From patchwork Thu Sep 10 03:08:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "yebin (H)" X-Patchwork-Id: 1361172 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=huawei.com Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4Bn3lv4n6Tz9sTp for ; Thu, 10 Sep 2020 13:10:03 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726426AbgIJDJx (ORCPT ); Wed, 9 Sep 2020 23:09:53 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:53452 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726714AbgIJDIx (ORCPT ); Wed, 9 Sep 2020 23:08:53 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 0AE58CEA07DC70774B83; Thu, 10 Sep 2020 11:08:51 +0800 (CST) Received: from huawei.com (10.175.127.227) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.487.0; Thu, 10 Sep 2020 11:08:43 +0800 From: Ye Bin To: , , , CC: Ye Bin Subject: [PATCH v2] ext4: Fix dead loop in ext4_mb_new_blocks Date: Thu, 10 Sep 2020 11:08:06 +0800 Message-ID: <20200910030806.223411-1-yebin10@huawei.com> X-Mailer: git-send-email 2.25.4 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-CFilter-Loop: Reflected Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org As we test disk offline/online with running fsstress, we find fsstress process is keeping running state. kworker/u32:3-262 [004] ...1 140.787471: ext4_mb_discard_preallocations: dev 8,32 needed 114 .... kworker/u32:3-262 [004] ...1 140.787471: ext4_mb_discard_preallocations: dev 8,32 needed 114 ext4_mb_new_blocks repeat: ext4_mb_discard_preallocations_should_retry(sb, ac, &seq) freed = ext4_mb_discard_preallocations ext4_mb_discard_group_preallocations this_cpu_inc(discard_pa_seq); ---> freed == 0 seq_retry = ext4_get_discard_pa_seq_sum for_each_possible_cpu(__cpu) __seq += per_cpu(discard_pa_seq, __cpu); if (seq_retry != *seq) { *seq = seq_retry; ret = true; } As we see seq_retry is sum of discard_pa_seq every cpu, if ext4_mb_discard_group_preallocations return zero discard_pa_seq in this cpu maybe increase one, so condition "seq_retry != *seq" have always been met. To Fix this problem, ext4_get_discard_pa_seq_sum function couldn't add own's cpu "discard_pa_seq" value. Fixes: 07b5b8e1ac40 ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling") Signed-off-by: Ye Bin --- fs/ext4/mballoc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 132c118d12e1..f386fe62727d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -372,11 +372,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac); static DEFINE_PER_CPU(u64, discard_pa_seq); static inline u64 ext4_get_discard_pa_seq_sum(void) { - int __cpu; + int __cpu, this_cpu; u64 __seq = 0; + this_cpu = smp_processor_id(); for_each_possible_cpu(__cpu) - __seq += per_cpu(discard_pa_seq, __cpu); + if (this_cpu != __cpu) + __seq += per_cpu(discard_pa_seq, __cpu); return __seq; }