Re: [PATCH 3/3] xfs: byte range granularity for XFS_IOC_ZERO_RANGE

[Dave Chinner <david@fromorbit.com>]

On Fri, Nov 23, 2012 at 03:34:03AM -0500, Christoph Hellwig wrote:
> On Fri, Nov 23, 2012 at 02:24:25PM +1100, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > 
> > XFS_IOC_ZERO_RANGE simply does not work properly for non page cache
> > aligned ranges. Neither test 242 or 290 exercise this correctly, so
> > the behaviour is completely busted even though the tests pass.
> > 
> > Fix it to support full byte range granularity as was originally
> > intended for this ioctl.
> 
> Looks good, but a couple cosmetic comments below:
> 
> > +	rounding = max_t(uint, 1 << mp->m_sb.sb_blocklog, PAGE_CACHE_SIZE);
> 
> I'd call this granularity.

OK. I just copied that from the hole punch code. ;)

> > +	/* round the range iof extents we are going to convert inwards */
> > +	start = round_up(offset, rounding);
> > +	end = round_down(offset + len, rounding);
> 
> start_boundary, end_boundary?

OK.

> > +	if (start < end - 1) {
> > +		/* punch out the page cache over the conversion range */
> > +		truncate_pagecache_range(VFS_I(ip), start, end - 1);
> > +		/* convert the blocks */
> > +		error = xfs_alloc_file_space(ip, start, end - start - 1,
> > +				    XFS_BMAPI_PREALLOC | XFS_BMAPI_CONVERT,
> > +				    attr_flags);
> > +		if (error)
> > +			goto out_unlock;
> > +	} else {
> > +		/* it's a sub-rounding range */
> > +		ASSERT(offset + len <= start);
> > +		error = xfs_iozero(ip, offset, len);
> > +		goto out_unlock;
> > +	}
> > +
> > +	/* now we've handled the interior of the range, handle the edges */
> > +	if (start != offset)
> > +		error = xfs_iozero(ip, offset, start - offset);
> > +	if (!error && end != offset + len)
> > +		error = xfs_iozero(ip, end, offset + len - end);
> 
> I'd move the edge iozero calls into the if branch, that gives a natural
> code flow and avoids the goto unlock in the sub-page case.

Sure. I added the sub-page case after the edge cases when I realised
the edge cases didn't handle that. I'll rework it.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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