Adding upstream version 18.2.2.upstream/18.2.2

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

1 files changed, 909 insertions, 0 deletions

diff --git a/src/librbd/io/ImageRequest.cc b/src/librbd/io/ImageRequest.cc
new file mode 100644
index 000000000..e4c41c229
--- /dev/null
+++ b/src/librbd/io/ImageRequest.cc
@@ -0,0 +1,909 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "librbd/io/ImageRequest.h"
+#include "librbd/ImageCtx.h"
+#include "librbd/internal.h"
+#include "librbd/Journal.h"
+#include "librbd/Types.h"
+#include "librbd/Utils.h"
+#include "librbd/asio/ContextWQ.h"
+#include "librbd/io/AioCompletion.h"
+#include "librbd/io/AsyncOperation.h"
+#include "librbd/io/ObjectDispatchInterface.h"
+#include "librbd/io/ObjectDispatchSpec.h"
+#include "librbd/io/ObjectDispatcherInterface.h"
+#include "librbd/io/Utils.h"
+#include "librbd/journal/Types.h"
+#include "include/rados/librados.hpp"
+#include "common/errno.h"
+#include "common/perf_counters.h"
+#include "osdc/Striper.h"
+#include <algorithm>
+#include <functional>
+#include <map>
+
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "librbd::io::ImageRequest: " << __func__ << ": "
+
+namespace librbd {
+namespace io {
+
+using librbd::util::data_object_name;
+using librbd::util::get_image_ctx;
+
+namespace {
+
+template <typename I>
+struct C_AssembleSnapshotDeltas : public C_AioRequest {
+  I* image_ctx;
+  SnapshotDelta* snapshot_delta;
+
+  ceph::mutex lock = ceph::make_mutex(
+    "librbd::io::C_AssembleSnapshotDeltas::lock", false);
+  std::map<uint64_t, SnapshotDelta> object_snapshot_delta;
+
+  C_AssembleSnapshotDeltas(I* image_ctx, AioCompletion* aio_comp,
+                           SnapshotDelta* snapshot_delta)
+    : C_AioRequest(aio_comp),
+      image_ctx(image_ctx), snapshot_delta(snapshot_delta) {
+  }
+
+  SnapshotDelta* get_snapshot_delta(uint64_t object_no) {
+    std::unique_lock locker{lock};
+    return &object_snapshot_delta[object_no];
+  }
+
+  void finish(int r) override {
+    auto cct = image_ctx->cct;
+
+    if (r < 0) {
+      lderr(cct) << "C_AssembleSnapshotDeltas: list snaps failed: "
+                 << cpp_strerror(r) << dendl;
+      C_AioRequest::finish(r);
+      return;
+    }
+
+    std::unique_lock locker{lock};
+    *snapshot_delta = {};
+    for (auto& [object_no, object_snapshot_delta] : object_snapshot_delta) {
+      SnapshotDelta image_snapshot_delta;
+      object_to_image_intervals(object_no, object_snapshot_delta,
+                                &image_snapshot_delta, snapshot_delta);
+
+      ldout(cct, 20) << "object_no=" << object_no << ", "
+                     << "object_snapshot_delta="
+                     << object_snapshot_delta << ", "
+                     << "image_snapshot_delta=" << image_snapshot_delta
+                     << dendl;
+    }
+
+    ldout(cct, 20) << "snapshot_delta=" << *snapshot_delta << dendl;
+    C_AioRequest::finish(0);
+  }
+
+  void object_to_image_intervals(
+      uint64_t object_no, const SnapshotDelta& object_snapshot_delta,
+      SnapshotDelta* image_snapshot_delta,
+      SnapshotDelta* assembled_image_snapshot_delta) {
+    for (auto& [key, object_extents] : object_snapshot_delta) {
+      for (auto& object_extent : object_extents) {
+        auto [image_extents, _] = io::util::object_to_area_extents(
+            image_ctx, object_no,
+            {{object_extent.get_off(), object_extent.get_len()}});
+
+        auto& intervals = (*image_snapshot_delta)[key];
+        auto& assembled_intervals = (*assembled_image_snapshot_delta)[key];
+        for (auto [image_offset, image_length] : image_extents) {
+          SparseExtent sparse_extent{object_extent.get_val().state,
+                                     image_length};
+          intervals.insert(image_offset, image_length, sparse_extent);
+          assembled_intervals.insert(image_offset, image_length,
+                                     sparse_extent);
+        }
+      }
+    }
+  }
+};
+
+template <typename I>
+struct C_RBD_Readahead : public Context {
+  I *ictx;
+  uint64_t object_no;
+  io::ReadExtents extents;
+
+  C_RBD_Readahead(I *ictx, uint64_t object_no, uint64_t offset, uint64_t length)
+    : ictx(ictx), object_no(object_no), extents({{offset, length}}) {
+    ictx->readahead.inc_pending();
+  }
+
+  void finish(int r) override {
+    ceph_assert(extents.size() == 1);
+    auto& extent = extents.front();
+    ldout(ictx->cct, 20) << "C_RBD_Readahead on "
+                         << data_object_name(ictx, object_no) << ": "
+                         << extent.offset << "~" << extent.length << dendl;
+    ictx->readahead.dec_pending();
+  }
+};
+
+template <typename I>
+void readahead(I *ictx, const Extents& image_extents, IOContext io_context) {
+  uint64_t total_bytes = 0;
+  for (auto& image_extent : image_extents) {
+    total_bytes += image_extent.second;
+  }
+
+  ictx->image_lock.lock_shared();
+  auto total_bytes_read = ictx->total_bytes_read.fetch_add(total_bytes);
+  bool abort = (
+    ictx->readahead_disable_after_bytes != 0 &&
+    total_bytes_read > ictx->readahead_disable_after_bytes);
+  if (abort) {
+    ictx->image_lock.unlock_shared();
+    return;
+  }
+
+  uint64_t data_size = ictx->get_area_size(ImageArea::DATA);
+  ictx->image_lock.unlock_shared();
+
+  auto readahead_extent = ictx->readahead.update(image_extents, data_size);
+  uint64_t readahead_offset = readahead_extent.first;
+  uint64_t readahead_length = readahead_extent.second;
+
+  if (readahead_length > 0) {
+    ldout(ictx->cct, 20) << "(readahead logical) " << readahead_offset << "~"
+                         << readahead_length << dendl;
+    LightweightObjectExtents readahead_object_extents;
+    io::util::area_to_object_extents(ictx, readahead_offset, readahead_length,
+                                     ImageArea::DATA, 0,
+                                     &readahead_object_extents);
+    for (auto& object_extent : readahead_object_extents) {
+      ldout(ictx->cct, 20) << "(readahead) "
+                           << data_object_name(ictx,
+                                               object_extent.object_no) << " "
+                           << object_extent.offset << "~"
+                           << object_extent.length << dendl;
+
+      auto req_comp = new C_RBD_Readahead<I>(ictx, object_extent.object_no,
+                                             object_extent.offset,
+                                             object_extent.length);
+      auto req = io::ObjectDispatchSpec::create_read(
+        ictx, io::OBJECT_DISPATCH_LAYER_NONE, object_extent.object_no,
+        &req_comp->extents, io_context, 0, 0, {}, nullptr, req_comp);
+      req->send();
+    }
+
+    ictx->perfcounter->inc(l_librbd_readahead);
+    ictx->perfcounter->inc(l_librbd_readahead_bytes, readahead_length);
+  }
+}
+
+template <typename I>
+struct C_UpdateTimestamp : public Context {
+public:
+  I& m_image_ctx;
+  bool m_modify; // if modify set to 'true', modify timestamp is updated,
+                 // access timestamp otherwise
+  AsyncOperation m_async_op;
+
+  C_UpdateTimestamp(I& ictx, bool m) : m_image_ctx(ictx), m_modify(m) {
+    m_async_op.start_op(*get_image_ctx(&m_image_ctx));
+  }
+  ~C_UpdateTimestamp() override {
+    m_async_op.finish_op();
+  }
+
+  void send() {
+    librados::ObjectWriteOperation op;
+    if (m_modify) {
+      cls_client::set_modify_timestamp(&op);
+    } else {
+      cls_client::set_access_timestamp(&op);
+    }
+
+    auto comp = librbd::util::create_rados_callback(this);
+    int r = m_image_ctx.md_ctx.aio_operate(m_image_ctx.header_oid, comp, &op);
+    ceph_assert(r == 0);
+    comp->release();
+  }
+
+  void finish(int r) override {
+    // ignore errors updating timestamp
+  }
+};
+
+bool should_update_timestamp(const utime_t& now, const utime_t& timestamp,
+                             uint64_t interval) {
+    return (interval &&
+            (static_cast<uint64_t>(now.sec()) >= interval + timestamp));
+}
+
+} // anonymous namespace
+
+#undef dout_prefix
+#define dout_prefix *_dout << "librbd::io::ImageRequest: " << this \
+                           << " " << __func__ << ": "
+
+template <typename I>
+void ImageRequest<I>::aio_read(I *ictx, AioCompletion *c,
+                               Extents &&image_extents, ImageArea area,
+                               ReadResult &&read_result, IOContext io_context,
+                               int op_flags, int read_flags,
+			       const ZTracer::Trace &parent_trace) {
+  ImageReadRequest<I> req(*ictx, c, std::move(image_extents), area,
+                          std::move(read_result), io_context, op_flags,
+                          read_flags, parent_trace);
+  req.send();
+}
+
+template <typename I>
+void ImageRequest<I>::aio_write(I *ictx, AioCompletion *c,
+                                Extents &&image_extents, ImageArea area,
+                                bufferlist &&bl, int op_flags,
+				const ZTracer::Trace &parent_trace) {
+  ImageWriteRequest<I> req(*ictx, c, std::move(image_extents), area,
+                           std::move(bl), op_flags, parent_trace);
+  req.send();
+}
+
+template <typename I>
+void ImageRequest<I>::aio_discard(I *ictx, AioCompletion *c,
+                                  Extents &&image_extents, ImageArea area,
+                                  uint32_t discard_granularity_bytes,
+                                  const ZTracer::Trace &parent_trace) {
+  ImageDiscardRequest<I> req(*ictx, c, std::move(image_extents), area,
+                             discard_granularity_bytes, parent_trace);
+  req.send();
+}
+
+template <typename I>
+void ImageRequest<I>::aio_flush(I *ictx, AioCompletion *c,
+                                FlushSource flush_source,
+                                const ZTracer::Trace &parent_trace) {
+  ImageFlushRequest<I> req(*ictx, c, flush_source, parent_trace);
+  req.send();
+}
+
+template <typename I>
+void ImageRequest<I>::aio_writesame(I *ictx, AioCompletion *c,
+                                    Extents &&image_extents, ImageArea area,
+                                    bufferlist &&bl, int op_flags,
+				    const ZTracer::Trace &parent_trace) {
+  ImageWriteSameRequest<I> req(*ictx, c, std::move(image_extents), area,
+                               std::move(bl), op_flags, parent_trace);
+  req.send();
+}
+
+template <typename I>
+void ImageRequest<I>::aio_compare_and_write(I *ictx, AioCompletion *c,
+                                            Extents &&image_extents,
+                                            ImageArea area,
+                                            bufferlist &&cmp_bl,
+                                            bufferlist &&bl,
+                                            uint64_t *mismatch_offset,
+                                            int op_flags,
+                                            const ZTracer::Trace &parent_trace) {
+  ImageCompareAndWriteRequest<I> req(*ictx, c, std::move(image_extents), area,
+                                     std::move(cmp_bl), std::move(bl),
+                                     mismatch_offset, op_flags, parent_trace);
+  req.send();
+}
+
+template <typename I>
+void ImageRequest<I>::send() {
+  I &image_ctx = this->m_image_ctx;
+  ceph_assert(m_aio_comp->is_initialized(get_aio_type()));
+  ceph_assert(m_aio_comp->is_started());
+
+  CephContext *cct = image_ctx.cct;
+  AioCompletion *aio_comp = this->m_aio_comp;
+  ldout(cct, 20) << get_request_type() << ": ictx=" << &image_ctx << ", "
+                 << "completion=" << aio_comp << dendl;
+
+  update_timestamp();
+  send_request();
+}
+
+template <typename I>
+void ImageRequest<I>::update_timestamp() {
+  bool modify = (get_aio_type() != AIO_TYPE_READ);
+  uint64_t update_interval;
+  if (modify) {
+    update_interval = m_image_ctx.mtime_update_interval;
+  } else {
+    update_interval = m_image_ctx.atime_update_interval;
+  }
+
+  if (update_interval == 0) {
+    return;
+  }
+
+  utime_t (I::*get_timestamp_fn)() const;
+  void (I::*set_timestamp_fn)(utime_t);
+  if (modify) {
+    get_timestamp_fn = &I::get_modify_timestamp;
+    set_timestamp_fn = &I::set_modify_timestamp;
+  } else {
+    get_timestamp_fn = &I::get_access_timestamp;
+    set_timestamp_fn = &I::set_access_timestamp;
+  }
+
+  utime_t ts = ceph_clock_now();
+  {
+    std::shared_lock timestamp_locker{m_image_ctx.timestamp_lock};
+    if(!should_update_timestamp(ts, std::invoke(get_timestamp_fn, m_image_ctx),
+                                update_interval)) {
+      return;
+    }
+  }
+
+  {
+    std::unique_lock timestamp_locker{m_image_ctx.timestamp_lock};
+    bool update = should_update_timestamp(
+      ts, std::invoke(get_timestamp_fn, m_image_ctx), update_interval);
+    if (!update) {
+      return;
+    }
+
+    std::invoke(set_timestamp_fn, m_image_ctx, ts);
+  }
+
+  // TODO we fire and forget this outside the IO path to prevent
+  // potential race conditions with librbd client IO callbacks
+  // between different threads (e.g. librados and object cacher)
+  ldout(m_image_ctx.cct, 10) << get_request_type() << dendl;
+  auto req = new C_UpdateTimestamp<I>(m_image_ctx, modify);
+  req->send();
+}
+
+template <typename I>
+ImageReadRequest<I>::ImageReadRequest(I &image_ctx, AioCompletion *aio_comp,
+                                      Extents &&image_extents, ImageArea area,
+                                      ReadResult &&read_result,
+                                      IOContext io_context, int op_flags,
+				      int read_flags,
+                                      const ZTracer::Trace &parent_trace)
+  : ImageRequest<I>(image_ctx, aio_comp, std::move(image_extents), area,
+                    "read", parent_trace),
+    m_io_context(io_context), m_op_flags(op_flags), m_read_flags(read_flags) {
+  aio_comp->read_result = std::move(read_result);
+}
+
+template <typename I>
+void ImageReadRequest<I>::send_request() {
+  I &image_ctx = this->m_image_ctx;
+  CephContext *cct = image_ctx.cct;
+
+  auto &image_extents = this->m_image_extents;
+  if (this->m_image_area == ImageArea::DATA &&
+      image_ctx.cache && image_ctx.readahead_max_bytes > 0 &&
+      !(m_op_flags & LIBRADOS_OP_FLAG_FADVISE_RANDOM)) {
+    readahead(get_image_ctx(&image_ctx), image_extents, m_io_context);
+  }
+
+  // map image extents to object extents
+  LightweightObjectExtents object_extents;
+  uint64_t buffer_ofs = 0;
+  for (auto &extent : image_extents) {
+    if (extent.second == 0) {
+      continue;
+    }
+
+    util::area_to_object_extents(&image_ctx, extent.first, extent.second,
+                                 this->m_image_area, buffer_ofs,
+                                 &object_extents);
+    buffer_ofs += extent.second;
+  }
+
+  AioCompletion *aio_comp = this->m_aio_comp;
+  aio_comp->read_result.set_image_extents(image_extents);
+
+  // issue the requests
+  aio_comp->set_request_count(object_extents.size());
+  for (auto &oe : object_extents) {
+    ldout(cct, 20) << data_object_name(&image_ctx, oe.object_no) << " "
+                   << oe.offset << "~" << oe.length << " from "
+                   << oe.buffer_extents << dendl;
+
+    auto req_comp = new io::ReadResult::C_ObjectReadRequest(
+      aio_comp, {{oe.offset, oe.length, std::move(oe.buffer_extents)}});
+    auto req = ObjectDispatchSpec::create_read(
+      &image_ctx, OBJECT_DISPATCH_LAYER_NONE, oe.object_no,
+      &req_comp->extents, m_io_context, m_op_flags, m_read_flags,
+      this->m_trace, nullptr, req_comp);
+    req->send();
+  }
+
+  image_ctx.perfcounter->inc(l_librbd_rd);
+  image_ctx.perfcounter->inc(l_librbd_rd_bytes, buffer_ofs);
+}
+
+template <typename I>
+void AbstractImageWriteRequest<I>::send_request() {
+  I &image_ctx = this->m_image_ctx;
+
+  bool journaling = false;
+
+  AioCompletion *aio_comp = this->m_aio_comp;
+  {
+    // prevent image size from changing between computing clip and recording
+    // pending async operation
+    std::shared_lock image_locker{image_ctx.image_lock};
+    journaling = (image_ctx.journal != nullptr &&
+                  image_ctx.journal->is_journal_appending());
+  }
+
+  uint64_t clip_len = 0;
+  LightweightObjectExtents object_extents;
+  for (auto &extent : this->m_image_extents) {
+    if (extent.second == 0) {
+      continue;
+    }
+
+    // map to object extents
+    io::util::area_to_object_extents(&image_ctx, extent.first, extent.second,
+                                     this->m_image_area, clip_len,
+                                     &object_extents);
+    clip_len += extent.second;
+  }
+
+  int ret = prune_object_extents(&object_extents);
+  if (ret < 0) {
+    aio_comp->fail(ret);
+    return;
+  }
+
+  // reflect changes in object_extents back to m_image_extents
+  if (ret == 1) {
+    this->m_image_extents.clear();
+    for (auto& object_extent : object_extents) {
+      auto [image_extents, _] = io::util::object_to_area_extents(
+          &image_ctx, object_extent.object_no,
+          {{object_extent.offset, object_extent.length}});
+      this->m_image_extents.insert(this->m_image_extents.end(),
+                                   image_extents.begin(), image_extents.end());
+    }
+  }
+
+  aio_comp->set_request_count(object_extents.size());
+  if (!object_extents.empty()) {
+    uint64_t journal_tid = 0;
+    if (journaling) {
+      // in-flight ops are flushed prior to closing the journal
+      ceph_assert(image_ctx.journal != NULL);
+      journal_tid = append_journal_event(m_synchronous);
+    }
+
+    // it's very important that IOContext is captured here instead of
+    // e.g. at the API layer so that an up-to-date snap context is used
+    // when owning the exclusive lock
+    send_object_requests(object_extents, image_ctx.get_data_io_context(),
+                         journal_tid);
+  }
+
+  update_stats(clip_len);
+}
+
+template <typename I>
+void AbstractImageWriteRequest<I>::send_object_requests(
+    const LightweightObjectExtents &object_extents, IOContext io_context,
+    uint64_t journal_tid) {
+  I &image_ctx = this->m_image_ctx;
+  CephContext *cct = image_ctx.cct;
+
+  AioCompletion *aio_comp = this->m_aio_comp;
+  bool single_extent = (object_extents.size() == 1);
+  for (auto& oe : object_extents) {
+    ldout(cct, 20) << data_object_name(&image_ctx, oe.object_no) << " "
+                   << oe.offset << "~" << oe.length << " from "
+                   << oe.buffer_extents << dendl;
+    C_AioRequest *req_comp = new C_AioRequest(aio_comp);
+    auto request = create_object_request(oe, io_context, journal_tid,
+                                         single_extent, req_comp);
+    request->send();
+  }
+}
+
+template <typename I>
+void ImageWriteRequest<I>::assemble_extent(
+    const LightweightObjectExtent &object_extent, bufferlist *bl) {
+  for (auto q = object_extent.buffer_extents.begin();
+       q != object_extent.buffer_extents.end(); ++q) {
+    bufferlist sub_bl;
+    sub_bl.substr_of(m_bl, q->first, q->second);
+    bl->claim_append(sub_bl);
+  }
+}
+
+template <typename I>
+uint64_t ImageWriteRequest<I>::append_journal_event(bool synchronous) {
+  I &image_ctx = this->m_image_ctx;
+
+  uint64_t tid = 0;
+  uint64_t buffer_offset = 0;
+  ceph_assert(!this->m_image_extents.empty());
+  for (auto &extent : this->m_image_extents) {
+    bufferlist sub_bl;
+    sub_bl.substr_of(m_bl, buffer_offset, extent.second);
+    buffer_offset += extent.second;
+
+    tid = image_ctx.journal->append_write_event(extent.first, extent.second,
+                                                sub_bl, synchronous);
+  }
+
+  return tid;
+}
+
+template <typename I>
+ObjectDispatchSpec *ImageWriteRequest<I>::create_object_request(
+    const LightweightObjectExtent &object_extent, IOContext io_context,
+    uint64_t journal_tid, bool single_extent, Context *on_finish) {
+  I &image_ctx = this->m_image_ctx;
+
+  bufferlist bl;
+  if (single_extent && object_extent.buffer_extents.size() == 1 &&
+      m_bl.length() == object_extent.length) {
+    // optimization for single object/buffer extent writes
+    bl = std::move(m_bl);
+  } else {
+    assemble_extent(object_extent, &bl);
+  }
+
+  auto req = ObjectDispatchSpec::create_write(
+    &image_ctx, OBJECT_DISPATCH_LAYER_NONE, object_extent.object_no,
+    object_extent.offset, std::move(bl), io_context, m_op_flags, 0,
+    std::nullopt, journal_tid, this->m_trace, on_finish);
+  return req;
+}
+
+template <typename I>
+void ImageWriteRequest<I>::update_stats(size_t length) {
+  I &image_ctx = this->m_image_ctx;
+  image_ctx.perfcounter->inc(l_librbd_wr);
+  image_ctx.perfcounter->inc(l_librbd_wr_bytes, length);
+}
+
+template <typename I>
+uint64_t ImageDiscardRequest<I>::append_journal_event(bool synchronous) {
+  I &image_ctx = this->m_image_ctx;
+
+  uint64_t tid = 0;
+  ceph_assert(!this->m_image_extents.empty());
+  for (auto &extent : this->m_image_extents) {
+    journal::EventEntry event_entry(
+      journal::AioDiscardEvent(extent.first,
+                               extent.second,
+                               this->m_discard_granularity_bytes));
+    tid = image_ctx.journal->append_io_event(std::move(event_entry),
+                                             extent.first, extent.second,
+                                             synchronous, 0);
+  }
+
+  return tid;
+}
+
+template <typename I>
+ObjectDispatchSpec *ImageDiscardRequest<I>::create_object_request(
+    const LightweightObjectExtent &object_extent, IOContext io_context,
+    uint64_t journal_tid, bool single_extent, Context *on_finish) {
+  I &image_ctx = this->m_image_ctx;
+  auto req = ObjectDispatchSpec::create_discard(
+    &image_ctx, OBJECT_DISPATCH_LAYER_NONE, object_extent.object_no,
+    object_extent.offset, object_extent.length, io_context,
+    OBJECT_DISCARD_FLAG_DISABLE_CLONE_REMOVE, journal_tid, this->m_trace,
+    on_finish);
+  return req;
+}
+
+template <typename I>
+void ImageDiscardRequest<I>::update_stats(size_t length) {
+  I &image_ctx = this->m_image_ctx;
+  image_ctx.perfcounter->inc(l_librbd_discard);
+  image_ctx.perfcounter->inc(l_librbd_discard_bytes, length);
+}
+
+template <typename I>
+int ImageDiscardRequest<I>::prune_object_extents(
+    LightweightObjectExtents* object_extents) const {
+  if (m_discard_granularity_bytes == 0) {
+    return 0;
+  }
+
+  // Align the range to discard_granularity_bytes boundary and skip
+  // and discards that are too small to free up any space.
+  //
+  // discard_granularity_bytes >= object_size && tail truncation
+  // is a special case for filestore
+  bool prune_required = false;
+  bool length_modified = false;
+  auto object_size = this->m_image_ctx.layout.object_size;
+  auto discard_granularity_bytes = std::min(m_discard_granularity_bytes,
+                                            object_size);
+  auto xform_lambda =
+    [discard_granularity_bytes, object_size, &prune_required, &length_modified]
+    (LightweightObjectExtent& object_extent) {
+      auto& offset = object_extent.offset;
+      auto& length = object_extent.length;
+      auto next_offset = offset + length;
+
+      if ((discard_granularity_bytes < object_size) ||
+          (next_offset < object_size)) {
+        offset = p2roundup<uint64_t>(offset, discard_granularity_bytes);
+        next_offset = p2align<uint64_t>(next_offset, discard_granularity_bytes);
+        if (offset >= next_offset) {
+          prune_required = true;
+          length = 0;
+        } else {
+          auto new_length = next_offset - offset;
+          if (length != new_length) {
+            length_modified = true;
+            length = new_length;
+          }
+        }
+      }
+    };
+  std::for_each(object_extents->begin(), object_extents->end(),
+                xform_lambda);
+
+  if (prune_required) {
+    // one or more object extents were skipped
+    auto remove_lambda =
+      [](const LightweightObjectExtent& object_extent) {
+        return (object_extent.length == 0);
+      };
+    object_extents->erase(
+      std::remove_if(object_extents->begin(), object_extents->end(),
+                     remove_lambda),
+      object_extents->end());
+  }
+
+  // object extents were modified, image extents needs updating
+  if (length_modified || prune_required) {
+    return 1;
+  }
+
+  return 0;
+}
+
+template <typename I>
+void ImageFlushRequest<I>::send_request() {
+  I &image_ctx = this->m_image_ctx;
+
+  bool journaling = false;
+  {
+    std::shared_lock image_locker{image_ctx.image_lock};
+    journaling = (m_flush_source == FLUSH_SOURCE_USER &&
+                  image_ctx.journal != nullptr &&
+                  image_ctx.journal->is_journal_appending());
+  }
+
+  AioCompletion *aio_comp = this->m_aio_comp;
+  aio_comp->set_request_count(1);
+
+  Context *ctx = new C_AioRequest(aio_comp);
+
+  // ensure no locks are held when flush is complete
+  ctx = librbd::util::create_async_context_callback(image_ctx, ctx);
+
+  uint64_t journal_tid = 0;
+  if (journaling) {
+    // in-flight ops are flushed prior to closing the journal
+    ceph_assert(image_ctx.journal != NULL);
+    journal_tid = image_ctx.journal->append_io_event(
+      journal::EventEntry(journal::AioFlushEvent()), 0, 0, false, 0);
+    image_ctx.journal->user_flushed();
+  }
+
+  auto object_dispatch_spec = ObjectDispatchSpec::create_flush(
+    &image_ctx, OBJECT_DISPATCH_LAYER_NONE, m_flush_source, journal_tid,
+    this->m_trace, ctx);
+  ctx = new LambdaContext([object_dispatch_spec](int r) {
+      object_dispatch_spec->send();
+    });
+
+  // ensure all in-flight IOs are settled if non-user flush request
+  if (m_flush_source == FLUSH_SOURCE_WRITEBACK) {
+    ctx->complete(0);
+  } else {
+    aio_comp->async_op.flush(ctx);
+  }
+
+  // might be flushing during image shutdown
+  if (image_ctx.perfcounter != nullptr) {
+    image_ctx.perfcounter->inc(l_librbd_flush);
+  }
+}
+
+template <typename I>
+uint64_t ImageWriteSameRequest<I>::append_journal_event(bool synchronous) {
+  I &image_ctx = this->m_image_ctx;
+
+  uint64_t tid = 0;
+  ceph_assert(!this->m_image_extents.empty());
+  for (auto &extent : this->m_image_extents) {
+    journal::EventEntry event_entry(journal::AioWriteSameEvent(extent.first,
+                                                               extent.second,
+                                                               m_data_bl));
+    tid = image_ctx.journal->append_io_event(std::move(event_entry),
+                                             extent.first, extent.second,
+                                             synchronous, 0);
+  }
+
+  return tid;
+}
+
+template <typename I>
+ObjectDispatchSpec *ImageWriteSameRequest<I>::create_object_request(
+    const LightweightObjectExtent &object_extent, IOContext io_context,
+    uint64_t journal_tid, bool single_extent, Context *on_finish) {
+  I &image_ctx = this->m_image_ctx;
+
+  bufferlist bl;
+  ObjectDispatchSpec *req;
+
+  if (util::assemble_write_same_extent(object_extent, m_data_bl, &bl, false)) {
+    auto buffer_extents{object_extent.buffer_extents};
+
+    req = ObjectDispatchSpec::create_write_same(
+      &image_ctx, OBJECT_DISPATCH_LAYER_NONE, object_extent.object_no,
+      object_extent.offset, object_extent.length, std::move(buffer_extents),
+      std::move(bl), io_context, m_op_flags, journal_tid,
+      this->m_trace, on_finish);
+    return req;
+  }
+  req = ObjectDispatchSpec::create_write(
+    &image_ctx, OBJECT_DISPATCH_LAYER_NONE, object_extent.object_no,
+    object_extent.offset, std::move(bl), io_context, m_op_flags, 0,
+    std::nullopt, journal_tid, this->m_trace, on_finish);
+  return req;
+}
+
+template <typename I>
+void ImageWriteSameRequest<I>::update_stats(size_t length) {
+  I &image_ctx = this->m_image_ctx;
+  image_ctx.perfcounter->inc(l_librbd_ws);
+  image_ctx.perfcounter->inc(l_librbd_ws_bytes, length);
+}
+
+template <typename I>
+uint64_t ImageCompareAndWriteRequest<I>::append_journal_event(
+    bool synchronous) {
+  I &image_ctx = this->m_image_ctx;
+
+  uint64_t tid = 0;
+  ceph_assert(this->m_image_extents.size() == 1);
+  auto &extent = this->m_image_extents.front();
+  tid = image_ctx.journal->append_compare_and_write_event(extent.first,
+                                                          extent.second,
+                                                          m_cmp_bl,
+                                                          m_bl,
+                                                          synchronous);
+
+  return tid;
+}
+
+template <typename I>
+void ImageCompareAndWriteRequest<I>::assemble_extent(
+    const LightweightObjectExtent &object_extent, bufferlist *bl,
+    bufferlist *cmp_bl) {
+  for (auto q = object_extent.buffer_extents.begin();
+       q != object_extent.buffer_extents.end(); ++q) {
+    bufferlist sub_bl;
+    sub_bl.substr_of(m_bl, q->first, q->second);
+    bl->claim_append(sub_bl);
+
+    bufferlist sub_cmp_bl;
+    sub_cmp_bl.substr_of(m_cmp_bl, q->first, q->second);
+    cmp_bl->claim_append(sub_cmp_bl);
+  }
+}
+
+template <typename I>
+ObjectDispatchSpec *ImageCompareAndWriteRequest<I>::create_object_request(
+    const LightweightObjectExtent &object_extent, IOContext io_context,
+    uint64_t journal_tid, bool single_extent, Context *on_finish) {
+  I &image_ctx = this->m_image_ctx;
+
+  bufferlist bl;
+  bufferlist cmp_bl;
+  assemble_extent(object_extent, &bl, &cmp_bl);
+  auto req = ObjectDispatchSpec::create_compare_and_write(
+    &image_ctx, OBJECT_DISPATCH_LAYER_NONE, object_extent.object_no,
+    object_extent.offset, std::move(cmp_bl), std::move(bl), io_context,
+    m_mismatch_offset, m_op_flags, journal_tid, this->m_trace, on_finish);
+  return req;
+}
+
+template <typename I>
+void ImageCompareAndWriteRequest<I>::update_stats(size_t length) {
+  I &image_ctx = this->m_image_ctx;
+  image_ctx.perfcounter->inc(l_librbd_cmp);
+  image_ctx.perfcounter->inc(l_librbd_cmp_bytes, length);
+}
+
+template <typename I>
+int ImageCompareAndWriteRequest<I>::prune_object_extents(
+    LightweightObjectExtents* object_extents) const {
+  if (object_extents->size() > 1)
+    return -EINVAL;
+
+  I &image_ctx = this->m_image_ctx;
+  uint64_t su = image_ctx.layout.stripe_unit;
+  auto& object_extent = object_extents->front();
+  if (su == 0 || (object_extent.offset % su + object_extent.length > su))
+    return -EINVAL;
+
+  return 0;
+}
+
+template <typename I>
+ImageListSnapsRequest<I>::ImageListSnapsRequest(
+    I& image_ctx, AioCompletion* aio_comp, Extents&& image_extents,
+    ImageArea area, SnapIds&& snap_ids, int list_snaps_flags,
+    SnapshotDelta* snapshot_delta, const ZTracer::Trace& parent_trace)
+  : ImageRequest<I>(image_ctx, aio_comp, std::move(image_extents), area,
+                    "list-snaps", parent_trace),
+    m_snap_ids(std::move(snap_ids)), m_list_snaps_flags(list_snaps_flags),
+    m_snapshot_delta(snapshot_delta) {
+}
+
+template <typename I>
+void ImageListSnapsRequest<I>::send_request() {
+  I &image_ctx = this->m_image_ctx;
+  CephContext *cct = image_ctx.cct;
+
+  // map image extents to object extents
+  auto &image_extents = this->m_image_extents;
+  std::map<uint64_t, Extents> object_number_extents;
+  for (auto& image_extent : image_extents) {
+    if (image_extent.second == 0) {
+      continue;
+    }
+
+    striper::LightweightObjectExtents object_extents;
+    io::util::area_to_object_extents(&image_ctx, image_extent.first,
+                                     image_extent.second, this->m_image_area, 0,
+                                     &object_extents);
+    for (auto& object_extent : object_extents) {
+      object_number_extents[object_extent.object_no].emplace_back(
+        object_extent.offset, object_extent.length);
+    }
+  }
+
+  // reassemble the deltas back into image-extents when complete
+  auto aio_comp = this->m_aio_comp;
+  aio_comp->set_request_count(1);
+  auto assemble_ctx = new C_AssembleSnapshotDeltas<I>(
+    &image_ctx, aio_comp, m_snapshot_delta);
+  auto sub_aio_comp = AioCompletion::create_and_start<
+    Context, &Context::complete>(assemble_ctx, get_image_ctx(&image_ctx),
+                                 AIO_TYPE_GENERIC);
+
+  // issue the requests
+  sub_aio_comp->set_request_count(object_number_extents.size());
+  for (auto& oe : object_number_extents) {
+    ldout(cct, 20) << data_object_name(&image_ctx, oe.first) << " "
+                   << oe.second << dendl;
+    auto ctx = new C_AioRequest(sub_aio_comp);
+    auto req = ObjectDispatchSpec::create_list_snaps(
+      &image_ctx, OBJECT_DISPATCH_LAYER_NONE, oe.first, std::move(oe.second),
+      SnapIds{m_snap_ids}, m_list_snaps_flags, this->m_trace,
+      assemble_ctx->get_snapshot_delta(oe.first), ctx);
+    req->send();
+  }
+}
+
+} // namespace io
+} // namespace librbd
+
+template class librbd::io::ImageRequest<librbd::ImageCtx>;
+template class librbd::io::ImageReadRequest<librbd::ImageCtx>;
+template class librbd::io::AbstractImageWriteRequest<librbd::ImageCtx>;
+template class librbd::io::ImageWriteRequest<librbd::ImageCtx>;
+template class librbd::io::ImageDiscardRequest<librbd::ImageCtx>;
+template class librbd::io::ImageFlushRequest<librbd::ImageCtx>;
+template class librbd::io::ImageWriteSameRequest<librbd::ImageCtx>;
+template class librbd::io::ImageCompareAndWriteRequest<librbd::ImageCtx>;
+template class librbd::io::ImageListSnapsRequest<librbd::ImageCtx>;