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Date: Tue, 24 Jun 2025 14:46:25 +0200
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Sagi Grimberg <sagi@grimberg.me>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Kanchan Joshi <joshi.k@samsung.com>,
	Leon Romanovsky <leon@kernel.org>,
	Nitesh Shetty <nj.shetty@samsung.com>,
	Logan Gunthorpe <logang@deltatee.com>, linux-block@vger.kernel.org,
	linux-nvme@lists.infradead.org
Subject: Re: [PATCH 3/8] nvme-pci: refactor nvme_pci_use_sgls
Message-ID: <20250624124625.GA19239@lst.de>
References: <20250623141259.76767-1-hch@lst.de> <20250623141259.76767-4-hch@lst.de> <aFlyYjALviyhQ-IE@kbusch-mbp>
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In-Reply-To: <aFlyYjALviyhQ-IE@kbusch-mbp>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Mon, Jun 23, 2025 at 09:27:30AM -0600, Keith Busch wrote:
> > -	if (nvme_pci_use_sgls(dev, req, iod->sgt.nents))
> > +	if (use_sgl == SGL_FORCED ||
> > +	    (use_sgl == SGL_SUPPORTED &&
> > +	     (!sgl_threshold || nvme_pci_avg_seg_size(req) >= sgl_threshold)))
> >  		ret = nvme_pci_setup_sgls(nvmeq, req, &cmnd->rw);
> 
> We historically interpreted sgl_threshold set to 0 to mean disable SGL
> usage, maybe because the controller is broken or something. It might be
> okay to have 0 mean to not consider segment sizes, but I just wanted to
> point out this is a different interpretation of the user parameter.

This is still a leftover from the threshold mess in the first version.
I'll fix it for the next one.