Re: [PATCH v1 02/39] mm/rmap: introduce and use hugetlb_remove_rmap()

David Hildenbrand
2023-12-11T16:35:51Z

On 11.12.23 17:33, Matthew Wilcox wrote:
> On Mon, Dec 11, 2023 at 04:56:15PM +0100, David Hildenbrand wrote:
>> hugetlb rmap handling differs quite a lot from "ordinary" rmap code.
>> For example, hugetlb currently only supports entire mappings, and treats
>> any mapping as mapped using a single "logical PTE". Let's move it out
>> of the way so we can overhaul our "ordinary" rmap.
>> implementation/interface.
>>
>> Let's introduce and use hugetlb_remove_rmap() and remove the hugetlb
>> code from page_remove_rmap(). This effectively removes one check on the
>> small-folio path as well.
>>
>> Note: all possible candidates that need care are page_remove_rmap() that
>> pass compound=true.
>>
>> Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>
> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
>
>> +++ b/mm/rmap.c
>> @@ -1482,13 +1482,6 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
>>
>> VM_BUG_ON_PAGE(compound && !PageHead(page), page);
>>
>> - /* Hugetlb pages are not counted in NR_*MAPPED */
>> - if (unlikely(folio_test_hugetlb(folio))) {
>> - /* hugetlb pages are always mapped with pmds */
>> - atomic_dec(&folio->_entire_mapcount);
>> - return;
>> - }
>
> Maybe add
> VM_BUG_ON_FOLIO(folio_test_hugetlb(folio), folio);
>

A bulk-add that in patch #6.

Thanks!

--
Cheers,

David / dhildenb