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[2003:cb:c709:6200:16ba:af70:999d:6a1a]) by smtp.gmail.com with ESMTPSA id f23-20020a7bc8d7000000b003fe2de3f94fsm1576513wml.12.2023.08.24.00.39.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Aug 2023 00:39:38 -0700 (PDT) Message-ID: <37c2b525-5c2c-d400-552c-9ccb91f4d7bf@redhat.com> Date: Thu, 24 Aug 2023 09:39:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v3] mm/thp: fix "mm: thp: kill __transhuge_page_enabled()" To: Zach O'Keefe , linux-mm@kvack.org, Yang Shi Cc: linux-kernel@vger.kernel.org, Saurabh Singh Sengar , Greg KH References: <20230821234844.699818-1-zokeefe@google.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230821234844.699818-1-zokeefe@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: zi3if4xxzbzdd33rkurgj1jo87ims3fu X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0CDF8C0007 X-HE-Tag: 1692862782-887170 X-HE-Meta: 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 f1kVyJeU 3IwpZ73dVqbxk7Blu7e/tp8w432vtf4PhRzQEb9k3XSAJr2zwVHf23GXe93GRua4LTFUAqM9kTy9xKnHq1mjm8mMQYlyfPdW1tkUeA/i6P7Gd6HoT5/cFxqCozmyZZlnTLXdcNPG1RzFIYx38e48uaqCiqyk6S8pnCJeaph3A8EdGIiOl6UNServNJsoWJJ/V08kg44y799f+7HKdCmjwOm+FKrbcMbv0sRAFd+UVNwQM1/iAgdNVI74MUVfStWogVVbEIH/x97Af0LBPglst+LpDXiIdSJCYtIOGWn6OEGnuIubgXUPKTNuzopG5pmF740uwEh69bZz+KtKREYP93CKxmCkGSBB0efGKrCtPA2EZSPsVv0bh68qUMgjZDHG89KaQ 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 22.08.23 01:48, Zach O'Keefe wrote: > The 6.0 commits: > > commit 9fec51689ff6 ("mm: thp: kill transparent_hugepage_active()") > commit 7da4e2cb8b1f ("mm: thp: kill __transhuge_page_enabled()") > > merged "can we have THPs in this VMA?" logic that was previously done > separately by fault-path, khugepaged, and smaps "THPeligible" checks. > > During the process, the semantics of the fault path check changed in two > ways: > > 1) A VM_NO_KHUGEPAGED check was introduced (also added to smaps path). > 2) We no longer checked if non-anonymous memory had a vm_ops->huge_fault > handler that could satisfy the fault. Previously, this check had been > done in create_huge_pud() and create_huge_pmd() routines, but after > the changes, we never reach those routines. > > During the review of the above commits, it was determined that in-tree > users weren't affected by the change; most notably, since the only relevant > user (in terms of THP) of VM_MIXEDMAP or ->huge_fault is DAX, which is > explicitly approved early in approval logic. However, there is at least > one occurrence where an out-of-tree driver that used > VM_HUGEPAGE|VM_MIXEDMAP with a vm_ops->huge_fault handler, was broken. ... so all we did is break an arbitrary out-of-tree driver? Sorry to say, but why should we care? Is there any in-tree code affected and needs a "Fixes:" ? -- Cheers, David / dhildenb