[PATCH] beginning of the shared-subtree proper

A private mount does not forward or receive propagation.  This patch
provides user the ability to convert any mount to private.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 4abee9ab009f..3782923d6d4d 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -24,6 +24,7 @@
 #include <linux/mount.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
+#include "pnode.h"
 
 extern int __init init_rootfs(void);
 
@@ -663,6 +664,27 @@ out_unlock:
 }
 
 /*
+ * recursively change the type of the mountpoint.
+ */
+static int do_change_type(struct nameidata *nd, int flag)
+{
+        struct vfsmount *m, *mnt = nd->mnt;
+        int recurse = flag & MS_REC;
+        int type = flag & ~MS_REC;
+
+        if (nd->dentry != nd->mnt->mnt_root)
+                return -EINVAL;
+
+        down_write(&namespace_sem);
+        spin_lock(&vfsmount_lock);
+        for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
+                change_mnt_propagation(m, type);
+        spin_unlock(&vfsmount_lock);
+        up_write(&namespace_sem);
+        return 0;
+}
+
+/*
  * do loopback mount.
  */
 static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
@@ -1091,6 +1113,8 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
                                     data_page);
         else if (flags & MS_BIND)
                 retval = do_loopback(&nd, dev_name, flags & MS_REC);
+        else if (flags & MS_PRIVATE)
+                retval = do_change_type(&nd, flags);
         else if (flags & MS_MOVE)
                 retval = do_move_mount(&nd, dev_name);
         else