block/qcow2: Make get_refcount() global

Reading the refcount of a cluster is an operation which can be useful in
all of the qcow2 code, so make that function globally available.

While touching this function, amend the comment describing the "addend"
parameter: It is (no longer, if it ever was) necessary to have it set to
-1 or 1; any value is fine.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NBenoît Canet <benoit.canet@nodalink.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NBenoit Canet <benoit@irqsave.net>
Message-id: 1414404776-4919-6-git-send-email-mreitz@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/qcow2-refcount.c

@@ -91,7 +91,7 @@ static int load_refcount_block(BlockDriverState *bs,
  * return value is the refcount of the cluster, negative values are -errno
  * and indicate an error.
  */
-static int get_refcount(BlockDriverState *bs, int64_t cluster_index)
+int qcow2_get_refcount(BlockDriverState *bs, int64_t cluster_index)
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t refcount_table_index, block_index;
@@ -629,8 +629,7 @@ fail:
 }
 
 /*
- * Increases or decreases the refcount of a given cluster by one.
- * addend must be 1 or -1.
+ * Increases or decreases the refcount of a given cluster.
  *
  * If the return value is non-negative, it is the new refcount of the cluster.
  * If it is negative, it is -errno and indicates an error.
@@ -649,7 +648,7 @@ int qcow2_update_cluster_refcount(BlockDriverState *bs,
         return ret;
     }
 
-    return get_refcount(bs, cluster_index);
+    return qcow2_get_refcount(bs, cluster_index);
 }
 
 
@@ -670,7 +669,7 @@ static int64_t alloc_clusters_noref(BlockDriverState *bs, uint64_t size)
 retry:
     for(i = 0; i < nb_clusters; i++) {
         uint64_t next_cluster_index = s->free_cluster_index++;
-        refcount = get_refcount(bs, next_cluster_index);
+        refcount = qcow2_get_refcount(bs, next_cluster_index);
 
         if (refcount < 0) {
             return refcount;
@@ -734,7 +733,7 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
         /* Check how many clusters there are free */
         cluster_index = offset >> s->cluster_bits;
         for(i = 0; i < nb_clusters; i++) {
-            refcount = get_refcount(bs, cluster_index++);
+            refcount = qcow2_get_refcount(bs, cluster_index++);
 
             if (refcount < 0) {
                 return refcount;
@@ -981,7 +980,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
                                     cluster_index, addend,
                                     QCOW2_DISCARD_SNAPSHOT);
                         } else {
-                            refcount = get_refcount(bs, cluster_index);
+                            refcount = qcow2_get_refcount(bs, cluster_index);
                         }
 
                         if (refcount < 0) {
@@ -1021,7 +1020,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
                 refcount = qcow2_update_cluster_refcount(bs, l2_offset >>
                         s->cluster_bits, addend, QCOW2_DISCARD_SNAPSHOT);
             } else {
-                refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
+                refcount = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits);
             }
             if (refcount < 0) {
                 ret = refcount;
@@ -1332,8 +1331,8 @@ fail:
  * Checks the OFLAG_COPIED flag for all L1 and L2 entries.
  *
  * This function does not print an error message nor does it increment
- * check_errors if get_refcount fails (this is because such an error will have
- * been already detected and sufficiently signaled by the calling function
+ * check_errors if qcow2_get_refcount fails (this is because such an error will
+ * have been already detected and sufficiently signaled by the calling function
  * (qcow2_check_refcounts) by the time this function is called).
  */
 static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res,
@@ -1354,7 +1353,7 @@ static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res,
             continue;
         }
 
-        refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
+        refcount = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits);
         if (refcount < 0) {
             /* don't print message nor increment check_errors */
             continue;
@@ -1396,7 +1395,8 @@ static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res,
 
             if ((cluster_type == QCOW2_CLUSTER_NORMAL) ||
                 ((cluster_type == QCOW2_CLUSTER_ZERO) && (data_offset != 0))) {
-                refcount = get_refcount(bs, data_offset >> s->cluster_bits);
+                refcount = qcow2_get_refcount(bs,
+                                              data_offset >> s->cluster_bits);
                 if (refcount < 0) {
                     /* don't print message nor increment check_errors */
                     continue;
@@ -1632,7 +1632,7 @@ static void compare_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
     int refcount1, refcount2, ret;
 
     for (i = 0, *highest_cluster = 0; i < nb_clusters; i++) {
-        refcount1 = get_refcount(bs, i);
+        refcount1 = qcow2_get_refcount(bs, i);
         if (refcount1 < 0) {
             fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n",
                 i, strerror(-refcount1));

block/qcow2.h

@@ -487,6 +487,8 @@ void qcow2_signal_corruption(BlockDriverState *bs, bool fatal, int64_t offset,
 int qcow2_refcount_init(BlockDriverState *bs);
 void qcow2_refcount_close(BlockDriverState *bs);
 
+int qcow2_get_refcount(BlockDriverState *bs, int64_t cluster_index);
+
 int qcow2_update_cluster_refcount(BlockDriverState *bs, int64_t cluster_index,
                                   int addend, enum qcow2_discard_type type);