Currently, if an image file is logically larger than its backing file, commiting it via 'qemu-img commit' will fail.
For instance, if we have a base image with a virtual size 10G, and a snapshot image of size 20G, then committing the snapshot offline with 'qemu-img commit' will likely fail. This will automatically attempt to resize the base image, if the snapshot image to be committed is larger. Signed-off-by: Jeff Cody <jc...@redhat.com> --- block.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/block.c b/block.c index 64e7d22..5e895fa 100644 --- a/block.c +++ b/block.c @@ -1876,10 +1876,10 @@ int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix) int bdrv_commit(BlockDriverState *bs) { BlockDriver *drv = bs->drv; - int64_t sector, total_sectors; + int64_t sector, total_sectors, length; int n, ro, open_flags; int ret = 0; - uint8_t *buf; + uint8_t *buf = NULL; char filename[PATH_MAX]; if (!drv) @@ -1904,7 +1904,19 @@ int bdrv_commit(BlockDriverState *bs) } } - total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS; + length = bdrv_getlength(bs); + + /* If our top snapshot is larger than the backing file image, + * grow the backing file image if possible. If not possible, + * we must return an error */ + if (length > bdrv_getlength(bs->backing_hd)) { + ret = bdrv_truncate(bs->backing_hd, length); + if (ret < 0) { + goto ro_cleanup; + } + } + + total_sectors = length >> BDRV_SECTOR_BITS; buf = g_malloc(COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE); for (sector = 0; sector < total_sectors; sector += n) { -- 1.8.3.1