mm/rmap: Turn page_lock_anon_vma_read() into folio_lock_anon_vma_read()

Add back page_lock_anon_vma_read() as a wrapper.  This saves a few calls
to compound_head().  If any callers were passing a tail page before,
this would have failed to lock the anon VMA as page->mapping is not
valid for tail pages.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

include/linux/rmap.h

@@ -267,6 +267,7 @@ void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked);
  * Called by memory-failure.c to kill processes.
  */
 struct anon_vma *page_lock_anon_vma_read(struct page *page);
+struct anon_vma *folio_lock_anon_vma_read(struct folio *folio);
 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 

mm/folio-compat.c

@@ -164,3 +164,10 @@ void putback_lru_page(struct page *page)
 {
 	folio_putback_lru(page_folio(page));
 }
+
+#ifdef CONFIG_MMU
+struct anon_vma *page_lock_anon_vma_read(struct page *page)
+{
+	return folio_lock_anon_vma_read(page_folio(page));
+}
+#endif

mm/memory-failure.c

@@ -487,12 +487,13 @@ static struct task_struct *task_early_kill(struct task_struct *tsk,
 static void collect_procs_anon(struct page *page, struct list_head *to_kill,
 				int force_early)
 {
+	struct folio *folio = page_folio(page);
 	struct vm_area_struct *vma;
 	struct task_struct *tsk;
 	struct anon_vma *av;
 	pgoff_t pgoff;
 
-	av = page_lock_anon_vma_read(page);
+	av = folio_lock_anon_vma_read(folio);
 	if (av == NULL)	/* Not actually mapped anymore */
 		return;
 

mm/rmap.c

@@ -526,28 +526,28 @@ struct anon_vma *page_get_anon_vma(struct page *page)
  * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
  * reference like with page_get_anon_vma() and then block on the mutex.
  */
-struct anon_vma *page_lock_anon_vma_read(struct page *page)
+struct anon_vma *folio_lock_anon_vma_read(struct folio *folio)
 {
 	struct anon_vma *anon_vma = NULL;
 	struct anon_vma *root_anon_vma;
 	unsigned long anon_mapping;
 
 	rcu_read_lock();
-	anon_mapping = (unsigned long)READ_ONCE(page->mapping);
+	anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
 	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 		goto out;
-	if (!page_mapped(page))
+	if (!folio_mapped(folio))
 		goto out;
 
 	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
 	root_anon_vma = READ_ONCE(anon_vma->root);
 	if (down_read_trylock(&root_anon_vma->rwsem)) {
 		/*
-		 * If the page is still mapped, then this anon_vma is still
+		 * If the folio is still mapped, then this anon_vma is still
 		 * its anon_vma, and holding the mutex ensures that it will
 		 * not go away, see anon_vma_free().
 		 */
-		if (!page_mapped(page)) {
+		if (!folio_mapped(folio)) {
 			up_read(&root_anon_vma->rwsem);
 			anon_vma = NULL;
 		}
@@ -560,7 +560,7 @@ struct anon_vma *page_lock_anon_vma_read(struct page *page)
 		goto out;
 	}
 
-	if (!page_mapped(page)) {
+	if (!folio_mapped(folio)) {
 		rcu_read_unlock();
 		put_anon_vma(anon_vma);
 		return NULL;