From c45479620c23bac1200c24644145ed2a130134a2 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 16 Mar 2011 13:52:40 -0300 Subject: [PATCH 10/11] qcow2: Fix order in L2 table COW RH-Author: Kevin Wolf Message-id: <1300283560-13085-9-git-send-email-kwolf@redhat.com> Patchwork-id: 20138 O-Subject: [RHEL-6.1 qemu-kvm PATCH 8/8] qcow2: Fix order in L2 table COW Bugzilla: 688146 RH-Acked-by: Juan Quintela RH-Acked-by: Jes Sorensen RH-Acked-by: Markus Armbruster Bugzilla: 688146 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 (cherry picked from commit 16fde5f2c2788232b16c06d34d0459a5c1ec1f6c) --- block/qcow2-cluster.c | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-) Signed-off-by: Luiz Capitulino --- 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 e49509e..612712a 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -508,13 +508,16 @@ 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; } -- 1.7.4.1.230.gae447