io_uring: hold locks for io_req_complete_failed

A preparation patch, make sure we always hold uring_lock around
io_req_complete_failed(). The only place deviating from the rule
is io_cancel_defer_files(), queue a tw instead.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/70760344eadaecf2939287084b9d4ba5c05a6984.1669203009.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -862,9 +862,12 @@ inline void __io_req_complete(struct io_kiocb *req, unsigned issue_flags)
 }
 
 void io_req_complete_failed(struct io_kiocb *req, s32 res)
+	__must_hold(&ctx->uring_lock)
 {
 	const struct io_op_def *def = &io_op_defs[req->opcode];
 
+	lockdep_assert_held(&req->ctx->uring_lock);
+
 	req_set_fail(req);
 	io_req_set_res(req, res, io_put_kbuf(req, IO_URING_F_UNLOCKED));
 	if (def->fail)
@@ -1615,6 +1618,7 @@ static u32 io_get_sequence(struct io_kiocb *req)
 }
 
 static __cold void io_drain_req(struct io_kiocb *req)
+	__must_hold(&ctx->uring_lock)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_defer_entry *de;
@@ -2849,7 +2853,7 @@ static __cold bool io_cancel_defer_files(struct io_ring_ctx *ctx,
 	while (!list_empty(&list)) {
 		de = list_first_entry(&list, struct io_defer_entry, list);
 		list_del_init(&de->list);
-		io_req_complete_failed(de->req, -ECANCELED);
+		io_req_task_queue_fail(de->req, -ECANCELED);
 		kfree(de);
 	}
 	return true;