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AJvYcCUNbUbuxiSgz4b4IYyIhnkOKBjEnNNAaTr9GZpD8jKbedvlLMlo/4MFapjS3JNS9zJpW8hza3GlQg==@kvack.org X-Gm-Message-State: AOJu0Yx9qGWU3YHiWjUo28jy6gvr6qRQNsmna6d02rsBDAyt7MRdOhVc F+VRvtW0Nsa3KVeyl8jmk6KSbFvQAcIoDRhtKNjGJniHMqlDZMEQ96VygVtTVLMdKDkUpGfztl7 ZjHplPf8Jv+PRgLBAO+iLo5VMi0hksYjGjjno X-Google-Smtp-Source: AGHT+IH0iRyJtUrU93XJ+DPiBi62y8rSBstCZOvrLtJz+l82/qtYFsRaQGGJ3beTy9fdroDR3Is5QPxMwnhk7Ke6ktU= X-Received: by 2002:a17:907:3f0d:b0:a7d:c464:d5f3 with SMTP id a640c23a62f3a-a8643f7712amr60252866b.11.1724094381681; Mon, 19 Aug 2024 12:06:21 -0700 (PDT) MIME-Version: 1.0 References: <20240814171800.23558-1-me@yhndnzj.com> <20240815150819.9873910fa73a3f9f5e37ef4d@linux-foundation.org> In-Reply-To: From: Yosry Ahmed Date: Mon, 19 Aug 2024 12:05:44 -0700 Message-ID: Subject: Re: [PATCH] mm/memcontrol: respect zswap.writeback setting from parent cg too To: Nhat Pham Cc: Andrew Morton , Mike Yuan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, Muchun Song , Shakeel Butt , Roman Gushchin , Michal Hocko , Johannes Weiner Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: qgqgn6drfmf4b6qq6f9u79g6at618rrm X-Rspamd-Queue-Id: E9DBB40010 X-Rspamd-Server: rspam11 X-HE-Tag: 1724094383-676554 X-HE-Meta: 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 v3carqC2 eAyvQgu49++0+kOFOGC3T8p8tD20FjnqRSYgS8A3PaaSf/wQWKmMuAqWrZvhy/GEYUTXGC9dhfhByI418FiVGhxz67VofdA+kJikwir7BxpeqwkOqPzKdJ/rTbnwpyKv7qZ4oWAB+0XbG2s5CT9vXXMuQ/pamcmkzTaVezhbKU2WDDFLOQy3sx9R/1BoVZWyU6TeN2f2BWmfppDc8cne0uMyruWgefqRQKAgd/A34OlAuGKkQoKQM3/0k/YkcMEpGK3hhWpR6Tvin4ZIhmpblqHtTDw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000007, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 15, 2024 at 4:32=E2=80=AFPM Nhat Pham wrote= : > > On Thu, Aug 15, 2024 at 3:10=E2=80=AFPM Yosry Ahmed wrote: > > > > On Thu, Aug 15, 2024 at 3:08=E2=80=AFPM Andrew Morton wrote: > > > > > > On Thu, 15 Aug 2024 12:12:26 -0700 Nhat Pham wrot= e: > > > > > > > > Yeah, I thought about the other way around and reached the same > > > > > conclusion. > > > > > And there's permission boundary in the mix too - if root disables= zswap > > > > > writeback for its cgroup, the subcgroups, which could possibly be= owned > > > > > by other users, should not be able to reenable this. > > > > > > > > Hmm yeah, I think I agree with your and Yosry's reasonings :) It > > > > doesn't affect our use case AFAICS, and the code looks solid to me, > > > > so: > > > > > > > > Reviewed-by: Nhat Pham > > > > > > But you'd still like an update to Documentation/admin-guide/cgroup-v2= .rst? > > > > > > Yeah I'd rather see a v2 with updated docs, and hopefully a selftest > > if the existing tests problem is resolved. > > Ah yeah, I was thinking this could be done in a follow-up patch. > > But yes, please - documentation. Preferably everything together as v2. > > > > > Also, do we want a Fixes tag and to backport this so that current > > users get the new behavior ASAP? > > Hmm, I wonder if it's more confusing for users to change the behavior > in older kernels. > > (OTOH, if this already is what people expect, then yeah it's a good > idea to backport). My rationale is that if people will inevitably get the behavior change when they upgrade their kernel, I'd rather they get it sooner rather than later, before more users start depending on the old behavior. I am guessing there is a chance this is not what backports are meant for. Andrew, any thoughts on this?