epoll: annotate racy check

Epoll relies on a racy fastpath check during __fput() in
eventpoll_release() to avoid the hit of pointlessly acquiring a
semaphore. Annotate that race by using WRITE_ONCE() and READ_ONCE().

Link: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/20240925-fungieren-anbauen-79b334b00542@brauner
Reviewed-by: Jan Kara <[email protected]>
Reported-by: [email protected]
Signed-off-by: Christian Brauner <[email protected]>
2 files changed