[dm-devel] [PATCH] dm rq: clear cloned bio ->bi_bdev to fix I/O accounting

[Ming Lei]

On Sun, Jan 16, 2022 at 11:51:17PM -0800, Christoph Hellwig wrote:
> So I actually noticed this during code inspection a while ago, but I
> think we need to use the actual underlying device instead of NULL here
> to keep our block layer gurantees.  See the patch in my queue below.
> 
> ---
> From 1e330b8e57fc0d6c6fb07c0ec2915dca5d7a585a Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch at lst.de>
> Date: Thu, 13 Jan 2022 10:53:59 +0100
> Subject: block: assign bi_bdev for cloned bios in blk_rq_prep_clone
> 
> The cloned bios for the cloned request in blk_rq_prep_clone currently
> still point to the original bi_bdev.  This is harmless because dm-mpath

It breaks io accounting, so not harmless, but the code in this patch is
fine:

Reviewed-by: Ming Lei <ming.lei at redhat.com>


Thanks,
Ming