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Date: Thu, 29 Oct 2026 13:20:58 +0100
From: Christoph Hellwig <hch@lst.de>
To: Kyle Bader <kbader@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Pavel Begunkov <asml.silence@gmail.com>,
	Kyle Bader <kbader@ibm.com>, Anuj Gupta <anuj20.g@samsung.com>,
	Kanchan Joshi <joshi.k@samsung.com>, Christoph Hellwig <hch@lst.de>,
	Keith Busch <kbusch@kernel.org>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Tushar Gohad <tushar.gohad@intel.com>, linux-block@vger.kernel.org,
	io-uring@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] block: only fail dma-buf bios that need block layer PI
Message-ID: <20261029122058.GA24811@lst.de>
References: <20261028181412.1919506-1-kbader@redhat.com>
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On Wed, Oct 28, 2026 at 06:14:12PM +0000, Kyle Bader wrote:
> From: Kyle Bader <kbader@ibm.com>
> 
> Any dma-buf I/O to a device with a PI checksum fails today.
> blkdev_init_dma_buf_io_ctx() returns -EOPNOTSUPP at registration, and
> blk_mq_submit_bio() fails each dma-buf bio with BLK_STS_NOTSUPP. The
> checks prevent a crash: bi_dmabuf_map shares a union with bi_io_vec,
> and bio_integrity_generate() and bio_integrity_verify() walk bi_io_vec
> to compute the guards over the data.

Please cut down the commit log to the essentials.  It's basicallyr
currently all P2P I/O to devices advertizing integrity data is rejected,
but it should only reject those walking the bio_vecs.