new helper: iterate_mounts()

apply function to vfsmounts in set returned by collect_mounts(),
stop if it returns non-zero.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namespace.c

@@ -1246,6 +1246,21 @@ void drop_collected_mounts(struct vfsmount *mnt)
 	release_mounts(&umount_list);
 }
 
+int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
+		   struct vfsmount *root)
+{
+	struct vfsmount *mnt;
+	int res = f(root, arg);
+	if (res)
+		return res;
+	list_for_each_entry(mnt, &root->mnt_list, mnt_list) {
+		res = f(mnt, arg);
+		if (res)
+			return res;
+	}
+	return 0;
+}
+
 static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
 {
 	struct vfsmount *p;

include/linux/fs.h

@@ -1794,7 +1794,8 @@ extern int may_umount(struct vfsmount *);
 extern long do_mount(char *, char *, char *, unsigned long, void *);
 extern struct vfsmount *collect_mounts(struct path *);
 extern void drop_collected_mounts(struct vfsmount *);
-
+extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,
+			  struct vfsmount *);
 extern int vfs_statfs(struct dentry *, struct kstatfs *);
 
 extern int current_umask(void);

kernel/audit_tree.c

@@ -548,6 +548,11 @@ int audit_remove_tree_rule(struct audit_krule *rule)
 	return 0;
 }
 
+static int compare_root(struct vfsmount *mnt, void *arg)
+{
+	return mnt->mnt_root->d_inode == arg;
+}
+
 void audit_trim_trees(void)
 {
 	struct list_head cursor;
@@ -559,7 +564,6 @@ void audit_trim_trees(void)
 		struct path path;
 		struct vfsmount *root_mnt;
 		struct node *node;
-		struct list_head list;
 		int err;
 
 		tree = container_of(cursor.next, struct audit_tree, list);
@@ -577,24 +581,16 @@ void audit_trim_trees(void)
 		if (!root_mnt)
 			goto skip_it;
 
-		list_add_tail(&list, &root_mnt->mnt_list);
 		spin_lock(&hash_lock);
 		list_for_each_entry(node, &tree->chunks, list) {
-			struct audit_chunk *chunk = find_chunk(node);
-			struct inode *inode = chunk->watch.inode;
-			struct vfsmount *mnt;
+			struct inode *inode = find_chunk(node)->watch.inode;
 			node->index |= 1U<<31;
-			list_for_each_entry(mnt, &list, mnt_list) {
-				if (mnt->mnt_root->d_inode == inode) {
+			if (iterate_mounts(compare_root, inode, root_mnt))
 				node->index &= ~(1U<<31);
-					break;
-				}
-			}
 		}
 		spin_unlock(&hash_lock);
 		trim_marked(tree);
 		put_tree(tree);
-		list_del_init(&list);
 		drop_collected_mounts(root_mnt);
 skip_it:
 		mutex_lock(&audit_filter_mutex);
@@ -622,13 +618,17 @@ void audit_put_tree(struct audit_tree *tree)
 	put_tree(tree);
 }
 
+static int tag_mount(struct vfsmount *mnt, void *arg)
+{
+	return tag_chunk(mnt->mnt_root->d_inode, arg);
+}
+
 /* called with audit_filter_mutex */
 int audit_add_tree_rule(struct audit_krule *rule)
 {
 	struct audit_tree *seed = rule->tree, *tree;
 	struct path path;
-	struct vfsmount *mnt, *p;
-	struct list_head list;
+	struct vfsmount *mnt;
 	int err;
 
 	list_for_each_entry(tree, &tree_list, list) {
@@ -654,16 +654,9 @@ int audit_add_tree_rule(struct audit_krule *rule)
 		err = -ENOMEM;
 		goto Err;
 	}
-	list_add_tail(&list, &mnt->mnt_list);
 
 	get_tree(tree);
-	list_for_each_entry(p, &list, mnt_list) {
-		err = tag_chunk(p->mnt_root->d_inode, tree);
-		if (err)
-			break;
-	}
-
-	list_del(&list);
+	err = iterate_mounts(tag_mount, tree, mnt);
 	drop_collected_mounts(mnt);
 
 	if (!err) {
@@ -700,7 +693,6 @@ int audit_tag_tree(char *old, char *new)
 	int failed = 0;
 	struct path path1, path2;
 	struct vfsmount *tagged;
-	struct list_head list;
 	int err;
 
 	err = kern_path(new, 0, &path2);
@@ -717,15 +709,12 @@ int audit_tag_tree(char *old, char *new)
 		return err;
 	}
 
-	list_add_tail(&list, &tagged->mnt_list);
-
 	mutex_lock(&audit_filter_mutex);
 	list_add(&barrier, &tree_list);
 	list_add(&cursor, &barrier);
 
 	while (cursor.next != &tree_list) {
 		struct audit_tree *tree;
-		struct vfsmount *p;
 		int good_one = 0;
 
 		tree = container_of(cursor.next, struct audit_tree, list);
@@ -746,12 +735,7 @@ int audit_tag_tree(char *old, char *new)
 			continue;
 		}
 
-		list_for_each_entry(p, &list, mnt_list) {
-			failed = tag_chunk(p->mnt_root->d_inode, tree);
-			if (failed)
-				break;
-		}
-
+		failed = iterate_mounts(tag_mount, tree, tagged);
 		if (failed) {
 			put_tree(tree);
 			mutex_lock(&audit_filter_mutex);
@@ -792,7 +776,6 @@ int audit_tag_tree(char *old, char *new)
 	}
 	list_del(&barrier);
 	list_del(&cursor);
-	list_del(&list);
 	mutex_unlock(&audit_filter_mutex);
 	path_put(&path1);
 	drop_collected_mounts(tagged);