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. Original-author: Valerie Aurora <vaurora@xxxxxxxxxx> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> --- fs/namespace.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index aa6b1ef..3c950fa 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2091,6 +2091,11 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) goto unlock; + /* Top layers of union mounts can't be mounted elsewhere */ + err = -EBUSY; + if (newmnt->mnt.mnt_sb->s_union_lower_mnts) + goto unlock; + newmnt->mnt.mnt_flags = mnt_flags; err = graft_tree(newmnt, path); -- 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
