don't bother with vfsmount_lock in mounts_poll()

wake_up_interruptible/poll_wait provide sufficient barriers;
just use ACCESS_ONCE() to fetch ns->event and that's it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 5fe34c355e85..439406e081af 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -20,15 +20,15 @@ static unsigned mounts_poll(struct file *file, poll_table *wait)
         struct proc_mounts *p = proc_mounts(file->private_data);
         struct mnt_namespace *ns = p->ns;
         unsigned res = POLLIN | POLLRDNORM;
+        int event;
 
         poll_wait(file, &p->ns->poll, wait);
 
-        br_read_lock(&vfsmount_lock);
-        if (p->m.poll_event != ns->event) {
-                p->m.poll_event = ns->event;
+        event = ACCESS_ONCE(ns->event);
+        if (p->m.poll_event != event) {
+                p->m.poll_event = event;
                 res |= POLLERR | POLLPRI;
         }
-        br_read_unlock(&vfsmount_lock);
 
         return res;
 }