Re: [PATCH] Make GFP_DMA allocations w/o ZONE_DMA emit a warning instead of failing

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Fri, Jun 10, 2011 at 12:11:42PM +0400, Dmitry Eremin-Solenikov wrote:
> On 6/10/11, Andrew Morton <akpm@linux-foundation.org> wrote:
> > On Fri, 10 Jun 2011 16:38:06 +0900 KOSAKI Motohiro
> > <kosaki.motohiro@jp.fujitsu.com> wrote:
> >
> >> Subject: [PATCH] Revert "mm: fail GFP_DMA allocations when ZONE_DMA is not
> >> configured"
> >
> > Confused.  We reverted this over a week ago.
> 
> Should one submit a patch adding a warning to GFP_DMA allocations
> w/o ZONE_DMA, or the idea of the original patch is wrong?

Linus was far from impressed by the original commit, saying:
| Using GFP_DMA is reasonable in a driver - on platforms where that
| matters, it should allocate from the DMA zone, on platforms where it
| doesn't matter it should be a no-op.

So no, not even a warning.

What is a useful exercise though is to remove GFP_DMA from those
allocations which should never have had GFP_DMA added - such as those
used for data structures which have nothing to do with DMA at all.
Also dma_alloc_coherent() should not be given GFP_DMA in any case.

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