Illumos 4924 - LZ4 Compression for metadata

Reviewed by Matthew Ahrens <mahrens@delphix.com>
Reviewed by Saso Kiselkov <skiselkov.ml@gmail.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>

References:
  https://github.com/illumos/illumos-gate/commit/b8289d2
  https://www.illumos.org/issues/3756

Porting notes:

The static function zfs_prop_activate_feature() was removed because
this change removes the only caller.  The function was not removed
from Illumos but instead left as dead code.  However, to keep gcc
happy it was removed from Linux and may be easily restored if needed.

Ported by: DHE <git@dehacked.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1540

man/man5/zpool-features.5

@@ -223,11 +223,14 @@ When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
 administrator can turn on \fBlz4\fR compression on any dataset on the
 pool using the \fBzfs\fR(8) command. Please note that doing so will
 immediately activate the \fBlz4_compress\fR feature on the underlying
-pool (even before any data is written), and the feature will not be
+pool using the \fBzfs\fR(1M) command. Also, all newly written metadata
-deactivated. Since this feature is not read-only compatible, this
+will be compressed with \fBlz4\fR algorithm. Since this feature is not
-operation will render the pool unimportable on systems without support
+read-only compatible, this operation will render the pool unimportable
-for the \fBlz4_compress\fR feature. Booting off of \fBlz4\fR-compressed
+on systems without support for the \fBlz4_compress\fR feature. Booting
-root pools is supported.
+off of \fBlz4\fR-compressed root pools is supported.
+
+This feature becomes \fBactive\fR as soon as it is enabled and will
+never return to being \fBenabled\fB.
 .RE
 
 .sp

module/zfs/dmu.c

@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
  */
 
 #include <sys/dmu.h>
@@ -43,6 +44,7 @@
 #include <sys/zio_checksum.h>
 #include <sys/zio_compress.h>
 #include <sys/sa.h>
+#include <sys/zfeature.h>
 #ifdef _KERNEL
 #include <sys/vmsystm.h>
 #include <sys/zfs_znode.h>
@@ -1765,8 +1767,16 @@ dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
 		 * XXX -- we should design a compression algorithm
 		 * that specializes in arrays of bps.
 		 */
-		compress = zfs_mdcomp_disable ? ZIO_COMPRESS_EMPTY :
+		boolean_t lz4_ac = spa_feature_is_active(os->os_spa,
-		    ZIO_COMPRESS_LZJB;
+		    SPA_FEATURE_LZ4_COMPRESS);
+
+		if (zfs_mdcomp_disable) {
+			compress = ZIO_COMPRESS_EMPTY;
+		} else if (lz4_ac) {
+			compress = ZIO_COMPRESS_LZ4;
+		} else {
+			compress = ZIO_COMPRESS_LZJB;
+		}
 
 		/*
 		 * Metadata always gets checksummed.  If the data

module/zfs/spa.c

@@ -22,7 +22,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
- * Copyright 2013 Nexenta Systems, Inc. All rights reserved.
+ * Copyright (c) 2013, 2014, Nexenta Systems, Inc.  All rights reserved.
  */
 
 /*
@@ -6209,6 +6209,22 @@ spa_sync_upgrades(spa_t *spa, dmu_tx_t *tx)
 	    spa->spa_uberblock.ub_version >= SPA_VERSION_FEATURES) {
 		spa_feature_create_zap_objects(spa, tx);
 	}
+
+	/*
+	 * LZ4_COMPRESS feature's behaviour was changed to activate_on_enable
+	 * when possibility to use lz4 compression for metadata was added
+	 * Old pools that have this feature enabled must be upgraded to have
+	 * this feature active
+	 */
+	if (spa->spa_uberblock.ub_version >= SPA_VERSION_FEATURES) {
+		boolean_t lz4_en = spa_feature_is_enabled(spa,
+		    SPA_FEATURE_LZ4_COMPRESS);
+		boolean_t lz4_ac = spa_feature_is_active(spa,
+		    SPA_FEATURE_LZ4_COMPRESS);
+
+		if (lz4_en && !lz4_ac)
+			spa_feature_incr(spa, SPA_FEATURE_LZ4_COMPRESS, tx);
+	}
 	rrw_exit(&dp->dp_config_rwlock, FTAG);
 }
 

module/zfs/zfeature_common.c

@@ -22,6 +22,7 @@
 /*
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
  */
 
 #ifdef _KERNEL
@@ -174,7 +175,7 @@ zpool_feature_init(void)
 	zfeature_register(SPA_FEATURE_LZ4_COMPRESS,
 	    "org.illumos:lz4_compress", "lz4_compress",
 	    "LZ4 compression algorithm support.", B_FALSE, B_FALSE,
-	    B_FALSE, NULL);
+	    B_TRUE, NULL);
 
 	zfeature_register(SPA_FEATURE_SPACEMAP_HISTOGRAM,
 	    "com.delphix:spacemap_histogram", "spacemap_histogram",

module/zfs/zfs_ioctl.c

@@ -29,6 +29,7 @@
  * Copyright (c) 201i3 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
+ * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
  */
 
 /*
@@ -246,8 +247,6 @@ static int zfs_fill_zplprops_root(uint64_t, nvlist_t *, nvlist_t *,
 int zfs_set_prop_nvlist(const char *, zprop_source_t, nvlist_t *, nvlist_t *);
 static int get_nvlist(uint64_t nvl, uint64_t size, int iflag, nvlist_t **nvp);
 
-static int zfs_prop_activate_feature(spa_t *spa, spa_feature_t feature);
-
 static void
 history_str_free(char *buf)
 {
@@ -2402,37 +2401,6 @@ zfs_prop_set_special(const char *dsname, zprop_source_t source,
 		}
 		break;
 	}
-	case ZFS_PROP_COMPRESSION:
-	{
-		if (intval == ZIO_COMPRESS_LZ4) {
-			spa_t *spa;
-
-			if ((err = spa_open(dsname, &spa, FTAG)) != 0)
-				return (err);
-
-			/*
-			 * Setting the LZ4 compression algorithm activates
-			 * the feature.
-			 */
-			if (!spa_feature_is_active(spa,
-			    SPA_FEATURE_LZ4_COMPRESS)) {
-				if ((err = zfs_prop_activate_feature(spa,
-				    SPA_FEATURE_LZ4_COMPRESS)) != 0) {
-					spa_close(spa, FTAG);
-					return (err);
-				}
-			}
-
-			spa_close(spa, FTAG);
-		}
-		/*
-		 * We still want the default set action to be performed in the
-		 * caller, we only performed zfeature settings here.
-		 */
-		err = -1;
-		break;
-	}
-
 	default:
 		err = -1;
 	}
@@ -3830,56 +3798,6 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 	return (zfs_secpolicy_setprop(dsname, prop, pair, CRED()));
 }
 
-/*
- * Checks for a race condition to make sure we don't increment a feature flag
- * multiple times.
- */
-static int
-zfs_prop_activate_feature_check(void *arg, dmu_tx_t *tx)
-{
-	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
-	spa_feature_t *featurep = arg;
-
-	if (!spa_feature_is_active(spa, *featurep))
-		return (0);
-	else
-		return (SET_ERROR(EBUSY));
-}
-
-/*
- * The callback invoked on feature activation in the sync task caused by
- * zfs_prop_activate_feature.
- */
-static void
-zfs_prop_activate_feature_sync(void *arg, dmu_tx_t *tx)
-{
-	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
-	spa_feature_t *featurep = arg;
-
-	spa_feature_incr(spa, *featurep, tx);
-}
-
-/*
- * Activates a feature on a pool in response to a property setting. This
- * creates a new sync task which modifies the pool to reflect the feature
- * as being active.
- */
-static int
-zfs_prop_activate_feature(spa_t *spa, spa_feature_t feature)
-{
-	int err;
-
-	/* EBUSY here indicates that the feature is already active */
-	err = dsl_sync_task(spa_name(spa),
-	    zfs_prop_activate_feature_check, zfs_prop_activate_feature_sync,
-	    &feature, 2);
-
-	if (err != 0 && err != EBUSY)
-		return (err);
-	else
-		return (0);
-}
-
 /*
  * Removes properties from the given props list that fail permission checks
  * needed to clear them and to restore them in case of a receive error. For each