nilfs2: convert nilfs_mdt_freeze_buffer to use a folio

Remove a number of folio->page->folio conversions.

Link: https://lkml.kernel.org/r/20231016201114.1928083-11-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/mdt.c

@@ -560,17 +560,19 @@ int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
 {
 	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
 	struct buffer_head *bh_frozen;
-	struct page *page;
+	struct folio *folio;
 	int blkbits = inode->i_blkbits;
 
-	page = grab_cache_page(shadow->inode->i_mapping, bh->b_folio->index);
-	if (!page)
-		return -ENOMEM;
+	folio = filemap_grab_folio(shadow->inode->i_mapping,
+			bh->b_folio->index);
+	if (IS_ERR(folio))
+		return PTR_ERR(folio);
 
-	if (!page_has_buffers(page))
-		create_empty_buffers(page, 1 << blkbits, 0);
+	bh_frozen = folio_buffers(folio);
+	if (!bh_frozen)
+		bh_frozen = folio_create_empty_buffers(folio, 1 << blkbits, 0);
 
-	bh_frozen = nilfs_page_get_nth_block(page, bh_offset(bh) >> blkbits);
+	bh_frozen = get_nth_bh(bh_frozen, bh_offset(bh) >> blkbits);
 
 	if (!buffer_uptodate(bh_frozen))
 		nilfs_copy_buffer(bh_frozen, bh);
@@ -582,8 +584,8 @@ int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
 		brelse(bh_frozen); /* already frozen */
 	}
 
-	unlock_page(page);
-	put_page(page);
+	folio_unlock(folio);
+	folio_put(folio);
 	return 0;
 }