[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>
diff --git a/fs/namespace.c b/fs/namespace.c
index 3782923..f6861a5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -68,6 +68,7 @@
INIT_LIST_HEAD(&mnt->mnt_mounts);
INIT_LIST_HEAD(&mnt->mnt_list);
INIT_LIST_HEAD(&mnt->mnt_expire);
+ INIT_LIST_HEAD(&mnt->mnt_share);
if (name) {
int size = strlen(name) + 1;
char *newname = kmalloc(size, GFP_KERNEL);
@@ -1113,7 +1114,7 @@
data_page);
else if (flags & MS_BIND)
retval = do_loopback(&nd, dev_name, flags & MS_REC);
- else if (flags & MS_PRIVATE)
+ else if (flags & (MS_SHARED | MS_PRIVATE))
retval = do_change_type(&nd, flags);
else if (flags & MS_MOVE)
retval = do_move_mount(&nd, dev_name);
diff --git a/fs/pnode.c b/fs/pnode.c
index aaa0dff..1e22165 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -11,7 +11,18 @@
#include <linux/fs.h>
#include "pnode.h"
+/* return the next shared peer mount of @p */
+static inline struct vfsmount *next_peer(struct vfsmount *p)
+{
+ return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
+}
+
void change_mnt_propagation(struct vfsmount *mnt, int type)
{
- mnt->mnt_flags &= ~MNT_PNODE_MASK;
+ if (type == MS_SHARED) {
+ mnt->mnt_flags |= MNT_SHARED;
+ } else {
+ list_del_init(&mnt->mnt_share);
+ mnt->mnt_flags &= ~MNT_PNODE_MASK;
+ }
}
diff --git a/fs/pnode.h b/fs/pnode.h
index 33549a3..ab1bdae 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -10,5 +10,9 @@
#include <linux/list.h>
#include <linux/mount.h>
+
+#define IS_MNT_SHARED(mnt) (mnt->mnt_flags & MNT_SHARED)
+#define CLEAR_MNT_SHARED(mnt) (mnt->mnt_flags &= ~MNT_SHARED)
+
void change_mnt_propagation(struct vfsmount *, int);
#endif /* _LINUX_PNODE_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6c43108..551fba3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -105,6 +105,7 @@
#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 8eadd3b..2582559 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 @@
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;
};