X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fpnode.c;h=5cc564a83149a5fc311b57d87793febbdcfd4f27;hb=01a05b337a5b647909e1d6670f57e7202318a5fb;hp=d18d66491a01ab5de2684b056692c424c0159c4f;hpb=719f5d7f0b90ac2c8f8ca4232eb322b266fea01e;p=safe%2Fjmp%2Flinux-2.6

diff --git a/fs/pnode.c b/fs/pnode.c
index d18d664..5cc564a 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -28,6 +28,57 @@ static inline struct vfsmount *next_slave(struct vfsmount *p)
 	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;
@@ -35,7 +86,7 @@ static int do_make_slave(struct vfsmount *mnt)
 
 	/*
 	 * 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 &&
@@ -96,6 +147,11 @@ void change_mnt_propagation(struct vfsmount *mnt, int type)
  * 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)
@@ -135,10 +191,6 @@ static struct vfsmount *get_source(struct vfsmount *dest,
 {
 	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;
@@ -151,13 +203,18 @@ static struct vfsmount *get_source(struct vfsmount *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;
 }
 
 /*