mnt: Don't propagate umounts in __detach_mounts

commit 8318e667f176f7ea34451a1a530634e293f216ac upstream.

Invoking mount propagation from __detach_mounts is inefficient and
wrong.

It is inefficient because __detach_mounts already walks the list of
mounts that where something needs to be done, and mount propagation
walks some subset of those mounts again.

It is actively wrong because if the dentry that is passed to
__detach_mounts is not part of the path to a mount that mount should
not be affected.

change_mnt_propagation(p,MS_PRIVATE) modifies the mount propagation
tree of a master mount so it's slaves are connected to another master
if possible.  Which means even removing a mount from the middle of a
mount tree with __detach_mounts will not deprive any mount propagated
mount events.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 5bb96c440b31e1a9453c7fb39048f0a33466ef5b..07d0562290a5f56376d0ed66a35d43d579dcf89b 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1497,7 +1497,7 @@ void __detach_mounts(struct dentry *dentry)
        lock_mount_hash();
        while (!hlist_empty(&mp->m_list)) {
                mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
-               umount_tree(mnt, UMOUNT_PROPAGATE);
+               umount_tree(mnt, 0);
        }
        unlock_mount_hash();
        put_mountpoint(mp);