nfs: don't return AOP_WRITEPAGE_ACTIVATE from nfs_do_writepage

nfs_do_writepage is a successful return that requires the caller to
unlock the folio.  Using it here requires special casing both in
nfs_do_writepage and nfs_writepages_callback and leaves a land mine in
nfs_wb_folio in case it ever set the flag.  Remove it and just
unconditionally unlock in nfs_writepages_callback.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

Author: Christoph Hellwig

fs/nfs/write.c

@@ -663,8 +663,6 @@ static int nfs_do_writepage(struct folio *folio, struct writeback_control *wbc,
 		 */
 		if (nfs_error_is_fatal_on_server(ret))
 			goto out_launder;
-		if (wbc->sync_mode == WB_SYNC_NONE)
-			ret = AOP_WRITEPAGE_ACTIVATE;
 		folio_redirty_for_writepage(wbc, folio);
 		nfs_redirty_request(req);
 		pgio->pg_error = 0;
@@ -703,8 +701,7 @@ static int nfs_writepages_callback(struct folio *folio,
 	int ret;
 
 	ret = nfs_do_writepage(folio, wbc, data);
-	if (ret != AOP_WRITEPAGE_ACTIVATE)
-		folio_unlock(folio);
+	folio_unlock(folio);
 	return ret;
 }