.The librbd compare-and-write operation is improved and new `rbd_aio_compare_and_writev` API method is introduced * *The semantics of compare-and-write C++ API now match those of C API.* + Previously, the compare-and-write C++ API, that is `Image::compare_and_write` and `Image::aio_compare_and_write` methods, would compare up to the size of the compare buffer. This would cause breakage after straddling a stripe unit boundary. + With this release, the compare-and-write C++ API matches the semantics of C API and both compare and write steps operate only on `len` bytes even if the respective buffers are larger. * *The compare-and-write operation is no longer limited to 512-byte sectors.* + With this release, the compare-and-write can operate on stripe units, if the access is aligned properly. The stripe units are 4 MB by default. * *New `rbd_aio_compare_and_writev` API method is now available.* + With this release, the `rbd_aio_compare_and_writev` API method is included to support scatter/gather on both compare and write buffers, which complements existing `rbd_aio_readv` and `rbd_aio_writev` methods.