linux-kernel - [PATCH] autofs - remove autofs dentry mount check

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Message-ID: <20130403031052.26816.9163.stgit@perseus.fritz.box>
Date:	Wed, 03 Apr 2013 11:10:53 +0800
From:	Ian Kent <raven@...maw.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	autofs mailing list <autofs@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org, David Jeffery <djeffery@...hat.com>
Subject: [PATCH] autofs - remove autofs dentry mount check

From: David Jeffery <djeffery@...hat.com>

When checking if an autofs mount point is busy it isn't sufficient to
only check if it's a mount point.

For example, if the mount of an offset mountpoint in a tree is denied
for this host by its export and the dentry becomes a process working
directory the check incorrectly returns the mount as not in use at expire.

This can happen since the default when mounting within a tree is nostrict,
which means ingnore mount fails on mounts within the tree and continue. The
nostrict option is meant to allow mounting in this case.

Signed-off-by: David Jeffery <djeffery@...hat.com>
Signed-off-by: Ian Kent <raven@...maw.net>
Cc: stable@...r.kernel.org
---
 fs/autofs4/expire.c |    9 ---------
 1 file changed, 9 deletions(-)

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 01443ce..13ddec9 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -61,15 +61,6 @@ static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
 		/* This is an autofs submount, we can't expire it */
 		if (autofs_type_indirect(sbi->type))
 			goto done;
-
-		/*
-		 * Otherwise it's an offset mount and we need to check
-		 * if we can umount its mount, if there is one.
-		 */
-		if (!d_mountpoint(path.dentry)) {
-			status = 0;
-			goto done;
-		}
 	}
 
 	/* Update the expiry counter if fs is busy */

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