linux-ext4 - Re: [PATCH v7 21/22] xfs: minimal conversion to errseq

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Date:   Mon, 26 Jun 2017 13:58:32 -0400
From:   jlayton@...hat.com
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...IV.linux.org.uk>, Jan Kara <jack@...e.cz>,
        tytso@....edu, axboe@...nel.dk, mawilcox@...rosoft.com,
        ross.zwisler@...ux.intel.com, corbet@....net,
        Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        Eryu Guan <eguan@...hat.com>,
        David Howells <dhowells@...hat.com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH v7 21/22] xfs: minimal conversion to errseq_t writeback
 error reporting

On Mon, 2017-06-26 at 08:22 -0700, Darrick J. Wong wrote:
> On Fri, Jun 16, 2017 at 03:34:26PM -0400, Jeff Layton wrote:
> > Just check and advance the data errseq_t in struct file before
> > before returning from fsync on normal files. Internal filemap_*
> > callers are left as-is.
> > 
> > Signed-off-by: Jeff Layton <jlayton@...hat.com>
> > ---
> >  fs/xfs/xfs_file.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> > index 5fb5a0958a14..bc3b1575e8db 100644
> > --- a/fs/xfs/xfs_file.c
> > +++ b/fs/xfs/xfs_file.c
> > @@ -134,7 +134,7 @@ xfs_file_fsync(
> >  	struct inode		*inode = file->f_mapping-
> > >host;
> >  	struct xfs_inode	*ip = XFS_I(inode);
> >  	struct xfs_mount	*mp = ip->i_mount;
> > -	int			error = 0;
> > +	int			error = 0, err2;
> >  	int			log_flushed = 0;
> >  	xfs_lsn_t		lsn = 0;
> >  
> > @@ -142,10 +142,12 @@ xfs_file_fsync(
> >  
> >  	error = filemap_write_and_wait_range(inode->i_mapping,
> > start, end);
> >  	if (error)
> > -		return error;
> > +		goto out;
> >  
> > -	if (XFS_FORCED_SHUTDOWN(mp))
> > -		return -EIO;
> > +	if (XFS_FORCED_SHUTDOWN(mp)) {
> > +		error = -EIO;
> > +		goto out;
> > +	}
> >  
> >  	xfs_iflags_clear(ip, XFS_ITRUNCATED);
> >  
> > @@ -197,6 +199,11 @@ xfs_file_fsync(
> >  	    mp->m_logdev_targp == mp->m_ddev_targp)
> >  		xfs_blkdev_issue_flush(mp->m_ddev_targp);
> >  
> > +out:
> > +	err2 = filemap_report_wb_err(file);
> 
> Could we have a comment here to remind anyone reading the code a year
> from now that filemap_report_wb_err has side effects?  Pre-coffee me
> was
> wondering why we'd bother calling filemap_report_wb_err in the
> XFS_FORCED_SHUTDOWN case, then remembered that it touches data
> structures.
> 
> The first sentence of the commit message (really, the word 'advance')
> added as a comment was adequate to remind me of the side effects.
> 
> Once that's added,
> Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
> 
> --D
> 

Yeah, definitely. I'm working on a respin of the series now to
incorporate HCH's suggestion too. I'll add that in as well.

Maybe I should rename that function to file_check_and_advance_wb_err()
? It would be good to make it clear that it does advance the errseq_t
cursor.

> > +	if (!error)
> > +		error = err2;
> > +
> >  	return error;
> >  }
> >  
> > -- 
> > 2.13.0
> > 
> > --
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> > xfs" in
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