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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id i28sm25764085qtc.57.2020.03.10.17.04.12 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 Mar 2020 17:04:13 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3608.60.0.2.5\)) Subject: Re: [PATCH] mm, numa: fix bad pmd by atomically check for pmd_trans_huge when marking page tables prot_numa From: Qian Cai In-Reply-To: <20200309150531.GD25642@optiplex-lnx> Date: Tue, 10 Mar 2020 20:04:11 -0400 Cc: Linus Torvalds , Linux Memory Management List , LKML , mgorman , Andrew Morton , Michal Hocko , Vlastimil Babka Content-Transfer-Encoding: quoted-printable Message-Id: <917137D2-FD66-4175-AC69-23F8206186C5@lca.pw> References: <20200216191800.22423-1-aquini@redhat.com> <2E0766B8-DDD1-4448-8605-8535A16670FC@lca.pw> <20200307030530.GB4093@t490s> <9124C8B9-FB47-44F5-8606-DD9261BCB383@lca.pw> <20200308231423.GA22348@t490s> <20200309150531.GD25642@optiplex-lnx> To: Rafael Aquini X-Mailer: Apple Mail (2.3608.60.0.2.5) 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 Mar 9, 2020, at 11:05 AM, Rafael Aquini wrote: > I'm still waiting on a similar system to become available, so I can > work on your reproducer case, as well as to dig and wrap my head = around it. >=20 > I still don't think that skipping the pmd_none() in the = change-protection walk=20 > should cause a big fuss like you observed here (yet, it seems it = does), and=20 > the fact that we need that race window to take the __split_huge_pmd() = suggests, > at least to me, that we might be missing this proper split somewhere = else. I have sent out another patch which should be more correct, https://lore.kernel.org/lkml/20200310235846.1319-1-cai@lca.pw/=