Activate per-dataset feature flags when the property is set

If a compression algorithm requires a feature flag, activate the
feature when the property is set, rather than waiting for the first
block to be born.  This is currently only used by zstd but can be
extended as needed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Allan Jude <allanjude@freebsd.org>

include/sys/dsl_dataset.h

@@ -435,6 +435,8 @@ int dsl_dataset_set_refquota(const char *dsname, zprop_source_t source,
     uint64_t quota);
 int dsl_dataset_set_refreservation(const char *dsname, zprop_source_t source,
     uint64_t reservation);
+int dsl_dataset_set_compression(const char *dsname, zprop_source_t source,
+    uint64_t compression);
 
 boolean_t dsl_dataset_is_before(dsl_dataset_t *later, dsl_dataset_t *earlier,
     uint64_t earlier_txg);

module/zfs/dsl_dataset.c

@@ -30,6 +30,10 @@
  * Copyright 2017 Nexenta Systems, Inc.
  * Copyright (c) 2019, Klara Inc.
  * Copyright (c) 2019, Allan Jude
+ * Copyright (c) 2020 The FreeBSD Foundation [1]
+ *
+ * [1] Portions of this software were developed by Allan Jude
+ *     under sponsorship from the FreeBSD Foundation.
  */
 
 #include <sys/dmu_objset.h>
@@ -4518,6 +4522,73 @@ dsl_dataset_set_refreservation(const char *dsname, zprop_source_t source,
 	    ZFS_SPACE_CHECK_EXTRA_RESERVED));
 }
 
+typedef struct dsl_dataset_set_compression_arg {
+	const char *ddsca_name;
+	zprop_source_t ddsca_source;
+	uint64_t ddsca_value;
+} dsl_dataset_set_compression_arg_t;
+
+/* ARGSUSED */
+static int
+dsl_dataset_set_compression_check(void *arg, dmu_tx_t *tx)
+{
+	dsl_dataset_set_compression_arg_t *ddsca = arg;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+
+	uint64_t compval = ZIO_COMPRESS_ALGO(ddsca->ddsca_value);
+	spa_feature_t f = zio_compress_to_feature(compval);
+
+	if (f == SPA_FEATURE_NONE)
+		return (SET_ERROR(EINVAL));
+
+	if (!spa_feature_is_enabled(dp->dp_spa, f))
+		return (SET_ERROR(ENOTSUP));
+
+	return (0);
+}
+
+static void
+dsl_dataset_set_compression_sync(void *arg, dmu_tx_t *tx)
+{
+	dsl_dataset_set_compression_arg_t *ddsca = arg;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+	dsl_dataset_t *ds = NULL;
+
+	uint64_t compval = ZIO_COMPRESS_ALGO(ddsca->ddsca_value);
+	spa_feature_t f = zio_compress_to_feature(compval);
+	ASSERT3S(spa_feature_table[f].fi_type, ==, ZFEATURE_TYPE_BOOLEAN);
+
+	VERIFY0(dsl_dataset_hold(dp, ddsca->ddsca_name, FTAG, &ds));
+	if (zfeature_active(f, ds->ds_feature[f]) != B_TRUE) {
+		dsl_dataset_activate_feature(ds->ds_object, f,
+		    ds->ds_feature_activation[f], tx);
+		ds->ds_feature[f] = ds->ds_feature_activation[f];
+	}
+	dsl_dataset_rele(ds, FTAG);
+}
+
+int
+dsl_dataset_set_compression(const char *dsname, zprop_source_t source,
+    uint64_t compression)
+{
+	dsl_dataset_set_compression_arg_t ddsca;
+
+	/*
+	 * The sync task is only required for zstd in order to activate
+	 * the feature flag when the property is first set.
+	 */
+	if (ZIO_COMPRESS_ALGO(compression) != ZIO_COMPRESS_ZSTD)
+		return (0);
+
+	ddsca.ddsca_name = dsname;
+	ddsca.ddsca_source = source;
+	ddsca.ddsca_value = compression;
+
+	return (dsl_sync_task(dsname, dsl_dataset_set_compression_check,
+	    dsl_dataset_set_compression_sync, &ddsca, 0,
+	    ZFS_SPACE_CHECK_EXTRA_RESERVED));
+}
+
 /*
  * Return (in *usedp) the amount of space referenced by "new" that was not
  * referenced at the time the bookmark corresponds to.  "New" may be a

module/zfs/zfs_ioctl.c

@@ -2482,6 +2482,9 @@ zfs_prop_set_special(const char *dsname, zprop_source_t source,
 	case ZFS_PROP_REFRESERVATION:
 		err = dsl_dataset_set_refreservation(dsname, source, intval);
 		break;
+	case ZFS_PROP_COMPRESSION:
+		err = dsl_dataset_set_compression(dsname, source, intval);
+		break;
 	case ZFS_PROP_VOLSIZE:
 		err = zvol_set_volsize(dsname, intval);
 		break;