librbd: describe the purpose of features constants

Signed-off-by: Josh Durgin <jdurgin@redhat.com>

diff --git a/src/include/rbd/features.h b/src/include/rbd/features.h
index b597bc089136bc158e24176b3698cbb9e67a03ea..ac7b55890f405c958bc248b4d2323e86d62cbdc5 100644 (file)
--- a/src/include/rbd/features.h
+++ b/src/include/rbd/features.h
@@ -8,9 +8,12 @@
 #define RBD_FEATURE_FAST_DIFF           (1<<4)
 #define RBD_FEATURE_DEEP_FLATTEN        (1<<5)
 
+/// features that make an image inaccessible for read or write by
+/// clients that don't understand them
 #define RBD_FEATURES_INCOMPATIBLE      (RBD_FEATURE_LAYERING |       \
                                         RBD_FEATURE_STRIPINGV2)
 
+/// features that make an image unwritable by clients that don't understand them
 #define RBD_FEATURES_RW_INCOMPATIBLE   (RBD_FEATURES_INCOMPATIBLE  | \
                                         RBD_FEATURE_EXCLUSIVE_LOCK | \
                                         RBD_FEATURE_OBJECT_MAP     | \
@@ -24,10 +27,13 @@
                                          RBD_FEATURE_FAST_DIFF      | \
                                          RBD_FEATURE_DEEP_FLATTEN)
 
+/// features that may be dynamically enabled or disabled
 #define RBD_FEATURES_MUTABLE            (RBD_FEATURE_EXCLUSIVE_LOCK | \
                                          RBD_FEATURE_OBJECT_MAP     | \
                                          RBD_FEATURE_FAST_DIFF)
 
+/// features that only work when used with a single client
+/// using the image for writes
 #define RBD_FEATURES_SINGLE_CLIENT (RBD_FEATURE_EXCLUSIVE_LOCK | \
                                     RBD_FEATURE_OBJECT_MAP     | \
                                     RBD_FEATURE_FAST_DIFF)