diff options
Diffstat (limited to 'block/qcow2.c')
| -rw-r--r-- | block/qcow2.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/block/qcow2.c b/block/qcow2.c index 0edc7f4..3e8b3d0 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -3989,9 +3989,12 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset, qemu_co_mutex_lock(&s->lock); - /* cannot proceed if image has snapshots */ - if (s->nb_snapshots) { - error_setg(errp, "Can't resize an image which has snapshots"); + /* + * Even though we store snapshot size for all images, it was not + * required until v3, so it is not safe to proceed for v2. + */ + if (s->nb_snapshots && s->qcow_version < 3) { + error_setg(errp, "Can't resize a v2 image which has snapshots"); ret = -ENOTSUP; goto fail; } @@ -5005,6 +5008,7 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version, BDRVQcow2State *s = bs->opaque; int current_version = s->qcow_version; int ret; + int i; /* This is qcow2_downgrade(), not qcow2_upgrade() */ assert(target_version < current_version); @@ -5022,6 +5026,21 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version, return -ENOTSUP; } + /* + * If any internal snapshot has a different size than the current + * image size, or VM state size that exceeds 32 bits, downgrading + * is unsafe. Even though we would still use v3-compliant output + * to preserve that data, other v2 programs might not realize + * those optional fields are important. + */ + for (i = 0; i < s->nb_snapshots; i++) { + if (s->snapshots[i].vm_state_size > UINT32_MAX || + s->snapshots[i].disk_size != bs->total_sectors * BDRV_SECTOR_SIZE) { + error_setg(errp, "Internal snapshots prevent downgrade of image"); + return -ENOTSUP; + } + } + /* clear incompatible features */ if (s->incompatible_features & QCOW2_INCOMPAT_DIRTY) { ret = qcow2_mark_clean(bs); |