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Tue, 17 Sep 2019 20:55:12 +0000 Received: from localhost (unknown [104.132.0.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 61CFD214AF; Tue, 17 Sep 2019 20:55:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568753702; bh=CpxsDxUjfYJQ4KuEuGgfHSNgs7HIa645JgYtKRt6fxQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tyxlsROx96EDroZ6JcZfRUqu8CMa8eEa8qHeXLMo17uCk/I05UWRhR98tbMQk7bx0 9oD8VzulHRg2o5/4u/x65fGB00cZdbU1TIp8OmLZh61fOdhw73oUyPG4D+Fw1PLEQv XOG+7hvJ6u9Lzc5CWqjvHYVBvGxanHl3MgheVdX4= Date: Tue, 17 Sep 2019 13:55:01 -0700 From: Jaegeuk Kim To: Chao Yu Message-ID: <20190917205501.GA60683@jaegeuk-macbookpro.roam.corp.google.com> References: <20190909012532.20454-1-jaegeuk@kernel.org> <69933b7f-48cc-47f9-ba6f-b5ca8f733cba@huawei.com> <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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.8.2 (2017-04-18) X-Headers-End: 1iAKVA-001esC-RE 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 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. > > 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