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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 8E7E3C4363D for ; Thu, 24 Sep 2020 15:12:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5FDD620888 for ; Thu, 24 Sep 2020 15:12:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728364AbgIXPMl (ORCPT ); Thu, 24 Sep 2020 11:12:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:36620 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728164AbgIXPMk (ORCPT ); Thu, 24 Sep 2020 11:12:40 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3282FACE3; Thu, 24 Sep 2020 15:12:39 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id F03391E12DD; Thu, 24 Sep 2020 17:12:38 +0200 (CEST) Date: Thu, 24 Sep 2020 17:12:38 +0200 From: Jan Kara To: "Theodore Y. Ts'o" Cc: Jan Kara , Ritesh Harjani , Ye Bin , adilger.kernel@dilger.ca, jack@suse.com, linux-ext4@vger.kernel.org Subject: Re: [PATCH v5 1/2] ext4: Discard preallocations before releasing group lock Message-ID: <20200924151238.GA3960@quack2.suse.cz> References: <20200916113859.1556397-1-yebin10@huawei.com> <20200916113859.1556397-2-yebin10@huawei.com> <0f17c3a5-2785-939b-47c5-55d39b4bf67b@linux.ibm.com> <20200918095653.GF18920@quack2.suse.cz> <20200924150034.GH482521@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200924150034.GH482521@mit.edu> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu 24-09-20 11:00:34, Theodore Y. Ts'o wrote: > On Fri, Sep 18, 2020 at 11:56:53AM +0200, Jan Kara wrote: > > On Fri 18-09-20 14:37:15, Ritesh Harjani wrote: > > > > > > > > > On 9/16/20 5:08 PM, Ye Bin wrote: > > > > From: Jan Kara > > > > > > > > ext4_mb_discard_group_preallocations() can be releasing group lock with > > > > preallocations accumulated on its local list. Thus although > > > > discard_pa_seq was incremented and concurrent allocating processes will > > > > be retrying allocations, it can happen that premature ENOSPC error is > > > > returned because blocks used for preallocations are not available for > > > > reuse yet. Make sure we always free locally accumulated preallocations > > > > before releasing group lock. > > > > > > > > Fixes: 07b5b8e1ac40 ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling") > > > > Signed-off-by: Jan Kara > > > > Signed-off-by: Ye Bin > > > > Reviewed-by: Ritesh Harjani > > ... > > > > + /* if we still need more blocks and some PAs were used, try again */ > > > > + if (free < needed && busy) { > > > > + ext4_unlock_group(sb, group); > > > > + cond_resched(); > > > > + busy = 0; > > > > + /* Make sure we increment discard_pa_seq again */ > > > > + needed -= free; > > > > + free = 0; > > > > > > Oops sorry about getting back to this. > > > But if we are making free 0 here so we may return a wrong free value > > > when we return from this function. We should fix that by also accounting > > > previous freed blocks at the time of final return from this function. > > > > Ah, good catch! I'll send v2 with this fixed up. > > Did you send a v2 of this patch? I can't find it in my inbox... Yeah, somehow I forgot to send it. I've sent it now: https://lore.kernel.org/linux-ext4/20200924150959.4335-1-jack@suse.cz Note that Ye Bin's patch will need trivial context fixup after applying this... Honza -- Jan Kara SUSE Labs, CR