mm: Add folio_mapcount()

This implements the same algorithm as total_mapcount(), which is transformed into a wrapper function.

Matthew Wilcox (Oracle) committed 4 years ago

Commit 4ba11191 parent 74e8ee43 files · +40 −25Browse files

Unified · Split

3 files

 	return atomic_read(&page->_mapcount) + 1;
 }
+int folio_mapcount(struct folio *folio);
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-int total_mapcount(struct page *page);
+static inline int total_mapcount(struct page *page)
+{
+	return folio_mapcount(page_folio(page));
+}
 int page_trans_huge_mapcount(struct page *page);
 #else
 static inline int total_mapcount(struct page *page)

@@ -2465,30 +2465,6 @@ static void __split_huge_page(struct page page, struct list_head list, · 2464 unmodified lines
2465	}	2465	}
2466	}	2466	}
2467		2467
2468	int total_mapcount(struct page *page)
2469	{
2470	int i, compound, nr, ret;
2471
2472	VM_BUG_ON_PAGE(PageTail(page), page);
2473
2474	if (likely(!PageCompound(page)))
2475	return atomic_read(&page->_mapcount) + 1;
2476
2477	compound = compound_mapcount(page);
2478	nr = compound_nr(page);
2479	if (PageHuge(page))
2480	return compound;
2481	ret = compound;
2482	for (i = 0; i < nr; i++)
2483	ret += atomic_read(&page[i]._mapcount) + 1;
2484	/* File pages has compound_mapcount included in _mapcount */
2485	if (!PageAnon(page))
2486	return ret - compound * nr;
2487	if (PageDoubleMap(page))
2488	ret -= nr;
2489	return ret;
2490	}
2491
2492	/*	2468	/*
2493	* This calculates accurately how many mappings a transparent hugepage	2469	* This calculates accurately how many mappings a transparent hugepage
2494	* has (unlike page_mapcount() which isn't fully accurate). This full	2470	* has (unlike page_mapcount() which isn't fully accurate). This full

@@ -740,6 +740,39 @@ int __page_mapcount(struct page *page) · 739 unmodified lines
740	}	740	}
741	EXPORT_SYMBOL_GPL(__page_mapcount);	741	EXPORT_SYMBOL_GPL(__page_mapcount);
742		742
		743	/**
		744	* folio_mapcount() - Calculate the number of mappings of this folio.
		745	* @folio: The folio.
		746	*
		747	* A large folio tracks both how many times the entire folio is mapped,
		748	* and how many times each individual page in the folio is mapped.
		749	* This function calculates the total number of times the folio is
		750	* mapped.
		751	*
		752	* Return: The number of times this folio is mapped.
		753	*/
		754	int folio_mapcount(struct folio *folio)
		755	{
		756	int i, compound, nr, ret;
		757
		758	if (likely(!folio_test_large(folio)))
		759	return atomic_read(&folio->_mapcount) + 1;
		760
		761	compound = folio_entire_mapcount(folio);
		762	nr = folio_nr_pages(folio);
		763	if (folio_test_hugetlb(folio))
		764	return compound;
		765	ret = compound;
		766	for (i = 0; i < nr; i++)
		767	ret += atomic_read(&folio_page(folio, i)->_mapcount) + 1;
		768	/* File pages has compound_mapcount included in _mapcount */
		769	if (!folio_test_anon(folio))
		770	return ret - compound * nr;
		771	if (folio_test_double_map(folio))
		772	ret -= nr;
		773	return ret;
		774	}
		775
743	/**	776	/**
744	* folio_copy - Copy the contents of one folio to another.	777	* folio_copy - Copy the contents of one folio to another.
745	* @dst: Folio to copy to.	778	* @dst: Folio to copy to.

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