linux-kernel - Re: [PATCH bpf-next v5 01/34] mm: memcontrol: use helpers to read page's memcg data

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Message-ID: <20201113171822.GB2955309@carbon.dhcp.thefacebook.com>
Date:   Fri, 13 Nov 2020 09:18:22 -0800
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Network Development <netdev@...r.kernel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Team <kernel-team@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH bpf-next v5 01/34] mm: memcontrol: use helpers to read
 page's memcg data

On Fri, Nov 13, 2020 at 06:25:53AM -0800, Shakeel Butt wrote:
> On Thu, Nov 12, 2020 at 8:02 PM Roman Gushchin <guro@...com> wrote:
> >
> > On Thu, Nov 12, 2020 at 07:25:48PM -0800, Alexei Starovoitov wrote:
> > > On Thu, Nov 12, 2020 at 7:18 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> > > >
> > > > On Thu, 12 Nov 2020 19:04:56 -0800 Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> > > >
> > > > > On Thu, Nov 12, 2020 at 04:26:10PM -0800, Roman Gushchin wrote:
> > > > > >
> > > > > > These patches are not intended to be merged through the bpf tree.
> > > > > > They are included into the patchset to make bpf selftests pass and for
> > > > > > informational purposes.
> > > > > > It's written in the cover letter.
> > > > > ...
> > > > > > Maybe I had to just list their titles in the cover letter. Idk what's
> > > > > > the best option for such cross-subsystem dependencies.
> > > > >
> > > > > We had several situations in the past releases where dependent patches
> > > > > were merged into multiple trees. For that to happen cleanly from git pov
> > > > > one of the maintainers need to create a stable branch/tag and let other
> > > > > maintainers pull that branch into different trees. This way the sha-s
> > > > > stay the same and no conflicts arise during the merge window.
> > > > > In this case sounds like the first 4 patches are in mm tree already.
> > > > > Is there a branch/tag I can pull to get the first 4 into bpf-next?
> > > >
> > > > Not really, at present.  This is largely by design, although it does cause
> > > > this problem once or twice a year.
> > > >
> > > > These four patches:
> > > >
> > > > mm-memcontrol-use-helpers-to-read-pages-memcg-data.patch
> > > > mm-memcontrol-slab-use-helpers-to-access-slab-pages-memcg_data.patch
> > > > mm-introduce-page-memcg-flags.patch
> > > > mm-convert-page-kmemcg-type-to-a-page-memcg-flag.patch
> > > >
> > > > are sufficiently reviewed - please pull them into the bpf tree when
> > > > convenient.  Once they hit linux-next, I'll drop the -mm copies and the
> > > > bpf tree maintainers will then be responsible for whether & when they
> > > > get upstream.
> > >
> > > That's certainly an option if they don't depend on other patches in the mm tree.
> > > Roman probably knows best ?
> >
> > Yes, they are self-contained and don't depend on any patches in the mm tree.
> >
> 
> The patch "mm, kvm: account kvm_vcpu_mmap to kmemcg" in mm tree
> depends on that series.

True, and I believe there are (or will be) more dependencies like this.
But it should be fine, we only have to make sure that these 4 patches
will be merged first.

Thanks!