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

Greg Kroah-Hartman
2020-03-03T17:45:46Z

From: Stefano Garzarella <sgarzare@redhat.com>

[ 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@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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