linux-kernel - [PATCH v2 2/2] mounts_poll() make consistent to mdstat

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Message-Id: <20090409135633.B3E9.A69D9226@jp.fujitsu.com>
Date:	Thu,  9 Apr 2009 13:57:59 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Neil Brown <neilb@...e.de>, Greg Kroah-Hartman <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	Ram Pai <linuxram@...ibm.com>,
	Miklos Szeredi <mszeredi@...e.cz>
Cc:	kosaki.motohiro@...fujitsu.com
Subject: [PATCH v2 2/2] mounts_poll() make consistent to mdstat_poll

In recently sysfs_poll discussion, Neil Brown pointed out /proc/mounts also should
be fixed.

SUSv3 says "Regular files shall always poll TRUE for reading and writing".
  see http://www.opengroup.org/onlinepubs/009695399/functions/poll.html

Then, mounts_poll()'s default should be "POLLIN | POLLRDNORM".
it mean always readable.

In addition, event trigger should use "POLLERR | POLLPRI" instead POLLERR.
it makes consistent to mdstat_poll() and sysfs_poll(). and, select(2) can
handle POLLPRI easily.


Reported-by: Neil Brown <neilb@...e.de>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Ram Pai <linuxram@...ibm.com>
Cc: Miklos Szeredi <mszeredi@...e.cz>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@...e.de>
--
 fs/proc/base.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index f715597..aa763ab 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -648,14 +648,14 @@ static unsigned mounts_poll(struct file *file, poll_table *wait)
 {
 	struct proc_mounts *p = file->private_data;
 	struct mnt_namespace *ns = p->ns;
-	unsigned res = 0;
+	unsigned res = POLLIN | POLLRDNORM;
 
 	poll_wait(file, &ns->poll, wait);
 
 	spin_lock(&vfsmount_lock);
 	if (p->event != ns->event) {
 		p->event = ns->event;
-		res = POLLERR;
+		res |= POLLERR | POLLPRI;
 	}
 	spin_unlock(&vfsmount_lock);
 



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