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qcow2: Rewrite qcow2_alloc_bytes() 

qcow2_alloc_bytes() is a function with insufficient error handling and
an unnecessary goto. This patch rewrites it.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2015-02-06 09:39:16 -05:00 committed by Kevin Wolf
parent 8e8cb375e0
commit 8c44dfbc62
1 changed files with 40 additions and 40 deletions
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80
block/qcow2-refcount.c
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@ -759,54 +759,54 @@ 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;
size_t free_in_cluster;
int ret;
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));
offset = s->free_byte_offset;
if (offset) {
int refcount = qcow2_get_refcount(bs, offset >> s->cluster_bits);
if (refcount < 0) {
return refcount;
}
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;
}
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;
if (refcount == 0xffff) {
offset = 0;
}
}
/* The cluster refcount was incremented, either by qcow2_alloc_clusters()
* or explicitly by qcow2_update_cluster_refcount(). Refcount blocks must
* be flushed before the caller's L2 table updates.
*/
free_in_cluster = s->cluster_size - offset_into_cluster(s, offset);
if (!offset || free_in_cluster < size) {
int64_t new_cluster = alloc_clusters_noref(bs, s->cluster_size);
if (new_cluster < 0) {
return new_cluster;
}
if (!offset || ROUND_UP(offset, s->cluster_size) != new_cluster) {
offset = new_cluster;
}
}
assert(offset);
ret = update_refcount(bs, offset, size, 1, QCOW2_DISCARD_NEVER);
if (ret < 0) {
return ret;
}
/* The cluster refcount was incremented; refcount blocks must be flushed
* before the caller's L2 table updates. */
qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);
s->free_byte_offset = offset + size;
if (!offset_into_cluster(s, s->free_byte_offset)) {
s->free_byte_offset = 0;
}
return offset;
}