[RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with GFP_ATOMIC

[Hiroshi Doyu]

Hi,

On Thu, 23 Aug 2012 07:58:34 +0200
Marek Szyprowski <m.szyprowski at samsung.com> wrote:

> Hello,
> 
> On Wednesday, August 22, 2012 3:37 PM Hiroshi Doyu wrote:
> 
> > KyongHo Cho <pullip.cho at samsung.com> wrote @ Wed, 22 Aug 2012 14:47:00 +0200:
> > 
> > > vzalloc() call in __iommu_alloc_buffer() also causes BUG() in atomic context.
> > 
> > Right.
> > 
> > I've been thinking that kzalloc() may be enough here, since
> > vzalloc() was introduced to avoid allocation failure for big chunk of
> > memory, but I think that it's unlikely that the number of page array
> > can be so big. So I propose to drop vzalloc() here, and just simply to
> > use kzalloc only as below(*1).
> 
> We already had a discussion about this, so I don't think it makes much sense to
> change it back to kzalloc. This vmalloc() call won't hurt anyone. It should not
> be considered a problem for atomic allocations, because no sane driver will try
> to allocate buffers larger than a dozen KiB with GFP_ATOMIC flag. I would call
> such try a serious bug, which we should not care here.

Ok, I've already sent v2 just now, where, instead of changing it back,
just with GFP_ATOMIC, kzalloc() would be selected, just in case. I guess
that this would be ok(a bit safer?)