Re: [PATCH 3/5] mm: make buffered writes work with RWF_UNCACHED

Dave Chinner
2019-12-11T00:28:22Z

On Wed, Dec 11, 2019 at 11:23:49AM +1100, Dave Chinner wrote:
> On Tue, Dec 10, 2019 at 09:24:52AM -0700, Jens Axboe wrote:
> > If RWF_UNCACHED is set for io_uring (or pwritev2(2)), we'll drop the
> > cache instantiated for buffered writes. If new pages aren't
> > instantiated, we leave them alone. This provides similar semantics to
> > reads with RWF_UNCACHED set.
>
> So what about filesystems that don't use generic_perform_write()?
> i.e. Anything that uses the iomap infrastructure (i.e.
> iomap_file_buffered_write()) instead of generic_file_write_iter())
> will currently ignore RWF_UNCACHED. That's XFS and gfs2 right now,
> but there are likely to be more in the near future as more
> filesystems are ported to the iomap infrastructure.

Hmmm - I'm missing part of this patchset, and I see a second version
has been posted that has iomap stuff in it. I'll go look at that
now...

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com