block: use the new _change_ API instead of _can_set_ and _set_

Replace all direct usage of ->can_set_aio_ctx and ->set_aio_ctx,
and call bdrv_child_try_change_aio_context() in
bdrv_try_set_aio_context(), the main function called through
the whole block layer.

From this point onwards, ->can_set_aio_ctx and ->set_aio_ctx
won't be used anymore.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221025084952.2139888-8-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -2924,17 +2924,21 @@ static void bdrv_attach_child_common_abort(void *opaque)
     }
 
     if (bdrv_child_get_parent_aio_context(s->child) != s->old_parent_ctx) {
-        GSList *ignore;
+        Transaction *tran;
+        GHashTable *visited;
+        bool ret;
 
-        /* No need to ignore `child`, because it has been detached already */
-        ignore = NULL;
-        s->child->klass->can_set_aio_ctx(s->child, s->old_parent_ctx, &ignore,
-                                         &error_abort);
-        g_slist_free(ignore);
+        tran = tran_new();
 
-        ignore = NULL;
-        s->child->klass->set_aio_ctx(s->child, s->old_parent_ctx, &ignore);
-        g_slist_free(ignore);
+        /* No need to visit `child`, because it has been detached already */
+        visited = g_hash_table_new(NULL, NULL);
+        ret = s->child->klass->change_aio_ctx(s->child, s->old_parent_ctx,
+                                              visited, tran, &error_abort);
+        g_hash_table_destroy(visited);
+
+        /* transaction is supposed to always succeed */
+        assert(ret == true);
+        tran_commit(tran);
     }
 
     bdrv_unref(bs);
@@ -2989,18 +2993,20 @@ static BdrvChild *bdrv_attach_child_common(BlockDriverState *child_bs,
         Error *local_err = NULL;
         int ret = bdrv_try_set_aio_context(child_bs, parent_ctx, &local_err);
 
-        if (ret < 0 && child_class->can_set_aio_ctx) {
-            GSList *ignore = g_slist_prepend(NULL, new_child);
-            if (child_class->can_set_aio_ctx(new_child, child_ctx, &ignore,
-                                             NULL))
-            {
+        if (ret < 0 && child_class->change_aio_ctx) {
+            Transaction *tran = tran_new();
+            GHashTable *visited = g_hash_table_new(NULL, NULL);
+            bool ret_child;
+
+            g_hash_table_add(visited, new_child);
+            ret_child = child_class->change_aio_ctx(new_child, child_ctx,
+                                                    visited, tran, NULL);
+            if (ret_child == true) {
                 error_free(local_err);
                 ret = 0;
-                g_slist_free(ignore);
-                ignore = g_slist_prepend(NULL, new_child);
-                child_class->set_aio_ctx(new_child, child_ctx, &ignore);
             }
-            g_slist_free(ignore);
+            tran_finalize(tran, ret_child == true ? 0 : -1);
+            g_hash_table_destroy(visited);
         }
 
         if (ret < 0) {
@@ -7601,7 +7607,7 @@ int bdrv_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,
                              Error **errp)
 {
     GLOBAL_STATE_CODE();
-    return bdrv_child_try_set_aio_context(bs, ctx, NULL, errp);
+    return bdrv_child_try_change_aio_context(bs, ctx, NULL, errp);
 }
 
 void bdrv_add_aio_context_notifier(BlockDriverState *bs,

block/block-backend.c

@@ -2153,8 +2153,12 @@ static int blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,
         bdrv_ref(bs);
 
         if (update_root_node) {
-            ret = bdrv_child_try_set_aio_context(bs, new_context, blk->root,
-                                                 errp);
+            /*
+             * update_root_node MUST be false for blk_root_set_aio_ctx_commit(),
+             * as we are already in the commit function of a transaction.
+             */
+            ret = bdrv_child_try_change_aio_context(bs, new_context, blk->root,
+                                                    errp);
             if (ret < 0) {
                 bdrv_unref(bs);
                 return ret;