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AJvYcCXzMX3JtfR5o9JNSlCjxX/Rdd4UnBGJ7jobaruCTi8Cn0Lgb5S2f3/dtqp/emrQ4DnFM8ryjs+zyzh8n2ZVvUah+RE= X-Gm-Message-State: AOJu0Yzds8fnclBhABrOHzfQWaFPGIaaLPtIDXXeopLcCnh1seRJghiO Ju3JCt++hDYhjT1rlKFoXT3y4palRaNpwUYEnYHwh3l0zL/mh+pSjHN5bCsqF6FsZ/C4t/8fVWC sBZ7O0wpLHnFuSN8ZHVsdxoO/tSU= X-Google-Smtp-Source: AGHT+IHU6G58rVKMj+aRmyqqW7vPgGFeK5cKETFFid5YSn9XIvkoyYNQs0na099XvSqN8a5PMEzJyhX64q6lif3Ag+c= X-Received: by 2002:a05:6214:5d01:b0:6bf:60b8:d4d7 with SMTP id 6a1803df08f44-6bf7d545f64mr12246996d6.15.1723764721380; Thu, 15 Aug 2024 16:32:01 -0700 (PDT) MIME-Version: 1.0 References: <20240814171800.23558-1-me@yhndnzj.com> <20240815150819.9873910fa73a3f9f5e37ef4d@linux-foundation.org> In-Reply-To: From: Nhat Pham Date: Thu, 15 Aug 2024 16:31:50 -0700 Message-ID: Subject: Re: [PATCH] mm/memcontrol: respect zswap.writeback setting from parent cg too To: Yosry Ahmed 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7830618000E X-Stat-Signature: i4fcrwutj67bhbggdhih5p43eozrbq5x X-Rspam-User: X-HE-Tag: 1723764722-97186 X-HE-Meta: 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 2aTeKstX c2ZTqrvaBJMZ2s/flq2SqZSUUoinbIqX4TjvzJkJcEFPuAHR8gMP0F5zcu95+JlbnIF8/QzvDv4mOGab9bzvP+xCf1YeA/Psl/bxewMUY1ASv6RFNipR1EjGRbzz4k+Bwo5sSwcYih8JrVhecqK9tEtgbKQgy++OmwqZWMCiHfytHjVX2EW1pEJZ4qjKKabugfO1nQYD8jSzpk818lJnEmhLgMgqShXOoociiqu8Hm52wMWmlUw48Lx0R6k77XQ73DJ5PyN5aJzX0QYG899cKhPwqnX8O6itC+8HEn+1AVbvWfkAkKKh2x9Brdp6qub3TdyoFYPAWhs8FZVdmwPoepvu7m7mdElwtHflNWfUPv1qSMGymNPCXzHIaZMK/1vkdIr1qhHhIcFeolyzV88w9kZJQrg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.031093, 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 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 wrote: > > > > > > 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 z= swap > > > > writeback for its cgroup, the subcgroups, which could possibly be o= wned > > > > 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.r= st? > > > 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).