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Commit 389c8178 authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
Browse files

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: default avatarMichal Hocko <mhocko@suse.com>
Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ebd63723

include/linux/hugetlb.h

+3 −2
Original line number Diff line number Diff line
@@ -358,7 +358,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, 
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

mm/hugetlb.c

+2 −3
Original line number Diff line number Diff line
@@ -1675,16 +1675,15 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, 
}



/* 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);

mm/mempolicy.c

+2 −1
Original line number Diff line number Diff line
@@ -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;