Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935186AbbKTV4j (ORCPT ); Fri, 20 Nov 2015 16:56:39 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:49977 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934903AbbKTV4i (ORCPT ); Fri, 20 Nov 2015 16:56:38 -0500 Subject: Re: [PATCH v1] mm: hugetlb: fix hugepage memory leak caused by wrong reserve count To: Hillf Danton , "'Naoya Horiguchi'" , "'Andrew Morton'" References: <1448004017-23679-1-git-send-email-n-horiguchi@ah.jp.nec.com> <050201d12369$167a0a10$436e1e30$@alibaba-inc.com> From: Mike Kravetz Cc: "'David Rientjes'" , "'Dave Hansen'" , "'Mel Gorman'" , "'Joonsoo Kim'" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "'Naoya Horiguchi'" Message-ID: <564F9702.5070007@oracle.com> Date: Fri, 20 Nov 2015 13:56:18 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <050201d12369$167a0a10$436e1e30$@alibaba-inc.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3220 Lines: 79 On 11/19/2015 11:57 PM, Hillf Danton 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. In general, I agree with the patch. If we allocate a huge page via the buddy allocator and that page will be used to satisfy a reservation, then we need to decrement the reservation count. As Hillf mentions, this code is not exactly the same in linux-next. Specifically, there is the new call to take the memory policy of the vma into account when calling the buddy allocator. I do not think, this impacts your proposed change but you may want to test with that in place. >> >> 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, I am curious about this scenario. When this second program attempts to allocate the page, I assume it creates a reservation first. Is this reservation before or after setting mempolicy? If the mempolicy was set first, I would have expected the reservation to allocate a page on node 1 to satisfy the reservation. -- Mike Kravetz >> - the allocation should fail but the reserve count is still hold. >> >> Signed-off-by: Naoya Horiguchi >> Cc: [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 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/