From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [Lsf] [RFC] writeback and cgroup
Date: Mon, 16 Apr 2012 11:52:07 -0400
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To: Fengguang Wu <fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
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On Mon, Apr 16, 2012 at 09:07:07PM +0800, Fengguang Wu wrote:

[..]
> Vivek, I noticed these lines in cfq code
> 
>                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
> 
> Why not use bdi->dev->devt?  The problem is that dev_name() will
> return "btrfs-X" for btrfs rather than "major:minor".

Isn't bdi->dev->devt 0?  I see following code.

add_disk()
   bdi_register_dev()
      bdi_register()
         device_create_vargs(MKDEV(0,0))
	      dev->devt = devt = MKDEV(0,0);

So for normal block devices, I think bdi->dev->devt will be zero, that's
why probably we don't use it.

Thanks
Vivek