epoll: fix epoll's own poll (update)

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 57 insertions, 53 deletions

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 8a23a91e1377..e24d137c93b6 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -454,9 +454,7 @@ static int ep_scan_ready_list(struct eventpoll *ep,
         int error, pwake = 0;
         unsigned long flags;
         struct epitem *epi, *nepi;
-        struct list_head txlist;
-
-        INIT_LIST_HEAD(&txlist);
+        LIST_HEAD(txlist);
 
         /*
          * We need to lock this because we could be hit by
@@ -473,8 +471,7 @@ static int ep_scan_ready_list(struct eventpoll *ep,
          * in a lockless way.
          */
         spin_lock_irqsave(&ep->lock, flags);
-        list_splice(&ep->rdllist, &txlist);
-        INIT_LIST_HEAD(&ep->rdllist);
+        list_splice_init(&ep->rdllist, &txlist);
         ep->ovflist = NULL;
         spin_unlock_irqrestore(&ep->lock, flags);
 
@@ -514,8 +511,8 @@ static int ep_scan_ready_list(struct eventpoll *ep,
 
         if (!list_empty(&ep->rdllist)) {
                 /*
-                 * Wake up (if active) both the eventpoll wait list and the ->poll()
-                 * wait list (delayed after we release the lock).
+                 * Wake up (if active) both the eventpoll wait list and
+                 * the ->poll() wait list (delayed after we release the lock).
                  */
                 if (waitqueue_active(&ep->wq))
                         wake_up_locked(&ep->wq);
@@ -632,7 +629,8 @@ static int ep_eventpoll_release(struct inode *inode, struct file *file)
         return 0;
 }
 
-static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, void *priv)
+static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
+                               void *priv)
 {
         struct epitem *epi, *tmp;
 
@@ -640,13 +638,14 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, voi
                 if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) &
                     epi->event.events)
                         return POLLIN | POLLRDNORM;
-                else
+                else {
                         /*
                          * Item has been dropped into the ready list by the poll
                          * callback, but it's not actually ready, as far as
                          * caller requested events goes. We can remove it here.
                          */
                         list_del_init(&epi->rdllink);
+                }
         }
 
         return 0;
@@ -674,7 +673,7 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
         pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS,
                                    ep_poll_readyevents_proc, ep, ep);
 
-        return pollflags != -1 ? pollflags: 0;
+        return pollflags != -1 ? pollflags : 0;
 }
 
 /* File callbacks that implement the eventpoll file behaviour */
@@ -872,9 +871,10 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
                 add_wait_queue(whead, &pwq->wait);
                 list_add_tail(&pwq->llink, &epi->pwqlist);
                 epi->nwait++;
-        } else
+        } else {
                 /* We have to signal that an error occurred */
                 epi->nwait = -1;
+        }
 }
 
 static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
@@ -1055,62 +1055,65 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
         return 0;
 }
 
-static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, void *priv)
+static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
+                               void *priv)
 {
         struct ep_send_events_data *esed = priv;
         int eventcnt;
-        unsigned int revents;
+        unsigned int revents;
         struct epitem *epi;
         struct epoll_event __user *uevent;
 
-        /*
+        /*
          * We can loop without lock because we are passed a task private list.
          * Items cannot vanish during the loop because ep_scan_ready_list() is
          * holding "mtx" during this call.
-         */
+         */
         for (eventcnt = 0, uevent = esed->events;
              !list_empty(head) && eventcnt < esed->maxevents;) {
                 epi = list_first_entry(head, struct epitem, rdllink);
 
                 list_del_init(&epi->rdllink);
 
-                revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) &
-                        epi->event.events;
+                revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) &
+                        epi->event.events;
 
-                /*
+                /*
                  * If the event mask intersect the caller-requested one,
                  * deliver the event to userspace. Again, ep_scan_ready_list()
                  * is holding "mtx", so no operations coming from userspace
                  * can change the item.
-                 */
-                if (revents) {
+                 */
+                if (revents) {
                         if (__put_user(revents, &uevent->events) ||
                             __put_user(epi->event.data, &uevent->data))
-                                return eventcnt ? eventcnt: -EFAULT;
-                        eventcnt++;
+                                return eventcnt ? eventcnt : -EFAULT;
+                        eventcnt++;
                         uevent++;
-                        if (epi->event.events & EPOLLONESHOT)
-                                epi->event.events &= EP_PRIVATE_BITS;
-                        else if (!(epi->event.events & EPOLLET))
-                                /*
-                                 * If this file has been added with Level Trigger
-                                 * mode, we need to insert back inside the ready
-                                 * list, so that the next call to epoll_wait()
-                                 * will check again the events availability.
-                                 * At this point, noone can insert into ep->rdllist
-                                 * besides us. The epoll_ctl() callers are locked
-                                 * out by ep_scan_ready_list() holding "mtx" and
-                                 * the poll callback will queue them in ep->ovflist.
-                                 */
-                                list_add_tail(&epi->rdllink, &ep->rdllist);
-                }
-        }
+                        if (epi->event.events & EPOLLONESHOT)
+                                epi->event.events &= EP_PRIVATE_BITS;
+                        else if (!(epi->event.events & EPOLLET)) {
+                                /*
+                                 * If this file has been added with Level
+                                 * Trigger mode, we need to insert back inside
+                                 * the ready list, so that the next call to
+                                 * epoll_wait() will check again the events
+                                 * availability. At this point, noone can insert
+                                 * into ep->rdllist besides us. The epoll_ctl()
+                                 * callers are locked out by
+                                 * ep_scan_ready_list() holding "mtx" and the
+                                 * poll callback will queue them in ep->ovflist.
+                                 */
+                                list_add_tail(&epi->rdllink, &ep->rdllist);
+                        }
+                }
+        }
 
         return eventcnt;
 }
 
-static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events,
-                          int maxevents)
+static int ep_send_events(struct eventpoll *ep,
+                          struct epoll_event __user *events, int maxevents)
 {
         struct ep_send_events_data esed;
 
@@ -1194,40 +1197,41 @@ retry:
  */
 SYSCALL_DEFINE1(epoll_create1, int, flags)
 {
-        int error;
-        struct eventpoll *ep = NULL;
+        int error, fd = -1;
+        struct eventpoll *ep;
 
         /* Check the EPOLL_* constant for consistency.  */
         BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC);
 
+        if (flags & ~EPOLL_CLOEXEC)
+                return -EINVAL;
+
         DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
                      current, flags));
 
-        error = -EINVAL;
-        if (flags & ~EPOLL_CLOEXEC)
-                goto error_return;
-
         /*
-         * Create the internal data structure ("struct eventpoll").
+         * Create the internal data structure ( "struct eventpoll" ).
          */
         error = ep_alloc(&ep);
-        if (error < 0)
+        if (error < 0) {
+                fd = error;
                 goto error_return;
+        }
 
         /*
          * Creates all the items needed to setup an eventpoll file. That is,
          * a file structure and a free file descriptor.
          */
-        error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep,
-                                 flags & O_CLOEXEC);
-        if (error < 0)
+        fd = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep,
+                              flags & O_CLOEXEC);
+        if (fd < 0)
                 ep_free(ep);
 
 error_return:
         DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
-                     current, flags, error));
+                     current, flags, fd));
 
-        return error;
+        return fd;
 }
 
 SYSCALL_DEFINE1(epoll_create, int, size)