MFC r286683: 5765 add support for estimating send stream size with

lzc_send_space when source is a bookmark

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Reviewed by: Bayard Bell <buffer.g.overflow@gmail.com>
Approved by: Albert Lee <trisk@nexenta.com>
Author: Max Grossman <max.grossman@delphix.com>

illumos/illumos-gate@643da460c8ca583e39ce053081754e24087f84c8

1 files changed, 17 insertions, 5 deletions

diff --git a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
index 52bd580..5ba660d 100644
--- a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
+++ b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  */
 
@@ -532,18 +532,30 @@ lzc_send(const char *snapname, const char *from, int fd,
 }
 
 /*
- * If fromsnap is NULL, a full (non-incremental) stream will be estimated.
+ * "from" can be NULL, a snapshot, or a bookmark.
+ *
+ * If from is NULL, a full (non-incremental) stream will be estimated.  This
+ * is calculated very efficiently.
+ *
+ * If from is a snapshot, lzc_send_space uses the deadlists attached to
+ * each snapshot to efficiently estimate the stream size.
+ *
+ * If from is a bookmark, the indirect blocks in the destination snapshot
+ * are traversed, looking for blocks with a birth time since the creation TXG of
+ * the snapshot this bookmark was created from.  This will result in
+ * significantly more I/O and be less efficient than a send space estimation on
+ * an equivalent snapshot.
  */
 int
-lzc_send_space(const char *snapname, const char *fromsnap, uint64_t *spacep)
+lzc_send_space(const char *snapname, const char *from, uint64_t *spacep)
 {
 	nvlist_t *args;
 	nvlist_t *result;
 	int err;
 
 	args = fnvlist_alloc();
-	if (fromsnap != NULL)
-		fnvlist_add_string(args, "fromsnap", fromsnap);
+	if (from != NULL)
+		fnvlist_add_string(args, "from", from);
 	err = lzc_ioctl(ZFS_IOC_SEND_SPACE, snapname, args, &result);
 	nvlist_free(args);
 	if (err == 0)