mm: use a folio in copy_present_pte()
We still have to keep the page around because we need to know which page in the folio we're copying, but we can replace five implict calls to compound_head() with one. Link: https://lkml.kernel.org/r/20230116191813.2145215-6-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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14ddee4126
15
mm/memory.c
15
mm/memory.c
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@ -906,25 +906,28 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
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unsigned long vm_flags = src_vma->vm_flags;
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unsigned long vm_flags = src_vma->vm_flags;
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pte_t pte = *src_pte;
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pte_t pte = *src_pte;
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struct page *page;
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struct page *page;
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struct folio *folio;
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page = vm_normal_page(src_vma, addr, pte);
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page = vm_normal_page(src_vma, addr, pte);
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if (page && PageAnon(page)) {
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if (page)
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folio = page_folio(page);
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if (page && folio_test_anon(folio)) {
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/*
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/*
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* If this page may have been pinned by the parent process,
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* If this page may have been pinned by the parent process,
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* copy the page immediately for the child so that we'll always
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* copy the page immediately for the child so that we'll always
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* guarantee the pinned page won't be randomly replaced in the
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* guarantee the pinned page won't be randomly replaced in the
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* future.
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* future.
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*/
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*/
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get_page(page);
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folio_get(folio);
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if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) {
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if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) {
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/* Page maybe pinned, we have to copy. */
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/* Page may be pinned, we have to copy. */
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put_page(page);
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folio_put(folio);
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return copy_present_page(dst_vma, src_vma, dst_pte, src_pte,
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return copy_present_page(dst_vma, src_vma, dst_pte, src_pte,
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addr, rss, prealloc, page);
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addr, rss, prealloc, page);
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}
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}
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rss[MM_ANONPAGES]++;
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rss[MM_ANONPAGES]++;
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} else if (page) {
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} else if (page) {
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get_page(page);
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folio_get(folio);
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page_dup_file_rmap(page, false);
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page_dup_file_rmap(page, false);
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rss[mm_counter_file(page)]++;
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rss[mm_counter_file(page)]++;
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}
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}
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@ -937,7 +940,7 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
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ptep_set_wrprotect(src_mm, addr, src_pte);
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ptep_set_wrprotect(src_mm, addr, src_pte);
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pte = pte_wrprotect(pte);
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pte = pte_wrprotect(pte);
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}
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}
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VM_BUG_ON(page && PageAnon(page) && PageAnonExclusive(page));
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VM_BUG_ON(page && folio_test_anon(folio) && PageAnonExclusive(page));
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/*
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/*
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* If it's a shared mapping, mark it clean in
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* If it's a shared mapping, mark it clean in
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