MFV r329718: 8520 7198 lzc_rollback_to should support rolling back to origin

illumos/illumos-gate@95643f75d2
95643f75d2

https://www.illumos.org/issues/8520
  lzc_rollback_to() should support rolling back to a clone's origin.
  The current checks in zfs_ioc_rollback() would not allow that because the
  origin snapshot belongs to a different filesystem.
  The overly restrictive check was introduced in 7600, but it was not a
  regression as none of the existing tools provided a way to rollback to the
  origin.

https://www.illumos.org/issues/7198
  EINVAL is returned when a dataset does not have any snapshots, so there is
  nothing to roll back to.
  Although the code in zfs_do_rollback checks for that condition in advance, it's
  still possible that the snapshot(s) gets removed after the check and before the
  rollback sync task is executed.
  At the moment zfs command would crash when that happens.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Andriy Gapon <avg@FreeBSD.org>
MFC after:	2 weeks

cddl/contrib/opensolaris/lib/libzfs/common/libzfs_dataset.c

@@ -4054,17 +4054,31 @@ zfs_rollback(zfs_handle_t *zhp, zfs_handle_t *snap, boolean_t force)
 	 * a new snapshot is created before this request is processed.
 	 */
 	err = lzc_rollback_to(zhp->zfs_name, snap->zfs_name);
-	if (err == EXDEV) {
-		zfs_error_aux(zhp->zfs_hdl, dgettext(TEXT_DOMAIN,
-		    "'%s' is not the latest snapshot"), snap->zfs_name);
-		(void) zfs_error_fmt(zhp->zfs_hdl, EZFS_BUSY,
-		    dgettext(TEXT_DOMAIN, "cannot rollback '%s'"),
-		    zhp->zfs_name);
-		return (err);
-	} else if (err != 0) {
-		(void) zfs_standard_error_fmt(zhp->zfs_hdl, errno,
+	if (err != 0) {
+		char errbuf[1024];
+
+		(void) snprintf(errbuf, sizeof (errbuf),
 		    dgettext(TEXT_DOMAIN, "cannot rollback '%s'"),
 		    zhp->zfs_name);
+		switch (err) {
+		case EEXIST:
+			zfs_error_aux(zhp->zfs_hdl, dgettext(TEXT_DOMAIN,
+			    "there is a snapshot or bookmark more recent "
+			    "than '%s'"), snap->zfs_name);
+			(void) zfs_error(zhp->zfs_hdl, EZFS_EXISTS, errbuf);
+			break;
+		case ESRCH:
+			zfs_error_aux(zhp->zfs_hdl, dgettext(TEXT_DOMAIN,
+			    "'%s' is not found among snapshots of '%s'"),
+			    snap->zfs_name, zhp->zfs_name);
+			(void) zfs_error(zhp->zfs_hdl, EZFS_NOENT, errbuf);
+			break;
+		case EINVAL:
+			(void) zfs_error(zhp->zfs_hdl, EZFS_BADTYPE, errbuf);
+			break;
+		default:
+			(void) zfs_standard_error(zhp->zfs_hdl, err, errbuf);
+		}
 		return (err);
 	}
 

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c

@@ -2553,7 +2553,7 @@ dsl_dataset_rollback_check(void *arg, dmu_tx_t *tx)
 	/* must have a most recent snapshot */
 	if (dsl_dataset_phys(ds)->ds_prev_snap_txg < TXG_INITIAL) {
 		dsl_dataset_rele(ds, FTAG);
-		return (SET_ERROR(EINVAL));
+		return (SET_ERROR(ESRCH));
 	}
 
 	/*
@@ -2573,11 +2573,46 @@ dsl_dataset_rollback_check(void *arg, dmu_tx_t *tx)
 	 * the latest snapshot is it.
 	 */
 	if (ddra->ddra_tosnap != NULL) {
-		char namebuf[ZFS_MAX_DATASET_NAME_LEN];
+		dsl_dataset_t *snapds;
 
-		dsl_dataset_name(ds->ds_prev, namebuf);
-		if (strcmp(namebuf, ddra->ddra_tosnap) != 0)
-			return (SET_ERROR(EXDEV));
+		/* Check if the target snapshot exists at all. */
+		error = dsl_dataset_hold(dp, ddra->ddra_tosnap, FTAG, &snapds);
+		if (error != 0) {
+			/*
+			 * ESRCH is used to signal that the target snapshot does
+			 * not exist, while ENOENT is used to report that
+			 * the rolled back dataset does not exist.
+			 * ESRCH is also used to cover other cases where the
+			 * target snapshot is not related to the dataset being
+			 * rolled back such as being in a different pool.
+			 */
+			if (error == ENOENT || error == EXDEV)
+				error = SET_ERROR(ESRCH);
+			dsl_dataset_rele(ds, FTAG);
+			return (error);
+		}
+		ASSERT(snapds->ds_is_snapshot);
+
+		/* Check if the snapshot is the latest snapshot indeed. */
+		if (snapds != ds->ds_prev) {
+			/*
+			 * Distinguish between the case where the only problem
+			 * is intervening snapshots (EEXIST) vs the snapshot
+			 * not being a valid target for rollback (ESRCH).
+			 */
+			if (snapds->ds_dir == ds->ds_dir ||
+			    (dsl_dir_is_clone(ds->ds_dir) &&
+			    dsl_dir_phys(ds->ds_dir)->dd_origin_obj ==
+			    snapds->ds_object)) {
+				error = SET_ERROR(EEXIST);
+			} else {
+				error = SET_ERROR(ESRCH);
+			}
+			dsl_dataset_rele(snapds, FTAG);
+			dsl_dataset_rele(ds, FTAG);
+			return (error);
+		}
+		dsl_dataset_rele(snapds, FTAG);
 	}
 
 	/* must not have any bookmarks after the most recent snapshot */
@@ -2586,8 +2621,10 @@ dsl_dataset_rollback_check(void *arg, dmu_tx_t *tx)
 	nvlist_t *bookmarks = fnvlist_alloc();
 	error = dsl_get_bookmarks_impl(ds, proprequest, bookmarks);
 	fnvlist_free(proprequest);
-	if (error != 0)
+	if (error != 0) {
+		dsl_dataset_rele(ds, FTAG);
 		return (error);
+	}
 	for (nvpair_t *pair = nvlist_next_nvpair(bookmarks, NULL);
 	    pair != NULL; pair = nvlist_next_nvpair(bookmarks, pair)) {
 		nvlist_t *valuenv =

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c

@@ -3852,11 +3852,14 @@ zfs_ioc_rollback(const char *fsname, nvlist_t *innvl, nvlist_t *outnvl)
 
 	(void) nvlist_lookup_string(innvl, "target", &target);
 	if (target != NULL) {
-		int fslen = strlen(fsname);
+		const char *cp = strchr(target, '@');
 
-		if (strncmp(fsname, target, fslen) != 0)
-			return (SET_ERROR(EINVAL));
-		if (target[fslen] != '@')
+		/*
+		 * The snap name must contain an @, and the part after it must
+		 * contain only valid characters.
+		 */
+		if (cp == NULL ||
+		    zfs_component_namecheck(cp + 1, NULL, NULL) != 0)
 			return (SET_ERROR(EINVAL));
 	}