linux-kernel - Re: [PATCH v3 14/15] nvme: Support atomic writes

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Message-ID: <20240214080024.GA10357@lst.de>
Date: Wed, 14 Feb 2024 09:00:24 +0100
From: Christoph Hellwig <hch@....de>
To: John Garry <john.g.garry@...cle.com>
Cc: Christoph Hellwig <hch@....de>, axboe@...nel.dk, kbusch@...nel.org,
	sagi@...mberg.me, jejb@...ux.ibm.com, martin.petersen@...cle.com,
	djwong@...nel.org, viro@...iv.linux.org.uk, brauner@...nel.org,
	dchinner@...hat.com, jack@...e.cz, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu, jbongio@...gle.com, linux-scsi@...r.kernel.org,
	ming.lei@...hat.com, ojaswin@...ux.ibm.com, bvanassche@....org,
	Alan Adamson <alan.adamson@...cle.com>
Subject: Re: [PATCH v3 14/15] nvme: Support atomic writes

On Tue, Feb 13, 2024 at 02:21:25PM +0000, John Garry wrote:
>> Please also read through TP4098(a) and look at the MAM field.
>
> It's not public, AFAIK.

Oracle is a member, so you can take a look at it easily.  If we need
it for Linux I can also work with the NVMe Board to release it.

> And I don't think a feature which allows us to straddle boundaries is too 
> interesting really.

Without MAM=1 NVMe can't support atomic writes larger than
AWUPF/NAWUPF, which is typically set to the indirection table
size.  You're leaving a lot of potential unused with that.