Re: [PATCH] Fix dirty page accounting in redirty_page_for_writepage()

[Ingo Molnar <mingo@elte.hu>]

* Christoph Lameter <cl@linux.com> wrote:

> On Thu, 30 Apr 2009, Ingo Molnar wrote:
> 
> > The patch below makes the fallback/slowpath irq safe.
> 
> Yes but sometimes you are already irq safe and such a fallback 
> would create significant irq/enable/disable stack operations etc 
> overhead for architectures that are using the fallback.

It's a fallback slowpath - non-x86 architectures should still fill 
in a real implementation of course.

> I think we really need another __xxx op here. Especially since 
> these operations are often in critical code paths.

That's a receipe for fragility: as using __xxx will still be 
irq-safe on x86, and 95% of the testing is done on x86, so this 
opens up the path to non-x86 bugs.

So we first have to see the list of architectures that _cannot_ 
implement an irq-safe op here via a single machine instruction.
x86, ia64 and powerpc should be fine.

	Ingo