[PATCH 2/5] xfs: do not immediately reuse busy extent ranges

[Alex Elder]

On Mon, 2011-03-28 at 17:06 -0400, Christoph Hellwig wrote:
> Every time we reallocate a busy extent, we cause a synchronous log force
> to occur to ensure the freeing transaction is on disk before we continue
> and use the newly allocated extent.  This is extremely sub-optimal as we
> have to mark every transaction with blocks that get reused as synchronous.
> 
> Instead of searching the busy extent list after deciding on the extent to
> allocate, check each candidate extent during the allocation decisions as
> to whether they are in the busy list.  If they are in the busy list, we
> trim the busy range out of the extent we have found and determine if that
> trimmed range is still OK for allocation. In many cases, this check can
> be incorporated into the allocation extent alignment code which already
> does trimming of the found extent before determining if it is a valid
> candidate for allocation.
> 
> Based on two earlier patches from Dave Chinner.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Looks good.

Reviewed-by: Alex Elder <aelder at sgi.com>