Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751397AbdGQQ4l (ORCPT ); Mon, 17 Jul 2017 12:56:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:35506 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751291AbdGQQ4j (ORCPT ); Mon, 17 Jul 2017 12:56:39 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2893A22B67 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: Mon, 17 Jul 2017 09:56:36 -0700 From: Jaegeuk Kim To: sylinux Cc: Yunlong Song , 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: <20170717165636.GB81128@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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3b3c1eba.b25.15d495786fe.Coremail.sylinux@163.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: 5757 Lines: 146 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