diff options
| -rw-r--r-- | block/qcow2-snapshot.c | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c index e91a286333..1976df7f00 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; } |