[patch] fs: umount on symlinlk leaks mnt count

Vasily Averin
2014-07-20T05:48:14Z

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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@openvz.org>

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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)