linux-kernel - Re: [PATCHv4 3/5] common: dma-mapping: Introduce common remapping functions

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Date:	Tue, 22 Jul 2014 17:04:08 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Laura Abbott <lauraa@...eaurora.org>
Cc:	Will Deacon <Will.Deacon@....com>,
	David Riley <davidriley@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Ritesh Harjain <ritesh.harjani@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv4 3/5] common: dma-mapping: Introduce common remapping
 functions

On Mon, Jul 21, 2014 at 08:33:48PM +0100, Laura Abbott wrote:
> On 7/18/2014 6:53 AM, Catalin Marinas wrote:
> > On Wed, Jul 02, 2014 at 07:03:36PM +0100, Laura Abbott wrote:
> >> +void *dma_common_pages_remap(struct page **pages, size_t size,
> >> +			unsigned long vm_flags, pgprot_t prot,
> >> +			const void *caller)
> >> +{
> >> +	struct vm_struct *area;
> >> +
> >> +	area = get_vm_area_caller(size, vm_flags, caller);
> >> +	if (!area)
> >> +		return NULL;
> >> +
> >> +	if (map_vm_area(area, prot, &pages)) {
> >> +		vunmap(area->addr);
> >> +		return NULL;
> >> +	}
> >> +
> >> +	return area->addr;
> >> +}
> > 
> > Why not just replace this function with vmap()? It is nearly identical.
> 
> With this version, the caller stored and printed via /proc/vmallocinfo
> is the actual caller of the DMA API whereas if we just call vmap we
> don't get any useful caller information. Going to vmap would change
> the existing behavior on ARM so it seems unwise to switch.

OK.

> Another option is to move this into vmalloc.c and add vmap_caller.

Maybe as a subsequent clean-up (once this series gets merged).

-- 
Catalin
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