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 <mhocko@suse.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -358,7 +358,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
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struct page *alloc_huge_page_node(struct hstate *h, int nid);
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struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
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nodemask_t *nmask);
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struct page *alloc_huge_page_vma(struct vm_area_struct *vma, unsigned long address);
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struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
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unsigned long address);
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int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
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pgoff_t idx);
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@ -536,7 +537,7 @@ struct hstate {};
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#define alloc_huge_page(v, a, r) NULL
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#define alloc_huge_page_node(h, nid) NULL
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#define alloc_huge_page_nodemask(h, preferred_nid, nmask) NULL
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#define alloc_huge_page_vma(vma, address) NULL
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#define alloc_huge_page_vma(h, vma, address) NULL
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#define alloc_bootmem_huge_page(h) NULL
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#define hstate_file(f) NULL
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#define hstate_sizelog(s) NULL
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@ -1675,16 +1675,15 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
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}
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/* mempolicy aware migration callback */
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struct page *alloc_huge_page_vma(struct vm_area_struct *vma, unsigned long address)
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struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
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unsigned long address)
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{
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struct mempolicy *mpol;
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nodemask_t *nodemask;
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struct page *page;
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struct hstate *h;
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gfp_t gfp_mask;
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int node;
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h = hstate_vma(vma);
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gfp_mask = htlb_alloc_mask(h);
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node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
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page = alloc_huge_page_nodemask(h, node, nodemask);
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@ -1121,7 +1121,8 @@ static struct page *new_page(struct page *page, unsigned long start, int **x)
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}
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if (PageHuge(page)) {
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return alloc_huge_page_vma(vma, address);
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return alloc_huge_page_vma(page_hstate(compound_head(page)),
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vma, address);
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} else if (thp_migration_supported() && PageTransHuge(page)) {
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struct page *thp;
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