ubifs support mount multitimes.

Signed-off-by: QiaoChong <qiaochong@loongson.cn>

pmon/fs/ubifs/super.c

@@ -1184,7 +1184,10 @@ int ubifs_mount(char *vol_name)
 	 * First unmount if allready mounted
 	 */
 	if (ubifs_sb)
+	{
 		ubifs_umount(ubifs_sb->s_fs_info);
+		ubifs_sb = NULL;
+	}
 
 	INIT_LIST_HEAD(&ubifs_infos);
 	INIT_LIST_HEAD(&ubifs_fs_type.fs_supers);

pmon/fs/ubifs/ubifs.c

@@ -1126,6 +1126,7 @@ ubifs_open(int fd, const char *path, int flags, int mode)
 	if(ubifs_mount(volname))
 	{
                 puts("ubifs mounted failed!!");
+		ubi_detach_mtd_dev(0, 1);
 		return -1;
 	}
         c = ubifs_sb->s_fs_info;