On Mon, Jun 09, 2025 at 09:04:20AM -0700, Darrick J. Wong wrote:
> > + if (iter->fbatch) {
> > + struct folio *folio = folio_batch_next(iter->fbatch);
> > +
> > + if (folio) {
> > + folio_get(folio);
> > + folio_lock(folio);
>
> Hrm. So each folio that is added to the batch isn't locked, nor does
> the batch (or iomap) hold a refcount on the folio until we get here.
find_get_entry references a folio, and filemap_get_folios_dirty
preserves that reference. It will be released in folio_batch_release.
So this just add an extra reference for local operation so that the
rest of iomap doesn't need to know about that magic.
> Do
> we have to re-check that folio->{mapping,index} match what iomap is
> trying to process? Or can we assume that nobody has removed the folio
> from the mapping?
That's a good point, though as without having the folio locked it
could get truncated, so I think we'll have to redo the truncate
check here.
