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