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Date: Mon, 21 Oct 2024 09:47:47 -0600
From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <kbusch@meta.com>, linux-block@vger.kernel.org,
	linux-nvme@lists.infradead.org, axboe@kernel.dk,
	io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	joshi.k@samsung.com, javier.gonz@samsung.com,
	Nitesh Shetty <nj.shetty@samsung.com>,
	Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCHv8 1/6] block, fs: restore kiocb based write hint
 processing
Message-ID: <ZxZ3o_HzN8HN6QPK@kbusch-mbp>
References: <20241017160937.2283225-1-kbusch@meta.com>
 <20241017160937.2283225-2-kbusch@meta.com>
 <20241018055032.GB20262@lst.de>
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In-Reply-To: <20241018055032.GB20262@lst.de>

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.