From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02D33C4346E for ; Fri, 25 Sep 2020 03:22:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 37C1020838 for ; Fri, 25 Sep 2020 03:22:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 37C1020838 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6405D8E0003; Thu, 24 Sep 2020 23:22:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5F1778E0001; Thu, 24 Sep 2020 23:22:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4B89B8E0003; Thu, 24 Sep 2020 23:22:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0198.hostedemail.com [216.40.44.198]) by kanga.kvack.org (Postfix) with ESMTP id 360818E0001 for ; Thu, 24 Sep 2020 23:22:04 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id E256B282D for ; Fri, 25 Sep 2020 03:22:03 +0000 (UTC) X-FDA: 77300134926.01.nail32_36104a327164 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id AED2F1004EF61 for ; Fri, 25 Sep 2020 03:22:03 +0000 (UTC) X-HE-Tag: nail32_36104a327164 X-Filterd-Recvd-Size: 4030 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Fri, 25 Sep 2020 03:22:02 +0000 (UTC) IronPort-SDR: UWO+yJ6YhGa1Vckbi49LNVJJDwdvT3Q3HSHDSHzzUAnkf0Kj0AQB+83Ejw5BjWZ4osJ60JZr7S 2i+AHPmYoBPg== X-IronPort-AV: E=McAfee;i="6000,8403,9754"; a="223019976" X-IronPort-AV: E=Sophos;i="5.77,300,1596524400"; d="scan'208";a="223019976" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2020 20:22:00 -0700 IronPort-SDR: 7/h2k/G71eK2mqvtVShZGj8Hdd7V4TgF8i5SgX76aYJZkbyrPcTCzi06utt13x3T9tiRbOTVkj alaBd3fsAPrQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,300,1596524400"; d="scan'208";a="349553146" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.65]) by orsmga007.jf.intel.com with ESMTP; 24 Sep 2020 20:21:58 -0700 From: "Huang\, Ying" To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH] mm: swapfile: avoid split_swap_cluster() NULL pointer dereference References: <20200922184838.978540-1-aquini@redhat.com> <878sd1qllb.fsf@yhuang-dev.intel.com> <20200923043459.GL795820@optiplex-lnx> <87sgb9oz1u.fsf@yhuang-dev.intel.com> <20200923130138.GM795820@optiplex-lnx> <87blhwng5f.fsf@yhuang-dev.intel.com> <20200924020928.GC1023012@optiplex-lnx> <877dsjessq.fsf@yhuang-dev.intel.com> <20200924063038.GD1023012@optiplex-lnx> <87tuvnd3db.fsf@yhuang-dev.intel.com> <20200924150833.GE1023012@optiplex-lnx> Date: Fri, 25 Sep 2020 11:21:58 +0800 In-Reply-To: <20200924150833.GE1023012@optiplex-lnx> (Rafael Aquini's message of "Thu, 24 Sep 2020 11:08:33 -0400") Message-ID: <87r1qqbkx5.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Rafael Aquini writes: >> Or, can you help to run the test with a debug kernel based on upstream >> kernel. I can provide some debug patch. >> > > Sure, I can set your patches to run with the test cases we have that tend to > reproduce the issue with some degree of success. Thanks! I found a race condition. During THP splitting, "head" may be unlocked before calling split_swap_cluster(), because head != page during deferred splitting. So we should call split_swap_cluster() before unlocking. The debug patch to do that is as below. Can you help to test it? Best Regards, Huang, Ying ------------------------8<---------------------------- >From 24ce0736a9f587d2dba12f12491c88d3e296a491 Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Fri, 25 Sep 2020 11:10:56 +0800 Subject: [PATCH] dbg: Call split_swap_clsuter() before unlock page during split THP --- mm/huge_memory.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index faadc449cca5..8d79e5e6b46e 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2444,6 +2444,12 @@ static void __split_huge_page(struct page *page, struct list_head *list, remap_page(head); + if (PageSwapCache(head)) { + swp_entry_t entry = { .val = page_private(head) }; + + split_swap_cluster(entry); + } + for (i = 0; i < HPAGE_PMD_NR; i++) { struct page *subpage = head + i; if (subpage == page) @@ -2678,12 +2684,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) } __split_huge_page(page, list, end, flags); - if (PageSwapCache(head)) { - swp_entry_t entry = { .val = page_private(head) }; - - ret = split_swap_cluster(entry); - } else - ret = 0; + ret = 0; } else { if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { pr_alert("total_mapcount: %u, page_count(): %u\n", -- 2.28.0