Pavel Emelyanov <[email protected]> writes: > On 06/03/2014 09:26 PM, Serge Hallyn wrote: >> Quoting Pavel Emelyanov ([email protected]): >>> On 05/29/2014 07:32 PM, Serge Hallyn wrote: >>>> Quoting Marian Marinov ([email protected]): >>>>> -----BEGIN PGP SIGNED MESSAGE----- >>>>> Hash: SHA1 >>>>> >>>>> On 05/29/2014 01:06 PM, Eric W. Biederman wrote: >>>>>> Marian Marinov <[email protected]> writes: >>>>>> >>>>>>> Hello, >>>>>>> >>>>>>> I have the following proposition. >>>>>>> >>>>>>> Number of currently running processes is accounted at the root user >>>>>>> namespace. The problem I'm facing is that >>>>>>> multiple containers in different user namespaces share the process >>>>>>> counters. >>>>>> >>>>>> That is deliberate. >>>>> >>>>> And I understand that very well ;) >>>>> >>>>>> >>>>>>> So if containerX runs 100 with UID 99, containerY should have NPROC >>>>>>> limit of above 100 in order to execute any >>>>>>> processes with ist own UID 99. >>>>>>> >>>>>>> I know that some of you will tell me that I should not provision all of >>>>>>> my containers with the same UID/GID maps, >>>>>>> but this brings another problem. >>>>>>> >>>>>>> We are provisioning the containers from a template. The template has a >>>>>>> lot of files 500k and more. And chowning >>>>>>> these causes a lot of I/O and also slows down provisioning considerably. >>>>>>> >>>>>>> The other problem is that when we migrate one container from one host >>>>>>> machine to another the IDs may be already >>>>>>> in use on the new machine and we need to chown all the files again. >>>>>> >>>>>> You should have the same uid allocations for all machines in your fleet >>>>>> as much as possible. That has been true >>>>>> ever since NFS was invented and is not new here. You can avoid the cost >>>>>> of chowning if you untar your files inside >>>>>> of your user namespace. You can have different maps per machine if you >>>>>> are crazy enough to do that. You can even >>>>>> have shared uids that you use to share files between containers as long >>>>>> as none of those files is setuid. And map >>>>>> those shared files to some kind of nobody user in your user namespace. >>>>> >>>>> We are not using NFS. We are using a shared block storage that offers us >>>>> snapshots. So provisioning new containers is >>>>> extremely cheep and fast. Comparing that with untar is comparing a race >>>>> car with Smart. Yes it can be done and no, I >>>>> do not believe we should go backwards. >>>>> >>>>> We do not share filesystems between containers, we offer them block >>>>> devices. >>>> >>>> Yes, this is a real nuisance for openstack style deployments. >>>> >>>> One nice solution to this imo would be a very thin stackable filesystem >>>> which does uid shifting, or, better yet, a non-stackable way of shifting >>>> uids at mount. >>> >>> I vote for non-stackable way too. Maybe on generic VFS level so that >>> filesystems >>> don't bother with it. From what I've seen, even simple stacking is quite a >>> challenge. >> >> Do you have any ideas for how to go about it? It seems like we'd have >> to have separate inodes per mapping for each file, which is why of >> course stacking seems "natural" here. > > I was thinking about "lightweight mapping" which is simple shifting. Since > we're trying to make this co-work with user-ns mappings, simple uid/gid shift > should be enough. Please, correct me if I'm wrong. > > If I'm not, then it looks to be enough to have two per-sb or per-mnt values > for uid and gid shift. Per-mnt for now looks more promising, since container's > FS may be just a bind-mount from shared disk. > >> Trying to catch the uid/gid at every kernel-userspace crossing seems >> like a design regression from the current userns approach. I suppose we >> could continue in the kuid theme and introduce a iiud/igid for the >> in-kernel inode uid/gid owners. Then allow a user privileged in some >> ns to create a new mount associated with a different mapping for any >> ids over which he is privileged. > > User-space crossing? From my point of view it would be enough if we just turn > uid/gid read from disk (well, from whenever FS gets them) into uids, that > would > match the user-ns's ones, this sould cover the VFS layer and related syscalls > only, which is, IIRC stat-s family and chown. > > Ouch, and the whole quota engine :\
And posix acls. But all of this is 90% done already. I think today we just have conversions to the initial user namespace. We just need a few tweaks to allow it and a per superblock user namespace setting. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
