[PATCH 11/17] don't bother with vfsmount_lock in mounts_poll()

From: Al Viro
Date: Thu Oct 03 2013 - 02:19:23 EST



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@xxxxxxxxxxxxxxxxxx>
---
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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