linux-kernel - [PATCH 11/17] don't bother with vfsmount_lock in mounts

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Message-Id: <E1VRcFo-0008Bn-Ah@ZenIV.linux.org.uk>
Date:	Thu, 03 Oct 2013 07:19:16 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	torvalds@...ux-foundation.org
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 11/17] 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@...iv.linux.org.uk>
---
 fs/proc_namespace.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 5fe34c3..439406e 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;
 }
-- 
1.7.2.5


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