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Date: Wed, 14 Feb 2024 09:00:24 +0100
From: Christoph Hellwig <hch@lst.de>
To: John Garry <john.g.garry@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>, axboe@kernel.dk, kbusch@kernel.org,
	sagi@grimberg.me, jejb@linux.ibm.com, martin.petersen@oracle.com,
	djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org,
	dchinner@redhat.com, jack@suse.cz, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	tytso@mit.edu, jbongio@google.com, linux-scsi@vger.kernel.org,
	ming.lei@redhat.com, ojaswin@linux.ibm.com, bvanassche@acm.org,
	Alan Adamson <alan.adamson@oracle.com>
Subject: Re: [PATCH v3 14/15] nvme: Support atomic writes
Message-ID: <20240214080024.GA10357@lst.de>
References: <20240124113841.31824-1-john.g.garry@oracle.com> <20240124113841.31824-15-john.g.garry@oracle.com> <20240213064204.GB23305@lst.de> <0323ba69-dff9-4465-817e-2c349141b753@oracle.com>
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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.