Started work on snapdirs.
WIP: snapshot mounts, missing refs

Aug 26 16:51:01 Lundmans-Mac kernel[0]: kxld[net.lundman.zfs]:  _dounmount
Aug 26 16:51:01 Lundmans-Mac kernel[0]: kxld[net.lundman.zfs]:  _lookupnameat
Aug 26 16:51:01 Lundmans-Mac kernel[0]: kxld[net.lundman.zfs]:  _mount_snapshot
Aug 26 16:51:01 Lundmans-Mac kernel[0]: kxld[net.lundman.zfs]:  _traverse
Aug 26 16:51:01 Lundmans-Mac kernel[0]: kxld[net.lundman.zfs]:  _vn_matchops
Aug 26 16:51:01 Lundmans-Mac kernel[0]: kxld[net.lundman.zfs]:  _vn_mountedvfs
Fix compile and link of snapdir support, still missing mounts
WIP: snapdirs. Fix up so ".zfs" show up
WIP: snapdir work
WIP: fix numdirent, and uio_offset to update correctly. Handle extended
readdir support.
WIP: Actually pass a_flags along so we can detect extended-dirent usage.
WIP: Fix the vnodeops init for snapdir and snapshot. Fix getattr recursive
call panic.
Illumos #2882, #2883, #2900

2882 implement libzfs_core
2883 changing "canmount" property to "on" should not always remount dataset
2900 "zfs snapshot" should be able to create multiple, arbitrary snapshots at once

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Chris Siden <christopher.siden@delphix.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Bill Pijewski <wdp@joyent.com>
Reviewed by: Dan Kruchinin <dan.kruchinin@gmail.com>
Approved by: Eric Schrock <Eric.Schrock@delphix.com>

References:
  https://www.illumos.org/issues/2882
  https://www.illumos.org/issues/2883
  https://www.illumos.org/issues/2900
  illumos/illumos-gate@4445fffbbb1ea25fd0e9ea68b9380dd7a6709025

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1293

Porting notes:

WARNING: This patch changes the user/kernel ABI.  That means that
the zfs/zpool utilities built from master are NOT compatible with
the 0.6.2 kernel modules.  Ensure you load the matching kernel
modules from master after updating the utilities.  Otherwise the
zfs/zpool commands will be unable to interact with your pool and
you will see errors similar to the following:

  $ zpool list
  failed to read pool configuration: bad address
  no pools available

  $ zfs list
  no datasets available

Add zvol minor device creation to the new zfs_snapshot_nvl function.

Remove the logging of the "release" operation in
dsl_dataset_user_release_sync().  The logging caused a null dereference
because ds->ds_dir is zeroed in dsl_dataset_destroy_sync() and the
logging functions try to get the ds name via the dsl_dataset_name()
function. I've got no idea why this particular code would have worked
in Illumos.  This code has subsequently been completely reworked in
Illumos commit 3b2aab1 (3464 zfs synctask code needs restructuring).

Squash some "may be used uninitialized" warning/erorrs.

Fix some printf format warnings for %lld and %llu.

Apply a few spa_writeable() changes that were made to Illumos in
illumos/illumos-gate.git@cd1c8b8 as part of the 3112, 3113, 3114 and
3115 fixes.

Add a missing call to fnvlist_free(nvl) in log_internal() that was added
in Illumos to fix issue 3085 but couldn't be ported to ZoL at the time
(zfsonlinux/zfs@9e11c73) because it depended on future work.
Illumos #3464

3464 zfs synctask code needs restructuring
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
  https://www.illumos.org/issues/3464
  illumos/illumos-gate@3b2aab18808792cbd248a12f1edf139b89833c13

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1495
WIP: snapdirs erach the attempt-mount point.
Bring back rezget as apparently it is used in 'rollback'.
WIP: more KINDS of panics
Remove Makefile.in
Merge branch 'master' into ctldir

Conflicts:
	module/zfs/zfs_ctldir.c
Fix dmu_objset_find_dp() KM_SLEEP warning

After the restructuring in 13fe019 The 'zfs rename' command will
result in a KM_SLEEP being called in the sync context.  This may
deadlock due to reclaim so it was changed to KM_PUSHPAGE.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1711
Allow libzfs to mount snapshots, as a temporary solution to snapshots.
Merge branch 'master' into ctldir

Conflicts:
	lib/libzfs/libzfs_mount.c
WIP: Allow 'zfs mount' and 'zfs umount' to also handle snapshot mounts
temporarily, allowing for the use of snapshots. Currently forced to
/mnt as the .zfs/snapshot dir needs more work. (panics)
Cleanup header inclusion from previous testing failure.
WIP: fix up the fsref work, and major panics. But unmount seems to timeout
even though is works.