io_uring: remove req init from io_get_req()

io_get_req() do two different things: io_kiocb allocation and
initialisation. Move init part out of it and rename into
io_alloc_req(). It's simpler this way and also have better data
locality.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1293,8 +1293,8 @@ static struct io_kiocb *io_get_fallback_req(struct io_ring_ctx *ctx)
 	return NULL;
 }
 
-static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
-				   struct io_submit_state *state)
+static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx,
+				     struct io_submit_state *state)
 {
 	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
 	struct io_kiocb *req;
@@ -1327,22 +1327,9 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 		req = state->reqs[state->free_reqs];
 	}
 
-got_it:
-	req->io = NULL;
-	req->file = NULL;
-	req->ctx = ctx;
-	req->flags = 0;
-	/* one is dropped after submission, the other at completion */
-	refcount_set(&req->refs, 2);
-	req->task = NULL;
-	req->result = 0;
-	INIT_IO_WORK(&req->work, io_wq_submit_work);
 	return req;
 fallback:
-	req = io_get_fallback_req(ctx);
-	if (req)
-		goto got_it;
-	return NULL;
+	return io_get_fallback_req(ctx);
 }
 
 static inline void io_put_file(struct io_kiocb *req, struct file *file,
@@ -5804,6 +5791,28 @@ static inline void io_consume_sqe(struct io_ring_ctx *ctx)
 	ctx->cached_sq_head++;
 }
 
+static void io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
+			const struct io_uring_sqe *sqe)
+{
+	/*
+	 * All io need record the previous position, if LINK vs DARIN,
+	 * it can be used to mark the position of the first IO in the
+	 * link list.
+	 */
+	req->sequence = ctx->cached_sq_head;
+	req->opcode = READ_ONCE(sqe->opcode);
+	req->user_data = READ_ONCE(sqe->user_data);
+	req->io = NULL;
+	req->file = NULL;
+	req->ctx = ctx;
+	req->flags = 0;
+	/* one is dropped after submission, the other at completion */
+	refcount_set(&req->refs, 2);
+	req->task = NULL;
+	req->result = 0;
+	INIT_IO_WORK(&req->work, io_wq_submit_work);
+}
+
 static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 			  struct file *ring_file, int ring_fd,
 			  struct mm_struct **mm, bool async)
@@ -5844,23 +5853,15 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 			io_consume_sqe(ctx);
 			break;
 		}
-		req = io_get_req(ctx, statep);
+		req = io_alloc_req(ctx, statep);
 		if (unlikely(!req)) {
 			if (!submitted)
 				submitted = -EAGAIN;
 			break;
 		}
 
-		/*
-		 * All io need record the previous position, if LINK vs DARIN,
-		 * it can be used to mark the position of the first IO in the
-		 * link list.
-		 */
-		req->sequence = ctx->cached_sq_head;
-		req->opcode = READ_ONCE(sqe->opcode);
-		req->user_data = READ_ONCE(sqe->user_data);
+		io_init_req(ctx, req, sqe);
 		io_consume_sqe(ctx);
-
 		/* will complete beyond this point, count as submitted */
 		submitted++;