Commit 62beb906 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

mm: convert page_remove_rmap() to use a folio internally 

The API for page_remove_rmap() needs to be page-based, because we can
remove mappings of pages individually.  But inside the function, we want
to only call compound_head() once and then use the folio APIs instead of
the page APIs that each call compound_head().

Link: https://lkml.kernel.org/r/20230111142915.1001531-6-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b14224fb

mm/rmap.c

+26 −21
Original line number Diff line number Diff line
@@ -1365,19 +1365,21 @@ void page_add_file_rmap(struct page *page, 
 *

 * The caller needs to hold the pte lock.

 */

void page_remove_rmap(struct page *page,

	struct vm_area_struct *vma, bool compound)

void page_remove_rmap(struct page *page, struct vm_area_struct *vma,

		bool compound)

{

	atomic_t *mapped;

	struct folio *folio = page_folio(page);

	atomic_t *mapped = &folio->_nr_pages_mapped;

	int nr = 0, nr_pmdmapped = 0;

	bool last;

	enum node_stat_item idx;



	VM_BUG_ON_PAGE(compound && !PageHead(page), page);



	/* Hugetlb pages are not counted in NR_*MAPPED */

	if (unlikely(PageHuge(page))) {

	if (unlikely(folio_test_hugetlb(folio))) {

		/* hugetlb pages are always mapped with pmds */

		atomic_dec(compound_mapcount_ptr(page));

		atomic_dec(&folio->_entire_mapcount);

		return;

	}
@@ -1385,20 +1387,18 @@ void page_remove_rmap(struct page *page, 
	if (likely(!compound)) {

		last = atomic_add_negative(-1, &page->_mapcount);

		nr = last;

		if (last && PageCompound(page)) {

			mapped = subpages_mapcount_ptr(compound_head(page));

		if (last && folio_test_large(folio)) {

			nr = atomic_dec_return_relaxed(mapped);

			nr = (nr < COMPOUND_MAPPED);

		}

	} else if (PageTransHuge(page)) {

	} else if (folio_test_pmd_mappable(folio)) {

		/* That test is redundant: it's for safety or to optimize out */



		last = atomic_add_negative(-1, compound_mapcount_ptr(page));

		last = atomic_add_negative(-1, &folio->_entire_mapcount);

		if (last) {

			mapped = subpages_mapcount_ptr(page);

			nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);

			if (likely(nr < COMPOUND_MAPPED)) {

				nr_pmdmapped = thp_nr_pages(page);

				nr_pmdmapped = folio_nr_pages(folio);

				nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);

				/* Raced ahead of another remove and an add? */

				if (unlikely(nr < 0))
@@ -1411,21 +1411,26 @@ void page_remove_rmap(struct page *page, 
	}



	if (nr_pmdmapped) {

		__mod_lruvec_page_state(page, PageAnon(page) ? NR_ANON_THPS :

				(PageSwapBacked(page) ? NR_SHMEM_PMDMAPPED :

				NR_FILE_PMDMAPPED), -nr_pmdmapped);

		if (folio_test_anon(folio))

			idx = NR_ANON_THPS;

		else if (folio_test_swapbacked(folio))

			idx = NR_SHMEM_PMDMAPPED;

		else

			idx = NR_FILE_PMDMAPPED;

		__lruvec_stat_mod_folio(folio, idx, -nr_pmdmapped);

	}

	if (nr) {

		__mod_lruvec_page_state(page, PageAnon(page) ? NR_ANON_MAPPED :

				NR_FILE_MAPPED, -nr);

		idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;

		__lruvec_stat_mod_folio(folio, idx, -nr);



		/*

		 * Queue anon THP for deferred split if at least one small

		 * page of the compound page is unmapped, but at least one

		 * small page is still mapped.

		 * Queue anon THP for deferred split if at least one

		 * page of the folio is unmapped and at least one page

		 * is still mapped.

		 */

		if (PageTransCompound(page) && PageAnon(page))

		if (folio_test_pmd_mappable(folio) && folio_test_anon(folio))

			if (!compound || nr < nr_pmdmapped)

				deferred_split_huge_page(compound_head(page));

				deferred_split_huge_page(&folio->page);

	}



	/*