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Biederman" , gregkh@linuxfoundation.org, containers@lists.linux.dev, linux-kernel@vger.kernel.org, lkml@metux.net References: <9157affa-b27a-c0f4-f6ee-def4a991fd4e@suse.de> <20210608142911.ievp2rpuquxjuyus@wittgenstein> <877dj4ff9g.fsf@disp2133> <20210609063818.xnod4rzvti3ujkvn@wittgenstein> <20210609072108.ldhsxfnfql4pacqx@wittgenstein> From: Hannes Reinecke Subject: Re: device namespaces Message-ID: <85a0d777-dea6-9574-8946-9fc8f912c1af@suse.de> Date: Wed, 9 Jun 2021 09:54:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <20210609072108.ldhsxfnfql4pacqx@wittgenstein> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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@ubuntu.com/ > > 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@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer