[PATCH v2] splice: pass a poll key when waking pipe readers and writers

[Breno Leitao]

wakeup_pipe_readers() and wakeup_pipe_writers() wake the pipe wait queues
with a NULL key.  ep_poll_callback() and pollwake() only filter on the
registered event mask when a key is supplied, so every epoll, poll() and
select() waiter on the pipe is woken, whether or not it asked for the
event that occurred.

anon_pipe_read() and anon_pipe_write() already pass EPOLLIN | EPOLLRDNORM
and EPOLLOUT | EPOLLWRNORM when waking the same wait queues.  Do the same
here.

This is not visible in common pipe use: ordinary pipelines move data with
read()/write(), which already passes the key.

While here, both helpers open-code wq_has_sleeper(); use it instead.

Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
Changes in v2:
- Use wq_has_sleeper() helper, as suggested by Oleg Nesterov
- Link to v1: https://patch.msgid.link/20260916-b4-splice-poll-key-v1-1-438a19351efb@xxxxxxxxxx
---
 fs/splice.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 9d8f63e2fd1ab..65f9090c3438c 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -177,9 +177,9 @@ static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 
 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 {
-	smp_mb();
-	if (waitqueue_active(&pipe->rd_wait))
-		wake_up_interruptible(&pipe->rd_wait);
+	if (wq_has_sleeper(&pipe->rd_wait))
+		wake_up_interruptible_poll(&pipe->rd_wait,
+					   EPOLLIN | EPOLLRDNORM);
 	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 }
 
@@ -413,9 +413,9 @@ EXPORT_SYMBOL(nosteal_pipe_buf_ops);
 
 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 {
-	smp_mb();
-	if (waitqueue_active(&pipe->wr_wait))
-		wake_up_interruptible(&pipe->wr_wait);
+	if (wq_has_sleeper(&pipe->wr_wait))
+		wake_up_interruptible_poll(&pipe->wr_wait,
+					   EPOLLOUT | EPOLLWRNORM);
 	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 }
 

---
base-commit: 587858367581b9c55c3690f4e63382ad622719d4
change-id: 20260915-b4-splice-poll-key-bc7d5d0d0f68

Best regards,
--  
Breno Leitao <leitao@xxxxxxxxxx>