nilfs2: convert nilfs_mdt_forget_block() to use a folio

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

Link: https://lkml.kernel.org/r/20231016201114.1928083-14-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

@@ -356,30 +356,28 @@ int nilfs_mdt_delete_block(struct inode *inode, unsigned long block)
  */
 int nilfs_mdt_forget_block(struct inode *inode, unsigned long block)
 {
-	pgoff_t index = (pgoff_t)block >>
-		(PAGE_SHIFT - inode->i_blkbits);
-	struct page *page;
-	unsigned long first_block;
+	pgoff_t index = block >> (PAGE_SHIFT - inode->i_blkbits);
+	struct folio *folio;
+	struct buffer_head *bh;
 	int ret = 0;
 	int still_dirty;
 
-	page = find_lock_page(inode->i_mapping, index);
-	if (!page)
+	folio = filemap_lock_folio(inode->i_mapping, index);
+	if (IS_ERR(folio))
 		return -ENOENT;
 
-	wait_on_page_writeback(page);
+	folio_wait_writeback(folio);
 
-	first_block = (unsigned long)index <<
-		(PAGE_SHIFT - inode->i_blkbits);
-	if (page_has_buffers(page)) {
-		struct buffer_head *bh;
-
-		bh = nilfs_page_get_nth_block(page, block - first_block);
+	bh = folio_buffers(folio);
+	if (bh) {
+		unsigned long first_block = index <<
+				(PAGE_SHIFT - inode->i_blkbits);
+		bh = get_nth_bh(bh, block - first_block);
 		nilfs_forget_buffer(bh);
 	}
-	still_dirty = PageDirty(page);
-	unlock_page(page);
-	put_page(page);
+	still_dirty = folio_test_dirty(folio);
+	folio_unlock(folio);
+	folio_put(folio);
 
 	if (still_dirty ||
 	    invalidate_inode_pages2_range(inode->i_mapping, index, index) != 0)