Re: [PATCH v7 0/3] FDP and per-io hints

[Keith Busch <kbusch@kernel.org>]

On Tue, Oct 08, 2024 at 02:25:35PM +0200, Christoph Hellwig wrote:
> On Mon, Oct 07, 2024 at 12:10:11PM +0200, Javier González wrote:
> > In summary, what we are asking for is to take the patches that cover the
> > current use-case, and work together on what might be needed for better
> > FS support.
> 
> And I really do not think it is a good idea.  For one it actually
> works against the stated intent of the FDP spec.  Second extending
> the hints to per per-I/O in the io_uring patch is actively breaking
> the nice per-file I/O hint abstraction we have right now, and is
> really unsuitable when actually used on a file and not just a block
> device.  And if you are only on a block device I think passthrough
> of some form is still the far better option, despite the problems
> with it mentioned by Keith.

Then let's just continue with patches 1 and 2. They introduce no new
user or kernel APIs, and people have already reported improvements using
it. Further, it is just a hint, it doesn't lock the kernel into anything
that may hinder future inovations and enhancements. So let's unblock
users and refocus *our* time to something more productive, please?

And to be honest, the per-io hints for generic read/write use is only
valuable for my users if metadata is also exposed to userspace. I know
Javier's team is working on that in parallel, so per-io hints are a
lower priority for me until that part settles.