Re: [PATCH 08/12] iomap: move folio_unlock out of iomap_writeback_folio

Christoph Hellwig
2025-06-30T05:45:46Z

On Fri, Jun 27, 2025 at 12:38:52PM -0400, Brian Foster wrote:
> > Move unlocking the folio out of iomap_writeback_folio into the caller.
> > This means the end writeback machinery is now run with the folio locked
> > when no writeback happend, or writeback completed extremely fast.
> >
>
> I notice that folio_end_dropbehind_write() (via folio_end_writeback())
> wants to trylock the folio in order to do its thing. Is this going to
> cause issues with that (i.e. prevent invalidations)?

Good point. It renders the filemap_end_dropbehind_write call (the
function got renamed in 6.16-rc) essentially useless. OTOH this is
the case where no writeback happened due to a race, so it isn't needed
to start with. But it might be worth documenting that fact.