[RFC PATCH 21/27] take the common part of ep_eventpoll_poll() and ep_item_poll() into helper

[Al Viro]

From: Al Viro <v...@zeniv.linux.org.uk>

The only reason why ep_item_poll() can't simply call ep_eventpoll_poll()
(or, better yet, call vfs_poll() in all cases) is that we need to tell
lockdep how deep into the hierarchy of ->mtx we are.  So let's add
a variant of ep_eventpoll_poll() that would take depth explicitly
and turn ep_eventpoll_poll() into wrapper for that.

Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
---
 fs/eventpoll.c | 57 +++++++++++++++++++++++++++------------------------------
 1 file changed, 27 insertions(+), 30 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 39947b71f7af..a50b48d26c55 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -732,6 +732,27 @@ static int ep_eventpoll_release(struct inode *inode, 
struct file *file)
 static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head 
*head,
                               int depth);
 
+static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int 
depth)
+{
+       struct eventpoll *ep = file->private_data;
+       LIST_HEAD(txlist);
+       __poll_t res;
+
+       /* Insert inside our poll wait queue */
+       poll_wait(file, &ep->poll_wait, wait);
+
+       /*
+        * Proceed to find out if wanted events are really available inside
+        * the ready list.
+        */
+       mutex_lock_nested(&ep->mtx, depth);
+       ep_start_scan(ep, &txlist);
+       res = ep_read_events_proc(ep, &txlist, depth + 1);
+       ep_done_scan(ep, &txlist);
+       mutex_unlock(&ep->mtx);
+       return res;
+}
+
 /*
  * Differs from ep_eventpoll_poll() in that internal callers already have
  * the ep->mtx so we need to start from depth=1, such that mutex_lock_nested()
@@ -740,22 +761,14 @@ static __poll_t ep_read_events_proc(struct eventpoll *ep, 
struct list_head *head
 static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt,
                                 int depth)
 {
-       struct eventpoll *ep;
-       LIST_HEAD(txlist);
+       struct file *file = epi->ffd.file;
        __poll_t res;
 
        pt->_key = epi->event.events;
-       if (!is_file_epoll(epi->ffd.file))
-               return vfs_poll(epi->ffd.file, pt) & epi->event.events;
-
-       ep = epi->ffd.file->private_data;
-       poll_wait(epi->ffd.file, &ep->poll_wait, pt);
-
-       mutex_lock_nested(&ep->mtx, depth);
-       ep_start_scan(ep, &txlist);
-       res = ep_read_events_proc(ep, &txlist, depth + 1);
-       ep_done_scan(ep, &txlist);
-       mutex_unlock(&ep->mtx);
+       if (!is_file_epoll(file))
+               res = vfs_poll(file, pt);
+       else
+               res = __ep_eventpoll_poll(file, pt, depth);
        return res & epi->event.events;
 }
 
@@ -786,23 +799,7 @@ static __poll_t ep_read_events_proc(struct eventpoll *ep, 
struct list_head *head
 
 static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait)
 {
-       struct eventpoll *ep = file->private_data;
-       LIST_HEAD(txlist);
-       __poll_t res;
-
-       /* Insert inside our poll wait queue */
-       poll_wait(file, &ep->poll_wait, wait);
-
-       /*
-        * Proceed to find out if wanted events are really available inside
-        * the ready list.
-        */
-       mutex_lock(&ep->mtx);
-       ep_start_scan(ep, &txlist);
-       res = ep_read_events_proc(ep, &txlist, 1);
-       ep_done_scan(ep, &txlist);
-       mutex_unlock(&ep->mtx);
-       return res;
+       return __ep_eventpoll_poll(file, wait, 0);
 }
 
 #ifdef CONFIG_PROC_FS
-- 
2.11.0