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Re: [Xen-devel] [PATCH] wrong accounting in direct_remap_pfn_range

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] wrong accounting in direct_remap_pfn_range
From: Steven Rostedt <srostedt@xxxxxxxxxx>
Date: Wed, 30 Aug 2006 20:47:14 -0400
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, quintela@xxxxxxxxxx
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Keir Fraser wrote:
On 31/8/06 1:37 am, "Steven Rostedt" <srostedt@xxxxxxxxxx> wrote:

grr, I take it back, I am the one that's confused :P

OK, this all happens because this whole blob of code is crazy because it
is missing a "if (size == 0)" check!

It's not really missing. We could have a size==0 check *or* we can have the
v!=u check. We don't need both and I think the latter is more obviously
correct, as the test is closer to the code that it 'protects'. Also it's a
fairly idiomatic way of generating and flushing batches of work.


Well it wasn't obvious to me :P

If a size == 0 is passed in (for whatever reason!), couldn't we skip the flush_cache_all, flush_tlb_all and the allocation and freeing of a page and just return?

If you want this in mainline Linux, you'll probably have others mention that too.

-- Steve


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