linux-kernel - Re: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with GFP

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Date:	Wed, 22 Aug 2012 14:52:28 +0200
From:	Hiroshi Doyu <hdoyu@...dia.com>
To:	"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"chunsang.jeong@...aro.org" <chunsang.jeong@...aro.org>,
	Krishna Reddy <vdumpa@...dia.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"subashrp@...il.com" <subashrp@...il.com>,
	"minchan@...nel.org" <minchan@...nel.org>
Subject: Re: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool
 with GFP_ATOMIC

Marek Szyprowski <m.szyprowski@...sung.com> wrote @ Wed, 22 Aug 2012 14:29:47 +0200:

> Hello,
> 
> On Wednesday, August 22, 2012 12:20 PM Hiroshi Doyu wrote:
> 
> > Makes use of the same atomic pool from DMA, and skips kernel page
> > mapping which can involves sleep'able operation at allocating a kernel
> > page table.
> > 
> > Signed-off-by: Hiroshi Doyu <hdoyu@...dia.com>
> > ---
> >  arch/arm/mm/dma-mapping.c |   22 ++++++++++++++++++----
> >  1 files changed, 18 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> > index aec0c06..9260107 100644
> > --- a/arch/arm/mm/dma-mapping.c
> > +++ b/arch/arm/mm/dma-mapping.c
> > @@ -1028,7 +1028,6 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t
> > size,
> >  	struct page **pages;
> >  	int count = size >> PAGE_SHIFT;
> >  	int array_size = count * sizeof(struct page *);
> > -	int err;
> > 
> >  	if (array_size <= PAGE_SIZE)
> >  		pages = kzalloc(array_size, gfp);
> > @@ -1037,9 +1036,20 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t
> > size,
> >  	if (!pages)
> >  		return NULL;
> > 
> > -	err = __alloc_fill_pages(&pages, count, gfp);
> > -	if (err)
> > -		goto error
> > +	if (gfp & GFP_ATOMIC) {
> > +		struct page *page;
> > +		int i;
> > +		void *addr = __alloc_from_pool(size, &page);
> > +		if (!addr)
> > +			goto err_out;
> > +
> > +		for (i = 0; i < count; i++)
> > +			pages[i] = page + i;
> > +	} else {
> > +		int err = __alloc_fill_pages(&pages, count, gfp);
> > +		if (err)
> > +			goto error;
> > +	}
> > 
> >  	return pages;
> >  error:
> > @@ -1055,6 +1065,10 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages,
> > size_t s
> >  	int count = size >> PAGE_SHIFT;
> >  	int array_size = count * sizeof(struct page *);
> >  	int i;
> > +
> > +	if (__free_from_pool(page_address(pages[0]), size))
> > +		return 0;
> 
> You leak memory here. pages array should be also freed.

Right, I'll fix as below:

	Modified arch/arm/mm/dma-mapping.c
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 47c4978..4656c0f 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1121,11 +1121,12 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages, size_t s
 	int i;
 
 	if (__free_from_pool(page_address(pages[0]), size))
-		return 0;
+		goto out;
 
 	for (i = 0; i < count; i++)
 		if (pages[i])
 			__free_pages(pages[i], 0);
+out:
 	if (array_size <= PAGE_SIZE)
 		kfree(pages);
 	else
--
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