Re: [PATCH 31/31] dma-mapping-common: skip kmemleak checks for page-less SG entries

From: Christoph Hellwig
Date: Thu Aug 13 2015 - 10:33:31 EST

On Wed, Aug 12, 2015 at 09:05:15AM -0700, Linus Torvalds wrote:
> [ Again, I'm responding to one random patch - this pattern was in
> other patches too. ]
> A question: do we actually expect to mix page-less and pageful SG
> entries in the same SG list?
> How does that happen?

Both for DAX and the video buffer case people could do direct I/O
spanning the boundary between such a VMA and a normal one unless
we add special code to prevent that. Right now I don't think it's
all that useful, but then again it doesn't seem harmful either
and adding those checks might add up.
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