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b=MmEvGNuS4AFAleo9RH3oaj/4hU71oUjr2weE3X45t3aN5V20ak+iRE+073fXmHpaS cxKzgqeqUZyvdNGdoZnrROTRi8OkMDXivWtnQLjKiwNOBqntm8ZK+4nDOBU+v72uLC mM+ujrNmRkjdDgUO3Vjx2BDKifHrhQ+0fSulbD1rc72dhINtKjt6gett7wZOeMnKAd ksBZsCzgaQpYcSDdW82QiF6cOHx3q8zZxcvXaVM8TuEqr00kmVjm0TaMt/Un1FeVUA xgUgWi3516UfcoIOQ8v0rwKIb5w4nkS7fd9DWKg52v+qZyIsEFKaLiBvr9vAR9+TaU QOKTbv4GzbqLQ== Message-ID: <29f79411-3ec9-4e03-a1f1-2869164dccd3@kernel.org> Date: Wed, 4 Feb 2026 22:14:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: WARNING in memory_failure() at include/linux/huge_mm.h:635 triggered To: Zi Yan Cc: =?UTF-8?B?5piv5Y+C5beu?= , linux-mm@kvack.org, linmiaohe@huawei.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Matthew Wilcox References: <1db245a8-f9ab-42e4-8cc6-cc7562961921@kernel.org> <48978612-6933-4897-85DD-6740B6C8570B@nvidia.com> <25CA4D90-A24E-49C6-92D2-08080EC81466@nvidia.com> <032058DC-CD8D-406A-B986-740E41C834B2@nvidia.com> <9E046323-740A-434A-8B60-B8A32D0955C0@nvidia.com> <11399c99-f966-47be-bbb4-a7d4e79c8c38@kernel.org> <86002E57-58EB-4940-A7F0-7AE4A60484DF@nvidia.com> <7bb98650-cb7a-4230-8868-7da2aab5923a@kernel.org> <0BBB65F0-7ED4-40DE-9949-761326993D7D@nvidia.com> From: "David Hildenbrand (arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: wahbunawcdi7xxio7fh7xbramxk1kuz9 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B0C6A4000B X-HE-Tag: 1770239694-18497 X-HE-Meta: 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 +Qm3m8Kn Et2uL9U4EB97wwc/7cz7UAPtWs9UYNVrk/uwduEQBNqKydN9+WViMzYOyoASRnbk/jIEslAgYJ88pgevzodXi+dcVlOTmZzB/vTkkeuBYgoe+iUS5OdtQun96ivY4dgwlAkZJjp5rG6SF6egr+uA69TnSHwnX2tRjXqIkvXubHo4FtUYQU72XQsUvMlRdq+w+5WgEApw9/Fa548WZl4kbHqEmt2zzpgtn8pPcjZd3fxHPcggrOprZmA+gudWxkuf1hwyJg4Y42lDLWAk+C/vqRKtk5D1xlfvkvteu7i7GmXn7IY47Qf4QvaxIyjH9qhxrydWPqEj+46xAiUvcdUZCc2fd6pkq4JyTBYvf 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: List-Subscribe: List-Unsubscribe: On 2/4/26 21:45, Zi Yan wrote: > On 4 Feb 2026, at 15:31, David Hildenbrand (arm) wrote: > >> On 2/4/26 21:13, Zi Yan wrote: >>> >>> >>> Yes. >>> >>> >>> Right. My patchset[1] is trying to add it, since hugetlb is used as a folio >>> in most places and large_rmappable is a folio flag. >>> >>> >>> [1] https://lore.kernel.org/all/20260130034818.472804-1-ziy@nvidia.com/ >> >> Still on my todo list :) > > Sure. Wait for your input there. :) Hoping I'll be able to dig through that pile in my inbox fairly quickly throughout the next days. Thanks for all the review you did why I was not paying a lot of attention. > >> >>> >>> Yes, I am thinking about removing mapcount in struct page to achieve that. >> >> On my todo list :) Stupid CONFIG_PAGE_MAPCOUNT that is still around and stupid partial-mapping handling. >> >> I worked on this after LPC but was distracted by PTO :D >> >>> And only pages used for vm_insert_*() and folios need mapcount. >> >> vm_insert_*() won't need it for non-folio things. Only folios. We just have to teach the zap code to also leave the mapcount of these non-folio things alone. IOW, identify them when we map/unmap as "not folio" and not touch the mapcount. > > Oh, that sounds great. I thought I would need to convert all drive code > that does vm_insert_*() to use folio. Heh, no. We really just have to identify them when mapping and unmapping them. "these are not folios". > Basically, I hit > __folio_large_mapcount_sanity_checks() on _mm_id_mapcount when I moved > _mm_id_mapcount and friends from prep_compound_page() to page_rmappable_folio(). Yes, exact same issue. I ran into something similar in the past and documented it in __folio_rmap_sanity_checks(): /* * TODO: we get driver-allocated folios that have nothing to do with * the rmap using vm_insert_page(); therefore, we cannot assume that * folio_test_large_rmappable() holds for large folios. We should * handle any desired mapcount+stats accounting for these folios in * VM_MIXEDMAP VMAs separately, and then sanity-check here that * we really only get rmappable folios. */ should have been "for these pages" now that it's clear that not all pages are/will-be folios. I added an rmappable check in there back then but found out about the other compound pages. > IIUC, __folio_add_file_rmap() can just return if a non-folio compound page > is encountered. Of course, remove part needs to do the same. We should never call that code, because ... we don't won't really have a folio :) With Willy's changes, page_folio() will return NULL for things that are not a folio IIRC. > > >> >>> Code >>> uses vm_insert_*() on pages would probably have a struct mappable_page >>> with mapcount. >> >> I don't think we'll need a mapcount for them. Only for folios. >> >>> >>> >>> I think it might the other way around. memdesc does not have mapcount, >>> if we do not have a separate struct for these mappable pages now, >>> what do we use at memdesc time? folio? >> >> Folios will have mapcount related information, yes. Long term, memdescs will for sure not have any. >> >> Real fun begins once we start messing with refcounts. vm_insert_*() will be "fun" on non-folio things. > > Yeah, maybe we will refcounts for every used memdescs. But who knows. Some of these things should probably be frozen pages and use a different interface then. A bunch of hard nuts to crack. -- Cheers, David