PendingReleaseNotes: add rbd_diff_iterate2 note

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 40e8813e9c705838eee42c98de717b20851aed72)

Conflicts:
	PendingReleaseNotes [ moved to >=17.2.8 section ]

diff --git a/PendingReleaseNotes b/PendingReleaseNotes
index 1dce4f83b03be87fcaac02a4c3c7989acc16f7b1..67001f2c66cec49d603f5813c8addad8ef7f0a24 100644 (file)
--- a/PendingReleaseNotes
+++ b/PendingReleaseNotes
@@ -4,6 +4,11 @@
 * RADOS: `get_pool_is_selfmanaged_snaps_mode` C++ API has been deprecated
   due to being prone to false negative results.  It's safer replacement is
   `pool_is_in_selfmanaged_snaps_mode`.
+* RBD: When diffing against the beginning of time (`fromsnapname == NULL`) in
+  fast-diff mode (`whole_object == true` with `fast-diff` image feature enabled
+  and valid), diff-iterate is now guaranteed to execute locally if exclusive
+  lock is available.  This brings a dramatic performance improvement for QEMU
+  live disk synchronization and backup use cases.
 
 >=17.2.7
 --------