nilfs2: convert nilfs_grab_buffer() to use a folio

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

Link: https://lkml.kernel.org/r/20231016201114.1928083-12-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/page.c

@@ -25,19 +25,19 @@
 	(BIT(BH_Uptodate) | BIT(BH_Mapped) | BIT(BH_NILFS_Node) |	\
 	 BIT(BH_NILFS_Volatile) | BIT(BH_NILFS_Checked))
 
-static struct buffer_head *
-__nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
-		       int blkbits, unsigned long b_state)
+static struct buffer_head *__nilfs_get_folio_block(struct folio *folio,
+		unsigned long block, pgoff_t index, int blkbits,
+		unsigned long b_state)
 
 {
 	unsigned long first_block;
-	struct buffer_head *bh;
+	struct buffer_head *bh = folio_buffers(folio);
 
-	if (!page_has_buffers(page))
-		create_empty_buffers(page, 1 << blkbits, b_state);
+	if (!bh)
+		bh = folio_create_empty_buffers(folio, 1 << blkbits, b_state);
 
 	first_block = (unsigned long)index << (PAGE_SHIFT - blkbits);
-	bh = nilfs_page_get_nth_block(page, block - first_block);
+	bh = get_nth_bh(bh, block - first_block);
 
 	touch_buffer(bh);
 	wait_on_buffer(bh);
@@ -51,17 +51,17 @@ struct buffer_head *nilfs_grab_buffer(struct inode *inode,
 {
 	int blkbits = inode->i_blkbits;
 	pgoff_t index = blkoff >> (PAGE_SHIFT - blkbits);
-	struct page *page;
+	struct folio *folio;
 	struct buffer_head *bh;
 
-	page = grab_cache_page(mapping, index);
-	if (unlikely(!page))
+	folio = filemap_grab_folio(mapping, index);
+	if (IS_ERR(folio))
 		return NULL;
 
-	bh = __nilfs_get_page_block(page, blkoff, index, blkbits, b_state);
+	bh = __nilfs_get_folio_block(folio, blkoff, index, blkbits, b_state);
 	if (unlikely(!bh)) {
-		unlock_page(page);
-		put_page(page);
+		folio_unlock(folio);
+		folio_put(folio);
 		return NULL;
 	}
 	return bh;