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>

diff --git a/mm/memory.c b/mm/memory.c
index 20a5c80..029f838 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -906,25 +906,28 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
        unsigned long vm_flags = src_vma->vm_flags;
        pte_t pte = *src_pte;
        struct page *page;
+       struct folio *folio;
 
        page = vm_normal_page(src_vma, addr, pte);
-       if (page && PageAnon(page)) {
+       if (page)
+               folio = page_folio(page);
+       if (page && folio_test_anon(folio)) {
                /*
                 * If this page may have been pinned by the parent process,
                 * copy the page immediately for the child so that we'll always
                 * guarantee the pinned page won't be randomly replaced in the
                 * future.
                 */
-               get_page(page);
+               folio_get(folio);
                if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) {
-                       /* Page maybe pinned, we have to copy. */
-                       put_page(page);
+                       /* Page may be pinned, we have to copy. */
+                       folio_put(folio);
                        return copy_present_page(dst_vma, src_vma, dst_pte, src_pte,
                                                 addr, rss, prealloc, page);
                }
                rss[MM_ANONPAGES]++;
        } else if (page) {
-               get_page(page);
+               folio_get(folio);
                page_dup_file_rmap(page, false);
                rss[mm_counter_file(page)]++;
        }
@@ -937,7 +940,7 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
                ptep_set_wrprotect(src_mm, addr, src_pte);
                pte = pte_wrprotect(pte);
        }
-       VM_BUG_ON(page && PageAnon(page) && PageAnonExclusive(page));
+       VM_BUG_ON(page && folio_test_anon(folio) && PageAnonExclusive(page));
 
        /*
         * If it's a shared mapping, mark it clean in