On Wed, 3 Dec 2014 15:25:24 -0800 Andrew Morton <a...@linux-foundation.org>
wrote:
> On Wed, 03 Dec 2014 15:41:21 +0300 Andrey Ryabinin <a.ryabi...@samsung.com>
> wrote:
>
> >
> > Use the 'unsigned long' type for 'zero' variable to fix this.
> > Changing type to 'unsigned long' shouldn't affect any other users
> > of this variable.
> >
> > Reported-by: Dmitry Vyukov <dvyu...@google.com>
> > Fixes: ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and
> > hugetlb_infinity")
> > Signed-off-by: Andrey Ryabinin <a.ryabi...@samsung.com>
> > ---
> > kernel/sysctl.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 15f2511..45c45c9 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -120,7 +120,7 @@ static int sixty = 60;
> >
> > static int __maybe_unused neg_one = -1;
> >
> > -static int zero;
> > +static unsigned long zero;
> > static int __maybe_unused one = 1;
> > static int __maybe_unused two = 2;
> > static int __maybe_unused four = 4;
>
> Yeah, this is ghastly.
>
> Look at
>
> {
> .procname = "numa_balancing",
> .data = NULL, /* filled in by handler */
> .maxlen = sizeof(unsigned int),
> .mode = 0644,
> .proc_handler = sysctl_numa_balancing,
> .extra1 = &zero,
> .extra2 = &one,
> },
>
> Now extra1 points at a long and extra2 points at an int.
> sysctl_numa_balancing() calls proc_dointvec_minmax() and I think your
> patch just broke big-endian 64-bit machines. "sched_autogroup_enabled"
> breaks as well.
Taking another look at this...
numa_balancing will continue to work on big-endian because of course
zero is still zero when byteswapped. But that's such a hack, isn't
documented and doesn't work for "one", "sixty", etc.
I'm thinking a better fix here is to switch hugetlb_sysctl_handler to
use `int's. 2^32 hugepages is enough for anybody.
hugetlb_overcommit_handler() will need conversion also.
Perhaps auditing all the proc_doulongvec_minmax callsites is the way to
attack this.
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