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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 1F688C2D0A3 for ; Tue, 10 Nov 2020 02:15:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9B7220789 for ; Tue, 10 Nov 2020 02:15:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730205AbgKJCPv (ORCPT ); Mon, 9 Nov 2020 21:15:51 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:7164 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725889AbgKJCPu (ORCPT ); Mon, 9 Nov 2020 21:15:50 -0500 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4CVWfz4ypBz15KWt; Tue, 10 Nov 2020 10:15:39 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.208) with Microsoft SMTP Server (TLS) id 14.3.487.0; Tue, 10 Nov 2020 10:15:43 +0800 Subject: Re: [f2fs-dev] [PATCH] f2fs: avoid race condition for shinker count To: Jaegeuk Kim , , , CC: Light Hsieh References: <20201109170012.2129411-1-jaegeuk@kernel.org> From: Chao Yu Message-ID: Date: Tue, 10 Nov 2020 10:15:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20201109170012.2129411-1-jaegeuk@kernel.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.136.114.67] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/10 1:00, Jaegeuk Kim wrote: > Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in I didn't get the problem clearly, did you mean __count_nat_entries() will give the wrong shrink count due to race condition? should there be a lock while reading these two variables? > wrong do_shinker work. Basically the two counts should not happen like that. > > So, I suspect this race condtion where: > - f2fs_try_to_free_nats __flush_nat_entry_set > nat_cnt=2, dirty_nat_cnt=2 > __clear_nat_cache_dirty > spin_lock(nat_list_lock) > list_move() > spin_unlock(nat_list_lock) > spin_lock(nat_list_lock) > list_del() > spin_unlock(nat_list_lock) > nat_cnt=1, dirty_nat_cnt=2 > nat_cnt=1, dirty_nat_cnt=1 nm_i->nat_cnt and nm_i->dirty_nat_cnt were protected by nm_i->nat_tree_lock, I didn't see why expanding nat_list_lock range will help... since there are still places nat_list_lock() didn't cover these two reference counts. Thanks, > > Reported-by: Light Hsieh > Signed-off-by: Jaegeuk Kim > --- > fs/f2fs/node.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > index 42394de6c7eb..e8ec65e40f06 100644 > --- a/fs/f2fs/node.c > +++ b/fs/f2fs/node.c > @@ -269,11 +269,10 @@ static void __clear_nat_cache_dirty(struct f2fs_nm_info *nm_i, > { > spin_lock(&nm_i->nat_list_lock); > list_move_tail(&ne->list, &nm_i->nat_entries); > - spin_unlock(&nm_i->nat_list_lock); > - > set_nat_flag(ne, IS_DIRTY, false); > set->entry_cnt--; > nm_i->dirty_nat_cnt--; > + spin_unlock(&nm_i->nat_list_lock); > } > > static unsigned int __gang_lookup_nat_set(struct f2fs_nm_info *nm_i, >