linux-kernel - Re: [PATCH -v2] pci: Check bridge resources after resource allocation.

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Date:	Mon, 16 May 2011 00:59:26 -0700
From:	Ram Pai <linuxram@...ibm.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH -v2] pci: Check bridge resources after resource
 allocation.

On Fri, May 13, 2011 at 06:06:17PM -0700, Yinghai Lu wrote:
> On 05/12/2011 12:34 PM, Jesse Barnes wrote:
> > On Thu, 12 May 2011 12:18:43 -0700
> > Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > 
> >> On Thu, May 12, 2011 at 11:37 AM, Jesse Barnes <jbarnes@...tuousgeek.org> wrote:
> >>>
> >>> Linus, I don't have anything else queued up, so you may as well take
> >>> this one directly if you want it in 2.6.39.  It's a regression fix, but
> >>> resource changes always make me nervous.  Alternately, I could put it
> >>> into 2.6.40 instead, the backport to 2.6.39.x if it survives until
> >>> 2.6.40-rc2 or so...
> >>
> >> Considering the trouble resource allocation always ends up being, I'd
> >> almost prefer that "mark it for stable and put it in the 2.6.40
> >> queue".
> >>
> >> Afaik this problem hasn't actually hit any "normal" users, has it? So ...
> > 
> > Sounds good, thanks.  Yeah I don't think it's hit anyone but Yinghai
> > (at least I don't know of any other reports).
> > 
> 
> please check this one, it should be safe for 2.6.39 ?

>  	size0 = calculate_iosize(size, min_size, size1,
>  			resource_size(b_res), 4096);
> -	size1 = !add_size? size0:
> +	size1 = (!add_head || (add_head && !add_size)) ? size0 :
>  		calculate_iosize(size, min_size+add_size, size1,
>  			resource_size(b_res), 4096);

This solves the problem you encountered.

But, I think, it still does not fix the following scenario:

adjust_resource() failing to allocate additional resource to a hotplug bridge
that has no children. In this case  ->flags of that 'struct resource'
continues to be set even when no resource is allocated to that hot-plug bridge.

RP
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