[patch] fs: umount on symlinlk leaks mnt count

[Vasily Averin]

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 <v...@openvz.org>

diff --git a/fs/namei.c b/fs/namei.c
index 985c6f3..0d32a0f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2305,6 +2305,7 @@ path_mountpoint(int dfd, const char *name, struct path 
*path, unsigned int flags
                        break;
                err = mountpoint_last(&nd, path);
                put_link(&nd, &link, cookie);
+               mntput(link.mnt);
        }
 out:
        if (base)