From 0c7fcc789fd4c5a4c860ff6d0ceda5a9457f306b Mon Sep 17 00:00:00 2001
Message-Id: <0c7fcc789fd4c5a4c860ff6d0ceda5a9457f306b.1368098699.git.minovotn@redhat.com>
In-Reply-To: <618a4b91ddb04b21f9dc0c1defe7693fb7cc1748.1368098699.git.minovotn@redhat.com>
References: <618a4b91ddb04b21f9dc0c1defe7693fb7cc1748.1368098699.git.minovotn@redhat.com>
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 5 Apr 2013 19:44:43 +0200
Subject: [PATCH 04/24] qcow2: Update snapshot table information at once
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1365191091-25631-5-git-send-email-kwolf@redhat.com>
Patchwork-id: 50164
O-Subject: [RHEL-6.5 qemu-kvm PATCH 04/12] qcow2: Update snapshot table information at once
Bugzilla: 796011
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>
Bugzilla: 796011
Failing in the middle wouldn't help with the integrity of the image, so
doing everything in a single request seems better.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
(cherry picked from commit d69969c4046a81af106e723ff1bc2740365e67c1)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/qcow2-snapshot.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
Signed-off-by: Michal Novotny <minovotn@redhat.com>
---
block/qcow2-snapshot.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 9f262ba..b2ab0c0 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -137,8 +137,10 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
QCowSnapshot *sn;
QCowSnapshotHeader h;
int i, name_size, id_str_size, snapshots_size;
- uint64_t data64;
- uint32_t data32;
+ struct {
+ uint32_t nb_snapshots;
+ uint64_t snapshots_offset;
+ } QEMU_PACKED header_data;
int64_t offset, snapshots_offset;
int ret;
@@ -200,24 +202,20 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
/*
* Update the header to point to the new snapshot table. This requires the
* new table and its refcounts to be stable on disk.
- *
- * FIXME This should be done with a single write
*/
ret = bdrv_flush(bs);
if (ret < 0) {
goto fail;
}
- data64 = cpu_to_be64(snapshots_offset);
- ret = bdrv_pwrite(bs->file, offsetof(QCowHeader, snapshots_offset),
- &data64, sizeof(data64));
- if (ret < 0) {
- goto fail;
- }
+ QEMU_BUILD_BUG_ON(offsetof(QCowHeader, snapshots_offset) !=
+ offsetof(QCowHeader, nb_snapshots) + sizeof(header_data.nb_snapshots));
+
+ header_data.nb_snapshots = cpu_to_be32(s->nb_snapshots);
+ header_data.snapshots_offset = cpu_to_be64(snapshots_offset);
- data32 = cpu_to_be32(s->nb_snapshots);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
- &data32, sizeof(data32));
+ &header_data, sizeof(header_data));
if (ret < 0) {
goto fail;
}
--
1.7.11.7