On 6/9/21 9:21 AM, Christian Brauner wrote: > On Wed, Jun 09, 2021 at 09:02:36AM +0200, Hannes Reinecke wrote: >> On 6/9/21 8:38 AM, Christian Brauner wrote: >>> On Tue, Jun 08, 2021 at 12:16:43PM -0500, Eric W. Biederman wrote: >>>> Hannes Reinecke <hare@xxxxxxx> writes: >>>> >>>>> On 6/8/21 4:29 PM, Christian Brauner wrote: >>>>>> On Tue, Jun 08, 2021 at 04:10:08PM +0200, Hannes Reinecke wrote: >> [ .. ] >>>>> Granted, modifying sysfs layout is not something for the faint-hearted, >>>>> and one really has to look closely to ensure you end up with a >>>>> consistent layout afterwards. >>>>> >>>>> But let's see how things go; might well be that it turns out to be too >>>>> complex to consider. Can't tell yet. >>>> >>>> I would suggest aiming for something like devptsfs without the >>>> complication of /dev/ptmx. >>>> >>>> That is a pseudo filesystem that has a control node and virtual block >>>> devices that were created using that control node. >>> >>> Also see android/binder/binderfs.c >>> >> Ah. Will have a look. > > I implemented this a few years back and I think it should've made it > onto Android by default now. So that approach does indeed work well, it > seems: > https://chromium.googlesource.com/aosp/platform/system/core/+/master/rootdir/init.rc#257 > > This should be easier to follow than the devpts case because you don't > need to wade through the {t,p}ty layer. > >> >>>> >>>> That is the cleanest solution I know and is not strictly limited to use >>>> with containers so it can also gain greater traction. The interaction >>>> with devtmpfs should be simply having devtmpfs create a mount point for >>>> that filesystem. >>>> >>>> This could be a new cleaner api for things like loopback devices. >>> >>> I sent a patchset that implemented this last year. >>> >> Do you have a pointer/commit hash for this? > > Yes, sure: > https://lore.kernel.org/linux-block/20200424162052.441452-1-christian.brauner@xxxxxxxxxx/ > > You can also just pull my branch. I think it's still based on v5.7 or sm: > https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=loopfs > > I'm happy to collaborate on this too. > How _very_ curious. 'kernfs: handle multiple namespace tags' and 'loop: preserve sysfs backwards compability' are essentially the same patches I did for my block namespaces prototyp; I named it 'KOBJ_NS_TYPE_BLK', not 'KOBJ_NS_TYPE_USER', though :-) Guess we really should cooperate. Speaking of which: why did you name it 'user' namespace? There already is a generic 'user_namespace' in include/linux/user_namespace.h, serving as a container for all namespaces; as such it probably should include this 'user' namespace, leading to quite some confusion. Or did I misunderstood something here? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@xxxxxxx +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer
