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b=RKU1dYlgBU82CoJq/FNbCLIs6Ou85063aqNpNlAtM2GDE4hEek++6HXCXxP2MQuha mGZ2sQpEMq2yfcqBbr/4kfY/D5fAD0P4Mgqr3rNS0JyOB7k6qaaRUio0FTTZVjVLtU ZDckc5TZWYAGsJ+62Bt5Nt07/TG+NYu1TKL1UFGK5gwtiw9TIs7i5CUfmIEaWfE+PN 32wgGPcQ7IMcsPTzveiZPkOUVZ99a/SyJeS7YTTxTo62K1zhmIYKHwJ7/HV4mqNqZu Kv/KPEHMH7BW0bB4Yu4W4Tex2fRE4EyVnD8qWMcB3z1DtGBsBTqVA+crebScEiyDSr WGzebGpd5zhHA== Message-ID: Date: Tue, 28 Apr 2026 22:19:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] selftests/mm: khugepaged: initialize file contents via mmap To: Zi Yan Cc: Vineet Agarwal , akpm@linux-foundation.org, ljs@kernel.org, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260428133138.88802-1-agarwal.vineet2006@gmail.com> <583F8EE1-5C49-4250-A24B-0D73372E3864@nvidia.com> <95714cec-205e-4b56-b8ff-9afaf9408020@kernel.org> <0FA813EA-5EFA-482F-B8BF-FE65D4169C44@nvidia.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 73628A000A X-Stat-Signature: j4fy4gadfnfxzkcxjg8iwe8ij4d4e9d7 X-HE-Tag: 1777407571-645555 X-HE-Meta: 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 Br8z8AWN LmN3aU3bQwjocpgvlUKCN4yF8zqmhkpJDcNSEOFieeA0EfL9RmHQTxUth2fWsu6MA5QP4PVhkRbfn94zLe1MpQorzmfT+ZGpq0ryoSny3w8M9vLSxdzdmjdBn2rg4IbChM7eR8oXkQnlobv6kADW4z/VQeoy7y4N99DEcoKD4fLL4GfmqoUUWiZK+nMvw7ysr0Vu71SKv+z2DYVKZs9eihpJ+HX+ypt7x+96vD0ekFDywlj7NCvj5nXliZqZn5uIVnO6fv7I1hvXeUDdei4sx9Aen3/akCv8+vASzWeL8I1TTNh8SEK04RYbBynHctEzP9S2j4RsPh+DswtA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/28/26 22:17, Zi Yan wrote: > On 28 Apr 2026, at 16:07, David Hildenbrand (Arm) wrote: > >> On 4/28/26 21:56, Zi Yan wrote: >>> >>> >>> This patch breaks the khugepaged test for READ_ONLY_THP_FOR_FS. >>> >>> When I ran sudo ./khugepaged all:file ~/ on ext4, >>> >>> collapse_max_ptes_none (khugepaged:file) fails. >> >> madvise() still works? Is it maybe because of dirty folios? (but that should >> also be the case on write ...) > > I asked codex instead. > > Basically, mmap(MMAP_SHARED) makes the written folio dirty and the folio > survives the later drop_caches. Adding msync() fixes the issue. But why doesn't the write() make the folios dirty? Or are we running into some race condition where the old code just worked by chance? -- Cheers, David