Re: [PATCH v1 05/18] mm: improve folio_likely_mapped_shared() using the mapcount of large folios

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On 19.04.24 15:47, Yin, Fengwei wrote:


On 4/19/2024 5:19 PM, David Hildenbrand wrote:
On 19.04.24 04:29, Yin, Fengwei wrote:


On 4/10/2024 3:22 AM, David Hildenbrand wrote:
@@ -2200,7 +2200,22 @@ static inline size_t folio_size(struct folio
*folio)
     */
    static inline bool folio_likely_mapped_shared(struct folio *folio)
    {
-    return page_mapcount(folio_page(folio, 0)) > 1;
+    int mapcount = folio_mapcount(folio);
+
+    /* Only partially-mappable folios require more care. */
+    if (!folio_test_large(folio) ||
unlikely(folio_test_hugetlb(folio)))
+        return mapcount > 1;
My understanding is that mapcount > folio_nr_pages(folio) can cover
order 0 folio. And also folio_entire_mapcount() can cover hugetlb (I am
not 100% sure for this one).  I am wondering whether we can drop above
two lines? Thanks.

folio_entire_mapcount() does not apply to small folios, so we must not
call that for small folios.
Right. I missed this part. Thanks for clarification.

Thanks for the review!

--
Cheers,

David / dhildenb





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