On Thu 06-01-11 12:38:58, Andrew Morton wrote:

On Thu, 6 Jan 2011 11:04:39 +0100
Michal Hocko [off-list ref] wrote:

quoted

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 <redacted>
---
 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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