On Thu 06-01-11 12:38:58, Andrew Morton wrote:
> On Thu, 6 Jan 2011 11:04:39 +0100
> Michal Hocko <mhocko@xxxxxxx> wrote:
>
> > NODEMASK_ALLOC can use kmalloc if nodemask_t > 256 bytes so it might
> > fail with NULL as a result. Let's check the resulting variable and
> > fail with -ENOMEM if NODEMASK_ALLOC failed.
> >
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
> > ---
> > mm/hugetlb.c | 18 +++++++++++++++---
> > 1 files changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 4c0606c..21f31b2 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -1439,14 +1439,19 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
> > struct hstate *h;
> > NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
> >
> > + if (!nodes_allowed) {
> > + err = -ENOMEM;
> > + goto out;
> > + }
>
> Looks good to me. I was going to complain that it adds extra unneeded
> instructions in the case where the nodemasks are allocated on the
> stack. But it appears that gcc assumes that stack-based variables
> cannot have address zero, so if gcc sees this:
>
> {
> nodemask_t foo;
>
> if (!&foo) {
> stuff
> }
> }
>
> if just removes it all for us.
Yes, I cannot find it anywhere (maybe just a bad searching pattern) but
this seems to be the case for -O1, -O2 and -Os. Anyway it makes a
perfect sense to me.
Thanks for the review.
>
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--
Michal Hocko
L3 team
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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