zonefs: remove ->writepage

->writepage is only used for single page writeback from memory reclaim,
and not called at all for cgroup writeback.  Follow the lead of XFS
and remove ->writepage and rely entirely on ->writepages.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/zonefs/super.c

@@ -232,13 +232,6 @@ static const struct iomap_writeback_ops zonefs_writeback_ops = {
 	.map_blocks		= zonefs_write_map_blocks,
 };
 
-static int zonefs_writepage(struct page *page, struct writeback_control *wbc)
-{
-	struct iomap_writepage_ctx wpc = { };
-
-	return iomap_writepage(page, wbc, &wpc, &zonefs_writeback_ops);
-}
-
 static int zonefs_writepages(struct address_space *mapping,
 			     struct writeback_control *wbc)
 {
@@ -266,7 +259,6 @@ static int zonefs_swap_activate(struct swap_info_struct *sis,
 static const struct address_space_operations zonefs_file_aops = {
 	.read_folio		= zonefs_read_folio,
 	.readahead		= zonefs_readahead,
-	.writepage		= zonefs_writepage,
 	.writepages		= zonefs_writepages,
 	.dirty_folio		= filemap_dirty_folio,
 	.release_folio		= iomap_release_folio,