linux-kernel - [RFC PATCH 19/27] ep_insert(): don't open-code ep

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Date:   Sun,  4 Oct 2020 03:39:21 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>
Subject: [RFC PATCH 19/27] ep_insert(): don't open-code ep_remove() on failure exits

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/eventpoll.c | 51 ++++++++++++++-------------------------------------
 1 file changed, 14 insertions(+), 37 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f9c567af1f5f..c987b61701e4 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1384,12 +1384,16 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 	epi->next = EP_UNACTIVE_PTR;
 	if (epi->event.events & EPOLLWAKEUP) {
 		error = ep_create_wakeup_source(epi);
-		if (error)
-			goto error_create_wakeup_source;
+		if (error) {
+			kmem_cache_free(epi_cache, epi);
+			return error;
+		}
 	} else {
 		RCU_INIT_POINTER(epi->ws, NULL);
 	}
 
+	atomic_long_inc(&ep->user->epoll_watches);
+
 	/* Add the current item to the list of active epoll hook for this file */
 	spin_lock(&tfile->f_lock);
 	list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
@@ -1402,9 +1406,10 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 	ep_rbtree_insert(ep, epi);
 
 	/* now check if we've created too many backpaths */
-	error = -EINVAL;
-	if (full_check && reverse_path_check())
-		goto error_remove_epi;
+	if (unlikely(full_check && reverse_path_check())) {
+		ep_remove(ep, epi);
+		return -EINVAL;
+	}
 
 	/* Initialize the poll table using the queue callback */
 	epq.epi = epi;
@@ -1424,9 +1429,10 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 	 * install process. Namely an allocation for a wait queue failed due
 	 * high memory pressure.
 	 */
-	error = -ENOMEM;
-	if (!epq.epi)
-		goto error_unregister;
+	if (unlikely(!epq.epi)) {
+		ep_remove(ep, epi);
+		return -ENOMEM;
+	}
 
 	/* We have to drop the new item inside our item list to keep track of it */
 	write_lock_irq(&ep->lock);
@@ -1448,40 +1454,11 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 
 	write_unlock_irq(&ep->lock);
 
-	atomic_long_inc(&ep->user->epoll_watches);
-
 	/* We have to call this outside the lock */
 	if (pwake)
 		ep_poll_safewake(ep, NULL);
 
 	return 0;
-
-error_unregister:
-	ep_unregister_pollwait(ep, epi);
-error_remove_epi:
-	spin_lock(&tfile->f_lock);
-	list_del_rcu(&epi->fllink);
-	spin_unlock(&tfile->f_lock);
-
-	rb_erase_cached(&epi->rbn, &ep->rbr);
-
-	/*
-	 * We need to do this because an event could have been arrived on some
-	 * allocated wait queue. Note that we don't care about the ep->ovflist
-	 * list, since that is used/cleaned only inside a section bound by "mtx".
-	 * And ep_insert() is called with "mtx" held.
-	 */
-	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));
-
-error_create_wakeup_source:
-	kmem_cache_free(epi_cache, epi);
-
-	return error;
 }
 
 /*
-- 
2.11.0