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Date: Tue, 18 Nov 2025 07:45:13 +0100
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@meta.com>
Cc: linux-block@vger.kernel.org, axboe@kernel.dk, hch@lst.de,
	ebiggers@kernel.org, Keith Busch <kbusch@kernel.org>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH] blk-integrity: support arbitrary buffer alignment
Message-ID: <20251118064513.GA24192@lst.de>
References: <20251117203935.1487303-1-kbusch@meta.com>
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On Mon, Nov 17, 2025 at 12:39:35PM -0800, Keith Busch wrote:
>   * Fixed up ip checksum when it's split among intervals. The previous
>   version would happen to work if the data interval was aligned in a
>   single segment, but it would have gotten the wrong final result if it
>   had to do multiple partial updates.
> 
>   Testing this type was a little more difficult than it sounds. The
>   scsi_debug driver would force alignment, so it would never hit the
>   partial condition that was previously broken.
> 
>   To test it, I hacked up a nvme qemu emulation for this checksum type,
>   taking some liberty with the protocol's undefined fields.  qemu has
>   its own checksum implementation, 'net_raw_checksum()', and it is
>   calculating the same result through its contiguous bounce buffer as

Hah.  Even if it doesn't work for the IP checksum, can we wire up some
of your tests in blktests?

I think the new split_interval_capable need to be stacked as we still
build I/O to limits.  Not just for that it might be nice to turn it
into a BLK_FEAT_* bit.

Otherwise this looks good to me.