On 27 Mar 2026, at 9:46, 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. > > 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.
OK. I will give this a try. Best Regards, Yan, Zi
