From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 29 Sep 2013 14:59:59 +0000 (-0400)
Subject: don't bother with vfsmount_lock in mounts_poll()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=aab407fc5c0ce63e9fd4a34a790d7290d3e116a1;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

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>
---

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;
 }