[PATCH 3/5] eventpoll: add epoll_sendevents() helper

[Jens Axboe <axboe@kernel.dk>]

Basic helper that copies ready events to the specified userspace
address. The event checking is quick and racy, it's up to the caller
to ensure it retries appropriately in case 0 events are copied.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/eventpoll.c            | 20 ++++++++++++++++++++
 include/linux/eventpoll.h |  4 ++++
 2 files changed, 24 insertions(+)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 14466765b85d..94b87aaad0f6 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2474,6 +2474,26 @@ static int ep_check_params(struct file *file, struct epoll_event __user *evs,
 	return 0;
 }
 
+int epoll_sendevents(struct file *file, struct epoll_event __user *events,
+		     int maxevents)
+{
+	struct eventpoll *ep;
+	int ret;
+
+	ret = ep_check_params(file, events, maxevents);
+	if (unlikely(ret))
+		return ret;
+
+	ep = file->private_data;
+	/*
+	 * Racy call, but that's ok - it should get retried based on
+	 * poll readiness anyway.
+	 */
+	if (ep_events_available(ep))
+		return ep_try_send_events(ep, events, maxevents);
+	return 0;
+}
+
 /*
  * Implement the event wait interface for the eventpoll file. It is the kernel
  * part of the user space epoll_wait(2).
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index 0c0d00fcd131..ccb478eb174b 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -25,6 +25,10 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long t
 /* Used to release the epoll bits inside the "struct file" */
 void eventpoll_release_file(struct file *file);
 
+/* Copy ready events to userspace */
+int epoll_sendevents(struct file *file, struct epoll_event __user *events,
+		     int maxevents);
+
 /*
  * This is called from inside fs/file_table.c:__fput() to unlink files
  * from the eventpoll interface. We need to have this facility to cleanup
-- 
2.47.2