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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v1 00/10] Remove READ_ONLY_THP_FOR_FS Kconfig Message-ID: <4007802e-f87c-41a4-8dcd-9af867eb3fac@lucifer.local> References: <20260327014255.2058916-1-ziy@nvidia.com> <10748785-08a9-41c7-bacd-88f05fdf1a88@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10748785-08a9-41c7-bacd-88f05fdf1a88@kernel.org> X-Rspamd-Queue-Id: 98BD71A0008 X-Stat-Signature: enx7y981b7gnet5ha1jddro1irtxqfpe X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1774621671-590931 X-HE-Meta: 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 CCbPjM/5 A8/s41xD8H8REh8sNRXbgEC8JR+MiGYz3slS5yIdqs1RFfhH5MbmBw/2mnTjtnYJ5xlVSVAallQLnX1BWSMikruGku0rpuYQC5KIDIT38JTGyWFmLmPmaWcCTitDbfa15FlgS572eoaUyascY+aE+k9nzmW3nHz8C7ykPn/UOW1Jq9l/kfQcLDcOYa+UUY5v7crHf45YOTnxbdDvWlvgDAdUu1NyxFbj/l+UALlojg2Vj2yg7AWap0JLpB3GmSeiHy36LNNIyuX3SVWw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 27, 2026 at 02:46:43PM +0100, David Hildenbrand (Arm) wrote: > On 3/27/26 02:42, Zi Yan wrote: > > Hi all, > > > > This patchset removes READ_ONLY_THP_FOR_FS Kconfig and enables creating > > read-only THPs for FSes with large folio support (the supported orders > > need to include PMD_ORDER) by default. > > > > The changes are: > > 1. collapse_file() from mm/khugepaged.c, instead of checking > > CONFIG_READ_ONLY_THP_FOR_FS, makes sure the mapping_max_folio_order() > > of struct address_space of the file is at least PMD_ORDER. > > 2. file_thp_enabled() also checks mapping_max_folio_order() instead. > > 3. truncate_inode_partial_folio() calls folio_split() directly instead > > of the removed try_folio_split_to_order(), since large folios can > > only show up on a FS with large folio support. > > 4. nr_thps is removed from struct address_space, since it is no longer > > needed to drop all read-only THPs from a FS without large folio > > support when the fd becomes writable. Its related filemap_nr_thps*() > > are removed too. > > 5. folio_check_splittable() no longer checks READ_ONLY_THP_FOR_FS. > > 6. Updated comments in various places. > > > > Changelog > > === > > From RFC[1]: > > 1. instead of removing READ_ONLY_THP_FOR_FS function entirely, turn it > > on by default for all FSes with large folio support and the supported > > orders includes PMD_ORDER. > > > > Suggestions and comments are welcome. > > Hi! :) > > The patch set might be better structured by > > 1) Teaching code paths to not only respect READ_ONLY_THP_FOR_FS but also > filesystems with large folios. At that point, READ_ONLY_THP_FOR_FS would > have no effect. And also please do some cleaning up of the mess we have in the code base if at all possible :) I feel like we're constantly building on sand with this, and should treat every major change as a chance to do this. Or otherwise we constantly keep leaving this mess around to deal with... > > 2) Removing READ_ONLY_THP_FOR_FS along with all the old cruft that is no > longer required > > MADV_COLLAPSE will keep working the whole time. Obviously everything should keep working throughout any version of this series. > > -- > Cheers, > > David Cheers, Lorenzo