[PATCH] shared mount handling: bind and rbind
Implement handling of MS_BIND in presense of shared mounts (see
Documentation/sharedsubtree.txt in the end of patch 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/pnode.c b/fs/pnode.c
index 1e22165..2d572b8 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -20,9 +20,88 @@
void change_mnt_propagation(struct vfsmount *mnt, int type)
{
if (type == MS_SHARED) {
- mnt->mnt_flags |= MNT_SHARED;
+ set_mnt_shared(mnt);
} else {
list_del_init(&mnt->mnt_share);
mnt->mnt_flags &= ~MNT_PNODE_MASK;
}
}
+
+/*
+ * get the next mount in the propagation tree.
+ * @m: the mount seen last
+ * @origin: the original mount from where the tree walk initiated
+ */
+static struct vfsmount *propagation_next(struct vfsmount *m,
+ struct vfsmount *origin)
+{
+ m = next_peer(m);
+ if (m == origin)
+ return NULL;
+ return m;
+}
+
+/*
+ * mount 'source_mnt' under the destination 'dest_mnt' at
+ * dentry 'dest_dentry'. And propagate that mount to
+ * all the peer and slave mounts of 'dest_mnt'.
+ * Link all the new mounts into a propagation tree headed at
+ * source_mnt. Also link all the new mounts using ->mnt_list
+ * headed at source_mnt's ->mnt_list
+ *
+ * @dest_mnt: destination mount.
+ * @dest_dentry: destination dentry.
+ * @source_mnt: source mount.
+ * @tree_list : list of heads of trees to be attached.
+ */
+int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
+ struct vfsmount *source_mnt, struct list_head *tree_list)
+{
+ struct vfsmount *m, *child;
+ int ret = 0;
+ struct vfsmount *prev_dest_mnt = dest_mnt;
+ struct vfsmount *prev_src_mnt = source_mnt;
+ LIST_HEAD(tmp_list);
+ LIST_HEAD(umount_list);
+
+ for (m = propagation_next(dest_mnt, dest_mnt); m;
+ m = propagation_next(m, dest_mnt)) {
+ int type = CL_PROPAGATION;
+
+ if (IS_MNT_NEW(m))
+ continue;
+
+ if (IS_MNT_SHARED(m))
+ type |= CL_MAKE_SHARED;
+
+ if (!(child = copy_tree(source_mnt, source_mnt->mnt_root,
+ type))) {
+ ret = -ENOMEM;
+ list_splice(tree_list, tmp_list.prev);
+ goto out;
+ }
+
+ if (is_subdir(dest_dentry, m->mnt_root)) {
+ mnt_set_mountpoint(m, dest_dentry, child);
+ list_add_tail(&child->mnt_hash, tree_list);
+ } else {
+ /*
+ * This can happen if the parent mount was bind mounted
+ * on some subdirectory of a shared/slave mount.
+ */
+ list_add_tail(&child->mnt_hash, &tmp_list);
+ }
+ prev_dest_mnt = m;
+ prev_src_mnt = child;
+ }
+out:
+ spin_lock(&vfsmount_lock);
+ while (!list_empty(&tmp_list)) {
+ child = list_entry(tmp_list.next, struct vfsmount, mnt_hash);
+ list_del_init(&child->mnt_hash);
+ umount_tree(child, &umount_list);
+ }
+ spin_unlock(&vfsmount_lock);
+ release_mounts(&umount_list);
+ return ret;
+}