On 05/12/2023 13:09, David Hildenbrand wrote:
>>> +static __always_inline void __folio_remove_rmap(struct folio *folio,
>>> + struct page *page, unsigned int nr_pages,
>>> + struct vm_area_struct *vma, enum rmap_mode mode)
>>> +{
>>> atomic_t *mapped = &folio->_nr_pages_mapped;
>>> - int nr = 0, nr_pmdmapped = 0;
>>> - bool last;
>>> + int last, nr = 0, nr_pmdmapped = 0;
>>
>> nit: you're being inconsistent across the functions with signed vs unsigned for
>> page counts (e.g. nr, nr_pmdmapped) - see __folio_add_rmap(),
>> __folio_add_file_rmap(), __folio_add_anon_rmap().
>>
>
> Definitely.
>
>> I suggest pick one and stick to it. Personally I'd go with signed int (since
>> that's what all the counters in struct folio that we are manipulating are,
>> underneath the atomic_t) then check that nr_pages > 0 in
>> __folio_rmap_sanity_checks().
>
> Can do, but note that the counters are signed to detect udnerflows. It doesn't
> make sense here to pass a negative number.
I agree it doesn't make sense to pass negative - hence the check.
These 2 functions are inconsistent on size, but agree on signed:
long folio_nr_pages(struct folio *folio)
int folio_nr_pages_mapped(struct folio *folio)
I don't have a strong opinon.
>
>>
>>> enum node_stat_item idx;
>>> - VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
>>> - VM_BUG_ON_PAGE(compound && !PageHead(page), page);
>>> + __folio_rmap_sanity_checks(folio, page, nr_pages, mode);
>>> /* Is page being unmapped by PTE? Is this its last map to be removed? */
>>> - if (likely(!compound)) {
>>> - last = atomic_add_negative(-1, &page->_mapcount);
>>> - nr = last;
>>> - if (last && folio_test_large(folio)) {
>>> - nr = atomic_dec_return_relaxed(mapped);
>>> - nr = (nr < COMPOUND_MAPPED);
>>> - }
>>> - } else if (folio_test_pmd_mappable(folio)) {
>>> - /* That test is redundant: it's for safety or to optimize out */
>>> + if (likely(mode == RMAP_MODE_PTE)) {
>>> + do {
>>> + last = atomic_add_negative(-1, &page->_mapcount);
>>> + if (last && folio_test_large(folio)) {
>>> + last = atomic_dec_return_relaxed(mapped);
>>> + last = (last < COMPOUND_MAPPED);
>>> + }
>>> + if (last)
>>> + nr++;
>>> + } while (page++, --nr_pages > 0);
>>> + } else if (mode == RMAP_MODE_PMD) {
>>> last = atomic_add_negative(-1, &folio->_entire_mapcount);
>>> if (last) {
>>> nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
>>> @@ -1517,7 +1528,7 @@ void page_remove_rmap(struct page *page, struct
>>> vm_area_struct *vma,
>>> * is still mapped.
>>> */
>>> if (folio_test_pmd_mappable(folio) && folio_test_anon(folio))
>>
>> folio_test_pmd_mappable() -> folio_test_large()
>>
>> Since you're converting this to support batch PTE removal, it might as well also
>> support smaller-than-pmd too?
>
> I remember that you have a patch for that, right? :)
>
>>
>> I currently have a patch to do this same change in the multi-size THP series.
>>
>
> Ah, yes, and that should go in first.
>
>
