linux-kernel - Re: [PATCH 2/12] pci: add pci_bridge_release_unused_res and pci_bus_release_unused_bridge

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Date:	Fri, 18 Dec 2009 16:40:43 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Yinghai Lu <yinghai@...nel.org>
cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Alex Chiang <achiang@...com>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 2/12] pci: add pci_bridge_release_unused_res and
 pci_bus_release_unused_bridge_res -v2

On Fri, 18 Dec 2009, Yinghai Lu wrote:
> 
> ok, please check attached is right or not
>  
> +static void __release_child_resources(struct resource *r)
> +{
> +	struct resource *tmp, *p;
> +	resource_size_t size;
> +
> +	p = r->child;
> +	r->child = NULL;
> +	while (p) {
> +		tmp = p;
> +		p = p->sibling;
> +
> +		tmp->parent = NULL;
> +		tmp->sibling = NULL;
> +		__release_child_resources(tmp);
> +
> +		printk(KERN_DEBUG "release child resource %pR\n", tmp);
> +		/* need to restore size, and keep flags */
> +		size = resource_size(tmp);
> +		tmp->start = 0;
> +		tmp->end = size - 1;
> +	}
> +}

Ok, this looks mostly right. I do worry about the alignment information: 
you lose that thing for any resource that had IORESOURCE_STARTALIGN set 
when you do this thing. That's pretty fundamental to the whole resource 
code, I suspect we should just finally add a 'alignment' field to the 
resource struct, so that alignment doesn't get lost when a resource is 
allocated.

(Do a "git grep IORESOURCE_.*ALIGN" to see the kind of stuff I'm talking 
about, and look at he PCI 'setup-bus.c' code that sets that STARTALIGN 
thing).

So a preliminary ack on the resource.c parts. The rest I'm still a bit 
dubious about, and the whole "we've lost alignment on the resources" is 
probably indicative of how none of the resource code has ever really been 
designed for this kind of "tear down and build back up again" behavior.

				Linus
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