[PATCH] handling of slave mounts
This makes bind, rbind, move, clone namespace and umount operations
aware of the semantics of slave mount (see Documentation/sharedsubtree.txt
in the last patch of the series for detailed description).
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 46f99bc..0896703 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -227,8 +227,17 @@
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
- if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
- list_add(&mnt->mnt_share, &old->mnt_share);
+ if (flag & CL_SLAVE) {
+ list_add(&mnt->mnt_slave, &old->mnt_slave_list);
+ mnt->mnt_master = old;
+ CLEAR_MNT_SHARED(mnt);
+ } else {
+ if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
+ list_add(&mnt->mnt_share, &old->mnt_share);
+ if (IS_MNT_SLAVE(old))
+ list_add(&mnt->mnt_slave, &old->mnt_slave);
+ mnt->mnt_master = old->mnt_master;
+ }
if (flag & CL_MAKE_SHARED)
set_mnt_shared(mnt);
@@ -689,18 +698,18 @@
*
* NOTE: in the table below explains the semantics when a source mount
* of a given type is attached to a destination mount of a given type.
- * ---------------------------------------------
- * | BIND MOUNT OPERATION |
- * |********************************************
- * | source-->| shared | private |
- * | dest | | |
- * | | | | |
- * | v | | |
- * |********************************************
- * | shared | shared (++) | shared (+) |
- * | | | |
- * |non-shared| shared (+) | private |
- * *********************************************
+ * -------------------------------------------------------------
+ * | BIND MOUNT OPERATION |
+ * |*************************************************************
+ * | source-->| shared | private | slave |
+ * | dest | | | |
+ * | | | | | |
+ * | v | | | |
+ * |*************************************************************
+ * | shared | shared (++) | shared (+) | shared(+++)|
+ * | | | | |
+ * |non-shared| shared (+) | private | slave (*) |
+ * **************************************************************
* A bind operation clones the source mount and mounts the clone on the
* destination mount.
*
@@ -710,21 +719,33 @@
* (+) the cloned mount is created under the destination mount and is marked
* as shared. The cloned mount is added to the peer group of the source
* mount.
- * ---------------------------------------------
- * | MOVE MOUNT OPERATION |
- * |********************************************
- * | source-->| shared | private |
- * | dest | | |
- * | | | | |
- * | v | | |
- * |********************************************
- * | shared | shared (+) | shared (+) |
- * | | | |
- * |non-shared| shared (+*) | private |
- * *********************************************
- * (+) the mount is moved to the destination. And is then propagated to all
- * the mounts in the propagation tree of the destination mount.
+ * (+++) the mount is propagated to all the mounts in the propagation tree
+ * of the destination mount and the cloned mount is made slave
+ * of the same master as that of the source mount. The cloned mount
+ * is marked as 'shared and slave'.
+ * (*) the cloned mount is made a slave of the same master as that of the
+ * source mount.
+ *
+ * --------------------------------------------------------------
+ * | MOVE MOUNT OPERATION |
+ * |*************************************************************
+ * | source-->| shared | private | slave |
+ * | dest | | | |
+ * | | | | | |
+ * | v | | | |
+ * |*************************************************************
+ * | shared | shared (+) | shared (+) | shared(+++) |
+ * | | | | |
+ * |non-shared| shared (+*) | private | slave (*) |
+ * **************************************************************
+ *
+ * (+) the mount is moved to the destination. And is then propagated to
+ * all the mounts in the propagation tree of the destination mount.
* (+*) the mount is moved to the destination.
+ * (+++) the mount is moved to the destination and is then propagated to
+ * all the mounts belonging to the destination mount's propagation tree.
+ * the mount is marked as 'shared and slave'.
+ * (*) the mount continues to be a slave at the new location.
*
* if the source mount is a tree, the operations explained above is
* applied to each mount in the tree.
diff --git a/fs/pnode.c b/fs/pnode.c
index f73eba2..3e266c5 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -17,6 +17,16 @@
return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
}
+static inline struct vfsmount *first_slave(struct vfsmount *p)
+{
+ return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);
+}
+
+static inline struct vfsmount *next_slave(struct vfsmount *p)
+{
+ return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
+}
+
static int do_make_slave(struct vfsmount *mnt)
{
struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
@@ -83,10 +93,64 @@
static struct vfsmount *propagation_next(struct vfsmount *m,
struct vfsmount *origin)
{
- m = next_peer(m);
- if (m == origin)
- return NULL;
- return m;
+ /* are there any slaves of this mount? */
+ if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
+ return first_slave(m);
+
+ while (1) {
+ struct vfsmount *next;
+ struct vfsmount *master = m->mnt_master;
+
+ if ( master == origin->mnt_master ) {
+ next = next_peer(m);
+ return ((next == origin) ? NULL : next);
+ } else if (m->mnt_slave.next != &master->mnt_slave_list)
+ return next_slave(m);
+
+ /* back at master */
+ m = master;
+ }
+}
+
+/*
+ * return the source mount to be used for cloning
+ *
+ * @dest the current destination mount
+ * @last_dest the last seen destination mount
+ * @last_src the last seen source mount
+ * @type return CL_SLAVE if the new mount has to be
+ * cloned as a slave.
+ */
+static struct vfsmount *get_source(struct vfsmount *dest,
+ struct vfsmount *last_dest,
+ struct vfsmount *last_src,
+ int *type)
+{
+ struct vfsmount *p_last_src = NULL;
+ struct vfsmount *p_last_dest = NULL;
+ *type = CL_PROPAGATION;;
+
+ if (IS_MNT_SHARED(dest))
+ *type |= CL_MAKE_SHARED;
+
+ while (last_dest != dest->mnt_master) {
+ p_last_dest = last_dest;
+ p_last_src = last_src;
+ last_dest = last_dest->mnt_master;
+ last_src = last_src->mnt_master;
+ }
+
+ if (p_last_dest) {
+ do {
+ p_last_dest = next_peer(p_last_dest);
+ } while (IS_MNT_NEW(p_last_dest));
+ }
+
+ if (dest != p_last_dest) {
+ *type |= CL_SLAVE;
+ return last_src;
+ } else
+ return p_last_src;
}
/*
@@ -114,16 +178,15 @@
for (m = propagation_next(dest_mnt, dest_mnt); m;
m = propagation_next(m, dest_mnt)) {
- int type = CL_PROPAGATION;
+ int type;
+ struct vfsmount *source;
if (IS_MNT_NEW(m))
continue;
- if (IS_MNT_SHARED(m))
- type |= CL_MAKE_SHARED;
+ source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
- if (!(child = copy_tree(source_mnt, source_mnt->mnt_root,
- type))) {
+ if (!(child = copy_tree(source, source->mnt_root, type))) {
ret = -ENOMEM;
list_splice(tree_list, tmp_list.prev);
goto out;