From c0b502933a26094be92f1427544cb07097ed659b Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 1 Feb 2011 13:32:41 -0200
Subject: [PATCH 21/28] qcow2: Batch flushes for COW
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1296567161-8837-6-git-send-email-kwolf@redhat.com>
Patchwork-id: 17412
O-Subject: [RHEL-6.1 qemu-kvm PATCH v2 5/5] qcow2: Batch flushes for COW
Bugzilla: 635527
RH-Acked-by: Markus Armbruster <armbru@redhat.com>
RH-Acked-by: Avi Kivity <avi@redhat.com>
RH-Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Bugzilla: 635527
qcow2 calls bdrv_flush() after performing COW in order to ensure that the
L2 table change is never written before the copy is safe on disk. Now that the
L2 table is cached, we can wait with flushing until we write out the next L2
table.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 3de0a2944bdb3047dce275560631834bcb4afe22)
---
block/qcow2-cache.c | 20 +++++++++++++++++---
block/qcow2-cluster.c | 2 +-
block/qcow2.h | 1 +
3 files changed, 19 insertions(+), 4 deletions(-)
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
block/qcow2-cache.c | 20 +++++++++++++++++---
block/qcow2-cluster.c | 2 +-
block/qcow2.h | 1 +
3 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index 5f1740b..8f2955b 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -38,6 +38,7 @@ struct Qcow2Cache {
int size;
Qcow2CachedTable* entries;
struct Qcow2Cache* depends;
+ bool depends_on_flush;
bool writethrough;
};
@@ -85,13 +86,15 @@ static int qcow2_cache_flush_dependency(BlockDriverState *bs, Qcow2Cache *c)
}
c->depends = NULL;
+ c->depends_on_flush = false;
+
return 0;
}
static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
{
BDRVQcowState *s = bs->opaque;
- int ret;
+ int ret = 0;
if (!c->entries[i].dirty || !c->entries[i].offset) {
return 0;
@@ -99,11 +102,17 @@ static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
if (c->depends) {
ret = qcow2_cache_flush_dependency(bs, c);
- if (ret < 0) {
- return ret;
+ } else if (c->depends_on_flush) {
+ ret = bdrv_flush(bs->file);
+ if (ret >= 0) {
+ c->depends_on_flush = false;
}
}
+ if (ret < 0) {
+ return ret;
+ }
+
if (c == s->refcount_block_cache) {
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART);
} else if (c == s->l2_table_cache) {
@@ -167,6 +176,11 @@ int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
return 0;
}
+void qcow2_cache_depends_on_flush(Qcow2Cache *c)
+{
+ c->depends_on_flush = true;
+}
+
static int qcow2_cache_find_entry_to_replace(Qcow2Cache *c)
{
int i;
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index d0eff2a..9779cca 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -630,7 +630,7 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
* handled.
*/
if (cow) {
- bdrv_flush(bs->file);
+ qcow2_cache_depends_on_flush(s->l2_table_cache);
}
qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);
diff --git a/block/qcow2.h b/block/qcow2.h
index d040cc9..bc3a4db 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -229,6 +229,7 @@ void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table);
int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c);
int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
Qcow2Cache *dependency);
+void qcow2_cache_depends_on_flush(Qcow2Cache *c);
int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
void **table);
--
1.7.4.rc1.16.gd2f15e