Re: [PULL] cpumask: finally make them variable size w/ CPUMASK_OFFSTACK.

From: KOSAKI Motohiro
Date: Wed May 09 2012 - 21:33:13 EST

(5/9/12 2:10 AM), Rusty Russell wrote:
Hi Ingo,

I finally rebased this on top of your tip tree, and tested it
locally. Some more old-style cpumask usages have crept in, but it's a
fairly simple series.

The final result is that if you enable CONFIG_CPUMASK_OFFSTACK, then
'struct cpumask' becomes an undefined type. You can't accidentally take
the size of it, assign it, or pass it by value. And thus it's safe for
us to make it smaller if nr_cpu_ids< NR_CPUS, as the final patch does.

It unfortunately requires the lglock cleanup patch, which Al already has
queued, so I've included it here.


Thanks this effort. This is very cleaner than I expected.
However I should NAK following one patch. sorry. because of, lru-drain is
called from memory reclaim context. It mean, additional allocation may not
work. Please just use bare NR_CPUS bitmap instead. space wasting is minor
issue than that.

commit fab26054c0500d426cf1bc2ce227a6a428dc815e
Author: Rusty Russell<rusty@xxxxxxxxxxxxxxx>
Date: Wed May 9 14:55:15 2012 +0930

page_alloc: use cpumask_var_t.

The BSS trick works, but it still wastes space. Especially since there's
a nice fallback in the case where we fail to allocate a temporary cpumask.

Signed-off-by: Rusty Russell<rusty@xxxxxxxxxxxxxxx>

Other patches looks very goold.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>


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