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Date:   Mon, 6 Nov 2017 19:26:36 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Yunlong Song <yunlong.song@huawei.com>
Cc:     chao@kernel.org, yuchao0@huawei.com, yunlong.song@icloud.com,
        miaoxie@huawei.com, bintian.wang@huawei.com,
        linux-fsdevel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] f2fs: add bug_on when f2fs_gc even fails to get one
 victim
Message-ID: <20171107032636.GB92599@jaegeuk-macbookpro.roam.corp.google.com>
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On 11/07, Yunlong Song wrote:
> Because I find that some out-of-free problem is caused by the failure
> of get victim target. For example, chao has pointed out that he has
> found out a bug when adding this bug_on last week.

That's NOT what I asked. Why not checking FG_GC all the time like this?

f2fs_bug_on(sbi, !total_freed && gc_type == FG_GC);

> 
> On 2017/11/7 10:40, Jaegeuk Kim wrote:
> > On 11/06, Jaegeuk Kim wrote:
> > > On 11/06, Yunlong Song wrote:
> > > > Agree.
> > > > 
> > > > On 2017/11/3 11:44, Jaegeuk Kim wrote:
> > > > > On 10/13, Yunlong Song wrote:
> > > > > > This can help us to debug on some corner case.
> > > > > > 
> > > > > > Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> > > > > > Signed-off-by: Chao Yu <yuchao0@huawei.com>
> > > > > > ---
> > > > > >    fs/f2fs/gc.c | 6 +++++-
> > > > > >    1 file changed, 5 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > > > > index 197ebf4..2b03202 100644
> > > > > > --- a/fs/f2fs/gc.c
> > > > > > +++ b/fs/f2fs/gc.c
> > > > > > @@ -986,6 +986,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> > > > > >    		.ilist = LIST_HEAD_INIT(gc_list.ilist),
> > > > > >    		.iroot = RADIX_TREE_INIT(GFP_NOFS),
> > > > > >    	};
> > > > > > +	bool need_fggc = false;
> > > > > >    	trace_f2fs_gc_begin(sbi->sb, sync, background,
> > > > > >    				get_pages(sbi, F2FS_DIRTY_NODES),
> > > > > > @@ -1018,8 +1019,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> > > > > >    			if (ret)
> > > > > >    				goto stop;
> > > > > >    		}
> > > > > > -		if (has_not_enough_free_secs(sbi, 0, 0))
> > > > > > +		if (has_not_enough_free_secs(sbi, 0, 0)) {
> > > > > >    			gc_type = FG_GC;
> > > > > > +			need_fggc = true;
> > > > > > +		}
> > > > > >    	}
> > > > > >    	/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
> > > > > > @@ -1028,6 +1031,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> > > > > >    		goto stop;
> > > > > >    	}
> > > > > >    	if (!__get_victim(sbi, &segno, gc_type)) {
> > > > > > +		f2fs_bug_on(sbi, !total_freed && need_fggc);
> > > > > Just like this?
> > > > That's OK.
> > > I'm not quite sure whether this is really a bug_on case.
> > > Let me make it WARN_ON() for debugging purpose first.
> > BTW, why is this the special case where BG_GC detects FG_GC?
> > 
> > > Thanks,
> > > 
> > > > > 		f2fs_bug_on(sbi, !total_freed && !sync && gc_type == FG_GC);
> > > > > 
> > > > > >    		ret = -ENODATA;
> > > > > >    		goto stop;
> > > > > >    	}
> > > > > > -- 
> > > > > > 1.8.5.2
> > > > > .
> > > > > 
> > > > -- 
> > > > Thanks,
> > > > Yunlong Song
> > > > 
> > .
> > 
> 
> -- 
> Thanks,
> Yunlong Song
> 

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