Lock ahead

LUG presentation is here: http://wiki.lustre.org/images/f/f9/Shared-File-Performance-in-Lustre_Farrell.pdf

Design doc is in the code: http://review.whamcloud.com/#/c/13564/ Go to "Documentation/lock_ahead.txt".

That version will be kept up to date.

Please contact paf@cray.com with any questions.