Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r268859: MFV r268851:

When a sync task is waiting for a txg to complete, we should hurry it along
by increasing the number of outstanding async writes (i.e. make
vdev_queue_max_async_writes() return a larger number).

Illumos issue:
4753 increase number of outstanding async writes when sync task is waiting

MFC r268855: MFV r268848:

Instead of asserting all zio's be properly aligned, only assert
on the logical ones.

Cap uberblocks at 8k, otherwise with ashift=17, there would be
only one uberblock.

This fixes a problem that zdb would trip assert on pools with
ashift >= 0xe (8k).

While there, also change the code so it only attempt to condense
space map unless the uncondensed size consumes greater than
zfs_metaslab_condense_block_threshold blocks.

Illumos issue:
4958 zdb trips assert on pools with ashift >= 0xe

MFC r268473: MFV r268455:

Use reserved space for ZFS administrative commands.

MFC r268079: MFV r267566:

4390 i/o errors when deleting filesystem/zvol can lead to space map
corruption

MFC r268075: MFV r267565:

4757 ZFS embedded-data block pointers ("zero block compression")
4913 zfs release should not be subject to space checks

MFC r260183: MFV r260154 + 260182:

4369 implement zfs bookmarks
4368 zfs send filesystems from readonly pools

Illumos/illumos-gate@78f171005391b928aaf1642b3206c534ed644332

MFC r260150: MFV r259170:

4370 avoid transmitting holes during zfs send

4371 DMU code clean up

illumos/illumos-gate@43466aae47bfcd2ad9bf501faec8e75c08095e4f

NOTE: Make sure the boot code is updated if a zpool upgrade is
done on boot zpool.

MFC r259813 + r259813: MFV r258374:

4171 clean up spa_feature_*() interfaces

4172 implement extensible_dataset feature for use by other zpool
features

illumos/illumos-gate@2acef22db7808606888f8f92715629ff3ba555b9

MFC r259052: Expose spa_asize_inflation

MFC r260185: MFV r260155: 4391 panic system rather than corrupting pool if we hit bug 4390

MFC r258717: MFV r258371,r258372: 4101 metaslab_debug should allow for
fine-grained control

MFC r258632,258704: MFV r255255: 4045 zfs write throttle & i/o scheduler
performance work

Sponsored by: HybridCluster [merge]

MFC r258638,258642: expose zfs_flags as debug.zfs_flags r/w tunable and sysctl

Sponsored by: HybridCluster

MFC r258137:
Introduce allocation cache to store LZ4 compression contexts without kicking
VM subsystem twice for every written record.

Tests on 24-core system show double reduction of CPU time spent on copying
single large well-compressed file.

This patch is not really needed on illumos (while not harm either) since
their memory allocator by default uses caching for all requests up to 128K.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFV r247844 (illumos-gate 13975:ef6409bc370f)

Illumos ZFS issues:
3582 zfs_delay() should support a variable resolution
3584 DTrace sdt probes for ZFS txg states

Provide a compatibility shim for Solaris's cv_timedwait_hires
to help aid future porting.

Approved by: re (ZFS blanket)

zfs: load zpool.cache after a root fs is mounted

MFC after: 3 weeks

MFV r251620:

ZFS comments need cleaner, more consistent style

Illumos ZFS issues:
3741 zfs comments need cleaner, more consistent style

MFC after: 2 weeks

MFV r248217:
Merge change from vendor to reduce diff only.
ZFS dtrace probes are not supported on FreeBSD yet.

Illumos ZFS issues:
3598 want to dtrace when errors are generated in zfs

MFC after: 3 weeks

Merge libzfs_core branch:
includes MFV 238590, 238592, 247580

MFV 238590, 238592:
In the first zfs ioctl restructuring phase, the libzfs_core library was
introduced. It is a new thin library that wraps around kernel ioctl's.
The idea is to provide a forward-compatible way of dealing with new
features. Arguments are passed in nvlists and not random zfs_cmd fields,
new-style ioctls are logged to pool history using a new method of
history logging.

http://blog.delphix.com/matt/2012/01/17/the-future-of-libzfs/

MFV 247580 [1]:
To address issues of several deadlocks and race conditions the locking
code around dsl_dataset was rewritten and the interface to synctasks
was changed.

User-Visible Changes:
"zfs snapshot" can create more arbitrary snapshots at once (atomically)
"zfs destroy" destroys multiple snapshots at once
"zfs recv" has improved performance

Backward Compatibility:
I have extended the compatibility layer to support full backward
compatibility by remapping or rewriting the responsible ioctl arguments.
Old utilities are fully supported by the new kernel module.

Forward Compatibility:
New utilities work with old kernels with the following restrictions:
- creating, destroying, holding and releasing of multiple snapshots
at once is not supported, this includes recursive (-r) commands

Illumos ZFS issues:
2882 implement libzfs_core
2900 "zfs snapshot" should be able to create multiple,
arbitrary snapshots at once
3464 zfs synctask code needs restructuring

References:
https://www.illumos.org/issues/2882
https://www.illumos.org/issues/2900
https://www.illumos.org/issues/3464 [1]

MFC after: 1 month
Sponsored by: Hybrid Logic Inc. [1]

Fix typo in sysctl description

Reported by: Jeremy Chadwick
MFC after: 3 days

MFV v242732:

Merge the ZFS I/O deadman thread from vendor (illumos).
This feature panics the system on hanging ZFS I/O, helps debugging
and resumes failed service.

The panic behavior can be controlled with the loader-only tunables:
vfs.zfs.deadman_enabled (enable or disable panic on stalled ZFS I/O)
vfs.zfs.deadman_synctime (expiration time for stalled ZFS I/O)

By default, ZFS I/O deadman is enabled by default on amd64 and i386
excluding virtual guest machines.

Illumos ZFS issues:
3246 ZFS I/O deadman thread

References:
https://www.illumos.org/issues/3246

MFC after: 2 weeks

MFV r242735:

Illumos 13879:4eac7a87eff2:
3329 spa_sync() spends 10-20% of its time in spa_free_sync_cb()
3330 space_seg_t should have its own kmem_cache
3331 deferred frees should happen after sync_pass 1
3335 make SYNC_PASS_* constants tunable

New loader-only tunables:
vfs.zfs.sync_pass_deferred_free
vfs.zfs.sync_pass_dont_compress
vfs.zfs.sync_pass_rewrite

References:
https://www.illumos.org/issues/3329
https://www.illumos.org/issues/3330
https://www.illumos.org/issues/3331
https://www.illumos.org/issues/3335

MFC after: 2 weeks

Merge recent vendor changes and sync code:
1862 incremental zfs receive fails for sparse file > 8PB
3112 ztest does not honor ZFS_DEBUG
3122 zfs destroy filesystem should prefetch blocks
3129 'zpool reopen' restarts resilvers
3130 ztest failure: Assertion failed:
0 == dmu_objset_destroy(name, B_FALSE) (0x0 == 0x10)

References:
https://www.illumos.org/issues/1862
https://www.illumos.org/issues/3112
https://www.illumos.org/issues/3122
https://www.illumos.org/issues/3129
https://www.illumos.org/issues/3130

Obtained from: illumos (vendor/illumos, vendor/illumos-sys)
MFC after: 2 weeks

Merge recent vendor changes:
3086 unnecessarily setting DS_FLAG_INCONSISTENT on async destroyed datasets
3090 vdev_reopen() during reguid causes vdev to be treated as corrupt
3102 vdev_uberblock_load() and vdev_validate() may read the wrong label

Referenes:
https://www.illumos.org/issues/3086
https://www.illumos.org/issues/3090
https://www.illumos.org/issues/3102

PR: kern/170912, kern/170914
Obtained from: illumos (changeset #13776, #13777)
MFC after: 2 weeks

Introduce "feature flags" for ZFS pools (bump SPA version to 5000).
Add first feature "com.delphix:async_destroy" (asynchronous destroy
of ZFS datasets).
Implement features support in ZFS boot code.

Illumos revisions merged:
13700:2889e2596bd6
13701:1949b688d5fb
2619 asynchronous destruction of ZFS file systems
2747 SPA versioning with zfs feature flags

References:
https://www.illumos.org/issues/2619
https://www.illumos.org/issues/2747

Obtained from: illumos (issue #2619, #2747)
MFC after: 1 month

Merge new ZFS features from illumos:

1644 add ZFS "clones" property
https://www.illumos.org/issues/1644

1645 add ZFS "written" and "written@..." properties
https://www.illumos.org/issues/1645

1646 "zfs send" should estimate size of stream
https://www.illumos.org/issues/1646

1647 "zfs destroy" should determine space reclaimed by destroying multiple
snapshots
https://www.illumos.org/issues/1647

1693 persistent 'comment' field for a zpool
https://www.illumos.org/issues/1693

1708 adjust size of zpool history data
https://www.illumos.org/issues/1708

1748 desire support for reguid in zfs
https://www.illumos.org/issues/1748

Obtained from: illumos (changesets 13514, 13524, 13525)
MFC after: 1 month

ZFS tries to allocate blocks evenly across all devices. This means when
devices are imbalanced zfs will lots of CPU searching for space on devices
which tend to be pretty full. It should instead fail quickly on the full
devices and move onto devices which have more availability.

New loader tunable: vfs.zfs.mg_alloc_failures (min = 8)

Illumos-gate changeset: 13379:4df42cc92254

Obtained from: Illumos (Bug #1051)
MFC after: 2 weeks

Finally... Import the latest open-source ZFS version - (SPA) 28.

Few new things available from now on:

- Data deduplication.
- Triple parity RAIDZ (RAIDZ3).
- zfs diff.
- zpool split.
- Snapshot holds.
- zpool import -F. Allows to rewind corrupted pool to earlier
transaction group.
- Possibility to import pool in read-only mode.

MFC after: 1 month

Merge ZFS version 15 and almost all OpenSolaris bugfixes referenced
in Solaris 10 updates 141445-09 and 142901-14.

Detailed information:
(OpenSolaris revisions and Bug IDs, Solaris 10 patch numbers)

7844:effed23820ae
6755435 zfs_open() and zfs_close() needs to use ZFS_ENTER/ZFS_VERIFY_ZP (141445-01)

7897:e520d8258820
6748436 inconsistent zpool.cache in boot_archive could panic a zfs root filesystem upon boot-up (141445-01)

7965:b795da521357
6740164 zpool attach can create an illegal root pool (141909-02)

8084:b811cc60d650
6769612 zpool_import() will continue to write to cachefile even if altroot is set (N/A)

8121:7fd09d4ebd9c
6757430 want an option for zdb to disable space map loading and leak tracking (141445-01)

8129:e4f45a0bfbb0
6542860 ASSERT: reason != VDEV_LABEL_REMOVE||vdev_inuse(vd, crtxg, reason, 0) (141445-01)

8188:fd00c0a81e80
6761100 want zdb option to select older uberblocks (141445-01)

8190:6eeea43ced42
6774886 zfs_setattr() won't allow ndmp to restore SUNWattr_rw (141445-01)

8225:59a9961c2aeb
6737463 panic while trying to write out config file if root pool import fails (141445-01)

8227:f7d7be9b1f56
6765294 Refactor replay (141445-01)

8228:51e9ca9ee3a5
6572357 libzfs should do more to avoid mnttab lookups (141909-01)
6572376 zfs_iter_filesystems and zfs_iter_snapshots get objset stats twice (141909-01)

8241:5a60f16123ba
6328632 zpool offline is a bit too conservative (141445-01)
6739487 ASSERT: txg <= spa_final_txg due to scrub/export race (141445-01)
6767129 ASSERT: cvd->vdev_isspare, in spa_vdev_detach() (141445-01)
6747698 checksum failures after offline -t / export / import / scrub (141445-01)
6745863 ZFS writes to disk after it has been offlined (141445-01)
6722540 50% slowdown on scrub/resilver with certain vdev configurations (141445-01)
6759999 resilver logic rewrites ditto blocks on both source and destination (141445-01)
6758107 I/O should never suspend during spa_load() (141445-01)
6776548 codereview(1) runs off the page when faced with multi-line comments (N/A)
6761406 AMD errata 91 workaround doesn't work on 64-bit systems (141445-01)

8242:e46e4b2f0a03
6770866 GRUB/ZFS should require physical path or devid, but not both (141445-01)

8269:03a7e9050cfd
6674216 "zfs share" doesn't work, but "zfs set sharenfs=on" does (141445-01)
6621164 $SRC/cmd/zfs/zfs_main.c seems to have a syntax error in the translation note (141445-01)
6635482 i18n problems in libzfs_dataset.c and zfs_main.c (141445-01)
6595194 "zfs get" VALUE column is as wide as NAME (141445-01)
6722991 vdev_disk.c: error checking for ddi_pathname_to_dev_t() must test for NODEV (141445-01)
6396518 ASSERT strings shouldn't be pre-processed (141445-01)

8274:846b39508aff
6713916 scrub/resilver needlessly decompress data (141445-01)

8343:655db2375fed
6739553 libzfs_status msgid table is out of sync (141445-01)
6784104 libzfs unfairly rejects numerical values greater than 2^63 (141445-01)
6784108 zfs_realloc() should not free original memory on failure (141445-01)

8525:e0e0e525d0f8
6788830 set large value to reservation cause core dump (141445-01)
6791064 want sysevents for ZFS scrub (141445-01)
6791066 need to be able to set cachefile on faulted pools (141445-01)
6791071 zpool_do_import() should not enable datasets on faulted pools (141445-01)
6792134 getting multiple properties on a faulted pool leads to confusion (141445-01)

8547:bcc7b46e5ff7
6792884 Vista clients cannot access .zfs (141445-01)

8632:36ef517870a3
6798384 It can take a village to raise a zio (141445-01)

8636:7e4ce9158df3
6551866 deadlock between zfs_write(), zfs_freesp(), and zfs_putapage() (141909-01)
6504953 zfs_getpage() misunderstands VOP_GETPAGE() interface (141909-01)
6702206 ZFS read/writer lock contention throttles sendfile() benchmark (141445-01)
6780491 Zone on a ZFS filesystem has poor fork/exec performance (141445-01)
6747596 assertion failed: DVA_EQUAL(BP_IDENTITY(&zio->io_bp_orig), BP_IDENTITY(zio->io_bp))); (141445-01)

8692:692d4668b40d
6801507 ZFS read aggregation should not mind the gap (141445-01)

8697:e62d2612c14d
6633095 creating a filesystem with many properties set is slow (141445-01)

8768:dfecfdbb27ed
6775697 oracle crashes when overwriting after hitting quota on zfs (141909-01)

8811:f8deccf701cf
6790687 libzfs mnttab caching ignores external changes (141445-01)
6791101 memory leak from libzfs_mnttab_init (141445-01)

8845:91af0d9c0790
6800942 smb_session_create() incorrectly stores IP addresses (N/A)
6582163 Access Control List (ACL) for shares (141445-01)
6804954 smb_search - shortname field should be space padded following the NULL terminator (N/A)
6800184 Panic at smb_oplock_conflict+0x35() (N/A)

8876:59d2e67b4b65
6803822 Reboot after replacement of system disk in a ZFS mirror drops to grub> prompt (141445-01)

8924:5af812f84759
6789318 coredump when issue zdb -uuuu poolname/ (141445-01)
6790345 zdb -dddd -e poolname coredump (141445-01)
6797109 zdb: 'zdb -dddddd pool_name/fs_name inode' coredump if the file with inode was deleted (141445-01)
6797118 zdb: 'zdb -dddddd poolname inum' coredump if I miss the fs name (141445-01)
6803343 shareiscsi=on failed, iscsitgtd failed request to share (141445-01)

9030:243fd360d81f
6815893 hang mounting a dataset after booting into a new boot environment (141445-01)

9056:826e1858a846
6809691 'zpool create -f' no longer overwrites ufs infomation (141445-01)

9179:d8fbd96b79b3
6790064 zfs needs to determine uid and gid earlier in create process (141445-01)

9214:8d350e5d04aa
6604992 forced unmount + being in .zfs/snapshot/<snap1> = not happy (141909-01)
6810367 assertion failed: dvp->v_flag & VROOT, file: ../../common/fs/gfs.c, line: 426 (141909-01)

9229:e3f8b41e5db4
6807765 ztest_dsl_dataset_promote_busy needs to clean up after ENOSPC (141445-01)

9230:e4561e3eb1ef
6821169 offlining a device results in checksum errors (141445-01)
6821170 ZFS should not increment error stats for unavailable devices (141445-01)
6824006 need to increase issue and interrupt taskqs threads in zfs (141445-01)

9234:bffdc4fc05c4
6792139 recovering from a suspended pool needs some work (141445-01)
6794830 reboot command hangs on a failed zfs pool (141445-01)

9246:67c03c93c071
6824062 System panicked in zfs_mount due to NULL pointer dereference when running btts and svvs tests (141909-01)

9276:a8a7fc849933
6816124 System crash running zpool destroy on broken zpool (141445-03)

9355:09928982c591
6818183 zfs snapshot -r is slow due to set_snap_props() doing txg_wait_synced() for each new snapshot (141445-03)

9391:413d0661ef33
6710376 log device can show incorrect status when other parts of pool are degraded (141445-03)

9396:f41cf682d0d3 (part already merged)
6501037 want user/group quotas on ZFS (141445-03)
6827260 assertion failed in arc_read(): hdr == pbuf->b_hdr (141445-03)
6815592 panic: No such hold X on refcount Y from zfs_znode_move (141445-03)
6759986 zfs list shows temporary %clone when doing online zfs recv (141445-03)

9404:319573cd93f8
6774713 zfs ignores canmount=noauto when sharenfs property != off (141445-03)

9412:4aefd8704ce0
6717022 ZFS DMU needs zero-copy support (141445-03)

9425:e7ffacaec3a8
6799895 spa_add_spares() needs to be protected by config lock (141445-03)
6826466 want to post sysevents on hot spare activation (141445-03)
6826468 spa 'allowfaulted' needs some work (141445-03)
6826469 kernel support for storing vdev FRU information (141445-03)
6826470 skip posting checksum errors from DTL regions of leaf vdevs (141445-03)
6826471 I/O errors after device remove probe can confuse FMA (141445-03)
6826472 spares should enjoy some of the benefits of cache devices (141445-03)

9443:2a96d8478e95
6833711 gang leaders shouldn't have to be logical (141445-03)

9463:d0bd231c7518
6764124 want zdb to be able to checksum metadata blocks only (141445-03)

9465:8372081b8019
6830237 zfs panic in zfs_groupmember() (141445-03)

9466:1fdfd1fed9c4
6833162 phantom log device in zpool status (141445-03)

9469:4f68f041ddcd
6824968 add ZFS userquota support to rquotad (141445-03)

9470:6d827468d7b5
6834217 godfather I/O should reexecute (141445-03)

9480:fcff33da767f
6596237 Stop looking and start ganging (141909-02)

9493:9933d599bc93
6623978 lwb->lwb_buf != NULL, file ../../../uts/common/fs/zfs/zil.c, line 787, function zil_lwb_commit (141445-06)

9512:64cafcbcc337
6801810 Commit of aligned streaming rewrites to ZIL device causes unwanted disk reads (N/A)

9515:d3b739d9d043
6586537 async zio taskqs can block out userland commands (142901-09)

9554:787363635b6a
6836768 zfs_userspace() callback has no way to indicate failure (N/A)

9574:1eb6a6ab2c57
6838062 zfs panics when an error is encountered in space_map_load() (141909-02)

9583:b0696cd037cc
6794136 Panic BAD TRAP: type=e when importing degraded zraid pool. (141909-03)

9630:e25a03f552e0
6776104 "zfs import" deadlock between spa_unload() and spa_async_thread() (141445-06)

9653:a70048a304d1
6664765 Unable to remove files when using fat-zap and quota exceeded on ZFS filesystem (141445-06)

9688:127be1845343
6841321 zfs userspace / zfs get userused@ doesn't work on mounted snapshot (N/A)
6843069 zfs get userused@S-1-... doesn't work (N/A)

9873:8ddc892eca6e
6847229 assertion failed: refcount_count(&tx->tx_space_written) + delta <= tx->tx_space_towrite in dmu_tx.c (141445-06)

9904:d260bd3fd47c
6838344 kernel heap corruption detected on zil while stress testing (141445-06)

9951:a4895b3dd543
6844900 zfs_ioc_userspace_upgrade leaks (N/A)

10040:38b25aeeaf7a
6857012 zfs panics on zpool import (141445-06)

10000:241a51d8720c
6848242 zdb -e no longer works as expected (N/A)

10100:4a6965f6bef8
6856634 snv_117 not booting: zfs_parse_bootfs: error2 (141445-07)

10160:a45b03783d44
6861983 zfs should use new name <-> SID interfaces (N/A)
6862984 userquota commands can hang (141445-06)

10299:80845694147f
6696858 zfs receive of incremental replication stream can dereference NULL pointer and crash (N/A)

10302:a9e3d1987706
6696858 zfs receive of incremental replication stream can dereference NULL pointer and crash (fix lint) (N/A)

10575:2a8816c5173b (partial merge)
6882227 spa_async_remove() shouldn't do a full clear (142901-14)

10800:469478b180d9
6880764 fsync on zfs is broken if writes are greater than 32kb on a hard crash and no log attached (142901-09)
6793430 zdb -ivvvv assertion failure: bp->blk_cksum.zc_word[2] == dmu_objset_id(zilog->zl_os) (N/A)

10801:e0bf032e8673 (partial merge)
6822816 assertion failed: zap_remove_int(ds_next_clones_obj) returns ENOENT (142901-09)

10810:b6b161a6ae4a
6892298 buf->b_hdr->b_state != arc_anon, file: ../../common/fs/zfs/arc.c, line: 2849 (142901-09)

10890:499786962772
6807339 spurious checksum errors when replacing a vdev (142901-13)

11249:6c30f7dfc97b
6906110 bad trap panic in zil_replay_log_record (142901-13)
6906946 zfs replay isn't handling uid/gid correctly (142901-13)

11454:6e69bacc1a5a
6898245 suspended zpool should not cause rest of the zfs/zpool commands to hang (142901-10)

11546:42ea6be8961b (partial merge)
6833999 3-way deadlock in dsl_dataset_hold_ref() and dsl_sync_task_group_sync() (142901-09)

Discussed with: pjd
Approved by: delphij (mentor)
Obtained from: OpenSolaris (multiple Bug IDs)
MFC after: 2 months

Import OpenSolaris revision 7837:001de5627df3
It includes the following changes:
- parallel reads in traversal code (Bug ID 6333409)
- faster traversal for zfs send (Bug ID 6418042)
- traversal code cleanup (Bug ID 6725675)
- fix for two scrub related bugs (Bug ID 6729696, 6730101)
- fix assertion in dbuf_verify (Bug ID 6752226)
- fix panic during zfs send with i/o errors (Bug ID 6577985)
- replace P2CROSS with P2BOUNDARY (Bug ID 6725680)

List of OpenSolaris Bug IDs:
6333409, 6418042, 6757112, 6725668, 6725675, 6725680,
6725698, 6729696, 6730101, 6752226, 6577985, 6755042

Approved by: pjd, delphij (mentor)
Obtained from: OpenSolaris (multiple Bug IDs)
MFC after: 1 week

Update ZFS from version 6 to 13 and bring some FreeBSD-specific changes.

This bring huge amount of changes, I'll enumerate only user-visible changes:

- Delegated Administration

Allows regular users to perform ZFS operations, like file system
creation, snapshot creation, etc.

- L2ARC

Level 2 cache for ZFS - allows to use additional disks for cache.
Huge performance improvements mostly for random read of mostly
static content.

- slog

Allow to use additional disks for ZFS Intent Log to speed up
operations like fsync(2).

- vfs.zfs.super_owner

Allows regular users to perform privileged operations on files stored
on ZFS file systems owned by him. Very careful with this one.

- chflags(2)

Not all the flags are supported. This still needs work.

- ZFSBoot

Support to boot off of ZFS pool. Not finished, AFAIK.

Submitted by: dfr

- Snapshot properties

- New failure modes

Before if write requested failed, system paniced. Now one
can select from one of three failure modes:
- panic - panic on write error
- wait - wait for disk to reappear
- continue - serve read requests if possible, block write requests

- Refquota, refreservation properties

Just quota and reservation properties, but don't count space consumed
by children file systems, clones and snapshots.

- Sparse volumes

ZVOLs that don't reserve space in the pool.

- External attributes

Compatible with extattr(2).

- NFSv4-ACLs

Not sure about the status, might not be complete yet.

Submitted by: trasz

- Creation-time properties

- Regression tests for zpool(8) command.

Obtained from: OpenSolaris

Fix namespace collision after src/sys/sys/file.h:1.78.

Forced commit to note that these files were repo copied.

MFp4: Allow to set zfs_recover via vfs.zfs.recover from /boot/loader.conf.

Please welcome ZFS - The last word in file systems.

ZFS file system was ported from OpenSolaris operating system. The code in under
CDDL license.

I'd like to thank all SUN developers that created this great piece of software.

Supported by: Wheel LTD (http://www.wheel.pl/)
Supported by: The FreeBSD Foundation (http://www.freebsdfoundation.org/)
Supported by: Sentex (http://www.sentex.net/)