[PATCH 03/10] xfs: allow assigning the tail lsn with the AIL lock held

[Dave Chinner]

On Tue, Mar 27, 2012 at 12:44:03PM -0400, Christoph Hellwig wrote:
> Provide a variant of xlog_assign_tail_lsn that has the AIL lock already
> held.  By doing so we do an additional atomic_read + atomic_set under
> the lock, which comes down to two instructions.
> 
> Switch xfs_trans_ail_update_bulk and xfs_trans_ail_delete_bulk to the
> new version to reduce the number of lock roundtrips, and prepare for
> a new addition that would require a third lock roundtrip in
> xfs_trans_ail_delete_bulk.  This addition is also the reason for
> slightly rearranging the conditionals and relying on xfs_log_space_wake
> for checking that the filesystem has been shut down internally.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Looks good, and will be slightly more efficient, too.

Reviewed-by: Dave Chinner <dchinner at redhat.com>

-- 
Dave Chinner
david at fromorbit.com