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Date: Wed, 12 Jun 2024 05:51:22 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>, Song Liu <song@kernel.org>,
	Yu Kuai <yukuai3@huawei.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>, Ira Weiny <ira.weiny@intel.com>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Chaitanya Kulkarni <kch@nvidia.com>, linux-block@vger.kernel.org,
	dm-devel@lists.linux.dev, linux-raid@vger.kernel.org,
	nvdimm@lists.linux.dev, linux-nvme@lists.infradead.org,
	linux-scsi@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>,
	Kanchan Joshi <joshi.k@samsung.com>
Subject: Re: [PATCH 03/11] block: remove the BIP_IP_CHECKSUM flag
Message-ID: <20240612035122.GA25733@lst.de>
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On Tue, Jun 11, 2024 at 03:51:27PM -0400, Martin K. Petersen wrote:
> > But how do you even toggle the flag?  There is no no code to do that.
> > And if you already have a special kernel module for that it really
> > should just use a passthrough request to take care of that.
> 
> A passthrough command to the controller?

A passthrough command to the LU that has a mismatching checksum.

> > Note that unlike the NOCHECK flag which I just cleaned up because they
> > were unused, this one actually does get in the way of the architecture
> > of the whole series :( We could add a per-bip csum_type but it would
> > feel really weird.
> 
> Why would it feel weird? That's how it currently works.

Because there's no way to have it set to anything but the per-queue
one.  

> The qualification tool issues a flurry of commands injecting errors at
> various places in the stack to identify that the right entity (block
> layer, controller, storage device) catch a bad checksum, reference tag,
> etc.

How does it do that?  There's no actualy way to make it mismatch.