linux-ext4 - Re: [PATCH v7 16/22] block: convert to errseq

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Date:   Tue, 20 Jun 2017 13:44:44 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
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>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        Eryu Guan <eguan@...hat.com>,
        David Howells <dhowells@...hat.com>,
        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 16/22] block: convert to errseq_t based writeback
 error tracking

On Tue, 2017-06-20 at 05:35 -0700, Christoph Hellwig wrote:
> >  	error = filemap_write_and_wait_range(filp->f_mapping, start, end);
> >  	if (error)
> > -		return error;
> > +		goto out;
> >  
> >  	/*
> >  	 * There is no need to serialise calls to blkdev_issue_flush with
> > @@ -640,6 +640,10 @@ int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
> >  	if (error == -EOPNOTSUPP)
> >  		error = 0;
> >  
> > +out:
> > +	wberr = filemap_report_wb_err(filp);
> > +	if (!error)
> > +		error = wberr;
> 
> Just curious: what's the reason filemap_write_and_wait_range couldn't
> query for the error using filemap_report_wb_err internally?

In order to query for errors with errseq_t, you need a previously-
sampled point from which to check. When you call
filemap_write_and_wait_range though you don't have a struct file and so
no previously-sampled value.

-- 
Jeff Layton <jlayton@...hat.com>