[PATCH 4/4] xfs: reduce the number of pagb_lock roundtrips in xfs_alloc_clear_busy

[Christoph Hellwig]

On Wed, Apr 27, 2011 at 11:56:21AM -0500, Alex Elder wrote:
> Perhaps you have other plans that make the model you
> have here more appropriate though.  Let me know
> if you intend to re-submit, otherwise I'll just take
> this version.

The discard support will call xfs_alloc_busy_clear twice for
each list, once to clear all items that don't need discarding,
and a second pass once we're done with the discards.  Keeping
the sorting separate just seems cleaner at that point.