Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755352AbdGXJXp (ORCPT ); Mon, 24 Jul 2017 05:23:45 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:9407 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751671AbdGXJXG (ORCPT ); Mon, 24 Jul 2017 05:23:06 -0400 Subject: Re: [PATCH] f2fs: let __get_victim successfully get a segno in corner case To: Jaegeuk Kim CC: sylinux , chao , yuchao0 , miaoxie , "bintian.wang" , linux-fsdevel , linux-f2fs-devel , linux-kernel References: <1500033432-57620-1-git-send-email-yunlong.song@huawei.com> <20170716010934.GC51202@jaegeuk-macbookpro.roam.corp.google.com> <3b3c1eba.b25.15d495786fe.Coremail.sylinux@163.com> <20170717165636.GB81128@jaegeuk-macbookpro.roam.corp.google.com> <5970A19F.4030000@huawei.com> <20170721210733.GB14361@jaegeuk-macbookpro.roam.corp.google.com> From: Yunlong Song Message-ID: <6f374ac6-b9a3-9d96-35c3-49ef2e45ea77@huawei.com> Date: Mon, 24 Jul 2017 17:18:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170721210733.GB14361@jaegeuk-macbookpro.roam.corp.google.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.111.220.140] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020201.5975BBA5.0026,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 6cc646f631ffc40cf4b81c3e7da91542 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6886 Lines: 177 Hi Jay, fggc_threshold is 507, reserved_segment is 462. On 2017/7/22 5:07, Jaegeuk Kim wrote: > Hi Yunlong, > > On 07/20, Yunlong Song wrote: >> Hi, Jay, >> The distribution is like this, unit is segment counts: >> cnt_free: 0 (free blocks) >> cnt_full: 25182 (segment which has 512 blocks) >> cnt_over: 25192 (segment which valid blocks over fggc_threshold) >> cnt_below: 870 (segment which valid blocks below fggc_threshold) > What are the values of fggc_threshold and ovp ratio or reserved_segments? > How was the proc/segment_info? > > Thanks, > >> The test is fragment test, add and delete small files over and over. >> >> On 2017/7/18 0:56, Jaegeuk Kim wrote: >>> On 07/16, sylinux wrote: >>>> In fact，this is not "suppose" case yet, we have already met this problem several times in some test suits for corner case, or I cannot notice that this could happen. >>> So, have you taken a look at distribution of valid blocks in that case? >>> I'm wondering what distribution can cause this. >>> >>> Thanks, >>> >>>> >>>> >>>> 发自网易邮箱大师 >>>> On 07/16/2017 09:09, Jaegeuk Kim wrote: >>>> Hi Yunlong, >>>> >>>> On 07/14, Yunlong Song wrote: >>>>> Suppose that the valid blocks of each section are all over sbi->fggc_threshold, >>>> How about adding a kernel message first to detect your *supposed* sceanrio? >>>> If that happens, it'll be a sort of bug which we haven't assumed. >>>> >>>> Thanks, >>>> >>>>> and even has_not_enough_free_secs is true, f2fs_gc cannot do its job since the >>>>> no_fggc_candidate always returns true. As a result, the reserved segments can be >>>>> used up, and finally there is no free segment at all, and get_new_segment cannot >>>>> get a free segment, filesystem will trap into a wrong status. >>>>> >>>>> To fix this, we record the segno which has a rough minimum cost and return it to >>>>> __get_victim to continue f2fs_gc's job. >>>>> >>>>> Signed-off-by: Yunlong Song >>>>> --- >>>>> fs/f2fs/gc.c | 19 ++++++++++++++----- >>>>> fs/f2fs/segment.h | 17 ++++++++++++++--- >>>>> 2 files changed, 28 insertions(+), 8 deletions(-) >>>>> >>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>> index fa3d2e2..965e783 100644 >>>>> --- a/fs/f2fs/gc.c >>>>> +++ b/fs/f2fs/gc.c >>>>> @@ -178,6 +178,8 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type, >>>>> p->offset = 0; >>>>> else >>>>> p->offset = SIT_I(sbi)->last_victim[p->gc_mode]; >>>>> + >>>>> + p->min_cost_r = UINT_MAX; >>>>> } >>>>> >>>>> static unsigned int get_max_cost(struct f2fs_sb_info *sbi, >>>>> @@ -194,7 +196,7 @@ static unsigned int get_max_cost(struct f2fs_sb_info *sbi, >>>>> return 0; >>>>> } >>>>> >>>>> -static unsigned int check_bg_victims(struct f2fs_sb_info *sbi) >>>>> +static unsigned int check_bg_victims(struct f2fs_sb_info *sbi, struct victim_sel_policy *p) >>>>> { >>>>> struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); >>>>> unsigned int secno; >>>>> @@ -208,11 +210,12 @@ static unsigned int check_bg_victims(struct f2fs_sb_info *sbi) >>>>> if (sec_usage_check(sbi, secno)) >>>>> continue; >>>>> >>>>> - if (no_fggc_candidate(sbi, secno)) >>>>> + p->cur_segno_r = GET_SEG_FROM_SEC(sbi, secno); >>>>> + if (no_fggc_candidate(sbi, secno, p)) >>>>> continue; >>>>> >>>>> clear_bit(secno, dirty_i->victim_secmap); >>>>> - return GET_SEG_FROM_SEC(sbi, secno); >>>>> + return p->cur_segno_r; >>>>> } >>>>> return NULL_SEGNO; >>>>> } >>>>> @@ -332,7 +335,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi, >>>>> >>>>> last_victim = sm->last_victim[p.gc_mode]; >>>>> if (p.alloc_mode == LFS && gc_type == FG_GC) { >>>>> - p.min_segno = check_bg_victims(sbi); >>>>> + p.min_segno = check_bg_victims(sbi, &p); >>>>> if (p.min_segno != NULL_SEGNO) >>>>> goto got_it; >>>>> } >>>>> @@ -369,8 +372,9 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi, >>>>> goto next; >>>>> if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap)) >>>>> goto next; >>>>> + p.cur_segno_r = segno; >>>>> if (gc_type == FG_GC && p.alloc_mode == LFS && >>>>> - no_fggc_candidate(sbi, secno)) >>>>> + no_fggc_candidate(sbi, secno, &p)) >>>>> goto next; >>>>> >>>>> cost = get_gc_cost(sbi, segno, &p); >>>>> @@ -403,6 +407,11 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi, >>>>> trace_f2fs_get_victim(sbi->sb, type, gc_type, &p, >>>>> sbi->cur_victim_sec, >>>>> prefree_segments(sbi), free_segments(sbi)); >>>>> + } else if (has_not_enough_free_secs(sbi, 0, 0)) { >>>>> + p.min_segno = p.min_segno_r; >>>>> + if (p.alloc_mode == LFS && gc_type == FG_GC) >>>>> + clear_bit(GET_SEC_FROM_SEG(sbi, p.min_segno), dirty_i->victim_secmap); >>>>> + goto got_it; >>>>> } >>>>> out: >>>>> mutex_unlock(&dirty_i->seglist_lock); >>>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h >>>>> index 6b871b4..7d2d0f3 100644 >>>>> --- a/fs/f2fs/segment.h >>>>> +++ b/fs/f2fs/segment.h >>>>> @@ -169,6 +169,9 @@ struct victim_sel_policy { >>>>> unsigned int ofs_unit; /* bitmap search unit */ >>>>> unsigned int min_cost; /* minimum cost */ >>>>> unsigned int min_segno; /* segment # having min. cost */ >>>>> + unsigned int min_cost_r; /* rough minimum cost */ >>>>> + unsigned int min_segno_r; /* segment # having rough min. cost */ >>>>> + unsigned int cur_segno_r; /* segment # rough process is handling */ >>>>> }; >>>>> >>>>> struct seg_entry { >>>>> @@ -743,11 +746,19 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type) >>>>> } >>>>> >>>>> static inline bool no_fggc_candidate(struct f2fs_sb_info *sbi, >>>>> - unsigned int secno) >>>>> + unsigned int secno, struct victim_sel_policy *p) >>>>> { >>>>> - if (get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true) >= >>>>> - sbi->fggc_threshold) >>>>> + unsigned int cur_cost; >>>>> + >>>>> + cur_cost = get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true); >>>>> + if (cur_cost >= sbi->fggc_threshold) { >>>>> + if (p->min_cost_r > cur_cost) { >>>>> + p->min_cost_r = cur_cost; >>>>> + p->min_segno_r = p->cur_segno_r; >>>>> + } >>>>> return true; >>>>> + } >>>>> + >>>>> return false; >>>>> } >>>>> >>>>> -- >>>>> 1.8.5.2 >>> . >>> >> >> -- >> Thanks, >> Yunlong Song >> > . > -- Thanks, Yunlong Song