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Date:   Fri, 8 Apr 2022 22:15:41 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Mike Snitzer <snitzer@redhat.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Dennis Zhou <dennis@kernel.org>,
        Mike Snitzer <snitzer@kernel.org>, tj@kernel.org,
        axboe@kernel.dk, linux-block@vger.kernel.org, dm-devel@redhat.com
Subject: Re: can we reduce bio_set_dev overhead due to bio_associate_blkg?
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On Fri, Apr 08, 2022 at 11:42:51AM -0400, Mike Snitzer wrote:
> I think we can achieve the goal of efficient cloning/remapping for
> both usecases simply by splitting out the bio_set_dev() and leaving it
> to the caller to pick which interface to use (e.g. clone vs
> clone_and_remap).

You can just pass a NULL bdev to bio_alloc_clone/bio_init_clone.
I've been hoping to get rid of that, but if we have a clear use case
it will have to stay.