rmap: add folio parameter to __page_set_anon_rmap()

Avoid the compound_head() call in PageAnon() by passing in the folio that
all callers have.  Also save me from wondering whether page->mapping can
ever be overwritten on a tail page (I don't think it can, but I'm not 100%
sure).

Link: https://lkml.kernel.org/r/20230116192959.2147032-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/rmap.c b/mm/rmap.c
index 0b5abdd..43760d6 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1131,19 +1131,20 @@ void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
 
 /**
  * __page_set_anon_rmap - set up new anonymous rmap
- * @page:      Page or Hugepage to add to rmap
+ * @folio:     Folio which contains page.
+ * @page:      Page to add to rmap.
  * @vma:       VM area to add page to.
  * @address:   User virtual address of the mapping     
  * @exclusive: the page is exclusively owned by the current process
  */
-static void __page_set_anon_rmap(struct page *page,
+static void __page_set_anon_rmap(struct folio *folio, struct page *page,
        struct vm_area_struct *vma, unsigned long address, int exclusive)
 {
        struct anon_vma *anon_vma = vma->anon_vma;
 
        BUG_ON(!anon_vma);
 
-       if (PageAnon(page))
+       if (folio_test_anon(folio))
                goto out;
 
        /*
@@ -1155,14 +1156,14 @@ static void __page_set_anon_rmap(struct page *page,
                anon_vma = anon_vma->root;
 
        /*
-        * page_idle does a lockless/optimistic rmap scan on page->mapping.
+        * page_idle does a lockless/optimistic rmap scan on folio->mapping.
         * Make sure the compiler doesn't split the stores of anon_vma and
         * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
         * could mistake the mapping for a struct address_space and crash.
         */
        anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
-       WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
-       page->index = linear_page_index(vma, address);
+       WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
+       folio->index = linear_page_index(vma, address);
 out:
        if (exclusive)
                SetPageAnonExclusive(page);
@@ -1254,7 +1255,7 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
        if (likely(!folio_test_ksm(folio))) {
                /* address might be in next vma when migration races vma_adjust */
                if (first)
-                       __page_set_anon_rmap(page, vma, address,
+                       __page_set_anon_rmap(folio, page, vma, address,
                                             !!(flags & RMAP_EXCLUSIVE));
                else
                        __page_check_anon_rmap(page, vma, address);
@@ -1297,7 +1298,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
        }
 
        __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
-       __page_set_anon_rmap(&folio->page, vma, address, 1);
+       __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
 }
 
 /**
@@ -2528,7 +2529,7 @@ void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
        VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
        VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
        if (first)
-               __page_set_anon_rmap(page, vma, address,
+               __page_set_anon_rmap(folio, page, vma, address,
                                     !!(flags & RMAP_EXCLUSIVE));
 }
 
@@ -2541,6 +2542,6 @@ void hugepage_add_new_anon_rmap(struct page *page,
        /* increment count (starts at -1) */
        atomic_set(&folio->_entire_mapcount, 0);
        folio_clear_hugetlb_restore_reserve(folio);
-       __page_set_anon_rmap(page, vma, address, 1);
+       __page_set_anon_rmap(folio, page, vma, address, 1);
 }
 #endif /* CONFIG_HUGETLB_PAGE */