[PATCH 4/6] io_uring: let fast poll support multishot

[Hao Xu <haoxu@linux.alibaba.com>]

For operations like accept, multishot is a useful feature, since we can
reduce a number of accept sqe. Let's integrate it to fast poll, it may
be good for other operations in the future.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
 fs/io_uring.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index d6df60c4cdb9..dae7044e0c24 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5277,8 +5277,15 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked)
 		return;
 	}
 
-	hash_del(&req->hash_node);
-	io_poll_remove_double(req);
+	if (READ_ONCE(apoll->poll.canceled))
+		apoll->poll.events |= EPOLLONESHOT;
+	if (apoll->poll.events & EPOLLONESHOT) {
+		hash_del(&req->hash_node);
+		io_poll_remove_double(req);
+	} else {
+		add_wait_queue(apoll->poll.head, &apoll->poll.wait);
+	}
+
 	spin_unlock(&ctx->completion_lock);
 
 	if (!READ_ONCE(apoll->poll.canceled))
@@ -5366,7 +5373,7 @@ static int io_arm_poll_handler(struct io_kiocb *req)
 	struct io_ring_ctx *ctx = req->ctx;
 	struct async_poll *apoll;
 	struct io_poll_table ipt;
-	__poll_t ret, mask = EPOLLONESHOT | POLLERR | POLLPRI;
+	__poll_t ret, mask = POLLERR | POLLPRI;
 	int rw;
 
 	if (!req->file || !file_can_poll(req->file))
@@ -5388,6 +5395,8 @@ static int io_arm_poll_handler(struct io_kiocb *req)
 		rw = WRITE;
 		mask |= POLLOUT | POLLWRNORM;
 	}
+	if (!(req->flags & REQ_F_APOLL_MULTISHOT))
+		mask |= EPOLLONESHOT;
 
 	/* if we can't nonblock try, then no point in arming a poll handler */
 	if (!io_file_supports_nowait(req, rw))
-- 
2.24.4