mm/migrate: Convert migrate_page() to migrate_folio()

Convert all callers to pass a folio.  Most have the folio
already available.  Switch all users from aops->migratepage to
aops->migrate_folio.  Also turn the documentation into kerneldoc.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Sterba <dsterba@suse.com>

drivers/gpu/drm/i915/gem/i915_gem_userptr.c

@@ -216,8 +216,8 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
 			 * However...!
 			 *
 			 * The mmu-notifier can be invalidated for a
-			 * migrate_page, that is alreadying holding the lock
-			 * on the page. Such a try_to_unmap() will result
+			 * migrate_folio, that is alreadying holding the lock
+			 * on the folio. Such a try_to_unmap() will result
 			 * in us calling put_pages() and so recursively try
 			 * to lock the page. We avoid that deadlock with
 			 * a trylock_page() and in exchange we risk missing

fs/btrfs/disk-io.c

@@ -968,7 +968,7 @@ static int btree_migrate_folio(struct address_space *mapping,
 	if (folio_get_private(src) &&
 	    !filemap_release_folio(src, GFP_KERNEL))
 		return -EAGAIN;
-	return migrate_page(mapping, &dst->page, &src->page, mode);
+	return migrate_folio(mapping, dst, src, mode);
 }
 #else
 #define btree_migrate_folio NULL

fs/nfs/write.c

@@ -2139,7 +2139,7 @@ int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
 		folio_wait_fscache(src);
 	}
 
-	return migrate_page(mapping, &dst->page, &src->page, mode);
+	return migrate_folio(mapping, dst, src, mode);
 }
 #endif
 

include/linux/migrate.h

@@ -62,9 +62,8 @@ extern const char *migrate_reason_names[MR_TYPES];
 #ifdef CONFIG_MIGRATION
 
 extern void putback_movable_pages(struct list_head *l);
-extern int migrate_page(struct address_space *mapping,
-			struct page *newpage, struct page *page,
-			enum migrate_mode mode);
+int migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, enum migrate_mode mode);
 extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
 		unsigned long private, enum migrate_mode mode, int reason,
 		unsigned int *ret_succeeded);

mm/migrate.c

@@ -593,34 +593,37 @@ EXPORT_SYMBOL(folio_migrate_copy);
  *                    Migration functions
  ***********************************************************/
 
-/*
- * Common logic to directly migrate a single LRU page suitable for
- * pages that do not use PagePrivate/PagePrivate2.
+/**
+ * migrate_folio() - Simple folio migration.
+ * @mapping: The address_space containing the folio.
+ * @dst: The folio to migrate the data to.
+ * @src: The folio containing the current data.
+ * @mode: How to migrate the page.
+ *
+ * Common logic to directly migrate a single LRU folio suitable for
+ * folios that do not use PagePrivate/PagePrivate2.
  *
- * Pages are locked upon entry and exit.
+ * Folios are locked upon entry and exit.
  */
-int migrate_page(struct address_space *mapping,
-		struct page *newpage, struct page *page,
-		enum migrate_mode mode)
+int migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, enum migrate_mode mode)
 {
-	struct folio *newfolio = page_folio(newpage);
-	struct folio *folio = page_folio(page);
 	int rc;
 
-	BUG_ON(folio_test_writeback(folio));	/* Writeback must be complete */
+	BUG_ON(folio_test_writeback(src));	/* Writeback must be complete */
 
-	rc = folio_migrate_mapping(mapping, newfolio, folio, 0);
+	rc = folio_migrate_mapping(mapping, dst, src, 0);
 
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
-		folio_migrate_copy(newfolio, folio);
+		folio_migrate_copy(dst, src);
 	else
-		folio_migrate_flags(newfolio, folio);
+		folio_migrate_flags(dst, src);
 	return MIGRATEPAGE_SUCCESS;
 }
-EXPORT_SYMBOL(migrate_page);
+EXPORT_SYMBOL(migrate_folio);
 
 #ifdef CONFIG_BLOCK
 /* Returns true if all buffers are successfully locked */
@@ -671,7 +674,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
 
 	head = folio_buffers(src);
 	if (!head)
-		return migrate_page(mapping, &dst->page, &src->page, mode);
+		return migrate_folio(mapping, dst, src, mode);
 
 	/* Check whether page does not have extra refs before we do more work */
 	expected_count = folio_expected_refs(mapping, src);
@@ -848,7 +851,7 @@ static int fallback_migrate_folio(struct address_space *mapping,
 	    !filemap_release_folio(src, GFP_KERNEL))
 		return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
 
-	return migrate_page(mapping, &dst->page, &src->page, mode);
+	return migrate_folio(mapping, dst, src, mode);
 }
 
 /*
@@ -875,7 +878,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 		struct address_space *mapping = folio_mapping(src);
 
 		if (!mapping)
-			rc = migrate_page(mapping, &dst->page, &src->page, mode);
+			rc = migrate_folio(mapping, dst, src, mode);
 		else if (mapping->a_ops->migrate_folio)
 			/*
 			 * Most folios have a mapping and most filesystems

mm/migrate_device.c

@@ -718,7 +718,8 @@ void migrate_vma_pages(struct migrate_vma *migrate)
 			continue;
 		}
 
-		r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
+		r = migrate_folio(mapping, page_folio(newpage),
+				page_folio(page), MIGRATE_SYNC_NO_COPY);
 		if (r != MIGRATEPAGE_SUCCESS)
 			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
 	}

mm/shmem.c

@@ -3801,7 +3801,7 @@ const struct address_space_operations shmem_aops = {
 	.write_end	= shmem_write_end,
 #endif
 #ifdef CONFIG_MIGRATION
-	.migratepage	= migrate_page,
+	.migrate_folio	= migrate_folio,
 #endif
 	.error_remove_page = shmem_error_remove_page,
 };

mm/swap_state.c

@@ -33,7 +33,7 @@ static const struct address_space_operations swap_aops = {
 	.writepage	= swap_writepage,
 	.dirty_folio	= noop_dirty_folio,
 #ifdef CONFIG_MIGRATION
-	.migratepage	= migrate_page,
+	.migrate_folio	= migrate_folio,
 #endif
 };