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Tue, 18 Feb 2020 17:58:27 -0800 (PST) Received: from localhost ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id e2sm206430pjs.25.2020.02.18.17.58.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Feb 2020 17:58:27 -0800 (PST) Date: Wed, 19 Feb 2020 09:58:19 +0800 From: Murphy Zhou To: Jeff Moyer Cc: Dan Williams , Murphy Zhou , linux-nvdimm , Jia He , Linux MM , "Shutemov, Kirill" , Linux Kernel Mailing List Subject: Re: [PATCH] mm: get rid of WARN if failed to cow user pages Message-ID: <20200219015819.otdnknxpyo52txy7@xzhoux.usersys.redhat.com> References: <20191225054227.gii6ctjkuddjnprs@xzhoux.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Tue, Feb 18, 2020 at 04:09:30PM -0500, Jeff Moyer wrote: > Dan Williams writes: > > > [ drop Ross, add Kirill, linux-mm, and lkml ] > > > > On Tue, Dec 24, 2019 at 9:42 PM Murphy Zhou wrote: > >> > >> By running xfstests with fsdax enabled, generic/437 always hits this > >> warning[1] since this commit: > >> > >> commit 83d116c53058d505ddef051e90ab27f57015b025 > >> Author: Jia He > >> Date: Fri Oct 11 22:09:39 2019 +0800 > >> > >> mm: fix double page fault on arm64 if PTE_AF is cleared > >> > >> Looking at the test program[2] generic/437 uses, it's pretty easy > >> to hit this warning. Remove this WARN as it seems not necessary. > > > > This is not sufficient justification. Does this same test fail without > > DAX? If not, why not? At a minimum you need to explain why this is not > > indicating a problem. > > I ran into this, too, and Kirill has posted a patch[1] to fix the issue. > Note that it's a potential data corrupter, so just removing the warning > is NOT the right approach. :) Agree :) Thanks! > > -Jeff > > [1] https://lore.kernel.org/linux-mm/20200218154151.13349-1-kirill.shutemov@linux.intel.com/T/#u >