Re: [PATCHv8 1/6] block, fs: restore kiocb based write hint processing

[Keith Busch <kbusch@kernel.org>]

On Mon, Oct 21, 2024 at 10:09:57AM -0700, Bart Van Assche wrote:
> On 10/21/24 8:47 AM, Keith Busch wrote:
> > On Fri, Oct 18, 2024 at 07:50:32AM +0200, Christoph Hellwig wrote:
> > > On Thu, Oct 17, 2024 at 09:09:32AM -0700, Keith Busch wrote:
> > > >   {
> > > >   	*kiocb = (struct kiocb) {
> > > >   		.ki_filp = filp,
> > > >   		.ki_flags = filp->f_iocb_flags,
> > > >   		.ki_ioprio = get_current_ioprio(),
> > > > +		.ki_write_hint = file_write_hint(filp),
> > > 
> > > And we'll need to distinguish between the per-inode and per file
> > > hint.  I.e. don't blindly initialize ki_write_hint to the per-inode
> > > one here, but make that conditional in the file operation.
> > 
> > Maybe someone wants to do direct-io with partions where each partition
> > has a different default "hint" when not provided a per-io hint? I don't
> > know of such a case, but it doesn't sound terrible. In any case, I feel
> > if you're directing writes through these interfaces, you get to keep all
> > the pieces: user space controls policy, kernel just provides the
> > mechanisms to do it.
> 
> Is it important to support partitions on top of FDP namespaces? 

It's already used with partitions, so yes, it's important. Breaking that
as a condition to make it work with the block stack is a non-starter.