From 389c8178d0904f944887ccca2256ff9d79c12e8e Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 31 Jan 2018 16:21:03 -0800 Subject: hugetlb, mbind: fall back to default policy if vma is NULL Dan Carpenter has noticed that mbind migration callback (new_page) can get a NULL vma pointer and choke on it inside alloc_huge_page_vma which relies on the VMA to get the hstate. We used to BUG_ON this case but the BUG_+ON has been removed recently by "hugetlb, mempolicy: fix the mbind hugetlb migration". The proper way to handle this is to get the hstate from the migrated page and rely on huge_node (resp. get_vma_policy) do the right thing with null VMA. We are currently falling back to the default mempolicy in that case which is in line what THP path is doing here. Link: http://lkml.kernel.org/r/20180110104712.GR1732@dhcp22.suse.cz Signed-off-by: Michal Hocko Reported-by: Dan Carpenter Cc: Naoya Horiguchi Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mempolicy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/mempolicy.c') diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 96823fa07f38..d879f1d8a44a 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1121,7 +1121,8 @@ static struct page *new_page(struct page *page, unsigned long start, int **x) } if (PageHuge(page)) { - return alloc_huge_page_vma(vma, address); + return alloc_huge_page_vma(page_hstate(compound_head(page)), + vma, address); } else if (thp_migration_supported() && PageTransHuge(page)) { struct page *thp; -- cgit v1.2.3-59-g8ed1b