[PATCH] introduce shared mounts

This creates shared mounts.  A shared mount when bind-mounted to some
mountpoint, propagates mount/umount events to each other.  All the
shared mounts that propagate events to each other belong to the same
peer-group.

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>

2 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6c431086abb3..551fba303cf8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -105,6 +105,7 @@ extern int dir_notify_enable;
 #define MS_REC          16384
 #define MS_VERBOSE      32768
 #define MS_PRIVATE      (1<<18) /* change to private */
+#define MS_SHARED       (1<<20) /* change to shared */
 #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 8eadd3b65899..2582559718fc 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -20,6 +20,7 @@
 #define MNT_NOSUID      0x01
 #define MNT_NODEV       0x02
 #define MNT_NOEXEC      0x04
+#define MNT_SHARED      0x10    /* if the vfsmount is a shared mount */
 #define MNT_PNODE_MASK  0x30    /* propogation flag mask */
 
 struct vfsmount {
@@ -36,6 +37,7 @@ struct vfsmount {
         char *mnt_devname;              /* Name of device e.g. /dev/dsk/hda1 */
         struct list_head mnt_list;
         struct list_head mnt_expire;    /* link in fs-specific expiry list */
+        struct list_head mnt_share;     /* circular list of shared mounts */
         struct namespace *mnt_namespace; /* containing namespace */
         int mnt_pinned;
 };