Pool allocation classes

Allocation Classes add the ability to have allocation classes in a
pool that are dedicated to serving specific block categories, such
as DDT data, metadata, and small file blocks. A pool can opt-in to
this feature by adding a 'special' or 'dedup' top-level VDEV.

Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Alek Pinchuk <apinchuk@datto.com>
Reviewed-by: Håkan Johansson <f96hajo@chalmers.se>
Reviewed-by: Andreas Dilger <andreas.dilger@chamcloud.com>
Reviewed-by: DHE <git@dehacked.net>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Gregor Kopka <gregor@kopka.net>
Reviewed-by: Kash Pande <kash@tripleback.net>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Don Brady <don.brady@delphix.com>
Closes #5182

module/zcommon/zfeature_common.c

@@ -20,10 +20,11 @@
  */
 
 /*
- * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
+ * Copyright (c) 2017, Intel Corporation.
  */
 
 #ifndef _KERNEL
@@ -408,6 +409,13 @@ zpool_feature_init(void)
 	    ZFEATURE_FLAG_READONLY_COMPAT | ZFEATURE_FLAG_PER_DATASET,
 	    project_quota_deps);
 	}
+
+	{
+	zfeature_register(SPA_FEATURE_ALLOCATION_CLASSES,
+	    "org.zfsonlinux:allocation_classes", "allocation_classes",
+	    "Support for separate allocation classes.",
+	    ZFEATURE_FLAG_READONLY_COMPAT, NULL);
+	}
 }
 
 #if defined(_KERNEL)

module/zcommon/zfs_prop.c

@@ -538,6 +538,9 @@ zfs_prop_init(void)
 	zprop_register_number(ZFS_PROP_RECORDSIZE, "recordsize",
 	    SPA_OLD_MAXBLOCKSIZE, PROP_INHERIT,
 	    ZFS_TYPE_FILESYSTEM, "512 to 1M, power of 2", "RECSIZE");
+	zprop_register_number(ZFS_PROP_SPECIAL_SMALL_BLOCKS,
+	    "special_small_blocks", 0, PROP_INHERIT, ZFS_TYPE_FILESYSTEM,
+	    "zero or 512 to 128K, power of 2", "SPECIAL_SMALL_BLOCKS");
 
 	/* hidden properties */
 	zprop_register_hidden(ZFS_PROP_NUMCLONES, "numclones", PROP_TYPE_NUMBER,