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Fix cluster freeing in qcow2 

Need to drop QCOW_OFLAG_COPIED from a cluster pointer before freeing it.

Add an explanation how thing meant to work.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
master
Gleb Natapov 2009-05-07 11:31:44 +03:00 committed by Anthony Liguori
parent a6d6552426
commit d4d698f020
1 changed files with 8 additions and 1 deletions
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9
block-qcow2.c
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@ -992,6 +992,12 @@ static int alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
goto err;
for (i = 0; i < m->nb_clusters; i++) {
/* if two concurrent writes happen to the same unallocated cluster
* each write allocates separate cluster and writes data concurrently.
* The first one to complete updates l2 table with pointer to its
* cluster the second one has to do RMW (which is done above by
* copy_sectors()), update l2 table with its cluster pointer and free
* old cluster. This is what this loop does */
if(l2_table[l2_index + i] != 0)
old_cluster[j++] = l2_table[l2_index + i];
@ -1005,7 +1011,8 @@ static int alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
goto err;
for (i = 0; i < j; i++)
free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1);
free_any_clusters(bs, be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED,
1);
ret = 0;
err: