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authorKevin Wolf <kwolf@redhat.com>2010-01-20 15:03:04 +0100
committerAnthony Liguori <aliguori@us.ibm.com>2010-01-26 14:59:19 -0600
commit09508d13f3874d07bf25f8dd9f5303cbd8139d1b (patch)
tree5ff5fa695dc03315235f225a91e74ffdbe3aa451 /block
parentf2b7c8b37045e0e030ef027cfb6d574558fb732a (diff)
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qcow2: Improve error handling in update_refcount
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>
Diffstat (limited to 'block')
-rw-r--r--block/qcow2-refcount.c32
1 files changed, 25 insertions, 7 deletions
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 6f449c6..a84620f 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -278,6 +278,7 @@ static int update_refcount(BlockDriverState *bs,
int64_t refcount_block_offset = 0;
int64_t table_index = -1, old_table_index;
int first_index = -1, last_index = -1;
+ int ret;
#ifdef DEBUG_ALLOC2
printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
@@ -292,6 +293,7 @@ static int update_refcount(BlockDriverState *bs,
{
int block_index, refcount;
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 */
old_table_index = table_index;
@@ -309,10 +311,12 @@ static int update_refcount(BlockDriverState *bs,
}
/* Load the refcount block and allocate it if needed */
- refcount_block_offset = alloc_refcount_block(bs, cluster_index);
- if (refcount_block_offset < 0) {
- return refcount_block_offset;
+ new_block = alloc_refcount_block(bs, cluster_index);
+ if (new_block < 0) {
+ ret = new_block;
+ goto fail;
}
+ refcount_block_offset = new_block;
/* we can update the count and save it */
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 += addend;
- if (refcount < 0 || refcount > 0xffff)
- return -EINVAL;
+ if (refcount < 0 || refcount > 0xffff) {
+ ret = -EINVAL;
+ goto fail;
+ }
if (refcount == 0 && cluster_index < s->free_cluster_index) {
s->free_cluster_index = cluster_index;
}
s->refcount_block_cache[block_index] = cpu_to_be16(refcount);
}
+ ret = 0;
+fail:
+
/* Write last changed block to disk */
if (refcount_block_offset != 0) {
if (write_refcount_block_entries(s, refcount_block_offset,
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 */