eventpoll: add epoll_sendevents() helper

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>
Link: https://lore.kernel.org/r/20250219172552.1565603-4-axboe@kernel.dk
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 14466765b85d6dddbd0a67b446cd7efd92e7c2f0..94b87aaad0f6e74735debab2f11e4cb8802e29bf 100644 (file)
--- 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 0c0d00fcd131f9ebfdbabdb1917f01e870435595..ccb478eb174bc2e4454cee59f805f10cfd5bb5fb 100644 (file)
--- 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