Illumos #3996

3996 want a libzfs_core API to rollback to latest snapshot
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Andy Stormont <andyjstormont@gmail.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

References:
  https://www.illumos.org/issues/3996
  illumos/illumos-gate@a7027df

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775

include/libzfs_core.h

@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
  */
 
 #ifndef	_LIBZFS_CORE_H
@@ -58,6 +58,7 @@ int lzc_send_space(const char *snapname, const char *fromsnap,
 
 boolean_t lzc_exists(const char *dataset);
 
+int lzc_rollback(const char *fsname, char *snapnamebuf, int snapnamelen);
 
 #ifdef	__cplusplus
 }

include/sys/dsl_dataset.h

@@ -265,7 +265,7 @@ int dsl_dataset_snap_lookup(dsl_dataset_t *ds, const char *name,
 int dsl_dataset_snap_remove(dsl_dataset_t *ds, const char *name, dmu_tx_t *tx);
 void dsl_dataset_set_refreservation_sync_impl(dsl_dataset_t *ds,
     zprop_source_t source, uint64_t value, dmu_tx_t *tx);
-int dsl_dataset_rollback(const char *fsname, void *owner);
+int dsl_dataset_rollback(const char *fsname, void *owner, nvlist_t *result);
 
 #ifdef ZFS_DEBUG
 #define	dprintf_ds(ds, fmt, ...) do { \

lib/libzfs/libzfs_dataset.c

@@ -3732,7 +3732,6 @@ zfs_rollback(zfs_handle_t *zhp, zfs_handle_t *snap, boolean_t force)
 {
 	rollback_data_t cb = { 0 };
 	int err;
-	zfs_cmd_t zc = {"\0"};
 	boolean_t restore_resv = 0;
 	uint64_t old_volsize = 0, new_volsize;
 	zfs_prop_t resv_prop = { 0 };
@@ -3766,22 +3765,15 @@ zfs_rollback(zfs_handle_t *zhp, zfs_handle_t *snap, boolean_t force)
 		    (old_volsize == zfs_prop_get_int(zhp, resv_prop));
 	}
 
-	(void) strlcpy(zc.zc_name, zhp->zfs_name, sizeof (zc.zc_name));
-
-	if (ZFS_IS_VOLUME(zhp))
-		zc.zc_objset_type = DMU_OST_ZVOL;
-	else
-		zc.zc_objset_type = DMU_OST_ZFS;
-
 	/*
 	 * We rely on zfs_iter_children() to verify that there are no
 	 * newer snapshots for the given dataset.  Therefore, we can
 	 * simply pass the name on to the ioctl() call.  There is still
 	 * an unlikely race condition where the user has taken a
 	 * snapshot since we verified that this was the most recent.
-	 *
 	 */
-	if ((err = zfs_ioctl(zhp->zfs_hdl, ZFS_IOC_ROLLBACK, &zc)) != 0) {
+	err = lzc_rollback(zhp->zfs_name, NULL, 0);
+	if (err != 0) {
 		(void) zfs_standard_error_fmt(zhp->zfs_hdl, errno,
 		    dgettext(TEXT_DOMAIN, "cannot rollback '%s'"),
 		    zhp->zfs_name);

lib/libzfs_core/libzfs_core.c

@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  */
 
@@ -581,3 +581,27 @@ lzc_receive(const char *snapname, nvlist_t *props, const char *origin,
 	free((void*)(uintptr_t)zc.zc_nvlist_dst);
 	return (error);
 }
+
+/*
+ * Roll back this filesystem or volume to its most recent snapshot.
+ * If snapnamebuf is not NULL, it will be filled in with the name
+ * of the most recent snapshot.
+ *
+ * Return 0 on success or an errno on failure.
+ */
+int
+lzc_rollback(const char *fsname, char *snapnamebuf, int snapnamelen)
+{
+	nvlist_t *args;
+	nvlist_t *result;
+	int err;
+
+	args = fnvlist_alloc();
+	err = lzc_ioctl(ZFS_IOC_ROLLBACK, fsname, args, &result);
+	nvlist_free(args);
+	if (err == 0 && snapnamebuf != NULL) {
+		const char *snapname = fnvlist_lookup_string(result, "target");
+		(void) strlcpy(snapnamebuf, snapname, snapnamelen);
+	}
+	return (err);
+}

module/zfs/dsl_dataset.c

@@ -1703,6 +1703,7 @@ dsl_dataset_handoff_check(dsl_dataset_t *ds, void *owner, dmu_tx_t *tx)
 typedef struct dsl_dataset_rollback_arg {
 	const char *ddra_fsname;
 	void *ddra_owner;
+	nvlist_t *ddra_result;
 } dsl_dataset_rollback_arg_t;
 
 static int
@@ -1774,9 +1775,13 @@ dsl_dataset_rollback_sync(void *arg, dmu_tx_t *tx)
 	dsl_pool_t *dp = dmu_tx_pool(tx);
 	dsl_dataset_t *ds, *clone;
 	uint64_t cloneobj;
+	char namebuf[ZFS_MAXNAMELEN];
 
 	VERIFY0(dsl_dataset_hold(dp, ddra->ddra_fsname, FTAG, &ds));
 
+	dsl_dataset_name(ds->ds_prev, namebuf);
+	fnvlist_add_string(ddra->ddra_result, "target", namebuf);
+
 	cloneobj = dsl_dataset_create_sync(ds->ds_dir, "%rollback",
 	    ds->ds_prev, DS_CREATE_FLAG_NODIRTY, kcred, tx);
 
@@ -1792,8 +1797,11 @@ dsl_dataset_rollback_sync(void *arg, dmu_tx_t *tx)
 }
 
 /*
- * If owner != NULL:
+ * Rolls back the given filesystem or volume to the most recent snapshot.
+ * The name of the most recent snapshot will be returned under key "target"
+ * in the result nvlist.
  *
+ * If owner != NULL:
  * - The existing dataset MUST be owned by the specified owner at entry
  * - Upon return, dataset will still be held by the same owner, whether we
  *   succeed or not.
@@ -1802,15 +1810,16 @@ dsl_dataset_rollback_sync(void *arg, dmu_tx_t *tx)
  * notes above zfs_suspend_fs() for further details.
  */
 int
-dsl_dataset_rollback(const char *fsname, void *owner)
+dsl_dataset_rollback(const char *fsname, void *owner, nvlist_t *result)
 {
 	dsl_dataset_rollback_arg_t ddra;
 
 	ddra.ddra_fsname = fsname;
 	ddra.ddra_owner = owner;
+	ddra.ddra_result = result;
 
 	return (dsl_sync_task(fsname, dsl_dataset_rollback_check,
-	    dsl_dataset_rollback_sync, (void *)&ddra, 1));
+	    dsl_dataset_rollback_sync, &ddra, 1));
 }
 
 struct promotenode {

module/zfs/zfs_ioctl.c

@@ -3488,29 +3488,32 @@ zfs_ioc_destroy(zfs_cmd_t *zc)
 }
 
 /*
- * inputs:
- * zc_name	name of dataset to rollback (to most recent snapshot)
+ * fsname is name of dataset to rollback (to most recent snapshot)
  *
- * outputs:	none
+ * innvl is not used.
+ *
+ * outnvl: "target" -> name of most recent snapshot
+ * }
  */
+/* ARGSUSED */
 static int
-zfs_ioc_rollback(zfs_cmd_t *zc)
+zfs_ioc_rollback(const char *fsname, nvlist_t *args, nvlist_t *outnvl)
 {
 	zfs_sb_t *zsb;
 	int error;
 
-	if (get_zfs_sb(zc->zc_name, &zsb) == 0) {
+	if (get_zfs_sb(fsname, &zsb) == 0) {
 		error = zfs_suspend_fs(zsb);
 		if (error == 0) {
 			int resume_err;
 
-			error = dsl_dataset_rollback(zc->zc_name, zsb);
-			resume_err = zfs_resume_fs(zsb, zc->zc_name);
+			error = dsl_dataset_rollback(fsname, zsb, outnvl);
+			resume_err = zfs_resume_fs(zsb, fsname);
 			error = error ? error : resume_err;
 		}
 		deactivate_super(zsb->z_sb);
 	} else {
-		error = dsl_dataset_rollback(zc->zc_name, NULL);
+		error = dsl_dataset_rollback(fsname, NULL, outnvl);
 	}
 	return (error);
 }
@@ -5273,6 +5276,10 @@ zfs_ioctl_init(void)
 	    zfs_ioc_get_holds, zfs_secpolicy_read, DATASET_NAME,
 	    POOL_CHECK_SUSPENDED, B_FALSE, B_FALSE);
 
+	zfs_ioctl_register("rollback", ZFS_IOC_ROLLBACK,
+	    zfs_ioc_rollback, zfs_secpolicy_rollback, DATASET_NAME,
+	    POOL_CHECK_SUSPENDED | POOL_CHECK_READONLY, B_FALSE, B_TRUE);
+
 	/* IOCTLS that use the legacy function signature */
 
 	zfs_ioctl_register_legacy(ZFS_IOC_POOL_FREEZE, zfs_ioc_pool_freeze,
@@ -5384,8 +5391,6 @@ zfs_ioctl_init(void)
 	    zfs_secpolicy_none);
 	zfs_ioctl_register_dataset_modify(ZFS_IOC_DESTROY, zfs_ioc_destroy,
 	    zfs_secpolicy_destroy);
-	zfs_ioctl_register_dataset_modify(ZFS_IOC_ROLLBACK, zfs_ioc_rollback,
-	    zfs_secpolicy_rollback);
 	zfs_ioctl_register_dataset_modify(ZFS_IOC_RENAME, zfs_ioc_rename,
 	    zfs_secpolicy_rename);
 	zfs_ioctl_register_dataset_modify(ZFS_IOC_RECV, zfs_ioc_recv,