epoll: replace gotos with a proper loop

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.

Link: https://lkml.kernel.org/r/20201106231635.3528496-8-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 63a7a6e..1e0030c 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1743,7 +1743,7 @@ 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;
@@ -1769,18 +1769,30 @@ 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;
@@ -1845,19 +1857,7 @@ fetch_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;
+       }
 }
 
 /**