Re: [f2fs-dev] [PATCH 1/3] f2fs: flush symlink path to avoid broken symlink after POR

[Jaegeuk Kim]

Hi Chao,

On Thu, Apr 16, 2015 at 06:33:29PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> > Sent: Thursday, April 16, 2015 3:31 PM
> > To: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx;
> > linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 1/3] f2fs: flush symlink path to avoid broken symlink after POR
> > 
> > This patch tries to avoid broken symlink case after POR in best effort.
> > This results in performance regression.
> > But, if f2fs has inline_data and the target path is under 3KB-sized long,
> > the page would be stored in its inode_block, so that there would be no
> > performance regression.
> > 
> > Note that, if user wants to keep this file atomically, it needs to trigger
> > dir->fsync.
> > And, there is still a hole to produce broken symlink.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > ---
> >  fs/f2fs/namei.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> > index 8055e30..5d990d8 100644
> > --- a/fs/f2fs/namei.c
> > +++ b/fs/f2fs/namei.c
> > @@ -324,6 +324,17 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
> >  	d_instantiate(dentry, inode);
> >  	unlock_new_inode(inode);
> > 
> > +	/*
> > +	 * Let's flush symlink data in order to avoid broken symlink as much as
> > +	 * possible. Nevertheless, fsyncing is the best way, but there is no
> > +	 * way to get a file descriptor in order to flush that.
> > +	 *
> > +	 * Note that, it needs to do dir->fsync to make this recoverable.
> > +	 * If the symlink path is stored into inline_data, there is no
> > +	 * performance regression.
> > +	 */
> > +	filemap_write_and_wait_range(inode->i_mapping, 0, symlen);
> 
> One minor thing.
> 
> filemap_write_and_wait_range(inode->i_mapping, 0, symlen - 1);
> 
> Because we don't need to write out data exceed isize here.

Thank you for the review.
I fixed this and merged.

Thanks,

> 
> Thanks,
> 
> > +
> >  	if (IS_DIRSYNC(dir))
> >  		f2fs_sync_fs(sbi->sb, 1);
> >  	return err;
> > --
> > 2.1.1
> > 
> > 
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