linux-kernel - Re: [PATCH] f2fs: prevent meta updates while checkpoint is in progress

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Date:   Mon, 30 Mar 2020 11:34:31 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Sahitya Tummala <stummala@...eaurora.org>
Cc:     Chao Yu <yuchao0@...wei.com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: prevent meta updates while checkpoint is in
 progress

On 03/30, Sahitya Tummala wrote:
> On Sat, Mar 28, 2020 at 04:38:00PM +0800, Chao Yu wrote:
> > Hi all,
> > 
> > On 2020/3/28 3:24, Jaegeuk Kim wrote:
> > > Hi Sahitya,
> > > 
> > > On 03/26, Sahitya Tummala wrote:
> > >> allocate_segment_for_resize() can cause metapage updates if
> > >> it requires to change the current node/data segments for resizing.
> > >> Stop these meta updates when there is a checkpoint already
> > >> in progress to prevent inconsistent CP data.
> > > 
> > > Doesn't freeze|thaw_bdev(sbi->sb->s_bdev); work for you?
> > 
> > That can avoid foreground ops racing? rather than background ops like
> > balance_fs() from kworker?
> > 
> 
> Yes, that can only prevent foreground ops but not the background ops
> invoked in the context of kworker thread.
> 
> > BTW, I found that {freeze,thaw}_bdev is not enough to freeze all
> > foreground fs ops, it needs to use {freeze,thaw}_super instead.
> > 
> 
> Yes, I agree.

sgtm. :)

> 
> Thanks,
> 
> > ---
> >  fs/f2fs/gc.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 26248c8936db..acdc8b99b543 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -1538,7 +1538,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> >  		return -EINVAL;
> >  	}
> > 
> > -	freeze_bdev(sbi->sb->s_bdev);
> > +	freeze_super(sbi->sb);
> > 
> >  	shrunk_blocks = old_block_count - block_count;
> >  	secs = div_u64(shrunk_blocks, BLKS_PER_SEC(sbi));
> > @@ -1551,7 +1551,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> >  		sbi->user_block_count -= shrunk_blocks;
> >  	spin_unlock(&sbi->stat_lock);
> >  	if (err) {
> > -		thaw_bdev(sbi->sb->s_bdev, sbi->sb);
> > +		thaw_super(sbi->sb);
> >  		return err;
> >  	}
> > 
> > @@ -1613,6 +1613,6 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> >  	}
> >  	clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
> >  	mutex_unlock(&sbi->resize_mutex);
> > -	thaw_bdev(sbi->sb->s_bdev, sbi->sb);
> > +	thaw_super(sbi->sb);
> >  	return err;
> >  }
> > -- 
> > 2.18.0.rc1
> > 
> > > 
> > >>
> > >> Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
> > >> ---
> > >>  fs/f2fs/gc.c | 2 ++
> > >>  1 file changed, 2 insertions(+)
> > >>
> > >> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > >> index 5bca560..6122bad 100644
> > >> --- a/fs/f2fs/gc.c
> > >> +++ b/fs/f2fs/gc.c
> > >> @@ -1399,8 +1399,10 @@ static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
> > >>  	int err = 0;
> > >>  
> > >>  	/* Move out cursegs from the target range */
> > >> +	f2fs_lock_op(sbi);
> > >>  	for (type = CURSEG_HOT_DATA; type < NR_CURSEG_TYPE; type++)
> > >>  		allocate_segment_for_resize(sbi, type, start, end);
> > >> +	f2fs_unlock_op(sbi);
> > >>  
> > >>  	/* do GC to move out valid blocks in the range */
> > >>  	for (segno = start; segno <= end; segno += sbi->segs_per_sec) {
> > >> -- 
> > >> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
> > >> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
> > > .
> > > 
> 
> -- 
> --
> Sent by a consultant of the Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.