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qcow2: Fix corruption after error in update_refcount 

After it is done with updating refcounts in the cache, update_refcount writes
all changed entries to disk. If a refcount block allocation fails, however,
there was no change yet and therefore first_index = last_index = -1. Don't
treat -1 as a normal sector index (resulting in a 512 byte write!) but return
without updating anything in this case.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2010-05-28 12:21:27 +02:00
parent 25408c0950
commit 86fa8da837
1 changed files with 4 additions and 0 deletions
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4
block/qcow2-refcount.c
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@ -417,6 +417,10 @@ static int write_refcount_block_entries(BlockDriverState *bs,
return 0; return 0;
} }
if (first_index < 0) {
return 0;
}
first_index &= ~(REFCOUNTS_PER_SECTOR - 1); first_index &= ~(REFCOUNTS_PER_SECTOR - 1);
last_index = (last_index + REFCOUNTS_PER_SECTOR) last_index = (last_index + REFCOUNTS_PER_SECTOR)
& ~(REFCOUNTS_PER_SECTOR - 1); & ~(REFCOUNTS_PER_SECTOR - 1);