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| author |   Kevin Wolf <kwolf@redhat.com> | 2010-05-28 12:05:45 +0200 |
|---|---|---|
| committer |   Doug Goldstein <cardoe@gentoo.org> | 2010-07-20 17:35:14 -0500 |
| commit | b422613ad5667f7a062121c354e795b197e9ed4c (patch) | |
| tree | 35f4c307bdefce84337953da594cbed9a894e7cc /block | |
| parent | block: Fix multiwrite with overlapping requests (diff) | |
| download | qemu-kvm-b422613ad5667f7a062121c354e795b197e9ed4c.tar.gz qemu-kvm-b422613ad5667f7a062121c354e795b197e9ed4c.tar.bz2 qemu-kvm-b422613ad5667f7a062121c354e795b197e9ed4c.zip | |
qcow2: Fix corruption after refblock allocation
Refblock allocation code needs to take into consideration that update_refcount
will load a different refcount block into the cache, so it must initialize the
cache for a new refcount block only afterwards. Not doing this means that not
only the refcount in the wrong block is updated, but also that the caller will
work on the wrong block.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 25408c09502be036e5575754fe54019ed4ed5dfa)
Diffstat (limited to 'block')
| -rw-r--r-- | block/qcow2-refcount.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 5ebbcb63d..fa78e46ee 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -215,8 +215,6 @@ static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index) /* Allocate the refcount block itself and mark it as used */ uint64_t new_block = alloc_clusters_noref(bs, s->cluster_size); - memset(s->refcount_block_cache, 0, s->cluster_size); - s->refcount_block_cache_offset = new_block; #ifdef DEBUG_ALLOC2 fprintf(stderr, "qcow2: Allocate refcount block %d for %" PRIx64 @@ -225,6 +223,10 @@ static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index) #endif if (in_same_refcount_block(s, new_block, cluster_index << s->cluster_bits)) { + /* Zero the new refcount block before updating it */ + memset(s->refcount_block_cache, 0, s->cluster_size); + s->refcount_block_cache_offset = new_block; + /* The block describes itself, need to update the cache */ int block_index = (new_block >> s->cluster_bits) & ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); @@ -236,6 +238,11 @@ static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index) if (ret < 0) { goto fail_block; } + + /* Initialize the new refcount block only after updating its refcount, + * update_refcount uses the refcount cache itself */ + memset(s->refcount_block_cache, 0, s->cluster_size); + s->refcount_block_cache_offset = new_block; } /* Now the new refcount block needs to be written to disk */ |