linux-kernel - Re: [PATCH] f2fs: fix fdatasync

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Date:   Wed, 16 Nov 2016 18:59:11 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] f2fs: fix fdatasync

On Thu, Nov 17, 2016 at 10:51:37AM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2016/11/17 3:13, Jaegeuk Kim wrote:
> > Hi Chao,
> > 
> > On Wed, Nov 16, 2016 at 08:12:11PM +0800, Chao Yu wrote:
> >> For below two cases, we can't guarantee data consistence:
> >>
> >> a)
> >> 1. xfs_io "pwrite 0 4195328" "fsync"
> >> 2. xfs_io "pwrite 4195328 1024" "fdatasync"
> >> 3. godown
> >> 4. umount & mount
> >> --> isize we updated before fdatasync won't be recovered
> >>
> >> b)
> >> 1. xfs_io "pwrite -S 0xcc 0 4202496" "fsync"
> >> 2. xfs_io "fpunch 4194304 4096" "fdatasync"
> >> 3. godown
> >> 4. umount & mount
> >> --> dnode we punched before fdatasync won't be recovered
> >>
> >> The reason is that normally fdatasync won't be aware of modification
> >> of metadata in file, e.g. isize changing, dnode updating, so in ->fsync
> >> we will skip flushing node pages for above cases, result in making
> >> fdatasynced file being lost during recovery.
> >>
> >> Introduce FDATASYNC_INO global ino cache for tracking node changing,
> >> later fdatasync choose to flush nodes depend on ino cache state.
> > 
> > We don't need to add this additionally, and would be better to consider other
> > major metadata as well.
> > 
> > How about this?
> 
> Seems it can't track file after evict?

Do we need that? That means inode page was already up-to-date?

> 
> Thanks,
> 
> > 
> > ---
> >  fs/f2fs/f2fs.h | 11 ++++++++++-
> >  fs/f2fs/file.c |  2 +-
> >  2 files changed, 11 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index c9672a3..50ffa4f 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1727,8 +1727,17 @@ static inline void f2fs_i_size_write(struct inode *inode, loff_t i_size)
> >  		set_inode_flag(inode, FI_AUTO_RECOVER);
> >  }
> >  
> > -static inline bool f2fs_skip_inode_update(struct inode *inode)
> > +static inline bool f2fs_skip_inode_update(struct inode *inode, int dsync)
> >  {
> > +	if (dsync) {
> > +		struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > +		bool ret;
> > +
> > +		spin_lock(&sbi->inode_lock[DIRTY_META]);
> > +		ret = list_empty(&F2FS_I(inode)->gdirty_list);
> > +		spin_unlock(&sbi->inode_lock[DIRTY_META]);
> > +		return ret;
> > +	}
> >  	if (!is_inode_flag_set(inode, FI_AUTO_RECOVER))
> >  		return false;
> >  	return F2FS_I(inode)->last_disk_size == i_size_read(inode);
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index d48c120..50123c6 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -212,7 +212,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
> >  	}
> >  
> >  	/* if the inode is dirty, let's recover all the time */
> > -	if (!datasync && !f2fs_skip_inode_update(inode)) {
> > +	if (!f2fs_skip_inode_update(inode, datasync)) {
> >  		f2fs_write_inode(inode, NULL);
> >  		goto go_write;
> >  	}
> >