[PATCH V6 00/10] namespaces: log namespaces per task
Richard Guy Briggs
rgb at redhat.com
Fri May 8 14:42:50 UTC 2015
On 15/04/27, Eric W. Biederman wrote:
> Richard Guy Briggs <rgb at redhat.com> writes:
> > On 15/04/24, Eric W. Biederman wrote:
> >> Richard Guy Briggs <rgb at redhat.com> writes:
> >> > On 15/04/22, Richard Guy Briggs wrote:
> >> >> On 15/04/20, Eric W. Biederman wrote:
> >> >> > Richard Guy Briggs <rgb at 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.
Alright, I'll change the device over to that... We can figure out how
to select the correct device number of nsfs instances if it increases
> >> >> 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.
Ah sorry, my mistake, I was thinking setns... I've added a call in
> > 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.
There is a bit of overhead to read that, so I've added a dev_t member to
ns_common. Simplest way I found was to call iterate_supers() since
struct file_system_type *nsfs isn't exposed.
> 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.
Richard Guy Briggs <rbriggs at redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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