Introduce MNT_UNION and MS_UNION flags. You need additional patches for
util-linux for that to work.

Signed-off-by: Jan Blunck <[EMAIL PROTECTED]>
---
 fs/namespace.c        |    6 +++++-
 include/linux/fs.h    |    1 +
 include/linux/mount.h |    1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -437,6 +437,7 @@ static int show_vfsmnt(struct seq_file *
                { MNT_NODIRATIME, ",nodiratime" },
                { MNT_RELATIME, ",relatime" },
                { MNT_NOMNT, ",nomnt" },
+               { MNT_UNION, ",union" },
                { 0, NULL }
        };
        struct proc_fs_info *fs_infop;
@@ -1558,9 +1559,12 @@ long do_mount(char *dev_name, char *dir_
                mnt_flags |= MNT_RELATIME;
        if (flags & MS_NOMNT)
                mnt_flags |= MNT_NOMNT;
+       if (flags & MS_UNION)
+               mnt_flags |= MNT_UNION;
 
        flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
-                  MS_NOATIME | MS_NODIRATIME | MS_RELATIME | MS_NOMNT);
+                  MS_NOATIME | MS_NODIRATIME | MS_RELATIME | MS_NOMNT |
+                  MS_UNION );
 
        /* ... and get the mountpoint */
        retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -114,6 +114,7 @@ extern int dir_notify_enable;
 #define MS_REMOUNT     32      /* Alter flags of a mounted FS */
 #define MS_MANDLOCK    64      /* Allow mandatory locks on an FS */
 #define MS_DIRSYNC     128     /* Directory modifications are synchronous */
+#define MS_UNION       256
 #define MS_NOATIME     1024    /* Do not update access times. */
 #define MS_NODIRATIME  2048    /* Do not update directory access times */
 #define MS_BIND                4096
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -36,6 +36,7 @@ struct mnt_namespace;
 #define MNT_SHARED     0x1000  /* if the vfsmount is a shared mount */
 #define MNT_UNBINDABLE 0x2000  /* if the vfsmount is a unbindable mount */
 #define MNT_PNODE_MASK 0x3000  /* propagation flag mask */
+#define MNT_UNION      0x4000  /* if the vfsmount is a union mount */
 
 struct vfsmount {
        struct list_head mnt_hash;

-- 

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