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Date: Mon, 1 Jul 2024 07:55:37 -0600
From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org
Subject: Re: [PATCH 3/3] nvme: don't set io_opt if NOWS is zero
Message-ID: <ZoK1WRFbr1dK86FK@kbusch-mbp>
References: <20240701051800.1245240-1-hch@lst.de>
 <20240701051800.1245240-4-hch@lst.de>
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In-Reply-To: <20240701051800.1245240-4-hch@lst.de>

On Mon, Jul 01, 2024 at 07:17:52AM +0200, Christoph Hellwig wrote:
> NOWS is one of the annoying "0's based values" in NVMe, where 0 means one
> and we thus can't detect if it isn't set.  

We can detect if it is set based on the namespace features flags,
though.

> Thus a NOWS value of 0 means
> that the Namespace Optimal Write Size is a single LBA, which is clearly
> bogus.  Ignore the value in that case and don't propagate an io_opt
> value to the block layer.

Hm, why is that clearly bogus? Optane SSDs were optimized for
single-sector writes.