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Date: Fri, 20 Feb 2026 17:11:55 +0100
From: Christoph Hellwig <hch@lst.de>
To: Caleb Sander Mateos <csander@purestorage.com>
Cc: Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	Chaitanya Kulkarni <kch@nvidia.com>, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/6] nvmet: report NPDGL and NPDAL
Message-ID: <20260220161155.GG15071@lst.de>
References: <20260220032809.758089-1-csander@purestorage.com> <20260220032809.758089-7-csander@purestorage.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, Feb 19, 2026 at 08:28:09PM -0700, Caleb Sander Mateos wrote:
> A block device with a very large discard_granularity queue limit may not
> be able to report it in the 16-bit NPDG and NPDA fields in the Identify
> Namespace data structure. For this reason, version 2.1 of the NVMe specs
> added 32-bit fields NPDGL and NPDAL to the NVM Command Set Specific
> Identify Namespace structure. So report the discard_granularity there
> too and set OPTPERF to 11b to indicate those fields are supported.

>From a pure mechanics point of view this looks fine.  I'll not that
actually aligning the discard to these granularities probably won't
really work for most file systems, though.