From 315be262eec6602d48e709783c67f7774707389c Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 23 Nov 2010 10:31:43 -0200
Subject: [RHEL6 qemu-kvm PATCH 15/21] qcow2: Get rid of additional sync on COW
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1290508306-11607-8-git-send-email-kwolf@redhat.com>
Patchwork-id: 13831
O-Subject: [RHEL-6.1 qemu-kvm PATCH v2 07/10] qcow2: Get rid of additional sync
on COW
Bugzilla: 653972
RH-Acked-by: Avi Kivity <avi@redhat.com>
RH-Acked-by: Christoph Hellwig <chellwig@redhat.com>
RH-Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Bugzilla: 653972
We always have a sync for the refcount update when a new cluster is
allocated. If we move this past the COW, we can save an additional sync.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 9f8e668eb1826434f61a63ff260d6c8b466e483a)
---
block/qcow2-cluster.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
block/qcow2-cluster.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 818c0db..cb2e33f 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -415,7 +415,7 @@ static int copy_sectors(BlockDriverState *bs, uint64_t start_sect,
&s->aes_encrypt_key);
}
BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);
- ret = bdrv_write_sync(bs->file, (cluster_offset >> 9) + n_start,
+ ret = bdrv_write(bs->file, (cluster_offset >> 9) + n_start,
s->cluster_data, n);
if (ret < 0)
return ret;
@@ -714,6 +714,13 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
(i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
}
+ /*
+ * Before we update the L2 table to actually point to the new cluster, we
+ * need to be sure that the refcounts have been increased and COW was
+ * handled.
+ */
+ bdrv_flush(bs->file);
+
ret = write_l2_entries(bs, l2_table, l2_offset, l2_index, m->nb_clusters);
if (ret < 0) {
qcow2_l2_cache_reset(bs);
@@ -865,7 +872,6 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
QLIST_REMOVE(m, next_in_flight);
return cluster_offset;
}
- bdrv_flush(bs->file);
/* save info needed for meta data update */
m->offset = offset;
--
1.7.3.2