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| author | Gleb Natapov <gleb@redhat.com> | 2009-05-07 11:31:44 +0300 |
|---|---|---|
| committer | Anthony Liguori <aliguori@us.ibm.com> | 2009-05-08 15:24:09 -0500 |
| commit | d4d698f020e50333d6eae48ce323752613b5c3ea (patch) | |
| tree | 9e4c666706c67da435842a5b6c8c5d049f9d6351 /block-qcow2.c | |
| parent | a6d6552426dcbf726e5549f08b70c9318d6be14b (diff) | |
| download | qemu-d4d698f020e50333d6eae48ce323752613b5c3ea.tar.gz | |
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>
Diffstat (limited to 'block-qcow2.c')
| -rw-r--r-- | block-qcow2.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/block-qcow2.c b/block-qcow2.c index 1f3312590c..9a49777ed1 100644 --- a/block-qcow2.c +++ b/block-qcow2.c @@ -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: |