PendingReleaseNotes: add rbd compare-and-write notes

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/PendingReleaseNotes b/PendingReleaseNotes
index 0f84597d62df140a07f8eca7ed26af9d9f895e0a..5b236aef086fcac8fe4d08cf3c9bf7a7b1ea507d 100644 (file)
--- a/PendingReleaseNotes
+++ b/PendingReleaseNotes
@@ -46,6 +46,15 @@
 * RGW: The beast frontend's HTTP access log line uses a new debug_rgw_access
   configurable. This has the same defaults as debug_rgw, but can now be controlled
   independently.
+* RBD: The semantics of compare-and-write C++ API (`Image::compare_and_write`
+  and `Image::aio_compare_and_write` methods) now match those of C API.  Both
+  compare and write steps operate only on `len` bytes even if the respective
+  buffers are larger. The previous behavior of comparing up to the size of
+  the compare buffer was prone to subtle breakage upon straddling a stripe
+  unit boundary.
+* RBD: compare-and-write operation is no longer limited to 512-byte sectors.
+  Assuming proper alignment, it now allows operating on stripe units (4M by
+  default).
 
 >=17.2.1