Re: [PATCH V6 00/10] namespaces: log namespaces per task

Richard Guy Briggs <rgb(a)redhat.com&gt; writes: > On 15/04/24, Eric W. Biederman wrote: >> Richard Guy Briggs <rgb(a)redhat.com&gt; writes: >> > On 15/04/22, Richard Guy Briggs wrote: >> >> On 15/04/20, Eric W. Biederman wrote: >> >> > Richard Guy Briggs <rgb(a)redhat.com&gt; writes: >> > Do I even need to report the device number anymore since I am concluding >> > s_dev is never set (or always zero) in the nsfs filesystem by >> > mount_pseudo() and isn't even mountable? >> >> We still need the dev. We do have a device number get_anon_bdev fills it in. > > Fine, it has a device number. There appears to be only one of these > allocated per kernel. I can get it from &nsfs->fs_supers (and take the > first instance given by hlist_for_each_entry and verify there are no > others). Why do I need it, again? Because if we have to preserve the inode number over a migration event I want to preserve the fact that we are talking about inode numbers from a superblock with a device number. Otherwise known as I am allergic to kernel global identifiers, because they can be major pains. I don't want to have to go back and implement a namespace for namespaces.

>> >> They are all covered: >> >> sys_unshare > unshare_userns > create_user_ns >> >> sys_unshare > unshare_nsproxy_namespaces > create_new_namespaces > copy_mnt_ns >> >> sys_unshare > unshare_nsproxy_namespaces > create_new_namespaces > copy_utsname > clone_uts_ns >> >> sys_unshare > unshare_nsproxy_namespaces > create_new_namespaces > copy_ipcs > get_ipc_ns >> >> sys_unshare > unshare_nsproxy_namespaces > create_new_namespaces > copy_pid_ns > create_pid_namespace >> >> sys_unshare > unshare_nsproxy_namespaces > create_new_namespaces > copy_net_ns >> >> Then why the special change to fork? That was not reflected on >> the unshare path as far as I could see. > > Fork can specify more than one CLONE flag at once, so collecting them > all in one statementn seemed helpful. setns can only set one at a time. unshare can also specify more than one CLONE flag at once. I just pointed that out becase that seemed really unsymmetrical.

> Ok, understood, we can't just punt this one to a higher layer... > > So this comes back to a question above, which is how do we determine > which device it is from? Sounds like we need something added to > ns_common or one of the 6 namespace types structs. Or we can just hard code reading it off of the appropriate magic filesystem. Probably what we want is a well named helper function that does the job.

I just care that when we talk about these things we are talking about inode numbers from a superblock that is associated with a given device number. That way I don't have nightmares about dealing with a namespace for namespaces. Eric