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Date: Fri, 11 Mar 2016 15:47:58 +0100
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 2/3] xfs: don't release bios on completion immediately
Message-ID: <20160311144758.GA2551@lst.de>
References: <1456302011-18915-1-git-send-email-hch@lst.de>
	<1456302011-18915-3-git-send-email-hch@lst.de>
	<20160303151722.GB57990@bfoster.bfoster>
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To: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <dchinner@redhat.com>, Christoph Hellwig <hch@lst.de>, xfs@oss.sgi.com

On Thu, Mar 03, 2016 at 10:17:22AM -0500, Brian Foster wrote:
> > +xfs_finish_page_writeback(
> > +	struct page	*page,
> > +	unsigned int	start,
> > +	unsigned int	end,
> > +	int		error)
> > +{
> > +	struct buffer_head	*head, *bh;
> > +	unsigned int		off = 0;
> > +
> > +	bh = head = page_buffers(page);
> > +
> > +	do {
> > +		if (start > off)
> > +			goto next_bh;
> 
> Probably not an issue for current usage, which appears to be on buffer
> size granularity, but shouldn't this check whether start is beyond the
> end of the current buffer (e.g., start >= off + bh->b_size)?

I don't understand that question.  We get called for a given page,
and a start and end offset inside that page.  These offsets by design
need to be aligned to the filesystem blocksize.  So what we basically
want is to skip a few buffers at the beginning and/or end of the page,
and the code seems to handle that fine.

> >  	mempool_free(ioend, xfs_ioend_pool);
> >  }
> >  
> > +
> 
> Unnecessary whitespace here.

Fixed.

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