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[91.12.99.188]) by smtp.gmail.com with ESMTPSA id p21sm16699366edw.18.2021.05.05.06.39.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 May 2021 06:39:09 -0700 (PDT) To: Michal Hocko , Andrew Morton Cc: linux-kernel@vger.kernel.org, "Michael S. Tsirkin" , Jason Wang , Alexey Dobriyan , Mike Rapoport , "Matthew Wilcox (Oracle)" , Oscar Salvador , Roman Gushchin , Alex Shi , Steven Price , Mike Kravetz , Aili Yao , Jiri Bohac , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Naoya Horiguchi , linux-hyperv@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20210429122519.15183-1-david@redhat.com> <20210429122519.15183-4-david@redhat.com> <0710d8d5-2608-aeed-10c7-50a272604d97@redhat.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v1 3/7] mm: rename and move page_is_poisoned() Message-ID: <57ac524c-b49a-99ec-c1e4-ef5027bfb61b@redhat.com> Date: Wed, 5 May 2021 15:39:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org >> Long story short, this should be good enough for the cases we actually can >> handle? What am I missing? > > I am not sure I follow. My point is that I fail to see any added value > of the check as it doesn't prevent the race (it fundamentally cannot as > the page can be poisoned at any time) but the failure path doesn't > put_page which is incorrect even for hwpoison pages. Oh, I think you are right. If we have a page and return NULL we would leak a reference. Actually, we discussed in that thread handling this entirely differently, which resulted in a v7 [1]; however Andrew moved forward with this (outdated?) patch, maybe that was just a mistake? Yes, I agree we should revert that patch for now. Regarding the race comment: AFAIU e.g., [2], it's not really a problem with a race, but rather some corner case issue that can happen if we fail in memory_failure(). [1] https://lkml.kernel.org/r/20210406104123.451ee3c3@alex-virtual-machine [2] https://lkml.kernel.org/r/20210331015258.GB22060@hori.linux.bs1.fc.nec.co.jp -- Thanks, David / dhildenb