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Date:   Mon, 9 Sep 2019 13:04:43 +0100
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: do not select same victim right
 again
Message-ID: <20190909120443.GA31108@jaegeuk-macbookpro.roam.corp.google.com>
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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.

> 
> Thanks,
> 
> >  		sbi->cur_victim_sec = NULL_SEGNO;
> >  
> >  	if (sync)
> >