rbd: Use rbd_create3 to create RBD format 2 images by default

This new RBD format supports snapshotting and cloning. By having
libvirt create images in format 2 end-users of the created images
can benefit from the new RBD format.

Older versions of libvirt can work with this new RBD format as long
as librbd supports format 2. RBD format is supported by librbd since
version 0.56 (Ceph Bobtail).
Signed-off-by: NWido den Hollander <wido@widodh.nl>

src/storage/storage_backend_rbd.c

@@ -458,6 +458,25 @@ virStorageBackendRBDCreateVol(virConnectPtr conn ATTRIBUTE_UNUSED,
     return 0;
 }
 
+static int virStorageBackendRBDCreateImage(rados_ioctx_t io,
+                                           char *name, long capacity)
+{
+    int order = 0;
+#if LIBRBD_VERSION_CODE > 260
+    uint64_t features = 3;
+    uint64_t stripe_count = 1;
+    uint64_t stripe_unit = 4194304;
+
+    if (rbd_create3(io, name, capacity, features, &order,
+                    stripe_count, stripe_unit) < 0) {
+#else
+    if (rbd_create(io, name, capacity, &order) < 0) {
+#endif
+        return -1;
+    }
+
+    return 0;
+}
 
 static int
 virStorageBackendRBDBuildVol(virConnectPtr conn,
@@ -468,7 +487,6 @@ virStorageBackendRBDBuildVol(virConnectPtr conn,
     virStorageBackendRBDState ptr;
     ptr.cluster = NULL;
     ptr.ioctx = NULL;
-    int order = 0;
     int ret = -1;
 
     VIR_DEBUG("Creating RBD image %s/%s with size %llu",
@@ -494,7 +512,7 @@ virStorageBackendRBDBuildVol(virConnectPtr conn,
         goto cleanup;
     }
 
-    if (rbd_create(ptr.ioctx, vol->name, vol->capacity, &order) < 0) {
+    if (virStorageBackendRBDCreateImage(ptr.ioctx, vol->name, vol->capacity) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        _("failed to create volume '%s/%s'"),
                        pool->def->source.name,