qcow2: Read refcount before L2 table in expand_zero_clusters_in_l1()

At the moment it doesn't really make a difference whether we call
qcow2_get_refcount() before of after reading the L2 table, but if we
want to support L2 slices we'll need to read the refcount first.

This patch simply changes the order of those two operations to prepare
for that. The patch with the actual semantic changes will be easier to
read because of this.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 947a91d934053a2dbfef979aeb9568f57ef57c5d.1517840877.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f440105f6cd2d6f68725a98ff8a1b7cc5c9bede6..1041dcb6dd2183c445d49436041c7a27d24a1f1f 100644 (file)
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1898,6 +1898,12 @@ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
             goto fail;
         }
 
+        ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits,
+                                 &l2_refcount);
+        if (ret < 0) {
+            goto fail;
+        }
+
         if (is_active_l1) {
             /* get active L2 tables from cache */
             ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
@@ -1911,12 +1917,6 @@ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
             goto fail;
         }
 
-        ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits,
-                                 &l2_refcount);
-        if (ret < 0) {
-            goto fail;
-        }
-
         for (j = 0; j < s->l2_size; j++) {
             uint64_t l2_entry = be64_to_cpu(l2_table[j]);
             int64_t offset = l2_entry & L2E_OFFSET_MASK;