block: Remove bdrv_set_aio_context()

All callers of bdrv_set_aio_context() are eliminated now, they have
moved to bdrv_try_set_aio_context() and related safe functions. Remove
bdrv_set_aio_context().

With this, we can now know that the .set_aio_ctx callback must be
present in bdrv_set_aio_context_ignore() because
bdrv_can_set_aio_context() would have returned false previously, so
instead of checking the condition, we can assert it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -5789,8 +5789,17 @@ static void bdrv_attach_aio_context(BlockDriverState *bs,
     bs->walking_aio_notifiers = false;
 }
 
-/* @ignore will accumulate all visited BdrvChild object. The caller is
- * responsible for freeing the list afterwards. */
+/*
+ * Changes the AioContext used for fd handlers, timers, and BHs by this
+ * BlockDriverState and all its children and parents.
+ *
+ * The caller must own the AioContext lock for the old AioContext of bs, but it
+ * must not own the AioContext lock for new_context (unless new_context is the
+ * same as the current context of bs).
+ *
+ * @ignore will accumulate all visited BdrvChild object. The caller is
+ * responsible for freeing the list afterwards.
+ */
 void bdrv_set_aio_context_ignore(BlockDriverState *bs,
                                  AioContext *new_context, GSList **ignore)
 {
@@ -5813,11 +5822,10 @@ void bdrv_set_aio_context_ignore(BlockDriverState *bs,
         if (g_slist_find(*ignore, child)) {
             continue;
         }
-        if (child->role->set_aio_ctx) {
+        assert(child->role->set_aio_ctx);
         *ignore = g_slist_prepend(*ignore, child);
         child->role->set_aio_ctx(child, new_context, ignore);
     }
-    }
 
     bdrv_detach_aio_context(bs);
 
@@ -5830,16 +5838,6 @@ void bdrv_set_aio_context_ignore(BlockDriverState *bs,
     aio_context_release(new_context);
 }
 
-/* The caller must own the AioContext lock for the old AioContext of bs, but it
- * must not own the AioContext lock for new_context (unless new_context is
- * the same as the current context of bs). */
-void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
-{
-    GSList *ignore_list = NULL;
-    bdrv_set_aio_context_ignore(bs, new_context, &ignore_list);
-    g_slist_free(ignore_list);
-}
-
 static bool bdrv_parent_can_set_aio_context(BdrvChild *c, AioContext *ctx,
                                             GSList **ignore, Error **errp)
 {

docs/devel/multiple-iothreads.txt

@@ -109,7 +109,7 @@ The AioContext originates from the QEMU block layer, even though nowadays
 AioContext is a generic event loop that can be used by any QEMU subsystem.
 
 The block layer has support for AioContext integrated.  Each BlockDriverState
-is associated with an AioContext using bdrv_set_aio_context() and
+is associated with an AioContext using bdrv_try_set_aio_context() and
 bdrv_get_aio_context().  This allows block layer code to process I/O inside the
 right AioContext.  Other subsystems may wish to follow a similar approach.
 
@@ -134,5 +134,5 @@ Long-running jobs (usually in the form of coroutines) are best scheduled in
 the BlockDriverState's AioContext to avoid the need to acquire/release around
 each bdrv_*() call.  The functions bdrv_add/remove_aio_context_notifier,
 or alternatively blk_add/remove_aio_context_notifier if you use BlockBackends,
-can be used to get a notification whenever bdrv_set_aio_context() moves a
+can be used to get a notification whenever bdrv_try_set_aio_context() moves a
 BlockDriverState to a different AioContext.

include/block/block.h

@@ -583,15 +583,6 @@ AioContext *bdrv_get_aio_context(BlockDriverState *bs);
  */
 void bdrv_coroutine_enter(BlockDriverState *bs, Coroutine *co);
 
-/**
- * bdrv_set_aio_context:
- *
- * Changes the #AioContext used for fd handlers, timers, and BHs by this
- * BlockDriverState and all its children.
- *
- * This function must be called with iothread lock held.
- */
-void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context);
 void bdrv_set_aio_context_ignore(BlockDriverState *bs,
                                  AioContext *new_context, GSList **ignore);
 int bdrv_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,