Re: [PATCH 2/2] block: remove the per-bio/request write hint

Dave Chinner
2022-03-06T23:17:44Z

On Sun, Mar 06, 2022 at 11:06:12AM -0700, Jens Axboe wrote:
> On 3/6/22 11:01 AM, Christoph Hellwig wrote:
> > On Sun, Mar 06, 2022 at 10:11:46AM -0700, Jens Axboe wrote:
> >> Yes, I think we should kill it. If we retain the inode hint, the f2fs
> >> doesn't need a any changes. And it should be safe to make the per-file
> >> fcntl hints return EINVAL, which they would on older kernels anyway.
> >> Untested, but something like the below.
> >
> > I've sent this off to the testing farm this morning, but EINVAL might
> > be even better:
> >
> > http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/more-hint-removal

Yup, I like that.

> I do think EINVAL is better, as it just tells the app it's not available
> like we would've done before. With just doing zeroes, that might break
> applications that set-and-verify. Of course there's also the risk of
> that since we retain inode hints (so they work), but fail file hints.
> That's a lesser risk though, and we only know of the inode hints being
> used.

Agreed, I think EINVAL would be better here - jsut make it behave
like it would on a kernel that never supported this functionality in
the first place. Seems simpler to me for user applications if we do
that.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com