linux-kernel - [patch] fs: umount on symlinlk leaks mnt count

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Message-ID: <53CB580E.6060804@parallels.com>
Date:	Sun, 20 Jul 2014 09:47:58 +0400
From:	Vasily Averin <vvs@...allels.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [patch] fs: umount on symlinlk leaks mnt count

Currently umount on symlink blocks following umount:

/vz is separate mount

# ls /vz/ -al | grep test
drwxr-xr-x.  2 root root       4096 Jul 19 01:14 testdir
lrwxrwxrwx.  1 root root         11 Jul 19 01:16 testlink -> /vz/testdir

# umount -l /vz/testlink
umount: /vz/testlink: not mounted (expected)

# lsof /vz
# umount /vz
umount: /vz: device is busy. (unexpected)

Looks like an extra refcount on mnt was taken in mountpoint_last()
Patch below fixes the problem on my test node.

Signed-off-by:	Vasily Averin <vvs@...nvz.org>

View attachment "diff-umount-symlink-ms" of type "text/plain" (328 bytes)