Channel programs: add zfs.sync.clone()

cmd/ztest.c

@@ -4916,7 +4916,7 @@ ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 		fatal(B_FALSE, "dmu_take_snapshot(%s) = %d", snap1name, error);
 	}
 
-	error = dmu_objset_clone(clone1name, snap1name);
+	error = dsl_dataset_clone(clone1name, snap1name);
 	if (error) {
 		if (error == ENOSPC) {
 			ztest_record_enospc(FTAG);
@@ -4943,7 +4943,7 @@ ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 		fatal(B_FALSE, "dmu_open_snapshot(%s) = %d", snap3name, error);
 	}
 
-	error = dmu_objset_clone(clone2name, snap3name);
+	error = dsl_dataset_clone(clone2name, snap3name);
 	if (error) {
 		if (error == ENOSPC) {
 			ztest_record_enospc(FTAG);
@@ -6334,13 +6334,13 @@ ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
 		fatal(B_FALSE, "dmu_objset_snapshot(%s) = %d", fullname, error);
 	}
 
-	error = dmu_objset_clone(clonename, fullname);
+	error = dsl_dataset_clone(clonename, fullname);
 	if (error) {
 		if (error == ENOSPC) {
-			ztest_record_enospc("dmu_objset_clone");
+			ztest_record_enospc("dsl_dataset_clone");
 			goto out;
 		}
-		fatal(B_FALSE, "dmu_objset_clone(%s) = %d", clonename, error);
+		fatal(B_FALSE, "dsl_dataset_clone(%s) = %d", clonename, error);
 	}
 
 	error = dsl_destroy_snapshot(fullname, B_TRUE);

include/sys/dmu.h

@@ -360,7 +360,6 @@ void dmu_objset_evict_dbufs(objset_t *os);
 int dmu_objset_create(const char *name, dmu_objset_type_t type, uint64_t flags,
     struct dsl_crypto_params *dcp, dmu_objset_create_sync_func_t func,
     void *arg);
-int dmu_objset_clone(const char *name, const char *origin);
 int dsl_destroy_snapshots_nvl(struct nvlist *snaps, boolean_t defer,
     struct nvlist *errlist);
 int dmu_objset_snapshot_one(const char *fsname, const char *snapname);

include/sys/dsl_dataset.h

@@ -276,6 +276,12 @@ dsl_dataset_phys(dsl_dataset_t *ds)
 	return ((dsl_dataset_phys_t *)ds->ds_dbuf->db_data);
 }
 
+typedef struct dsl_dataset_clone_arg_t {
+	const char *ddca_clone;
+	const char *ddca_origin;
+	cred_t *ddca_cred;
+} dsl_dataset_clone_arg_t;
+
 typedef struct dsl_dataset_promote_arg {
 	const char *ddpa_clonename;
 	dsl_dataset_t *ddpa_clone;
@@ -364,6 +370,9 @@ uint64_t dsl_dataset_create_sync_dd(dsl_dir_t *dd, dsl_dataset_t *origin,
 void dsl_dataset_snapshot_sync(void *arg, dmu_tx_t *tx);
 int dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx);
 int dsl_dataset_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t *errors);
+void dsl_dataset_clone_sync(void *arg, dmu_tx_t *tx);
+int dsl_dataset_clone_check(void *arg, dmu_tx_t *tx);
+int dsl_dataset_clone(const char *clone, const char *origin);
 void dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx);
 int dsl_dataset_promote_check(void *arg, dmu_tx_t *tx);
 int dsl_dataset_promote(const char *name, char *conflsnap);

man/man8/zfs-program.8

@@ -12,8 +12,9 @@
 .\" Copyright (c) 2016, 2019 by Delphix. All Rights Reserved.
 .\" Copyright (c) 2019, 2020 by Christian Schwarz. All Rights Reserved.
 .\" Copyright 2020 Joyent, Inc.
+.\" Copyright (c) 2025, Rob Norris <[email protected]>
 .\"
-.Dd May 27, 2021
+.Dd June 5, 2025
 .Dt ZFS-PROGRAM 8
 .Os
 .
@@ -347,6 +348,32 @@ They are executed in "syncing context".
 .Pp
 The available sync submodule functions are as follows:
 .Bl -tag -width "xx"
+.It Fn zfs.sync.clone snapshot newdataset
+Create a new filesystem from a snapshot.
+Returns 0 if the filesystem was successfully created,
+and a nonzero error code otherwise.
+.Pp
+Note: Due to general limitations in channel programs, a filesystem created
+this way will not be mounted, regardless of the value of the
+.Sy mountpoint
+and
+.Sy canmount
+properties.
+This limitation may be removed in the future,
+so it is recommended that you set
+.Sy mountpoint Ns = Ns Sy none
+or
+.Sy canmount Ns = Ns Sy off
+or
+.Sy noauto
+to avoid surprises.
+.Pp
+.Bl -tag -compact -width "newbookmark (string)"
+.It Ar snapshot Pq string
+Name of the source snapshot to clone.
+.It Ar newdataset Pq string
+Name of the target dataset to create.
+.El
 .It Sy zfs.sync.destroy Ns Pq Ar dataset , Op Ar defer Ns = Ns Sy true Ns | Ns Sy false
 Destroy the given dataset.
 Returns 0 on successful destroy, or a nonzero error code if the dataset could
@@ -474,6 +501,7 @@ The available
 .Sy zfs.check
 functions are:
 .Bl -tag -compact -width "xx"
+.It Fn zfs.check.clone snapshot newdataset
 .It Sy zfs.check.destroy Ns Pq Ar dataset , Op Ar defer Ns = Ns Sy true Ns | Ns Sy false
 .It Fn zfs.check.promote dataset
 .It Fn zfs.check.rollback filesystem

module/zfs/dmu_objset.c

@@ -1383,112 +1383,6 @@ dmu_objset_create(const char *name, dmu_objset_type_t type, uint64_t flags,
 	return (rv);
 }
 
-typedef struct dmu_objset_clone_arg {
-	const char *doca_clone;
-	const char *doca_origin;
-	cred_t *doca_cred;
-} dmu_objset_clone_arg_t;
-
-static int
-dmu_objset_clone_check(void *arg, dmu_tx_t *tx)
-{
-	dmu_objset_clone_arg_t *doca = arg;
-	dsl_dir_t *pdd;
-	const char *tail;
-	int error;
-	dsl_dataset_t *origin;
-	dsl_pool_t *dp = dmu_tx_pool(tx);
-
-	if (strchr(doca->doca_clone, '@') != NULL)
-		return (SET_ERROR(EINVAL));
-
-	if (strlen(doca->doca_clone) >= ZFS_MAX_DATASET_NAME_LEN)
-		return (SET_ERROR(ENAMETOOLONG));
-
-	error = dsl_dir_hold(dp, doca->doca_clone, FTAG, &pdd, &tail);
-	if (error != 0)
-		return (error);
-	if (tail == NULL) {
-		dsl_dir_rele(pdd, FTAG);
-		return (SET_ERROR(EEXIST));
-	}
-
-	error = dsl_fs_ss_limit_check(pdd, 1, ZFS_PROP_FILESYSTEM_LIMIT, NULL,
-	    doca->doca_cred);
-	if (error != 0) {
-		dsl_dir_rele(pdd, FTAG);
-		return (SET_ERROR(EDQUOT));
-	}
-
-	error = dsl_dataset_hold(dp, doca->doca_origin, FTAG, &origin);
-	if (error != 0) {
-		dsl_dir_rele(pdd, FTAG);
-		return (error);
-	}
-
-	/* You can only clone snapshots, not the head datasets. */
-	if (!origin->ds_is_snapshot) {
-		dsl_dataset_rele(origin, FTAG);
-		dsl_dir_rele(pdd, FTAG);
-		return (SET_ERROR(EINVAL));
-	}
-
-	dsl_dataset_rele(origin, FTAG);
-	dsl_dir_rele(pdd, FTAG);
-
-	return (0);
-}
-
-static void
-dmu_objset_clone_sync(void *arg, dmu_tx_t *tx)
-{
-	dmu_objset_clone_arg_t *doca = arg;
-	dsl_pool_t *dp = dmu_tx_pool(tx);
-	dsl_dir_t *pdd;
-	const char *tail;
-	dsl_dataset_t *origin, *ds;
-	uint64_t obj;
-	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
-
-	VERIFY0(dsl_dir_hold(dp, doca->doca_clone, FTAG, &pdd, &tail));
-	VERIFY0(dsl_dataset_hold(dp, doca->doca_origin, FTAG, &origin));
-
-	obj = dsl_dataset_create_sync(pdd, tail, origin, 0,
-	    doca->doca_cred, NULL, tx);
-
-	VERIFY0(dsl_dataset_hold_obj(pdd->dd_pool, obj, FTAG, &ds));
-	dsl_dataset_name(origin, namebuf);
-	spa_history_log_internal_ds(ds, "clone", tx,
-	    "origin=%s (%llu)", namebuf, (u_longlong_t)origin->ds_object);
-	dsl_dataset_rele(ds, FTAG);
-	dsl_dataset_rele(origin, FTAG);
-	dsl_dir_rele(pdd, FTAG);
-}
-
-int
-dmu_objset_clone(const char *clone, const char *origin)
-{
-	dmu_objset_clone_arg_t doca;
-
-	cred_t *cr = CRED();
-	crhold(cr);
-
-	doca.doca_clone = clone;
-	doca.doca_origin = origin;
-	doca.doca_cred = cr;
-
-	int rv = dsl_sync_task(clone,
-	    dmu_objset_clone_check, dmu_objset_clone_sync, &doca,
-	    6, ZFS_SPACE_CHECK_NORMAL);
-
-	if (rv == 0)
-		zvol_create_minor(clone);
-
-	crfree(cr);
-
-	return (rv);
-}
-
 int
 dmu_objset_snapshot_one(const char *fsname, const char *snapname)
 {
@@ -3165,7 +3059,6 @@ EXPORT_SYMBOL(dmu_objset_rele_flags);
 EXPORT_SYMBOL(dmu_objset_disown);
 EXPORT_SYMBOL(dmu_objset_from_ds);
 EXPORT_SYMBOL(dmu_objset_create);
-EXPORT_SYMBOL(dmu_objset_clone);
 EXPORT_SYMBOL(dmu_objset_stats);
 EXPORT_SYMBOL(dmu_objset_fast_stat);
 EXPORT_SYMBOL(dmu_objset_spa);

module/zfs/dsl_dataset.c

@@ -3320,6 +3320,106 @@ dsl_dataset_rollback(const char *fsname, const char *tosnap, void *owner,
 	    1, ZFS_SPACE_CHECK_RESERVED));
 }
 
+int
+dsl_dataset_clone_check(void *arg, dmu_tx_t *tx)
+{
+	dsl_dataset_clone_arg_t *ddca = arg;
+	dsl_dir_t *pdd;
+	const char *tail;
+	int error;
+	dsl_dataset_t *origin;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+
+	if (strchr(ddca->ddca_clone, '@') != NULL)
+		return (SET_ERROR(EINVAL));
+
+	if (strlen(ddca->ddca_clone) >= ZFS_MAX_DATASET_NAME_LEN)
+		return (SET_ERROR(ENAMETOOLONG));
+
+	error = dsl_dir_hold(dp, ddca->ddca_clone, FTAG, &pdd, &tail);
+	if (error != 0)
+		return (error);
+	if (tail == NULL) {
+		dsl_dir_rele(pdd, FTAG);
+		return (SET_ERROR(EEXIST));
+	}
+
+	error = dsl_fs_ss_limit_check(pdd, 1, ZFS_PROP_FILESYSTEM_LIMIT, NULL,
+	    ddca->ddca_cred);
+	if (error != 0) {
+		dsl_dir_rele(pdd, FTAG);
+		return (SET_ERROR(EDQUOT));
+	}
+
+	error = dsl_dataset_hold(dp, ddca->ddca_origin, FTAG, &origin);
+	if (error != 0) {
+		dsl_dir_rele(pdd, FTAG);
+		return (error);
+	}
+
+	/* You can only clone snapshots, not the head datasets. */
+	if (!origin->ds_is_snapshot) {
+		dsl_dataset_rele(origin, FTAG);
+		dsl_dir_rele(pdd, FTAG);
+		return (SET_ERROR(EINVAL));
+	}
+
+	dsl_dataset_rele(origin, FTAG);
+	dsl_dir_rele(pdd, FTAG);
+
+	return (0);
+}
+
+void
+dsl_dataset_clone_sync(void *arg, dmu_tx_t *tx)
+{
+	dsl_dataset_clone_arg_t *ddca = arg;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+	dsl_dir_t *pdd;
+	const char *tail;
+	dsl_dataset_t *origin, *ds;
+	uint64_t obj;
+	char namebuf[ZFS_MAX_DATASET_NAME_LEN];
+
+	VERIFY0(dsl_dir_hold(dp, ddca->ddca_clone, FTAG, &pdd, &tail));
+	VERIFY0(dsl_dataset_hold(dp, ddca->ddca_origin, FTAG, &origin));
+
+	obj = dsl_dataset_create_sync(pdd, tail, origin, 0,
+	    ddca->ddca_cred, NULL, tx);
+
+	VERIFY0(dsl_dataset_hold_obj(pdd->dd_pool, obj, FTAG, &ds));
+	dsl_dataset_name(origin, namebuf);
+	spa_history_log_internal_ds(ds, "clone", tx,
+	    "origin=%s (%llu)", namebuf, (u_longlong_t)origin->ds_object);
+	dsl_dataset_rele(ds, FTAG);
+	dsl_dataset_rele(origin, FTAG);
+	dsl_dir_rele(pdd, FTAG);
+}
+
+int
+dsl_dataset_clone(const char *clone, const char *origin)
+{
+	dsl_dataset_clone_arg_t ddca;
+
+	cred_t *cr = CRED();
+	crhold(cr);
+
+	ddca.ddca_clone = clone;
+	ddca.ddca_origin = origin;
+	ddca.ddca_cred = cr;
+
+	int rv = dsl_sync_task(clone,
+	    dsl_dataset_clone_check, dsl_dataset_clone_sync, &ddca,
+	    6, ZFS_SPACE_CHECK_NORMAL);
+
+	if (rv == 0)
+		zvol_create_minor(clone);
+
+	crfree(cr);
+
+	return (rv);
+}
+
 struct promotenode {
 	list_node_t link;
 	dsl_dataset_t *ds;