io_uring: use tw for putting rsrc

Use task_work for completing rsrc removals, it'll be needed later for
spinlock optimisations.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cbba5d53a11ee6fc2194dacea262c1d733c8b529.1670384893.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/io_uring_types.h

@@ -328,6 +328,7 @@ struct io_ring_ctx {
 	struct io_rsrc_data		*buf_data;
 
 	struct delayed_work		rsrc_put_work;
+	struct callback_head		rsrc_put_tw;
 	struct llist_head		rsrc_put_llist;
 	struct list_head		rsrc_ref_list;
 	spinlock_t			rsrc_ref_lock;

io_uring/io_uring.c

@@ -326,6 +326,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	spin_lock_init(&ctx->rsrc_ref_lock);
 	INIT_LIST_HEAD(&ctx->rsrc_ref_list);
 	INIT_DELAYED_WORK(&ctx->rsrc_put_work, io_rsrc_put_work);
+	init_task_work(&ctx->rsrc_put_tw, io_rsrc_put_tw);
 	init_llist_head(&ctx->rsrc_put_llist);
 	init_llist_head(&ctx->work_llist);
 	INIT_LIST_HEAD(&ctx->tctx_list);

io_uring/rsrc.c

@@ -204,6 +204,14 @@ void io_rsrc_put_work(struct work_struct *work)
 	}
 }
 
+void io_rsrc_put_tw(struct callback_head *cb)
+{
+	struct io_ring_ctx *ctx = container_of(cb, struct io_ring_ctx,
+					       rsrc_put_tw);
+
+	io_rsrc_put_work(&ctx->rsrc_put_work.work);
+}
+
 void io_wait_rsrc_data(struct io_rsrc_data *data)
 {
 	if (data && !atomic_dec_and_test(&data->refs))
@@ -242,8 +250,15 @@ static __cold void io_rsrc_node_ref_zero(struct percpu_ref *ref)
 	}
 	spin_unlock_irqrestore(&ctx->rsrc_ref_lock, flags);
 
-	if (first_add)
-		mod_delayed_work(system_wq, &ctx->rsrc_put_work, delay);
+	if (!first_add)
+		return;
+
+	if (ctx->submitter_task) {
+		if (!task_work_add(ctx->submitter_task, &ctx->rsrc_put_tw,
+				   ctx->notify_method))
+			return;
+	}
+	mod_delayed_work(system_wq, &ctx->rsrc_put_work, delay);
 }
 
 static struct io_rsrc_node *io_rsrc_node_alloc(void)

io_uring/rsrc.h

@@ -53,6 +53,7 @@ struct io_mapped_ubuf {
 	struct bio_vec	bvec[];
 };
 
+void io_rsrc_put_tw(struct callback_head *cb);
 void io_rsrc_put_work(struct work_struct *work);
 void io_rsrc_refs_refill(struct io_ring_ctx *ctx);
 void io_wait_rsrc_data(struct io_rsrc_data *data);