Improve robustness of the Xen balloon driver. sys/dev/xen/balloon/balloon.c: Remove unused and commented out code. Fix deadlock caused by performing a sleepable malloc while holding the balloon mutex. Perform proper accounting of the memory used by the domain. Submitted by: Roger Pau Monné Sponsored by: Citrix Systems R&D Reviewed by: gibbs Approved by: gibbs (mentor) Approved by: re (gjb)