diff options
Diffstat (limited to 'block/qcow2.c')
| -rw-r--r-- | block/qcow2.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/block/qcow2.c b/block/qcow2.c index e9a86b7443..f2731a7cb5 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -376,6 +376,8 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset, default: /* unknown magic - save it in case we need to rewrite the header */ + /* If you add a new feature, make sure to also update the fast + * path of qcow2_make_empty() to deal with it. */ { Qcow2UnknownHeaderExtension *uext; @@ -3600,15 +3602,16 @@ static int qcow2_make_empty(BlockDriverState *bs) l1_clusters = DIV_ROUND_UP(s->l1_size, s->cluster_size / sizeof(uint64_t)); - if (s->qcow_version >= 3 && !s->snapshots && + if (s->qcow_version >= 3 && !s->snapshots && !s->nb_bitmaps && 3 + l1_clusters <= s->refcount_block_size && s->crypt_method_header != QCOW_CRYPT_LUKS) { - /* The following function only works for qcow2 v3 images (it requires - * the dirty flag) and only as long as there are no snapshots (because - * it completely empties the image). Furthermore, the L1 table and three - * additional clusters (image header, refcount table, one refcount - * block) have to fit inside one refcount block. It cannot be used - * for LUKS (yet) as it throws away the LUKS header cluster(s) */ + /* The following function only works for qcow2 v3 images (it + * requires the dirty flag) and only as long as there are no + * features that reserve extra clusters (such as snapshots, + * LUKS header, or persistent bitmaps), because it completely + * empties the image. Furthermore, the L1 table and three + * additional clusters (image header, refcount table, one + * refcount block) have to fit inside one refcount block. */ return make_completely_empty(bs); } |