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Date: Wed, 20 May 2026 10:30:43 +0200
From: Christoph Hellwig <hch@lst.de>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
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	Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
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	Nitesh Shetty <nj.shetty@samsung.com>,
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	William Power <william.power@intel.com>,
	Phil Cayton <phil.cayton@intel.com>,
	Jason Gunthorpe <jgg@nvidia.com>
Subject: Re: [PATCH v3 04/10] block: introduce dma map backed bio type
Message-ID: <20260520083043.GA18893@lst.de>
References: <cover.1777475843.git.asml.silence@gmail.com> <646ecd6fde8d9e146cb051efb514deb27ce3883e.1777475843.git.asml.silence@gmail.com> <20260513081929.GD5477@lst.de> <24833f76-2289-4859-86d1-9215b11a1258@gmail.com>
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On Mon, May 18, 2026 at 11:29:54AM +0100, Pavel Begunkov wrote:
>>>   	BIO_ZONE_WRITE_PLUGGING, /* bio handled through zone write plugging */
>>>   	BIO_EMULATES_ZONE_APPEND, /* bio emulates a zone append operation */
>>> +	BIO_DMABUF_MAP, /* Using premmaped dma buffers */
>>
>> Shouldn't this be a REQ_ flag as we should never mix and match bios with
>> and without this flag in a single request?
>
> Do you mean adding both and propagating it from bio to req? submit_bio()
> takes a bio, so we still need to set it there before it reaches blk-mq.
> And there might be bio-based drivers using it in the future.

I think I forgot to reply to this, so let's do this now.

REQ_ is actually used by both bios and requests, so if you set it in
bio->bi_opf it will automatically get propagated to the request, but
it can also always be tested on the bio, including by bio-based
drivers.