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. It's confusing, but truncate would never stumble over such folios, correct? -- Cheers, David
