io_uring: refactor provide/remove buffer locking

Always complete request holding the mutex instead of doing that strange
dancing with conditional ordering.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3966,14 +3966,9 @@ static int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
 	if (ret < 0)
 		req_set_fail_links(req);
 
-	/* need to hold the lock to complete IOPOLL requests */
-	if (ctx->flags & IORING_SETUP_IOPOLL) {
-		__io_req_complete(req, issue_flags, ret, 0);
-		io_ring_submit_unlock(ctx, !force_nonblock);
-	} else {
-		io_ring_submit_unlock(ctx, !force_nonblock);
-		__io_req_complete(req, issue_flags, ret, 0);
-	}
+	/* complete before unlock, IOPOLL may need the lock */
+	__io_req_complete(req, issue_flags, ret, 0);
+	io_ring_submit_unlock(ctx, !force_nonblock);
 	return 0;
 }
 
@@ -4055,15 +4050,9 @@ static int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
 	}
 	if (ret < 0)
 		req_set_fail_links(req);
-
-	/* need to hold the lock to complete IOPOLL requests */
-	if (ctx->flags & IORING_SETUP_IOPOLL) {
-		__io_req_complete(req, issue_flags, ret, 0);
-		io_ring_submit_unlock(ctx, !force_nonblock);
-	} else {
-		io_ring_submit_unlock(ctx, !force_nonblock);
-		__io_req_complete(req, issue_flags, ret, 0);
-	}
+	/* complete before unlock, IOPOLL may need the lock */
+	__io_req_complete(req, issue_flags, ret, 0);
+	io_ring_submit_unlock(ctx, !force_nonblock);
 	return 0;
 }