On 10 Mar 2025, at 13:00, Matthew Wilcox wrote: > On Mon, Mar 10, 2025 at 12:42:06PM -0400, Zi Yan wrote: >>> Because of the “Careful” comment. But new_folio->* should be fine, >>> since it is the same as new_head. So I probably can replace all >>> new_head with new_folio except those VM_BUG_ON_PAGE checks? > > Why not also the VM_BUG_ON_PAGE check? I mean: > >> @@ -3364,8 +3364,8 @@ static void __split_folio_to_order(struct folio *folio, int old_order, >> /* ->mapping in first and second tail page is replaced by other uses */ >> VM_BUG_ON_PAGE(new_nr_pages > 2 && new_head->mapping != TAIL_MAPPING, >> new_head); > > VM_BUG_ON_PAGE(new_nr_pages > 2 && new_folio->mapping != TAIL_MAPPING, new_head); We are checking new_folio but dump new_head, so it can cause some confusion. But it might not be that bad. > > (or we could just ditch the assert entirely; it's not all that useful) I am open to that. > >> - new_head->mapping = head->mapping; >> - new_head->index = head->index + index; >> + new_folio->mapping = head->mapping; >> + new_folio->index = head->index + index; > > new_folio->mapping = folio->mapping > new_folio->index = folio->index +index; > > (um, and that index + index looks weird; better name might be just 'i') OK. Let me make the changes you suggested and fold it to Hugh’s fix patch, before Andrew picks that up. Best Regards, Yan, Zi
