RE: [PATCHv3 2/3] mm: vmalloc: add VM_DMA flag to indicate areas usedby dma-mapping framework

From: Marek Szyprowski
Date: Thu Jun 21 2012 - 08:38:37 EST


Hi,

On Thursday, June 21, 2012 10:36 AM Minchan Kim wrote:

> On 06/13/2012 08:01 PM, Marek Szyprowski wrote:
>
> > Add new type of vm_area intented to be used for mappings created by
> > dma-mapping framework.
> >
> > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Reviewed-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> > ---
> > include/linux/vmalloc.h | 1 +
> > mm/vmalloc.c | 3 +++
> > 2 files changed, 4 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index 2e28f4d..e725b7b 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/include/linux/vmalloc.h
> > @@ -14,6 +14,7 @@ struct vm_area_struct; /* vma defining user mapping in
> mm_types.h */
> > #define VM_USERMAP 0x00000008 /* suitable for remap_vmalloc_range */
> > #define VM_VPAGES 0x00000010 /* buffer for pages was vmalloc'ed */
> > #define VM_UNLIST 0x00000020 /* vm_struct is not listed in vmlist */
> > +#define VM_DMA 0x00000040 /* used by dma-mapping framework */
> > /* bits [20..32] reserved for arch specific ioremap internals */
> >
> > /*
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 11308f0..e04d59b 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2575,6 +2575,9 @@ static int s_show(struct seq_file *m, void *p)
> > if (v->flags & VM_IOREMAP)
> > seq_printf(m, " ioremap");
> >
> > + if (v->flags & VM_DMA)
> > + seq_printf(m, " dma");
> > +
> > if (v->flags & VM_ALLOC)
> > seq_printf(m, " vmalloc");
> >
>
>
> I still don't make sure that we should add new type for only ARM arch.
> I remember you said "It would be used for other architectures once we add" and
> Paul said he has a plan for SH. So at least, you should add such comment in changelog
> for persuading grumpy maintainers. :)
>
> Frankly speaking, I could add my Reviewed-by but I think it wouldn't carry much weight
> because code is very tiny so you need Acked-by rather than Reviewed-by.
> IMHO, This problem is the thing only maintainer should decide.
> So I will toss the decision to akpm. Ccing akpm.(Ccing KOSAKI because he had a concern about
> this).
>
> If anyone have a question to me, I'm Acked-by iff other architecture will use it.

Ok, if this flag is so controversial, I can change it to arch specific VM flag and utilize
'bits [20..32] reserved for arch specific ioremap internals'. Later, when other architectures
start using similar flag, one can unify them and add such generic flag.

Best regards
--
Marek Szyprowski
Samsung Poland R&D Center


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