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[70.44.39.90]) by smtp.gmail.com with ESMTPSA id y17sm108505qth.59.2020.03.16.09.19.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2020 09:19:08 -0700 (PDT) Date: Mon, 16 Mar 2020 12:19:07 -0400 From: Johannes Weiner To: Chris Down Cc: Andrew Morton , Tejun Heo , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 1/2] mm, memcg: Fix corruption on 64-bit divisor in memory.high throttling Message-ID: <20200316161907.GE67986@cmpxchg.org> References: <80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@chrisdown.name> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 12, 2020 at 06:02:54PM +0000, Chris Down wrote: > 0e4b01df8659 had a bunch of fixups to use the right division method. > However, it seems that after all that it still wasn't right -- div_u64 > takes a 32-bit divisor. > > The headroom is still large (2^32 pages), so on mundane systems you > won't hit this, but this should definitely be fixed. > > Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") > Reported-by: Johannes Weiner > Signed-off-by: Chris Down > Cc: Andrew Morton > Cc: Tejun Heo > Cc: linux-mm@kvack.org > Cc: cgroups@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@fb.com > Cc: stable@vger.kernel.org # 5.4.x div_u64 versus div64_u64 is really a handgrenade. We just fixed a bunch of those in psi as well. Acked-by: Johannes Weiner