ext4: convert ac_bitmap_page to ac_bitmap_folio

This just carries around the bd_bitmap_folio so should also be a folio.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20240416172900.244637-5-willy@infradead.orgSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -2161,8 +2161,8 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
 	 * double allocate blocks. The reference is dropped
 	 * in ext4_mb_release_context
 	 */
-	ac->ac_bitmap_page = &e4b->bd_bitmap_folio->page;
-	get_page(ac->ac_bitmap_page);
+	ac->ac_bitmap_folio = e4b->bd_bitmap_folio;
+	folio_get(ac->ac_bitmap_folio);
 	ac->ac_buddy_page = &e4b->bd_buddy_folio->page;
 	get_page(ac->ac_buddy_page);
 	/* store last allocated for subsequent stream allocation */
@@ -6002,8 +6002,8 @@ static void ext4_mb_release_context(struct ext4_allocation_context *ac)
 
 		ext4_mb_put_pa(ac, ac->ac_sb, pa);
 	}
-	if (ac->ac_bitmap_page)
-		put_page(ac->ac_bitmap_page);
+	if (ac->ac_bitmap_folio)
+		folio_put(ac->ac_bitmap_folio);
 	if (ac->ac_buddy_page)
 		put_page(ac->ac_buddy_page);
 	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)

fs/ext4/mballoc.h

@@ -204,7 +204,7 @@ struct ext4_allocation_context {
 	__u8 ac_2order;		/* if request is to allocate 2^N blocks and
 				 * N > 0, the field stores N, otherwise 0 */
 	__u8 ac_op;		/* operation, for history only */
-	struct page *ac_bitmap_page;
+	struct folio *ac_bitmap_folio;
 	struct page *ac_buddy_page;
 	struct ext4_prealloc_space *ac_pa;
 	struct ext4_locality_group *ac_lg;