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 r268126: MFV r268121:

4924 LZ4 Compression for metadata

MFC r268075: MFV r267565:

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

MFC r264835 (MFV r264829):

3897 zfs filesystem and snapshot limits

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

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

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

MFV r254750:

Add support of Illumos dumps on zvol over RAID-Z.

Note that this only adds the features. FreeBSD would
still need more work to support dumping on zvols.

Illumos ZFS issues:
2932 support crash dumps to raidz, etc. pools

MFC after: 1 month
Approved by: re (ZFS blanket)

MFV r245512:

* Illumos zfs issue #3035 [1] LZ4 compression support in ZFS.

LZ4 is a new high-speed BSD-licensed compression algorithm created
by Yann Collet that delivers very high compression and decompression
performance compared to lzjb (>50% faster on compression, >80% faster
on decompression and around 3x faster on compression of incompressible
data), while giving better compression ratio [1].

This version of LZ4 corresponds to upstream's [2] revision 85.

Please note that for obvious reasons this is not backward read
compatible. This means once a pool have LZ4 compressed data, these
data can no longer be read by older ZFS implementations.

Local changes:

- On-stack hash table disabled and using kernel slab allocator
instead, at this time. This requires larger kernel thread stack
for zio workers. This may change in the future should we adjusted
the zio workers' thread stack size.
- likely and unlikely will be undefined if they are already defined,
this is required for i386 XEN build.
- Removed De Bruijn sequence based __builtin_ctz family of builtins
in favor of the latter. Both GCC and clang supports these builtins.
- Changed the way the LZ4 code detects endianness.
- Manual pages modifications to mention the feature based on Illumos
counterpart.
- Boot loader changes to make it support LZ4 decompression.

[1] https://www.illumos.org/issues/3035
[2] http://code.google.com/p/lz4/source/list

Obtained from: Illumos (13921:9d721847e469)
Tested on: FreeBSD/amd64
MFC after: 1 month

Merge recent vendor changes:
3100 zvol rename fails with EBUSY when dirty
3104 eliminate empty bpobjs
3120 zinject hangs in zfsdev_ioctl() due to uninitialized zc

References:
https://www.illumos.org/issues/3100
https://www.illumos.org/issues/3104
https://www.illumos.org/issues/3120

Obtained from: illumos (vendor/illumos, vendor/illumos-sys)
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