qcow2_alloc_bytes() is a function with insufficient error handling and
an unnecessary goto. This patch rewrites it.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
v2:
- s/free_cluster_index/free_byte_index/ [Eric]
- added an assertion at the start of the function that
s->free_byte_offset is either 0 or points to the tail of a cluster
(but never to the start)
- use ROUND_UP() instead of start_of_cluster() + cluster_size [Eric]
- added an assertion that s->free_byte_offset is set before using it
[Eric]
---
block/qcow2-refcount.c | 77 +++++++++++++++++++++++++++++---------------------
1 file changed, 45 insertions(+), 32 deletions(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 9afdb40..eede60d 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -759,46 +759,51 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs,
uint64_t offset,
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
{
BDRVQcowState *s = bs->opaque;
- int64_t offset, cluster_offset;
- int free_in_cluster;
+ int64_t offset, new_cluster = 0, cluster_end;
+ size_t free_in_cluster;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES);
assert(size > 0 && size <= s->cluster_size);
- if (s->free_byte_offset == 0) {
- offset = qcow2_alloc_clusters(bs, s->cluster_size);
- if (offset < 0) {
- return offset;
+ assert(!s->free_byte_offset || offset_into_cluster(s,
s->free_byte_offset));
+
+ if (s->free_byte_offset) {
+ int refcount = qcow2_get_refcount(bs,
+ s->free_byte_offset >> s->cluster_bits);
+ if (refcount < 0) {
+ return refcount;
+ }
+
+ if (refcount == 0xffff) {
+ s->free_byte_offset = 0;
}
- s->free_byte_offset = offset;
}
- redo:
+
free_in_cluster = s->cluster_size -
offset_into_cluster(s, s->free_byte_offset);
- if (size <= free_in_cluster) {
- /* enough space in current cluster */
- offset = s->free_byte_offset;
- s->free_byte_offset += size;
- free_in_cluster -= size;
- if (free_in_cluster == 0)
- s->free_byte_offset = 0;
- if (offset_into_cluster(s, offset) != 0)
- qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
- QCOW2_DISCARD_NEVER);
- } else {
- offset = qcow2_alloc_clusters(bs, s->cluster_size);
- if (offset < 0) {
- return offset;
+
+ if (!s->free_byte_offset || free_in_cluster < size) {
+ new_cluster = qcow2_alloc_clusters(bs, s->cluster_size);
+ if (new_cluster < 0) {
+ return new_cluster;
+ }
+
+ cluster_end = ROUND_UP(s->free_byte_offset, s->cluster_size);
+ if (!s->free_byte_offset || cluster_end != new_cluster) {
+ s->free_byte_offset = new_cluster;
}
- cluster_offset = start_of_cluster(s, s->free_byte_offset);
- if ((cluster_offset + s->cluster_size) == offset) {
- /* we are lucky: contiguous data */
- offset = s->free_byte_offset;
- qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
- QCOW2_DISCARD_NEVER);
- s->free_byte_offset += size;
- } else {
- s->free_byte_offset = offset;
- goto redo;
+ }
+
+ assert(s->free_byte_offset);
+ if (offset_into_cluster(s, s->free_byte_offset)) {
+ int ret = qcow2_update_cluster_refcount(bs,
+ s->free_byte_offset >> s->cluster_bits, 1,
+ QCOW2_DISCARD_NEVER);
+ if (ret < 0) {
+ if (new_cluster > 0) {
+ qcow2_free_clusters(bs, new_cluster, s->cluster_size,
+ QCOW2_DISCARD_OTHER);
+ }
+ return ret;
}
}
@@ -807,6 +812,14 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
* be flushed before the caller's L2 table updates.
*/
qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);
+
+ offset = s->free_byte_offset;
+
+ s->free_byte_offset += size;
+ if (!offset_into_cluster(s, s->free_byte_offset)) {
+ s->free_byte_offset = 0;
+ }
+
return offset;
}
--
2.1.0
