linux-kernel - Re: [PATCH] f2fs: fix wrong sum_page pointer in f2fs

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Date:   Thu, 13 Oct 2016 10:14:21 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH] f2fs: fix wrong sum_page pointer in f2fs_gc

On Thu, Oct 13, 2016 at 06:33:19PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2016/10/13 7:23, Jaegeuk Kim wrote:
> > This patch fixes using a wrong pointer for sum_page in f2fs_gc.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >  fs/f2fs/gc.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index e48142f..9c18917 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -854,16 +854,16 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >  
> >  	for (segno = start_segno; segno < end_segno; segno++) {
> >  
> > -		if (get_valid_blocks(sbi, segno, 1) == 0 ||
> > -					unlikely(f2fs_cp_error(sbi)))
> > -			goto next;
> > -
> >  		/* find segment summary of victim */
> >  		sum_page = find_get_page(META_MAPPING(sbi),
> >  					GET_SUM_BLOCK(sbi, segno));
> > -		f2fs_bug_on(sbi, !PageUptodate(sum_page));
> >  		f2fs_put_page(sum_page, 0);
> >  
> > +		if (get_valid_blocks(sbi, segno, 1) == 0 ||
> > +				!PageUptodate(sum_page) ||
> 
> Why uptodate flag of summary page can be cleared? someone truncates it?

Well, it looks like no problem to remove this, since it will hit
f2fs_cp_error(). I just intended to handle the above f2fs_bug_on here.

I found you added the above bug_on, but it's not a big deal to remain tho. :)

718e53fa: f2fs: enhance foreground GC

Thanks,

> 
> Thanks,
> 
> > +				unlikely(f2fs_cp_error(sbi)))
> > +			goto next;
> > +
> >  		sum = page_address(sum_page);
> >  		f2fs_bug_on(sbi, type != GET_SUM_TYPE((&sum->footer)));
> >  
> >