From: Michal Hocko <mhocko@xxxxxxxx> 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@xxxxxxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/hugetlb.h | 5 +++-- mm/hugetlb.c | 5 ++--- mm/mempolicy.c | 3 ++- 3 files changed, 7 insertions(+), 6 deletions(-) diff -puN include/linux/hugetlb.h~hugetlb-mbind-fall-back-to-default-policy-if-vma-is-null include/linux/hugetlb.h --- a/include/linux/hugetlb.h~hugetlb-mbind-fall-back-to-default-policy-if-vma-is-null +++ a/include/linux/hugetlb.h @@ -358,7 +358,8 @@ struct page *alloc_huge_page(struct vm_a struct page *alloc_huge_page_node(struct hstate *h, int nid); struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask); -struct page *alloc_huge_page_vma(struct vm_area_struct *vma, unsigned long address); +struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma, + unsigned long address); int huge_add_to_page_cache(struct page *page, struct address_space *mapping, pgoff_t idx); @@ -536,7 +537,7 @@ struct hstate {}; #define alloc_huge_page(v, a, r) NULL #define alloc_huge_page_node(h, nid) NULL #define alloc_huge_page_nodemask(h, preferred_nid, nmask) NULL -#define alloc_huge_page_vma(vma, address) NULL +#define alloc_huge_page_vma(h, vma, address) NULL #define alloc_bootmem_huge_page(h) NULL #define hstate_file(f) NULL #define hstate_sizelog(s) NULL diff -puN mm/hugetlb.c~hugetlb-mbind-fall-back-to-default-policy-if-vma-is-null mm/hugetlb.c --- a/mm/hugetlb.c~hugetlb-mbind-fall-back-to-default-policy-if-vma-is-null +++ a/mm/hugetlb.c @@ -1675,16 +1675,15 @@ struct page *alloc_huge_page_nodemask(st } /* mempolicy aware migration callback */ -struct page *alloc_huge_page_vma(struct vm_area_struct *vma, unsigned long address) +struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma, + unsigned long address) { struct mempolicy *mpol; nodemask_t *nodemask; struct page *page; - struct hstate *h; gfp_t gfp_mask; int node; - h = hstate_vma(vma); gfp_mask = htlb_alloc_mask(h); node = huge_node(vma, address, gfp_mask, &mpol, &nodemask); page = alloc_huge_page_nodemask(h, node, nodemask); diff -puN mm/mempolicy.c~hugetlb-mbind-fall-back-to-default-policy-if-vma-is-null mm/mempolicy.c --- a/mm/mempolicy.c~hugetlb-mbind-fall-back-to-default-policy-if-vma-is-null +++ a/mm/mempolicy.c @@ -1121,7 +1121,8 @@ static struct page *new_page(struct page } 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; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
