io_uring: add a helper for apoll alloc

Extract a helper function for apoll allocation, makes the code easier to
read.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2f93282b47dd678e805dd0d7097f66968ced495c.1655990418.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/poll.c

@@ -508,10 +508,33 @@ static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
 	__io_queue_proc(&apoll->poll, pt, head, &apoll->double_poll);
 }
 
+static struct async_poll *io_req_alloc_apoll(struct io_kiocb *req,
+					     unsigned issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct async_poll *apoll;
+
+	if (req->flags & REQ_F_POLLED) {
+		apoll = req->apoll;
+		kfree(apoll->double_poll);
+	} else if (!(issue_flags & IO_URING_F_UNLOCKED) &&
+		   !list_empty(&ctx->apoll_cache)) {
+		apoll = list_first_entry(&ctx->apoll_cache, struct async_poll,
+						poll.wait.entry);
+		list_del_init(&apoll->poll.wait.entry);
+	} else {
+		apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
+		if (unlikely(!apoll))
+			return NULL;
+	}
+	apoll->double_poll = NULL;
+	req->apoll = apoll;
+	return apoll;
+}
+
 int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
 {
 	const struct io_op_def *def = &io_op_defs[req->opcode];
-	struct io_ring_ctx *ctx = req->ctx;
 	struct async_poll *apoll;
 	struct io_poll_table ipt;
 	__poll_t mask = POLLPRI | POLLERR | EPOLLET;
@@ -546,21 +569,10 @@ int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
 	}
 	if (def->poll_exclusive)
 		mask |= EPOLLEXCLUSIVE;
-	if (req->flags & REQ_F_POLLED) {
-		apoll = req->apoll;
-		kfree(apoll->double_poll);
-	} else if (!(issue_flags & IO_URING_F_UNLOCKED) &&
-		   !list_empty(&ctx->apoll_cache)) {
-		apoll = list_first_entry(&ctx->apoll_cache, struct async_poll,
-						poll.wait.entry);
-		list_del_init(&apoll->poll.wait.entry);
-	} else {
-		apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
-		if (unlikely(!apoll))
-			return IO_APOLL_ABORTED;
-	}
-	apoll->double_poll = NULL;
-	req->apoll = apoll;
+
+	apoll = io_req_alloc_apoll(req, issue_flags);
+	if (!apoll)
+		return IO_APOLL_ABORTED;
 	req->flags |= REQ_F_POLLED;
 	ipt.pt._qproc = io_async_queue_proc;