Re: [PATCH V6 00/10] namespaces: log namespaces per task
Richard Guy Briggs <rgb(a)redhat.com> writes:
On 15/04/24, Eric W. Biederman wrote:
> Richard Guy Briggs <rgb(a)redhat.com> writes:
> > On 15/04/22, Richard Guy Briggs wrote:
> >> On 15/04/20, Eric W. Biederman wrote:
> >> > Richard Guy Briggs <rgb(a)redhat.com> 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