Force child process output to write before abort/exit.
Protect ztest_vdev_add_remove() from spa_passivate_log().
Rely on PATH to find zdb.
Name locking fixes for rarely-encountered failures.
Send vdev remove events only after the SPA updates the vdev's status.
zfs_ioc_objset_stats_impl(): Fix race with zvol destroy.

zvol_get_stats() may return ENOENT if the zvol's parent dataset was in the
process of being destroyed; the ZAP would still exist but appear to have no
entries.

Submitted by:	Alan Somers <alans@spectralogic.com>
zfs_ioc_create(): Always destroy the objset on failure.
Don't needlessly check for '@' when calling zfs_unmount_snap().
Fix a race condition in the ZRL implementation.

It was possible for a reference to be added even with the lock held, and
for references added just after a lock release to be lost.

This bug was also independently found and reported in wesunsolve.net
issues 6985013 6995524.

In zrl_add(), always use an atomic operation to update the refcount.
The mutex in the ZRL only guarantees that wakeups occur for waiters on the
lock.  It offers no protection against concurrent updates of the refcount.
The only refcount transition that is safe to perform without an atomic
operation is from ZRL_LOCKED back to 0, since this can only be performed
by the thread which has the ZRL locked.

Submitted by:	Justin Gibbs <justing@spectralogic.com>
Fix commit callbacks by moving the callbacks to the task's list.
Check the commit callback threshold correctly.