Messages in this thread | | | From | "Hillf Danton" <> | Subject | Re: [PATCH v1] mm: hugetlb: fix hugepage memory leak caused by wrong reserve count | Date | Fri, 20 Nov 2015 15:57:21 +0800 |
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> > When dequeue_huge_page_vma() in alloc_huge_page() fails, we fall back to > alloc_buddy_huge_page() to directly create a hugepage from the buddy allocator. > In that case, however, if alloc_buddy_huge_page() succeeds we don't decrement > h->resv_huge_pages, which means that successful hugetlb_fault() returns without > releasing the reserve count. As a result, subsequent hugetlb_fault() might fail > despite that there are still free hugepages. > > This patch simply adds decrementing code on that code path. > > I reproduced this problem when testing v4.3 kernel in the following situation: > - the test machine/VM is a NUMA system, > - hugepage overcommiting is enabled, > - most of hugepages are allocated and there's only one free hugepage > which is on node 0 (for example), > - another program, which calls set_mempolicy(MPOL_BIND) to bind itself to > node 1, tries to allocate a hugepage, > - the allocation should fail but the reserve count is still hold. > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > Cc: <stable@vger.kernel.org> [3.16+] > --- > - the reason why I set stable target to "3.16+" is that this patch can be > applied easily/automatically on these versions. But this bug seems to be > old one, so if you are interested in backporting to older kernels, > please let me know. > --- > mm/hugetlb.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git v4.3/mm/hugetlb.c v4.3_patched/mm/hugetlb.c > index 9cc7734..77c518c 100644 > --- v4.3/mm/hugetlb.c > +++ v4.3_patched/mm/hugetlb.c > @@ -1790,7 +1790,10 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, > page = alloc_buddy_huge_page(h, NUMA_NO_NODE); > if (!page) > goto out_uncharge_cgroup; > - > + if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) { > + SetPagePrivate(page); > + h->resv_huge_pages--; > + }
I am wondering if this patch was prepared against the next tree.
> spin_lock(&hugetlb_lock); > list_move(&page->lru, &h->hugepage_activelist); > /* Fall through */ > -- > 1.7.1
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