[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>

6 files changed, 62 insertions, 6 deletions

diff --git a/fs/Makefile b/fs/Makefile
index 1972da186272..4c2655759078 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -10,7 +10,7 @@ obj-y :=	open.o read_write.o file_table.o buffer.o  bio.o super.o \
                 ioctl.o readdir.o select.o fifo.o locks.o dcache.o inode.o \
                 attr.o bad_inode.o file.o filesystems.o namespace.o aio.o \
                 seq_file.o xattr.o libfs.o fs-writeback.o mpage.o direct-io.o \
-                ioprio.o
+                ioprio.o pnode.o
 
 obj-$(CONFIG_INOTIFY)           += inotify.o
 obj-$(CONFIG_EPOLL)             += eventpoll.o
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
diff --git a/fs/pnode.c b/fs/pnode.c
new file mode 100644
index 000000000000..aaa0dffda12a
--- /dev/null
+++ b/fs/pnode.c
@@ -0,0 +1,17 @@
+/*
+ *  linux/fs/pnode.c
+ *
+ * (C) Copyright IBM Corporation 2005.
+ *      Released under GPL v2.
+ *      Author : Ram Pai (linuxram@us.ibm.com)
+ *
+ */
+#include <linux/namespace.h>
+#include <linux/mount.h>
+#include <linux/fs.h>
+#include "pnode.h"
+
+void change_mnt_propagation(struct vfsmount *mnt, int type)
+{
+        mnt->mnt_flags &= ~MNT_PNODE_MASK;
+}
diff --git a/fs/pnode.h b/fs/pnode.h
new file mode 100644
index 000000000000..33549a3a74eb
--- /dev/null
+++ b/fs/pnode.h
@@ -0,0 +1,14 @@
+/*
+ *  linux/fs/pnode.h
+ *
+ * (C) Copyright IBM Corporation 2005.
+ *      Released under GPL v2.
+ *
+ */
+#ifndef _LINUX_PNODE_H
+#define _LINUX_PNODE_H
+
+#include <linux/list.h>
+#include <linux/mount.h>
+void change_mnt_propagation(struct vfsmount *, int);
+#endif /* _LINUX_PNODE_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9a593ef262ef..6c431086abb3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -104,6 +104,7 @@ extern int dir_notify_enable;
 #define MS_MOVE         8192
 #define MS_REC          16384
 #define MS_VERBOSE      32768
+#define MS_PRIVATE      (1<<18) /* change to private */
 #define MS_POSIXACL     (1<<16) /* VFS does not apply the umask */
 #define MS_ACTIVE       (1<<30)
 #define MS_NOUSER       (1<<31)
diff --git a/include/linux/mount.h b/include/linux/mount.h
index ffb0b5089880..8eadd3b65899 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -17,12 +17,12 @@
 #include <linux/spinlock.h>
 #include <asm/atomic.h>
 
-#define MNT_NOSUID      1
-#define MNT_NODEV       2
-#define MNT_NOEXEC      4
+#define MNT_NOSUID      0x01
+#define MNT_NODEV       0x02
+#define MNT_NOEXEC      0x04
+#define MNT_PNODE_MASK  0x30    /* propogation flag mask */
 
-struct vfsmount
-{
+struct vfsmount {
         struct list_head mnt_hash;
         struct vfsmount *mnt_parent;    /* fs we are mounted on */
         struct dentry *mnt_mountpoint;  /* dentry of mountpoint */