fix bug introduced in r297521, set canmount=on doesn't mount filesystem

There are two cases where changing canmount should result in an action:
- canmount is set to off for a mounted filesystem
- canmount is set to on for an unmounted filesystem
Before r297521 we could unmount and re-mount a filesystem when that was
not necessary, but after r297521 we only handled the first of the above
cases.

MFC after:	5 days

1 files changed, 8 insertions, 3 deletions

diff --git a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_dataset.c b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_dataset.c
index dbafaa99c276..5babb7b3196d 100644
--- a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_dataset.c
+++ b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_dataset.c
@@ -1630,12 +1630,17 @@ zfs_prop_set_list(zfs_handle_t *zhp, nvlist_t *props)
 		assert(cl_idx < nvl_len);
 		/*
 		 * We don't want to unmount & remount the dataset when changing
-		 * its canmount property to 'on' or 'noauto'.  We only use
-		 * the changelist logic to unmount when setting canmount=off.
+		 * its canmount property.  We only use the changelist logic to
+		 * unmount when setting canmount=off for a mounted filesystem
+		 * or when setting canmount=on for an unmounted filesystem.
+		 * For all other changes to canmount property the filesystem
+		 * remains the same.
 		 */
 		if (prop != ZFS_PROP_CANMOUNT ||
 		    (fnvpair_value_uint64(elem) == ZFS_CANMOUNT_OFF &&
-		     zfs_is_mounted(zhp, NULL))) {
+		     zfs_is_mounted(zhp, NULL)) ||
+		    (fnvpair_value_uint64(elem) == ZFS_CANMOUNT_ON &&
+		     !zfs_is_mounted(zhp, NULL))) {
 			cls[cl_idx] = changelist_gather(zhp, prop, 0, 0);
 			if (cls[cl_idx] == NULL)
 				goto error;