io_uring: refactor req allocation

Follow the io_get_sqe pattern returning the result via a pointer
and hide request cache refill inside io_alloc_req().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8c37c2e8a3cb5e4cd6a8ae3b91371227a92708a6.1674484266.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -2415,9 +2415,8 @@ int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
 		const struct io_uring_sqe *sqe;
 		struct io_kiocb *req;
 
-		if (unlikely(!io_alloc_req_refill(ctx)))
+		if (unlikely(!io_alloc_req(ctx, &req)))
 			break;
-		req = io_alloc_req(ctx);
 		if (unlikely(!io_get_sqe(ctx, &sqe))) {
 			io_req_add_to_cache(req, ctx);
 			break;
@@ -2736,14 +2735,14 @@ static int io_eventfd_unregister(struct io_ring_ctx *ctx)
 
 static void io_req_caches_free(struct io_ring_ctx *ctx)
 {
+	struct io_kiocb *req;
 	int nr = 0;
 
 	mutex_lock(&ctx->uring_lock);
 	io_flush_cached_locked_reqs(ctx, &ctx->submit_state);
 
 	while (!io_req_cache_empty(ctx)) {
-		struct io_kiocb *req = io_alloc_req(ctx);
-
+		req = io_extract_req(ctx);
 		kmem_cache_free(req_cachep, req);
 		nr++;
 	}

io_uring/io_uring.h

@@ -341,16 +341,9 @@ static inline bool io_req_cache_empty(struct io_ring_ctx *ctx)
 	return !ctx->submit_state.free_list.next;
 }
 
-static inline bool io_alloc_req_refill(struct io_ring_ctx *ctx)
-{
-	if (unlikely(io_req_cache_empty(ctx)))
-		return __io_alloc_req_refill(ctx);
-	return true;
-}
-
 extern struct kmem_cache *req_cachep;
 
-static inline struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
+static inline struct io_kiocb *io_extract_req(struct io_ring_ctx *ctx)
 {
 	struct io_kiocb *req;
 
@@ -360,6 +353,16 @@ static inline struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
 	return req;
 }
 
+static inline bool io_alloc_req(struct io_ring_ctx *ctx, struct io_kiocb **req)
+{
+	if (unlikely(io_req_cache_empty(ctx))) {
+		if (!__io_alloc_req_refill(ctx))
+			return false;
+	}
+	*req = io_extract_req(ctx);
+	return true;
+}
+
 static inline bool io_allowed_defer_tw_run(struct io_ring_ctx *ctx)
 {
 	return likely(ctx->submitter_task == current);

io_uring/notif.c

@@ -68,9 +68,8 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
 	struct io_kiocb *notif;
 	struct io_notif_data *nd;
 
-	if (unlikely(!io_alloc_req_refill(ctx)))
+	if (unlikely(!io_alloc_req(ctx, &notif)))
 		return NULL;
-	notif = io_alloc_req(ctx);
 	notif->opcode = IORING_OP_NOP;
 	notif->flags = 0;
 	notif->file = NULL;