async_requests_waiters.push_back(on_finish);
        return;
      }
    }

    on_finish->complete(0);
  }

  void ImageCtx::clear_pending_completions() {
    Mutex::Locker l(completed_reqs_lock);
    ldout(cct, 10) << "clear pending AioCompletion: count="
                   << completed_reqs.size() << dendl;
    completed_reqs.clear();
  }

  bool ImageCtx::_filter_metadata_confs(const string &prefix,
                                        map<string, bool> &configs,
                                        const map<string, bufferlist> &pairs,
                                        map<string, bufferlist> *res) {
    size_t conf_prefix_len = prefix.size();

    for (auto it : pairs) {
      if (it.first.compare(0, MIN(conf_prefix_len, it.first.size()), prefix) > 0)
        return false;

      if (it.first.size() <= conf_prefix_len)
        continue;

      string key = it.first.substr(conf_prefix_len, it.first.size() - conf_prefix_len);
      auto cit = configs.find(key);
      if (cit != configs.end()) {
        cit->second = true;
        res->insert(make_pair(key, it.second));
      }
    }
    return true;
  }

  void ImageCtx::apply_metadata(const std::map<std::string, bufferlist> &meta) {
    ldout(cct, 20) << __func__ << dendl;
    std::map<string, bool> configs = boost::assign::map_list_of(
        "rbd_non_blocking_aio", false)(
        "rbd_cache", false)(
        "rbd_cache_writethrough_until_flush", false)(
        "rbd_cache_size", false)(
        "rbd_cache_max_dirty", false)(
        "rbd_cache_target_dirty", false)(
        "rbd_cache_max_dirty_age", false)(
        "rbd_cache_max_dirty_object", false)(
        "rbd_cache_block_writes_upfront", false)(
        "rbd_concurrent_management_ops", false)(
        "rbd_balance_snap_reads", false)(
        "rbd_localize_snap_reads", false)(
        "rbd_balance_parent_reads", false)(
        "rbd_localize_parent_reads", false)(
        "rbd_readahead_trigger_requests", false)(
        "rbd_readahead_max_bytes", false)(
        "rbd_readahead_disable_after_bytes", false)(
        "rbd_clone_copy_on_read", false)(
        "rbd_blacklist_on_break_lock", false)(
        "rbd_blacklist_expire_seconds", false)(
        "rbd_request_timed_out_seconds", false)(
        "rbd_journal_order", false)(
        "rbd_journal_splay_width", false)(
        "rbd_journal_commit_age", false)(
        "rbd_journal_object_flush_interval", false)(
        "rbd_journal_object_flush_bytes", false)(
        "rbd_journal_object_flush_age", false)(
        "rbd_journal_pool", false)(
        "rbd_journal_max_payload_bytes", false)(
        "rbd_journal_max_concurrent_object_sets", false)(
        "rbd_mirroring_resync_after_disconnect", false)(
        "rbd_mirroring_replay_delay", false)(
        "rbd_skip_partial_discard", false);

    md_config_t local_config_t;
    std::map<std::string, bufferlist> res;

    _filter_metadata_confs(METADATA_CONF_PREFIX, configs, meta, &res);
    for (auto it : res) {
      std::string val(it.second.c_str(), it.second.length());
      int j = local_config_t.set_val(it.first.c_str(), val);
      if (j < 0) {
        lderr(cct) << __func__ << " failed to set config " << it.first
                   << " with value " << it.second.c_str() << ": " << j
                   << dendl;
      }
    }

#define ASSIGN_OPTION(config)                                                  \
    do {                                                                       \
      string key = "rbd_";						       \
      key = key + #config;					      	       \
      if (configs[key])                                                        \
        config = local_config_t.rbd_##config;                                  \
      else                                                                     \
        config = cct->_conf->rbd_##config;                                     \
    } while (0);

    ASSIGN_OPTION(non_blocking_aio);
    ASSIGN_OPTION(cache);
    ASSIGN_OPTION(cache_writethrough_until_flush);
    ASSIGN_OPTION(cache_size);
    ASSIGN_OPTION(cache_max_dirty);
    ASSIGN_OPTION(cache_target_dirty);
    ASSIGN_OPTION(cache_max_dirty_age);
    ASSIGN_OPTION(cache_max_dirty_object);
    ASSIGN_OPTION(cache_block_writes_upfront);
    ASSIGN_OPTION(concurrent_management_ops);
    ASSIGN_OPTION(balance_snap_reads);
    ASSIGN_OPTION(localize_snap_reads);
    ASSIGN_OPTION(balance_parent_reads);
    ASSIGN_OPTION(localize_parent_reads);
    ASSIGN_OPTION(readahead_trigger_requests);
    ASSIGN_OPTION(readahead_max_bytes);
    ASSIGN_OPTION(readahead_disable_after_bytes);
    ASSIGN_OPTION(clone_copy_on_read);
    ASSIGN_OPTION(blacklist_on_break_lock);
    ASSIGN_OPTION(blacklist_expire_seconds);
    ASSIGN_OPTION(request_timed_out_seconds);
    ASSIGN_OPTION(enable_alloc_hint);
    ASSIGN_OPTION(journal_order);
    ASSIGN_OPTION(journal_splay_width);
    ASSIGN_OPTION(journal_commit_age);
    ASSIGN_OPTION(journal_object_flush_interval);
    ASSIGN_OPTION(journal_object_flush_bytes);
    ASSIGN_OPTION(journal_object_flush_age);
    ASSIGN_OPTION(journal_pool);
    ASSIGN_OPTION(journal_max_payload_bytes);
    ASSIGN_OPTION(journal_max_concurrent_object_sets);
    ASSIGN_OPTION(mirroring_resync_after_disconnect);
    ASSIGN_OPTION(mirroring_replay_delay);
    ASSIGN_OPTION(skip_partial_discard);
  }

  ExclusiveLock<ImageCtx> *ImageCtx::create_exclusive_lock() {
    return new ExclusiveLock<ImageCtx>(*this);
  }

  ObjectMap<ImageCtx> *ImageCtx::create_object_map(uint64_t snap_id) {
    return new ObjectMap<ImageCtx>(*this, snap_id);
  }

  Journal<ImageCtx> *ImageCtx::create_journal() {
    return new Journal<ImageCtx>(*this);
  }

  void ImageCtx::set_image_name(const std::string &image_name) {
    // update the name so rename can be invoked repeatedly
    RWLock::RLocker owner_locker(owner_lock);
    RWLock::WLocker snap_locker(snap_lock);
    name = image_name;
    if (old_format) {
      header_oid = util::old_header_name(image_name);
    }
  }

  void ImageCtx::notify_update() {
    state->handle_update_notification();
    ImageWatcher<>::notify_header_update(md_ctx, header_oid);
  }

  void ImageCtx::notify_update(Context *on_finish) {
    state->handle_update_notification();
    image_watcher->notify_header_update(on_finish);
  }

  exclusive_lock::Policy *ImageCtx::get_exclusive_lock_policy() const {
    assert(owner_lock.is_locked());
    assert(exclusive_lock_policy != nullptr);
    return exclusive_lock_policy;
  }

  void ImageCtx::set_exclusive_lock_policy(exclusive_lock::Policy *policy) {
    assert(owner_lock.is_wlocked());
    assert(policy != nullptr);
    delete exclusive_lock_policy;
    exclusive_lock_policy = policy;
  }

  journal::Policy *ImageCtx::get_journal_policy() const {
    assert(snap_lock.is_locked());
    assert(journal_policy != nullptr);
    return journal_policy;
  }

  void ImageCtx::set_journal_policy(journal::Policy *policy) {
    assert(snap_lock.is_wlocked());
    assert(policy != nullptr);
    delete journal_policy;
    journal_policy = policy;
  }

  void ImageCtx::get_thread_pool_instance(CephContext *cct,
                                          ThreadPool **thread_pool,
                                          ContextWQ **op_work_queue) {
    ThreadPoolSingleton *thread_pool_singleton;
    cct->lookup_or_create_singleton_object<ThreadPoolSingleton>(
      thread_pool_singleton, "librbd::thread_pool");
    *thread_pool = thread_pool_singleton;
    *op_work_queue = thread_pool_singleton->op_work_queue;
  }

  void ImageCtx::get_timer_instance(CephContext *cct, SafeTimer **timer,
                                    Mutex **timer_lock) {
    SafeTimerSingleton *safe_timer_singleton;
    cct->lookup_or_create_singleton_object<SafeTimerSingleton>(
      safe_timer_singleton, "librbd::journal::safe_timer");
    *timer = safe_timer_singleton;
    *timer_lock = &safe_timer_singleton->lock;
  }
}