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

[Roman Penyaev]

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@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

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