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 Date: Fri, 5 Apr 2013 19:44:43 +0200 Subject: [PATCH 04/24] qcow2: Update snapshot table information at once RH-Author: Kevin Wolf 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 RH-Acked-by: Laszlo Ersek RH-Acked-by: Fam Zheng 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 Reviewed-by: Stefan Hajnoczi (cherry picked from commit d69969c4046a81af106e723ff1bc2740365e67c1) Signed-off-by: Kevin Wolf --- block/qcow2-snapshot.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) Signed-off-by: Michal Novotny --- 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