On Mon, Dec 05, 2022 at 01:29:25PM +0100, Jan Kara wrote: > Now we don't need .writepage hook for anything anymore. Reclaim is fine > with relying on .writepages to clean pages and we often couldn't do much > from the .writepage callback anyway. We only need to provide > .migrate_folio callback for the ext4_journalled_aops - let's use > buffer_migrate_page_norefs() there so that buffers cannot be modified ^^^^^^^^^^^^^^^^^^^^^^^^^^ this should be buffer_migrate_folio_norefs, no? > under jdb2's hands. > > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Signed-off-by: Jan Kara <jack@xxxxxxx> Could you clarify in the commit how critical it is to use the _norefs() variant? It's not entirely clear what you mean by "let's use...". I think what is meant is that we need to use ..._noref() or we can get in trouble if while the page update is getting committed, there is an attempted to migrate the folio containing the page. buffer_migrate_folio_norefs() is currently not exported (although buffer_migrate_folio is). So if we need it for ext4, we're going to have to EXPORT_SYMBOL buffer_migrate_folio_norefs. Any objections from the mm folks? - Ted
