From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f42.google.com (mail-qa0-f42.google.com [209.85.216.42]) by kanga.kvack.org (Postfix) with ESMTP id 038136B0035 for ; Thu, 17 Jul 2014 18:38:29 -0400 (EDT) Received: by mail-qa0-f42.google.com with SMTP id j15so2488531qaq.1 for ; Thu, 17 Jul 2014 15:38:29 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id q15si7450815qay.78.2014.07.17.15.38.29 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 Jul 2014 15:38:29 -0700 (PDT) Date: Thu, 17 Jul 2014 18:38:24 -0400 From: Naoya Horiguchi Subject: [PATCH] mm: hugetlb: fix copy_hugetlb_page_range() (Re: [BUG] new copy_hugetlb_page_range() causing crashes) Message-ID: <20140717223824.GA828@nhori.bos.redhat.com> References: <019768ac467043a4aaea3e455cb74db7@BPXC18GP.gisp.nec.co.jp> <20140717201203.GA23591@bender.morinfr.org> <20140717213332.GA20284@nhori.bos.redhat.com> <20140717215936.GA28949@bender.morinfr.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140717215936.GA28949@bender.morinfr.org> Sender: owner-linux-mm@kvack.org List-ID: To: Guillaume Morin , Andrew Morton Cc: Hugh Dickins , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Naoya Horiguchi , linux-mm@kvack.org # CCed Andrew, and linux-mm On Thu, Jul 17, 2014 at 11:59:36PM +0200, Guillaume Morin wrote: > On 17 Jul 17:33, Naoya Horiguchi wrote: ... > > And it seems that this also happens on v3.16-rc5. > > So it might be an upstream bug, not a stable-specific matter. > > That's my understanding as well. I just reported it for 3.4 and 3.14 > since these were the kernels I could easily try my original test with. OK. I've checked the fix you suggested below on mainline, and it passed our test program. > > It looks strange to me that the problem is gone by removing the commit > > 4a705fef98 (although I confirmed it is,) because the kernel's behavior > > shouldn't change unless (is_hugetlb_entry_migration(entry) || > > is_hugetlb_entry_hwpoisoned(entry)) is true. And I checked with systemtap > > that both these check returned false in the above test program. > > So I'm wondering why the commit makes difference for this test program. > > I don't know why I am just thinking about that now. Isn't this the fact > that your patch moved the huge_ptep_get() before > huge_ptep_set_wrprotect() in the pte_present() cow case? Ah, right. I was really blind :( > > Actually, I've just tried to re-add the huge_ptep_get call for that > case and it's fixing the problem for me... > > Hmm, want a patch? Thanks, but it's just a oneliner, so I wrote the one. Naoya Horiguchi --- From: Naoya Horiguchi Date: Thu, 17 Jul 2014 18:11:22 -0400 Subject: [PATCH] mm: hugetlb: fix copy_hugetlb_page_range() commit 4a705fef98 ("hugetlb: fix copy_hugetlb_page_range() to handle migration/hwpoisoned entry") changed the order of huge_ptep_set_wrprotect() and huge_ptep_get(), which leads to break some workload like hugepage-backed heap allocation via libhugetlbfs. This patch fixes it. The test program for the problem is shown below: $ cat heap.c #include #include #include #define HPS 0x200000 int main() { int i; char *p = malloc(HPS); memset(p, '1', HPS); for (i = 0; i < 5; i++) { if (!fork()) { memset(p, '2', HPS); p = malloc(HPS); memset(p, '3', HPS); free(p); return 0; } } sleep(1); free(p); return 0; } $ export HUGETLB_MORECORE=yes ; export HUGETLB_NO_PREFAULT= ; hugectl --heap ./heap Reported-by: Guillaume Morin Suggested-by: Guillaume Morin Signed-off-by: Naoya Horiguchi Cc: stable@vger.kernel.org --- mm/hugetlb.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a8d4155eb019..7263c770e9b3 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2597,6 +2597,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, } else { if (cow) huge_ptep_set_wrprotect(src, addr, src_pte); + entry = huge_ptep_get(src_pte); ptepage = pte_page(entry); get_page(ptepage); page_dup_rmap(ptepage); -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org