setxattr takes inode lock and sends reint to MDS.
truncate takes MDS_INODELOCK_DOM lock and wants
to acquire inode lock.

MDS locks are for different bits
MDS_INODELOCK_UPDATE|MDS_INODELOCK_XATTR vs
MDS_INODELOCK_DOM but they blocks each other if
some blocking lock was present earlier.

If IBITS waiting lock has no conflicts with any lock in the
granted queue or any lock ahead in the waiting queue then
it can be granted.

Use separate waiting lists for each ibit to eliminate full
lr_waiting list scan.

Cray-bug-id: LUS-6970
Change-Id: I95b2ed0b1a0063b7ece5277a5ee06e2511d44e5f
Signed-off-by: Andriy Skulysh <c17819@cray.com>
Reviewed-on: https://review.whamcloud.com/35057


Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>