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librbd: copyup state machine needs to handle empty write ops

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The compare-and-write object operation cannot be executed
concurrently within a copyup operation since the object might not
exist yet (if not performing a deep-copy).

Signed-off-by: Jason Dillaman <dillaman@redhat.com>
This commit is contained in:
Jason Dillaman 2017-11-09 15:15:58 -05:00
parent e79c0cf200
commit f6db9b8027
2 changed files with 16 additions and 18 deletions
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31
src/librbd/io/CopyupRequest.cc
View File

@ -87,7 +87,7 @@ CopyupRequest<I>::CopyupRequest(I *ictx, const std::string &oid,
: m_ictx(util::get_image_ctx(ictx)), m_oid(oid), m_object_no(objectno),
m_image_extents(image_extents),
m_trace(util::create_trace(*m_ictx, "copy-up", parent_trace)),
m_state(STATE_READ_FROM_PARENT)
m_state(STATE_READ_FROM_PARENT), m_lock("CopyupRequest", false, false)
{
m_async_op.start_op(*m_ictx);
}
@ -117,12 +117,10 @@ void CopyupRequest<I>::complete_requests(int r) {
template <typename I>
bool CopyupRequest<I>::send_copyup() {
bool add_copyup_op = !m_copyup_data.is_zero();
bool copy_on_read = m_pending_requests.empty();
if (!add_copyup_op && copy_on_read) {
// copyup empty object to prevent future CoR attempts
bool add_copyup_op = !m_copyup_data.is_zero();
if (!add_copyup_op) {
m_copyup_data.clear();
add_copyup_op = true;
}
ldout(m_ictx->cct, 20) << "oid " << m_oid << dendl;
@ -134,17 +132,13 @@ bool CopyupRequest<I>::send_copyup() {
std::vector<librados::snap_t> snaps;
if (!copy_on_read) {
m_pending_copyups++;
}
Mutex::Locker locker(m_lock);
int r;
if (copy_on_read || (!snapc.snaps.empty() && add_copyup_op)) {
assert(add_copyup_op);
add_copyup_op = false;
librados::ObjectWriteOperation copyup_op;
copyup_op.exec("rbd", "copyup", m_copyup_data);
m_copyup_data.clear();
// send only the copyup request with a blank snapshot context so that
// all snapshots are detected from the parent for this object. If
@ -168,10 +162,7 @@ bool CopyupRequest<I>::send_copyup() {
if (!copy_on_read) {
librados::ObjectWriteOperation write_op;
if (add_copyup_op) {
// CoW did not need to handle existing snapshots
write_op.exec("rbd", "copyup", m_copyup_data);
}
write_op.exec("rbd", "copyup", m_copyup_data);
// merge all pending write ops into this single RADOS op
for (size_t i=0; i<m_pending_requests.size(); ++i) {
@ -180,7 +171,8 @@ bool CopyupRequest<I>::send_copyup() {
bool set_hints = (i == 0);
req->add_copyup_ops(&write_op, set_hints);
}
assert(write_op.size() != 0);
m_pending_copyups++;
snaps.insert(snaps.end(), snapc.snaps.begin(), snapc.snaps.end());
librados::AioCompletion *comp = util::create_rados_callback(this);
@ -263,8 +255,11 @@ bool CopyupRequest<I>::should_complete(int r)
return send_copyup();
case STATE_COPYUP:
// invoked via a finisher in librados, so thread safe
pending_copyups = --m_pending_copyups;
{
Mutex::Locker locker(m_lock);
assert(m_pending_copyups > 0);
pending_copyups = --m_pending_copyups;
}
ldout(cct, 20) << "COPYUP (" << pending_copyups << " pending)"
<< dendl;
if (r == -ENOENT) {

3
src/librbd/io/CopyupRequest.h
View File

@ -7,6 +7,7 @@
#include "include/int_types.h"
#include "include/rados/librados.hpp"
#include "include/buffer.h"
#include "common/Mutex.h"
#include "common/zipkin_trace.h"
#include "librbd/io/AsyncOperation.h"
#include "librbd/io/Types.h"
@ -100,6 +101,8 @@ private:
std::vector<uint64_t> m_snap_ids;
librados::IoCtx m_data_ctx; // for empty SnapContext
Mutex m_lock;
void complete_requests(int r);
bool should_complete(int r);