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dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="fdKGDBZs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3DAB4218AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1iAkhx-0007mK-Hc; Thu, 19 Sep 2019 00:54:05 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1iAkhv-0007ls-9L for linux-f2fs-devel@lists.sourceforge.net; Thu, 19 Sep 2019 00:54:03 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:CC:To:Subject:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; 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Thu, 19 Sep 2019 00:54:03 +0000 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id D63DBB24693A9CBEFC49; Thu, 19 Sep 2019 08:53:53 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.203) with Microsoft SMTP Server (TLS) id 14.3.439.0; Thu, 19 Sep 2019 08:53:50 +0800 To: Jaegeuk Kim References: <20190909080654.GD21625@jaegeuk-macbookpro.roam.corp.google.com> <97237da2-897a-8420-94de-812e94aa751f@huawei.com> <20190909120443.GA31108@jaegeuk-macbookpro.roam.corp.google.com> <27725e65-53fe-5731-0201-9959b8ef6b49@huawei.com> <20190916153736.GA2493@jaegeuk-macbookpro.roam.corp.google.com> <20190917205501.GA60683@jaegeuk-macbookpro.roam.corp.google.com> <20190918031257.GA82722@jaegeuk-macbookpro.roam.corp.google.com> <20190918164754.GA88624@jaegeuk-macbookpro.roam.corp.google.com> From: Chao Yu Message-ID: <7d7e8e46-0261-ddec-881a-e720ca2badac@huawei.com> Date: Thu, 19 Sep 2019 08:53:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190918164754.GA88624@jaegeuk-macbookpro.roam.corp.google.com> Content-Language: en-US X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Headers-End: 1iAkhs-0037Fh-Nt Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: do not select same victim right again X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2019/9/19 0:47, Jaegeuk Kim wrote: > On 09/18, Chao Yu wrote: >> On 2019/9/18 11:12, Jaegeuk Kim wrote: >>> On 09/18, Chao Yu wrote: >>>> On 2019/9/18 4:55, Jaegeuk Kim wrote: >>>>> On 09/17, Chao Yu wrote: >>>>>> On 2019/9/16 23:37, Jaegeuk Kim wrote: >>>>>>> On 09/16, Chao Yu wrote: >>>>>>>> On 2019/9/9 20:04, Jaegeuk Kim wrote: >>>>>>>>> On 09/09, Chao Yu wrote: >>>>>>>>>> On 2019/9/9 16:06, Jaegeuk Kim wrote: >>>>>>>>>>> On 09/09, Chao Yu wrote: >>>>>>>>>>>> On 2019/9/9 9:25, Jaegeuk Kim wrote: >>>>>>>>>>>>> GC must avoid select the same victim again. >>>>>>>>>>>> >>>>>>>>>>>> Blocks in previous victim will occupy addition free segment, I doubt after this >>>>>>>>>>>> change, FGGC may encounter out-of-free space issue more frequently. >>>>>>>>>>> >>>>>>>>>>> Hmm, actually this change seems wrong by sec_usage_check(). >>>>>>>>>>> We may be able to avoid this only in the suspicious loop? >>>>>>>>>>> >>>>>>>>>>> --- >>>>>>>>>>> fs/f2fs/gc.c | 2 +- >>>>>>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>>>>>>> >>>>>>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>>>>>>>> index e88f98ddf396..5877bd729689 100644 >>>>>>>>>>> --- a/fs/f2fs/gc.c >>>>>>>>>>> +++ b/fs/f2fs/gc.c >>>>>>>>>>> @@ -1326,7 +1326,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, >>>>>>>>>>> round++; >>>>>>>>>>> } >>>>>>>>>>> >>>>>>>>>>> - if (gc_type == FG_GC) >>>>>>>>>>> + if (gc_type == FG_GC && seg_freed) >>>>>>>>>> >>>>>>>>>> That's original solution Sahitya provided to avoid infinite loop of GC, but I >>>>>>>>>> suggest to find the root cause first, then we added .invalid_segmap for that >>>>>>>>>> purpose. >>>>>>>>> >>>>>>>>> I've checked the Sahitya's patch. So, it seems the problem can happen due to >>>>>>>>> is_alive or atomic_file. >>>>>>>> >>>>>>>> For some conditions, this doesn't help, for example, two sections contain the >>>>>>>> same fewest valid blocks, it will cause to loop selecting them if it fails to >>>>>>>> migrate blocks. >>>>>>>> >>>>>>>> How about keeping it as it is to find potential bug. >>>>>>> >>>>>>> I think it'd be fine to merge this. Could you check the above scenario in more >>>>>>> detail? >>>>>> >>>>>> I haven't saw this in real scenario yet. >>>>>> >>>>>> What I mean is if there is a bug (maybe in is_alive()) failing us to GC on one >>>>>> section, when that bug happens in two candidates, there could be the same >>>>>> condition that GC will run into loop (select A, fail to migrate; select B, fail >>>>>> to migrate, select A...). >>>>>> >>>>>> But I guess the benefit of this change is, if FGGC fails to migrate block due to >>>>>> i_gc_rwsem race, selecting another section and later retrying previous one may >>>>>> avoid lock race, right? >>>>> >>>>> In any case, I think this can avoid potenial GC loop. At least to me, it'd be >>>>> quite risky, if we remain this just for debugging purpose only. >>>> >>>> Yup, >>>> >>>> One more concern is would this cur_victim_sec remain after FGGC? then BGGC/SSR >>>> will always skip the section cur_victim_sec points to. >>> >>> Then, we can get another loop before using it by BGGC/SSR. >> >> I guess I didn't catch your point, do you mean, if we reset it in the end of >> FGGC, we may encounter the loop during BGGC/SSR? > > FGGC failed in a loop and last victim was remained in cur_victim_sec. It won't run into a loop because we keep below condition? + if (gc_type == FG_GC && seg_freed) + sbi->cur_victim_sec = NULL_SEGNO; if (sync) goto stop; I meant add below logic in addition: + if (gc_type == FG_GC) + sbi->cur_victim_sec = NULL_SEGNO; mutex_unlock(&sbi->gc_mutex); Thanks, > Next FGGC kicked in and did the same thing again. I don't expect BGGC/SSR > wants to select this victim much, since it will have CB policy. > >> >> I meant: >> >> f2fs_gc() >> ... >> >> + if (gc_type == FG_GC) >> + sbi->cur_victim_sec = NULL_SEGNO; >> >> mutex_unlock(&sbi->gc_mutex); >> >> put_gc_inode(&gc_list); >> ... >> >> Thanks, >> >>> >>>> >>>> So could we reset cur_victim_sec in the end of FGGC? >>>> >>>> Thanks, >>>> >>>>> >>>>>> >>>>>> Thanks, >>>>>> >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>>> >>>>>>>> Thanks, >>>>>>>> >>>>>>>>> >>>>>>>>>> >>>>>>>>>> Thanks, >>>>>>>>>> >>>>>>>>>>> sbi->cur_victim_sec = NULL_SEGNO; >>>>>>>>>>> >>>>>>>>>>> if (sync) >>>>>>>>>>> >>>>>>>>> . >>>>>>>>> >>>>>>> . >>>>>>> >>>>> . >>>>> >>> . >>> > . > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel