Re: [PATCH v2 2/3] selftests/mm: add check_folio_orders() helper.

On Mon, Aug 11, 2025 at 02:39:08PM -0400, Zi Yan wrote: [...]

...

...

+static int gather_folio_orders(char *vaddr_start, size_t len,

• 	       int pagemap_file, int kpageflags_file,
  

• 	       int orders[], int nr_orders)
  

+{

• uint64_t page_flags = 0;
• int cur_order = -1;
• char *vaddr;
• if (!pagemap_file || !kpageflags_file)

• return -1;
  

• if (nr_orders <= 0)

• return -1;
  

• for (vaddr = vaddr_start; vaddr < vaddr_start + len; ) {

• char *next_folio_vaddr;
  

• int status;
  

• if (get_page_flags(vaddr, pagemap_file, kpageflags_file, &page_flags))
  

• 	return -1;
  

• /* all order-0 pages with possible false postive (non folio) */
  

• if (!(page_flags & (KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL))) {
  

• 	orders[0]++;
  

• 	vaddr += psize();
  

• 	continue;
  

• }
  

• /* skip non thp compound pages */
  

• if (!(page_flags & KPF_THP)) {
  

• 	vaddr += psize();
  

• 	continue;
  

• }
  

• /* vpn points to part of a THP at this point */
  

• if (page_flags & KPF_COMPOUND_HEAD)
  

• 	cur_order = 1;
  

• else {
  

• 	/* not a head nor a tail in a THP? */
  

• 	if (!(page_flags & KPF_COMPOUND_TAIL))
  

• 		return -1;
  

• 	continue;
  

• }
  

• next_folio_vaddr = vaddr + (1UL << (cur_order + pshift()));
  

• if (next_folio_vaddr >= vaddr_start + len)
  

• 	break;
  

Would we skip order 1 folio at the last position?

For example, vaddr_start is 0x2000, len is 0x2000 and the folio at vaddr_start is an order 1 folio, whose size is exactly 0x2000.

Then we will get next_folio_vaddr == vaddr_start + len.

Could that happen?

No. After the loop, there is code checking cur_order and updating orders[].

Oh, I missed this.