[PATCH RESEND] userns: enable tmpfs support for user namespace

[Gao feng]

From: gaofeng <gaofeng at cn.fujitsu.com>

Since the memory used by tmpfs is under control of
memory cgroup. and the files under the tmpfs will not
be leak to other tmpfs.

So mounting tmpfs in user namespace does no harm to the
host,we can allow tmpfs to be mounted in user namespace.

Signed-off-by: gaofeng <gaofeng at cn.fujitsu.com>
---
 mm/shmem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index 5dd56f6..8eff60a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2766,6 +2766,7 @@ static struct file_system_type shmem_fs_type = {
 	.name		= "tmpfs",
 	.mount		= shmem_mount,
 	.kill_sb	= kill_litter_super,
+	.fs_flags	= FS_USERNS_MOUNT,
 };
 
 int __init shmem_init(void)
-- 
1.7.11.7