Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754431AbdGUVHg (ORCPT ); Fri, 21 Jul 2017 17:07:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:49772 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbdGUVHf (ORCPT ); Fri, 21 Jul 2017 17:07:35 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 61EB322B4E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jaegeuk@kernel.org Date: Fri, 21 Jul 2017 14:07:33 -0700 From: Jaegeuk Kim To: Yunlong Song Cc: sylinux , chao , yuchao0 , miaoxie , "bintian.wang" , linux-fsdevel , linux-f2fs-devel , linux-kernel Subject: Re: [PATCH] f2fs: let __get_victim successfully get a segno in corner case Message-ID: <20170721210733.GB14361@jaegeuk-macbookpro.roam.corp.google.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5970A19F.4030000@huawei.com> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6679 Lines: 170 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 >