linux-kernel - [PATCH 7/8] epoll: replace gotos with a proper loop

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Date:   Fri,  6 Nov 2020 18:16:34 -0500
From:   Soheil Hassas Yeganeh <soheil.kdev@...il.com>
To:     torvalds@...ux-foundation.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        dave@...olabs.net, edumazet@...gle.com, willemb@...gle.com,
        khazhy@...gle.com, guantaol@...gle.com,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: [PATCH 7/8] epoll: replace gotos with a proper loop

From: Soheil Hassas Yeganeh <soheil@...gle.com>

The existing loop is pointless, and the labels make it really
hard to follow the structure.

Replace that control structure with a simple loop that returns
when there are new events, there is a signal, or the thread has
timed out.

Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Khazhismel Kumykov <khazhy@...gle.com>
---
 fs/eventpoll.c | 42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index b29bbebe8ca4..f4e1be7ada26 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1830,7 +1830,7 @@ static inline struct timespec64 ep_set_mstimeout(long ms)
 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 		   int maxevents, long timeout)
 {
-	int res, eavail, timed_out = 0;
+	int res, eavail = 0, timed_out = 0;
 	u64 slack = 0;
 	wait_queue_entry_t wait;
 	ktime_t expires, *to = NULL;
@@ -1856,18 +1856,30 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 		write_lock_irq(&ep->lock);
 		eavail = ep_events_available(ep);
 		write_unlock_irq(&ep->lock);
-
-		goto send_events;
 	}
 
-fetch_events:
-	do {
+	while (1) {
+		if (eavail) {
+			/*
+			 * Try to transfer events to user space. In case we get
+			 * 0 events and there's still timeout left over, we go
+			 * trying again in search of more luck.
+			 */
+			res = ep_send_events(ep, events, maxevents);
+			if (res)
+				return res;
+		}
+
+		if (timed_out)
+			return 0;
+
 		eavail = ep_events_available(ep);
-		if (!eavail)
-			eavail = ep_busy_loop(ep, timed_out);
+		if (eavail)
+			continue;
 
+		eavail = ep_busy_loop(ep, timed_out);
 		if (eavail)
-			goto send_events;
+			continue;
 
 		if (signal_pending(current))
 			return -EINTR;
@@ -1932,19 +1944,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 			__remove_wait_queue(&ep->wq, &wait);
 			write_unlock_irq(&ep->lock);
 		}
-	} while (0);
-
-send_events:
-	/*
-	 * Try to transfer events to user space. In case we get 0 events and
-	 * there's still timeout left over, we go trying again in search of
-	 * more luck.
-	 */
-	if (eavail &&
-	    !(res = ep_send_events(ep, events, maxevents)) && !timed_out)
-		goto fetch_events;
-
-	return res;
+	}
 }
 
 /**
-- 
2.29.1.341.ge80a0c044ae-goog