cleanup quota locking v2

[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.

Changes since v1:
 - use min instead of the incorrect max for s_incoredqs
 - add a patch to fix a pre-existing leak identified by the build bot
 - fix a new locking issue identified by the buildbot
 - reorder patches a bit to avoid inconsistent intermediate states
 - add a patch to not retry non-EEXIST errors from radix_tree_insert

Diffstat:
 libxfs/xfs_quota_defs.h   |    4 -
 scrub/quota.c             |    8 --
 scrub/quota_repair.c      |   18 ++---
 scrub/quotacheck.c        |   11 +--
 scrub/quotacheck_repair.c |   21 +-----
 xfs_dquot.c               |  143 +++++++++++++++++-------------------------
 xfs_dquot.h               |   22 ------
 xfs_dquot_item.c          |    6 -
 xfs_qm.c                  |  154 ++++++++++++----------------------------------
 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, 148 insertions(+), 281 deletions(-)