Date: Sat, 25 Mar 2017 14:27:42 -0700
From: Jaegeuk Kim <jaegeuk@kernel.org>
To: Chao Yu <yuchao0@huawei.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 1/5] f2fs: relax node version check for victim
 data in gc
Message-ID: <20170325212742.GA24857@jaegeuk.local>
References: <20170325075933.21072-1-jaegeuk@kernel.org>
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On 03/25, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2017/3/25 15:59, Jaegeuk Kim wrote:
> > - has_not_enough_free_secs
> > node_secs: 0  dent_secs: 0  freed:0  free_segments:103  reserved:104
> > 
> >           - f2fs_gc
> >              - get_victim_by_default
> > alloc_mode 0, gc_mode 1, max_search 2672, offset 4654, ofs_unit 1
> > 
> >                 - do_garbage_collect
> > start_segno 3976, end_segno 3977   type 0
> > 
> >                   - is_alive
> > nid 22797, blkaddr 2131882, ofs_in_node 0, version 0x8/0x0
> > 
> >                    - gc_data_segment 766, segno 3976, block 512/426 not alive
> > 
> > So, this patch fixes subtle corrupted case where node version does not match
> > to summary version which results in infinite loop by gc.
> > 
> > Reported-by: Yunlei He <heyunlei@huawei.com>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/gc.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 939be88a8833..bbeee41aaf73 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -551,8 +551,10 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> >  	get_node_info(sbi, nid, dni);
> >  
> >  	if (sum->version != dni->version) {
> 
> If the node was been truncated, we will increase its version number, since it
> was been truncated, so it will never be writebacked to storage, so the version
> in summary will not be updated.

That's covered by node page lock, so we shouldn't be reached out to this point.
Let's think more about this.

Thanks,

> So this case can happen, shouldn't we just set SBI_NEED_FSCK for the case:
> sum->version != dni->version - 1
> 
> Thanks,
> 
> > -		f2fs_put_page(node_page, 1);
> > -		return false;
> > +		f2fs_msg(sbi->sb, KERN_WARNING,
> > +				"%s: valid data with mismatched node version.",
> > +				__func__);
> > +		set_sbi_flag(sbi, SBI_NEED_FSCK);
> >  	}
> >  
> >  	*nofs = ofs_of_node(node_page);
> >