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.
--
Wei Yang
Help you, Help me
