diff options
| author | Kevin Wolf <kwolf@redhat.com> | 2011-02-09 17:36:19 +0100 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2011-02-10 13:24:29 +0100 |
| commit | 16fde5f2c2788232b16c06d34d0459a5c1ec1f6c (patch) | |
| tree | e92076b0f8ebc5a78a68a6ae347fc5744c06e9f0 | |
| parent | a9ae2bffea62ce5158be7475fe41e5fba6d026c1 (diff) | |
qcow2: Fix order in L2 table COW
When copying L2 tables (this happens only with internal snapshots), the order
wasn't completely safe, so that after a crash you could end up with a L2 table
that has too low refcount, possibly leading to corruption in the long run.
This patch puts the operations in the right order: First allocate the new
L2 table and replace the reference, and only then decrease the refcount of the
old table.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
| -rw-r--r-- | block/qcow2-cluster.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 437aaa8174..750abe37d4 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -515,13 +515,16 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset, return ret; } } else { - /* FIXME Order */ - if (l2_offset) - qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t)); + /* First allocate a new L2 table (and do COW if needed) */ ret = l2_allocate(bs, l1_index, &l2_table); if (ret < 0) { return ret; } + + /* Then decrease the refcount of the old table */ + if (l2_offset) { + qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t)); + } l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED; } |