On 24 Apr 2026, at 8:54, David Hildenbrand (Arm) wrote: > On 4/24/26 04:49, Zi Yan wrote: >> After READ_ONLY_THP_FOR_FS is removed, FS either supports large folio or >> not. folio_split() can be used on a FS with large folio support without >> worrying about getting a THP on a FS without large folio support. >> >> When READ_ONLY_THP_FOR_FS was present, a PMD large pagecache folio can >> appear in a FS without large folio support after khugepaged or >> madvise(MADV_COLLAPSE) creates it. During truncate_inode_partial_folio(), >> such a PMD large pagecache folio is split and if the FS does not support >> large folio, it needs to be split to order-0 ones and could not be split >> non uniformly to ones with various orders. try_folio_split_to_order() was >> added to handle this situation by checking folio_check_splittable(..., >> SPLIT_TYPE_NON_UNIFORM) to detect if the large folio is created due to >> READ_ONLY_THP_FOR_FS and the FS does not support large folio. Now >> READ_ONLY_THP_FOR_FS is removed, all large pagecache folios are created >> with FSes supporting large folio, this function is no longer needed and all >> large pagecache folios can be split non uniformly. > > In general looks good. Just one question: > > folio_check_splittable() also rejects SPLIT_TYPE_NON_UNIFORM / new_order for > swapcache pages.
Since swapcache only supports PMD order or 0 order yet. > > It's confusing, but truncate would never stumble over such folios, correct? Right. Best Regards, Yan, Zi
