From 35d7ace74bd07e3d6983c1fd7cbfab4e11175689 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 5 Aug 2011 12:06:11 +0200 Subject: [PATCH] qcow2: Fix L1 table size after bdrv_snapshot_goto When loading an internal snapshot whose L1 table is smaller than the current L1 table, the size of the current L1 would be shrunk to the snapshot's L1 size in memory, but not on disk. This lead to incorrect refcount updates and eventuelly to image corruption. Instead of writing the new L1 size to disk, this simply retains the bigger L1 size that is currently in use and makes sure that the unused part is zeroed. Signed-off-by: Kevin Wolf Tested-by: Philipp Hahn Signed-off-by: Anthony Liguori --- block/qcow2-snapshot.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c index 74823a5ebf..e32bcf084c 100644 --- a/block/qcow2-snapshot.c +++ b/block/qcow2-snapshot.c @@ -317,7 +317,8 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id) { BDRVQcowState *s = bs->opaque; QCowSnapshot *sn; - int i, snapshot_index, l1_size2; + int i, snapshot_index; + int cur_l1_bytes, sn_l1_bytes; snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id); if (snapshot_index < 0) @@ -330,14 +331,19 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id) if (qcow2_grow_l1_table(bs, sn->l1_size, true) < 0) goto fail; - s->l1_size = sn->l1_size; - l1_size2 = s->l1_size * sizeof(uint64_t); + cur_l1_bytes = s->l1_size * sizeof(uint64_t); + sn_l1_bytes = sn->l1_size * sizeof(uint64_t); + + if (cur_l1_bytes > sn_l1_bytes) { + memset(s->l1_table + sn->l1_size, 0, cur_l1_bytes - sn_l1_bytes); + } + /* copy the snapshot l1 table to the current l1 table */ if (bdrv_pread(bs->file, sn->l1_table_offset, - s->l1_table, l1_size2) != l1_size2) + s->l1_table, sn_l1_bytes) < 0) goto fail; if (bdrv_pwrite_sync(bs->file, s->l1_table_offset, - s->l1_table, l1_size2) < 0) + s->l1_table, cur_l1_bytes) < 0) goto fail; for(i = 0;i < s->l1_size; i++) { be64_to_cpus(&s->l1_table[i]);