Re: cpumask: fix compat getaffinity

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> On Tuesday 11 May 2010, Rusty Russell wrote:
> > cpumask: use nr_cpu_ids for printing and parsing cpumasks
> > 
> > Commit a45185d2d "cpumask: convert kernel/compat.c" broke
> > libnuma, which abuses sched_getaffinity to find out NR_CPUS
> > in order to parse /sys/devices/system/node/node*/cpumap.
> > 
> > However, the result now returned reflects nr_cpu_ids, and
> > cpumask_scnprintf et al. use nr_cpumask_bits which is NR_CPUS (for
> > CONFIG_CPUMASK_OFFSTACK=n) or nr_cpu_ids (for
> > CONFIG_CPUMASK_OFFSTACK=y).
> > 
> > We should use nr_cpu_ids consistently.
> > 
> > Reported-by: Arnd Bergmann <arnd@arndb.de>
> > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> > Cc: stable@kernel.org
> 
> It looks like this changes fixes the compat case, but now
> the native system call would be inconsistent with the
> sysfs output. 
> 
> Wouldn't you also need something like the change below
> to make the return value of sched_getaffinity() independent
> of NR_CPUS?
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Looks good. but please rebase it on latest linus-tree. in linus tree,
we are already using nr_cpu_ids instead NR_CPUS.

And I'm sorry. at making such change, I've forgot to care compat
syscall, your patch fixes it ;)