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Date: Tue, 24 Nov 2015 05:03:34 +0000 From: Naoya Horiguchi <n-horiguchi@...jp.nec.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Hillf Danton <hillf.zj@...baba-inc.com>, "'David Rientjes'" <rientjes@...gle.com>, "'Dave Hansen'" <dave.hansen@...el.com>, "'Mel Gorman'" <mgorman@...e.de>, "'Joonsoo Kim'" <iamjoonsoo.kim@....com>, "'Mike Kravetz'" <mike.kravetz@...cle.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "'Naoya Horiguchi'" <nao.horiguchi@...il.com> Subject: Re: [PATCH v1] mm: hugetlb: fix hugepage memory leak caused by wrong reserve count On Fri, Nov 20, 2015 at 02:26:38PM -0800, Andrew Morton wrote: > On Fri, 20 Nov 2015 15:57:21 +0800 "Hillf Danton" <hillf.zj@...baba-inc.com> wrote: > > > > > > > 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@...jp.nec.com> > > > Cc: <stable@...r.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. > > It's against 4.3. Hi Hillf, Andrew, That's right, this was against 4.3, and I agree with the adjustment for next as done below. > Here's the version I have, against current -linus: > > --- a/mm/hugetlb.c~mm-hugetlb-fix-hugepage-memory-leak-caused-by-wrong-reserve-count > +++ a/mm/hugetlb.c > @@ -1886,7 +1886,10 @@ struct page *alloc_huge_page(struct vm_a > page = __alloc_buddy_huge_page_with_mpol(h, vma, addr); > if (!page) > goto out_uncharge_cgroup; > - > + if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) { > + SetPagePrivate(page); > + h->resv_huge_pages--; > + } > spin_lock(&hugetlb_lock); > list_move(&page->lru, &h->hugepage_activelist); > /* Fall through */ > > It needs a careful re-review and, preferably, retest please. I retested and made sure that the fix works on next-20151123. Thanks, Naoya Horiguchi > Probably when Greg comes to merge this he'll hit problems and we'll > need to provide him with the against-4.3 patch. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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