[PATCH v3 09/13] epoll: support polling from userspace for ep_remove()

Roman Penyaev
2019-05-16T08:59:09Z

On ep_remove() simply mark a user item with EPOLLREMOVE if the item was
ready (i.e. has some bits set). That will prevent further user index
entry creation on item ->bit reuse.

Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f1ffccfcca67..630f473973da 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1025,10 +1025,14 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)

rb_erase_cached(&epi->rbn, &ep->rbr);

- write_lock_irq(&ep->lock);
- if (ep_is_linked(epi))
- list_del_init(&epi->rdllink);
- write_unlock_irq(&ep->lock);
+ if (ep_polled_by_user(ep)) {
+ ep_remove_user_item(epi);
+ } else {
+ write_lock_irq(&ep->lock);
+ if (ep_is_linked(epi))
+ list_del_init(&epi->rdllink);
+ write_unlock_irq(&ep->lock);
+ }

wakeup_source_unregister(ep_wakeup_source(epi));
/*
--
2.21.0