bcachefs: set FMODE_CAN_ODIRECT instead of a dummy direct_IO method

Since commit a2ad63da ("VFS: add FMODE_CAN_ODIRECT file flag") file
systems can just set the FMODE_CAN_ODIRECT flag at open time instead of
wiring up a dummy direct_IO method to indicate support for direct I/O.
Do that for bcachefs so that noop_direct_IO can eventually be removed.

Similar to commit b2943499 ("xfs: set FMODE_CAN_ODIRECT instead of
a dummy direct_IO method").
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs.c

@@ -1145,6 +1145,8 @@ static int bch2_open(struct inode *vinode, struct file *file)
 			return ret;
 	}
 
+	file->f_mode |= FMODE_CAN_ODIRECT;
+
 	return generic_file_open(vinode, file);
 }
 
@@ -1237,7 +1239,6 @@ static const struct address_space_operations bch_address_space_operations = {
 	.write_end	= bch2_write_end,
 	.invalidate_folio = bch2_invalidate_folio,
 	.release_folio	= bch2_release_folio,
-	.direct_IO	= noop_direct_IO,
 #ifdef CONFIG_MIGRATION
 	.migrate_folio	= filemap_migrate_folio,
 #endif