[PATCH 5.5 033/176] io_uring: flush overflowed CQ events in the io_uring_poll()

[Greg Kroah-Hartman]

From: Stefano Garzarella <sgarzare@xxxxxxxxxx>

[ Upstream commit 63e5d81f72af1bf370bf8a6745b0a8d71a7bb37d ]

In io_uring_poll() we must flush overflowed CQ events before to
check if there are CQ events available, to avoid missing events.

We call the io_cqring_events() that checks and flushes any overflow
and returns the number of CQ events available.

Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 678c62782ba3b..de4bd647cd1df 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4970,7 +4970,7 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 	if (READ_ONCE(ctx->rings->sq.tail) - ctx->cached_sq_head !=
 	    ctx->rings->sq_ring_entries)
 		mask |= EPOLLOUT | EPOLLWRNORM;
-	if (READ_ONCE(ctx->rings->cq.head) != ctx->cached_cq_tail)
+	if (io_cqring_events(ctx, false))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
 	return mask;
-- 
2.20.1