return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
}
+/*
+ * Return true if path is reachable from root
+ *
+ * namespace_sem is held, and mnt is attached
+ */
+static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
+ const struct path *root)
+{
+ while (mnt != root->mnt && mnt->mnt_parent != mnt) {
+ dentry = mnt->mnt_mountpoint;
+ mnt = mnt->mnt_parent;
+ }
+ return mnt == root->mnt && is_subdir(dentry, root->dentry);
+}
+
+static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,
+ struct mnt_namespace *ns,
+ const struct path *root)
+{
+ struct vfsmount *m = mnt;
+
+ do {
+ /* Check the namespace first for optimization */
+ if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root))
+ return m;
+
+ m = next_peer(m);
+ } while (m != mnt);
+
+ return NULL;
+}
+
+/*
+ * Get ID of closest dominating peer group having a representative
+ * under the given root.
+ *
+ * Caller must hold namespace_sem
+ */
+int get_dominating_id(struct vfsmount *mnt, const struct path *root)
+{
+ struct vfsmount *m;
+
+ for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
+ struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root);
+ if (d)
+ return d->mnt_group_id;
+ }
+
+ return 0;
+}
+
static int do_make_slave(struct vfsmount *mnt)
{
struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
/*
* slave 'mnt' to a peer mount that has the
- * same root dentry. If none is available than
+ * same root dentry. If none is available then
* slave it to anything that is available.
*/
while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
if (peer_mnt == mnt)
peer_mnt = NULL;
}
+ if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
+ mnt_release_group_id(mnt);
+
list_del_init(&mnt->mnt_share);
+ mnt->mnt_group_id = 0;
if (peer_mnt)
master = peer_mnt;
}
mnt->mnt_master = master;
CLEAR_MNT_SHARED(mnt);
- INIT_LIST_HEAD(&mnt->mnt_slave_list);
return 0;
}
* get the next mount in the propagation tree.
* @m: the mount seen last
* @origin: the original mount from where the tree walk initiated
+ *
+ * Note that peer groups form contiguous segments of slave lists.
+ * We rely on that in get_source() to be able to find out if
+ * vfsmount found while iterating with propagation_next() is
+ * a peer of one we'd found earlier.
*/
static struct vfsmount *propagation_next(struct vfsmount *m,
struct vfsmount *origin)
{
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;
do {
p_last_dest = next_peer(p_last_dest);
} while (IS_MNT_NEW(p_last_dest));
+ /* is that a peer of the earlier? */
+ if (dest == p_last_dest) {
+ *type = CL_MAKE_SHARED;
+ return p_last_src;
+ }
}
-
- if (dest != p_last_dest) {
- *type |= CL_SLAVE;
- return last_src;
- } else
- return p_last_src;
+ /* slave of the earlier, then */
+ *type = CL_SLAVE;
+ /* beginning of peer group among the slaves? */
+ if (IS_MNT_SHARED(dest))
+ *type |= CL_MAKE_SHARED;
+ return last_src;
}
/*