4929 want prevsnap property

Reviewed by: Adam Leventhal <adam.leventhal@delphix.com>
Reviewed by: Matt Amdur <matt.amdur@delphix.com>
Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com>
Reviewed by: Boris Protopopov <bprotopopov@hotmail.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Dan McDonald <danmcd@omniti.com>

illumos/illumos-gate@b461c7460e

common/zfs/zfs_prop.c

@@ -423,6 +423,8 @@ zfs_prop_init(void)
 	    PROP_READONLY, ZFS_TYPE_DATASET, "OBJSETID");
 	zprop_register_hidden(ZFS_PROP_INCONSISTENT, "inconsistent",
 	    PROP_TYPE_NUMBER, PROP_READONLY, ZFS_TYPE_DATASET, "INCONSISTENT");
+	zprop_register_hidden(ZFS_PROP_PREV_SNAP, "prevsnap", PROP_TYPE_STRING,
+	    PROP_READONLY, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "PREVSNAP");
 
 	/* oddball properties */
 	zprop_register_impl(ZFS_PROP_CREATION, "creation", PROP_TYPE_NUMBER, 0,

uts/common/fs/zfs/dsl_dataset.c

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2014 by Delphix. All rights reserved.
  * Copyright (c) 2014, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014 RackTop Systems.
  */
@@ -1543,6 +1543,12 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
 		    ds->ds_phys->ds_unique_bytes);
 		get_clones_stat(ds, nv);
 	} else {
+		if (ds->ds_prev != NULL && ds->ds_prev != dp->dp_origin_snap) {
+			char buf[MAXNAMELEN];
+			dsl_dataset_name(ds->ds_prev, buf);
+			dsl_prop_nvlist_add_string(nv, ZFS_PROP_PREV_SNAP, buf);
+		}
+
 		dsl_dir_stats(ds->ds_dir, nv);
 	}
 

uts/common/sys/fs/zfs.h

@@ -147,6 +147,7 @@ typedef enum {
 	ZFS_PROP_FILESYSTEM_COUNT,
 	ZFS_PROP_SNAPSHOT_COUNT,
 	ZFS_PROP_REDUNDANT_METADATA,
+	ZFS_PROP_PREV_SNAP,
 	ZFS_NUM_PROPS
 } zfs_prop_t;