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qcow2: Improve error handling in update_refcount

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If update_refcount fails, try to undo any changes made so far to avoid
inconsistencies in the image file.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Kevin Wolf 2010-01-20 15:03:04 +01:00 committed by Anthony Liguori
parent f2b7c8b370
commit 09508d13f3
1 changed files with 25 additions and 7 deletions
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32
block/qcow2-refcount.c
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@ -278,6 +278,7 @@ static int update_refcount(BlockDriverState *bs,
int64_t refcount_block_offset = 0; int64_t refcount_block_offset = 0;
int64_t table_index = -1, old_table_index; int64_t table_index = -1, old_table_index;
int first_index = -1, last_index = -1; int first_index = -1, last_index = -1;
int ret;
#ifdef DEBUG_ALLOC2 #ifdef DEBUG_ALLOC2
printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n", printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
@ -292,6 +293,7 @@ static int update_refcount(BlockDriverState *bs,
{ {
int block_index, refcount; int block_index, refcount;
int64_t cluster_index = cluster_offset >> s->cluster_bits; int64_t cluster_index = cluster_offset >> s->cluster_bits;
int64_t new_block;
/* Only write refcount block to disk when we are done with it */ /* Only write refcount block to disk when we are done with it */
old_table_index = table_index; old_table_index = table_index;
@ -309,10 +311,12 @@ static int update_refcount(BlockDriverState *bs,
} }
/* Load the refcount block and allocate it if needed */ /* Load the refcount block and allocate it if needed */
refcount_block_offset = alloc_refcount_block(bs, cluster_index); new_block = alloc_refcount_block(bs, cluster_index);
if (refcount_block_offset < 0) { if (new_block < 0) {
return refcount_block_offset; ret = new_block;
goto fail;
} }
refcount_block_offset = new_block;
/* we can update the count and save it */ /* we can update the count and save it */
block_index = cluster_index & block_index = cluster_index &
@ -326,24 +330,38 @@ static int update_refcount(BlockDriverState *bs,
refcount = be16_to_cpu(s->refcount_block_cache[block_index]); refcount = be16_to_cpu(s->refcount_block_cache[block_index]);
refcount += addend; refcount += addend;
if (refcount < 0 || refcount > 0xffff) if (refcount < 0 || refcount > 0xffff) {
return -EINVAL; ret = -EINVAL;
goto fail;
}
if (refcount == 0 && cluster_index < s->free_cluster_index) { if (refcount == 0 && cluster_index < s->free_cluster_index) {
s->free_cluster_index = cluster_index; s->free_cluster_index = cluster_index;
} }
s->refcount_block_cache[block_index] = cpu_to_be16(refcount); s->refcount_block_cache[block_index] = cpu_to_be16(refcount);
} }
ret = 0;
fail:
/* Write last changed block to disk */ /* Write last changed block to disk */
if (refcount_block_offset != 0) { if (refcount_block_offset != 0) {
if (write_refcount_block_entries(s, refcount_block_offset, if (write_refcount_block_entries(s, refcount_block_offset,
first_index, last_index) < 0) first_index, last_index) < 0)
{ {
return -EIO; return ret < 0 ? ret : -EIO;
} }
} }
return 0; /*
* Try do undo any updates if an error is returned (This may succeed in
* some cases like ENOSPC for allocating a new refcount block)
*/
if (ret < 0) {
int dummy;
dummy = update_refcount(bs, offset, cluster_offset - offset, -addend);
}
return ret;
} }
/* addend must be 1 or -1 */ /* addend must be 1 or -1 */