linux-kernel - Re: [PATCH] f2fs: fix to redirty page if fail to gc data page

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Date:	Thu, 2 Jun 2016 22:08:58 -0700
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Chao Yu <yuchao0@...wei.com>
Cc:	Chao Yu <chao@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: fix to redirty page if fail to gc data page

On Tue, May 31, 2016 at 02:10:50PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2016/5/30 10:37, Jaegeuk Kim wrote:
> > Hi Chao,
> > 
> > On Sat, May 21, 2016 at 01:19:11PM +0800, Chao Yu wrote:
> >> From: Chao Yu <yuchao0@...wei.com>
> >>
> >> If we fail to move data page during foreground GC, we should give another
> >> chance to writeback that page which was set dirty previously by writer.
> >>
> >> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> >> ---
> >>  fs/f2fs/gc.c | 5 ++++-
> >>  1 file changed, 4 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> >> index 38d56f6..ee213a8 100644
> >> --- a/fs/f2fs/gc.c
> >> +++ b/fs/f2fs/gc.c
> >> @@ -653,12 +653,15 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type)
> >>  			.page = page,
> >>  			.encrypted_page = NULL,
> >>  		};
> >> +		bool is_dirty = PageDirty(page);
> >> +
> >>  		set_page_dirty(page);
> >>  		f2fs_wait_on_page_writeback(page, DATA, true);
> >>  		if (clear_page_dirty_for_io(page))
> >>  			inode_dec_dirty_pages(inode);
> >>  		set_cold_data(page);
> >> -		do_write_data_page(&fio);
> >> +		if (do_write_data_page(&fio) && is_dirty)
> >> +			set_page_dirty(page);
> > 
> > If this page is truncated with -ENOENT, we don't need to set it dirty again.
> 
> Agree
> 
> > I expect that, if we get an error here, do_garbage_collect() would retry FG_GC
> 
> IIRC, you have reworked the FG_GC flows changed from an infinite loop to trying
> do the movement just one time. Here, I think if there are just few of blocks are
> failed to be moved, we can give one more time for retrying. How do you think?

Mostly I expected here -ENOENT caused by race condition.
Do we have another expectation?

Thanks,

> 
> > again.
> > 
> > Thanks,
> > 
> >>  		clear_cold_data(page);
> >>  	}
> >>  out:
> >> -- 
> >> 2.7.2
> > .
> >