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

Hi,

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

On 06/13/2012 08:01 PM, Marek Szyprowski wrote:

quoted

Add new type of vm_area intented to be used for mappings created by
dma-mapping framework.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 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 */

quoted

 #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