Hello Everyone, Now superblock has a reference to userns. Is there a way to discover an owning userns for a superblock from user-space? In CRIU, we need this information to dump and restore mount namespaces. For other users, this information can be useful too to analyze and understand the running system. Recently we solved a similar problem for namespaces: https://lkml.org/lkml/2016/7/6/158 In that case, we added two ioctl-s for nsfs files. Here we have a deal regular files and I am not sure that adding a new ioctl for them is a good idea. Another way to solve a problem is use the kcmp() system call. We will need to add two commands. One is to compare user namespaces and another one is to compare a supper block userns with another userns. The first command is required to create a sorted list of user namespaces and the second command allows to find a proper userns in this list. Maybe someone has a better idea about this? Thanks, Andrei
