mount: Add lookup_mnt_id and lookup_mnt_sdev helpers

We will need to lookup mount points by mount id
and device for fanotify restore.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/mount.h

@@ -18,4 +18,8 @@ int prepare_mnt_ns(int pid);
 
 extern int pivot_root(const char *new_root, const char *put_old);
 
+struct mount_info;
+extern struct mount_info *lookup_mnt_id(unsigned int id);
+extern struct mount_info *lookup_mnt_sdev(unsigned int s_dev);
+
 #endif /* __CR_MOUNT_H__ */

mount.c

@@ -50,7 +50,7 @@ int collect_mount_info(void)
 	return 0;
 }
 
-static struct mount_info *mnt_find_by_id(struct mount_info *list, int id)
+static struct mount_info *__lookup_mnt_id(struct mount_info *list, int id)
 {
 	struct mount_info *m;
 
@@ -61,6 +61,22 @@ static struct mount_info *mnt_find_by_id(struct mount_info *list, int id)
 	return NULL;
 }
 
+struct mount_info *lookup_mnt_id(unsigned int id)
+{
+	return __lookup_mnt_id(mntinfo, id);
+}
+
+struct mount_info *lookup_mnt_sdev(unsigned int s_dev)
+{
+	struct mount_info *m;
+
+	for (m = mntinfo; m != NULL; m = m->next)
+		if (m->s_dev == s_dev)
+			return m;
+
+	return NULL;
+}
+
 static struct mount_info *mnt_build_ids_tree(struct mount_info *list)
 {
 	struct mount_info *m, *root = NULL;
@@ -74,7 +90,7 @@ static struct mount_info *mnt_build_ids_tree(struct mount_info *list)
 		struct mount_info *p;
 
 		pr_debug("\t\tWorking on %d->%d\n", m->mnt_id, m->parent_mnt_id);
-		p = mnt_find_by_id(list, m->parent_mnt_id);
+		p = __lookup_mnt_id(list, m->parent_mnt_id);
 		if (!p) {
 			/* This should be / */
 			if (root == NULL && !strcmp(m->mountpoint, "/")) {