rbd: advertise support for RBD_FEATURE_DEEP_FLATTEN

All copyups perform deep-copyup regardless of whether deep-flatten
feature is enabled.  The feature bit is used to ensure that image is
written to only by new-enough clients that always perform deep-copyup.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

drivers/block/rbd.c

@@ -115,12 +115,14 @@ static int atomic_dec_return_safe(atomic_t *v)
 #define RBD_FEATURE_LAYERING		(1ULL<<0)
 #define RBD_FEATURE_STRIPINGV2		(1ULL<<1)
 #define RBD_FEATURE_EXCLUSIVE_LOCK	(1ULL<<2)
+#define RBD_FEATURE_DEEP_FLATTEN	(1ULL<<5)
 #define RBD_FEATURE_DATA_POOL		(1ULL<<7)
 #define RBD_FEATURE_OPERATIONS		(1ULL<<8)
 
 #define RBD_FEATURES_ALL	(RBD_FEATURE_LAYERING |		\
 				 RBD_FEATURE_STRIPINGV2 |	\
 				 RBD_FEATURE_EXCLUSIVE_LOCK |	\
+				 RBD_FEATURE_DEEP_FLATTEN |	\
 				 RBD_FEATURE_DATA_POOL |	\
 				 RBD_FEATURE_OPERATIONS)