jfs: remove ->writepage

->writepage is a very inefficient method to write back data, and only
used through write_cache_pages or a a fallback when no ->migrate_folio
method is present.

Set ->migrate_folio to the generic buffer_head based helper, and remove
the ->writepage implementation.

Link: https://lkml.kernel.org/r/20221202102644.770505-7-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/jfs/inode.c

@@ -264,11 +264,6 @@ int jfs_get_block(struct inode *ip, sector_t lblock,
 	return rc;
 }
 
-static int jfs_writepage(struct page *page, struct writeback_control *wbc)
-{
-	return block_write_full_page(page, jfs_get_block, wbc);
-}
-
 static int jfs_writepages(struct address_space *mapping,
 			struct writeback_control *wbc)
 {
@@ -355,12 +350,12 @@ const struct address_space_operations jfs_aops = {
 	.invalidate_folio = block_invalidate_folio,
 	.read_folio	= jfs_read_folio,
 	.readahead	= jfs_readahead,
-	.writepage	= jfs_writepage,
 	.writepages	= jfs_writepages,
 	.write_begin	= jfs_write_begin,
 	.write_end	= jfs_write_end,
 	.bmap		= jfs_bmap,
 	.direct_IO	= jfs_direct_IO,
+	.migrate_folio	= buffer_migrate_folio,
 };
 
 /*