Re: [PATCH 2/5] xfs: Introduce writeback context for writepages

[Dave Chinner <david@fromorbit.com>]

On Tue, Feb 09, 2016 at 09:22:26AM -0500, Brian Foster wrote:
> On Mon, Feb 08, 2016 at 04:44:15PM +1100, Dave Chinner wrote:
> > +	/*
> > +	 * We have to fail the iohead here because we buffers locked in the
> > +	 * ioend chain. If we don't do this, we'll deadlock invalidating the
> > +	 * page as that tries to lock the buffers on the page. Also, because we
> > +	 * have set pages under writeback, we have to run IO completion to mark
> > +	 * the error state of the IO appropriately, so we can't cancel the ioend
> > +	 * directly here. That means we have to mark this page as under
> > +	 * writeback if we included any buffers from it in the ioend chain.
> > +	 */
> > +	if (count)
> > +		xfs_start_page_writeback(page, 0, count);
> > +	xfs_writepage_submit(wpc, wbc, err);
> 
> We make the xfs_writepage_submit() error case call here because...
...
> >  STATIC int
> > +xfs_vm_writepage(
> > +	struct page		*page,
> > +	struct writeback_control *wbc)
> > +{
> > +	struct xfs_writepage_ctx wpc = {
> > +		.io_type = XFS_IO_OVERWRITE,
> > +	};
> > +	int			ret;
> > +
> > +	ret = xfs_do_writepage(page, wbc, &wpc);
> > +	if (ret)
> > +		return ret;
> > +	return xfs_writepage_submit(&wpc, wbc, ret);
> 
> 
> ... the callers only call it when ret == 0. Can we eliminate the error
> call down in xfs_do_writepage() and just invoke this consistently from
> the writepage(s) callers?

Probably - I think this is left over from an early concoction that
exploded badly when it was stirred too vigorously...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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