From: Valerie Aurora <vaurora@xxxxxxxxxx> The device underlying the topmost read-write layer of a file system cannot be mounted anywhere else on the system. We keep a pointer to the union stack in the dentry of the topmost directory, so that dentry can't be part of a different mount, since dentries are shared between different mounts of the same device. Signed-off-by: Valerie Aurora <valerie.aurora@xxxxxxxxx> --- fs/namespace.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 2b8f329..3ac8198 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2044,6 +2044,11 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path, if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) goto unlock; + /* Top layers of union mounts can't be mounted elsewhere */ + err = -EBUSY; + if (newmnt->mnt_sb->s_union_lower_mnts) + goto unlock; + newmnt->mnt_flags = mnt_flags; if ((err = graft_tree(newmnt, path))) goto unlock; -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
