mount: Reset mountinfos when mntns recreated

The list of mounts is used by inotify to restore a watch with open-by-handle. The problem
is that after the clean_mnt_ns is done the mntinfo list is no longer relevant.

Fix it by freeing the old one and initializing the new with the read-from-image stuff.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -389,6 +389,7 @@ static int do_umount_one(struct mount_info *mi)
 
 static int clean_mnt_ns(void)
 {
+	int ret;
 	struct mount_info *pm;
 
 	pr_info("Cleaning mount namespace\n");
@@ -401,7 +402,15 @@ static int clean_mnt_ns(void)
 	if (!pm)
 		return -1;
 
-	return mnt_tree_for_each_reverse(pm, do_umount_one);
+	ret = mnt_tree_for_each_reverse(pm, do_umount_one);
+
+	while (mntinfo) {
+		pm = mntinfo->next;
+		xfree(mntinfo);
+		mntinfo = pm;
+	}
+
+	return ret;
 }
 
 static int populate_mnt_ns(int ns_pid)
@@ -469,6 +478,7 @@ static int populate_mnt_ns(int ns_pid)
 		mnt_entry__free_unpacked(me, NULL);
 
 	close(img);
+	mntinfo = pms;
 
 	pms = mnt_build_tree(pms);
 	if (!pms)