[v4,14/45] block/snapshot: drop indirection around bdrv_snapshot_fallback_ptr

Commit Message

Vladimir Sementsov-Ogievskiy March 29, 2022, 8:40 p.m. UTC

Now the indirection is not actually used, we can safely reduce it to
simple pointer.

Signed-off-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
---
 block/snapshot.c | 39 +++++++++++++++++----------------------
 1 file changed, 17 insertions(+), 22 deletions(-)

Patch

diff --git a/block/snapshot.c b/block/snapshot.c
index cb184d70b4..e32f9cb2ad 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -148,34 +148,29 @@  bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
 }
 
 /**
- * Return a pointer to the child BDS pointer to which we can fall
+ * Return a pointer to child of given BDS to which we can fall
  * back if the given BDS does not support snapshots.
  * Return NULL if there is no BDS to (safely) fall back to.
- *
- * We need to return an indirect pointer because bdrv_snapshot_goto()
- * has to modify the BdrvChild pointer.
  */
-static BdrvChild **bdrv_snapshot_fallback_ptr(BlockDriverState *bs)
+static BdrvChild *bdrv_snapshot_fallback_ptr(BlockDriverState *bs)
 {
-    BdrvChild **fallback;
-    BdrvChild *child = bdrv_primary_child(bs);
+    BdrvChild *fallback = bdrv_primary_child(bs);
+    BdrvChild *child;
 
     /* We allow fallback only to primary child */
-    if (!child) {
+    if (!fallback) {
         return NULL;
     }
-    fallback = (child == bs->file ? &bs->file : &bs->backing);
-    assert(*fallback == child);
 
     /*
      * Check that there are no other children that would need to be
      * snapshotted.  If there are, it is not safe to fall back to
-     * *fallback.
+     * fallback.
      */
     QLIST_FOREACH(child, &bs->children, next) {
         if (child->role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
                            BDRV_CHILD_FILTERED) &&
-            child != *fallback)
+            child != fallback)
         {
             return NULL;
         }
@@ -186,8 +181,8 @@  static BdrvChild **bdrv_snapshot_fallback_ptr(BlockDriverState *bs)
 
 static BlockDriverState *bdrv_snapshot_fallback(BlockDriverState *bs)
 {
-    BdrvChild **child_ptr = bdrv_snapshot_fallback_ptr(bs);
-    return child_ptr ? (*child_ptr)->bs : NULL;
+    BdrvChild *child_ptr = bdrv_snapshot_fallback_ptr(bs);
+    return child_ptr ? child_ptr->bs : NULL;
 }
 
 int bdrv_can_snapshot(BlockDriverState *bs)
@@ -230,7 +225,7 @@  int bdrv_snapshot_goto(BlockDriverState *bs,
                        Error **errp)
 {
     BlockDriver *drv = bs->drv;
-    BdrvChild **fallback_ptr;
+    BdrvChild *fallback;
     int ret, open_ret;
 
     if (!drv) {
@@ -251,13 +246,13 @@  int bdrv_snapshot_goto(BlockDriverState *bs,
         return ret;
     }
 
-    fallback_ptr = bdrv_snapshot_fallback_ptr(bs);
-    if (fallback_ptr) {
+    fallback = bdrv_snapshot_fallback_ptr(bs);
+    if (fallback) {
         QDict *options;
         QDict *file_options;
         Error *local_err = NULL;
-        BlockDriverState *fallback_bs = (*fallback_ptr)->bs;
-        char *subqdict_prefix = g_strdup_printf("%s.", (*fallback_ptr)->name);
+        BlockDriverState *fallback_bs = fallback->bs;
+        char *subqdict_prefix = g_strdup_printf("%s.", fallback->name);
 
         options = qdict_clone_shallow(bs->options);
 
@@ -268,8 +263,8 @@  int bdrv_snapshot_goto(BlockDriverState *bs,
         qobject_unref(file_options);
         g_free(subqdict_prefix);
 
-        /* Force .bdrv_open() below to re-attach fallback_bs on *fallback_ptr */
-        qdict_put_str(options, (*fallback_ptr)->name,
+        /* Force .bdrv_open() below to re-attach fallback_bs on fallback */
+        qdict_put_str(options, fallback->name,
                       bdrv_get_node_name(fallback_bs));
 
         /* Now close bs, apply the snapshot on fallback_bs, and re-open bs */
@@ -278,7 +273,7 @@  int bdrv_snapshot_goto(BlockDriverState *bs,
         }
 
         /* .bdrv_open() will re-attach it */
-        bdrv_unref_child(bs, *fallback_ptr);
+        bdrv_unref_child(bs, fallback);
 
         ret = bdrv_snapshot_goto(fallback_bs, snapshot_id, errp);
         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);