Patchwork [RFC,V8,20/24] qcow2: Serialize write requests when deduplication is activated.

login
register
mail settings
Submitter Benoît Canet
Date June 20, 2013, 2:26 p.m.
Message ID <1371738392-9594-21-git-send-email-benoit@irqsave.net>
Download mbox | patch
Permalink /patch/253015/
State New
Headers show

Comments

Benoît Canet - June 20, 2013, 2:26 p.m.
This fixes the sub cluster sized writes race conditions while waiting
for a faster solution.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
---
 block/qcow2.c |   14 ++++++++++++++
 block/qcow2.h |    1 +
 2 files changed, 15 insertions(+)

Patch

diff --git a/block/qcow2.c b/block/qcow2.c
index 8eb63f1..11c115f 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -534,6 +534,7 @@  static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
 
     /* Initialise locks */
     qemu_co_mutex_init(&s->lock);
+    qemu_co_mutex_init(&s->dedup_lock);
 
     /* Repair image if dirty */
     if (!(flags & BDRV_O_CHECK) && !bs->read_only &&
@@ -841,6 +842,15 @@  static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
 
     s->cluster_cache_offset = -1; /* disable compressed cache */
 
+    if (s->has_dedup) {
+        /* This mutex is used to serialize the write requests in the dedup case.
+         * The goal is to avoid that the dedup process concurrents requests to
+         * the same clusters and corrupt data.
+         * With qcow2_dedup_read_missing_and_concatenate that would not work.
+         */
+        qemu_co_mutex_lock(&s->dedup_lock);
+    }
+
     qemu_co_mutex_lock(&s->lock);
 
     if (s->has_dedup) {
@@ -1018,6 +1028,10 @@  fail:
         l2meta = next;
     }
 
+    if (s->has_dedup) {
+        qemu_co_mutex_unlock(&s->dedup_lock);
+    }
+
     qemu_iovec_destroy(&hd_qiov);
     qemu_vfree(cluster_data);
     qemu_vfree(dedup_cluster_data);
diff --git a/block/qcow2.h b/block/qcow2.h
index 6f85e03..3c6e685 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -364,6 +364,7 @@  typedef struct BDRVQcowState {
     Coroutine *load_filter_co;          /* used to load incarnations filters */
 
     CoMutex lock;
+    CoMutex dedup_lock;
 
     uint32_t crypt_method; /* current crypt method, 0 if no key yet */
     uint32_t crypt_method_header;