cleanup quota locking

[Christoph Hellwig <hch@lst.de>]

Hi all,

this series cleans up the xfs quota locking, but splitting the
synchronization of the quota refcount from the protection of the data
in the object, and then leveraging that to push down the content locking
only into the places that need it.

Diffstat:
 libxfs/xfs_quota_defs.h   |    4 -
 scrub/quota.c             |    8 --
 scrub/quota_repair.c      |   11 +--
 scrub/quotacheck.c        |    6 +
 scrub/quotacheck_repair.c |   15 +---
 xfs_dquot.c               |  112 ++++++++++++----------------------
 xfs_dquot.h               |   22 ------
 xfs_dquot_item.c          |    6 -
 xfs_qm.c                  |  150 +++++++++++-----------------------------------
 xfs_qm.h                  |    2 
 xfs_qm_bhv.c              |    4 -
 xfs_qm_syscalls.c         |   10 +--
 xfs_quotaops.c            |    2 
 xfs_trace.h               |    6 -
 xfs_trans_dquot.c         |   18 ++---
 15 files changed, 124 insertions(+), 252 deletions(-)