[PATCH 13/25] xfs: introduce xfs_bmap_last_extent

[Christoph Hellwig]

On Fri, Sep 09, 2011 at 03:23:46PM -0500, Alex Elder wrote:
> On Wed, 2011-08-24 at 02:04 -0400, Christoph Hellwig wrote:
> > plain text document attachment (xfs-simplify-xfs_bmap_isaeof)
> > Add a common helper for finding the last extent in a file.
> > 
> > Largely based on a patch from Dave Chinner.
> 
> 
> The new version of xfs_bmap_isaeof() no longer asserts
> that the data fork is the one being operated on.  Why?

Because it would work perfectly fine for the attr fork, too - even
if it's fairly useless for it.

> fork is empty, so mention that case in the comment header:
>  
>     Returns 0 in *aeof if the file (fork) is empty.
> 
> (Maybe you could explain why this is true at a more
> abstract level though.)

I've done both.

> This logic could be shortened:
> 
> 		*aeof = off >= rec.br_startoff + rec.br_blockcount ||
> 			(off >= rec.br_startoff &&
> 				 isnullstartblock(rec.br_startblock);

Done (including a comment update)

> > +	return 0;
> > +}
> > +
> > +/*
> > + * Check if the endoff is outside the last extent. If so the caller will grow
> > + * the allocation to a stripe unit boundary.
> 
>     All offsets are considered outside the end of file for an
>     empty file (fork), so 1 is returned in *eof in that case.

Ok.