libceph: MOSDOpReply v7 encoding

Empty request_redirect_t (struct ceph_request_redirect in the kernel
client) is now encoded with a bool.  NEW_OSDOPREPLY_ENCODING feature
bit overlaps with already supported CRUSH_TUNABLES5.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>

include/linux/ceph/ceph_features.h

@@ -73,6 +73,8 @@
 #define CEPH_FEATURE_MON_STATEFUL_SUB (1ULL<<57) /* stateful mon subscription */
 #define CEPH_FEATURE_MON_ROUTE_OSDMAP (1ULL<<57) /* peon sends osdmaps */
 #define CEPH_FEATURE_CRUSH_TUNABLES5	(1ULL<<58) /* chooseleaf stable mode */
+// duplicated since it was introduced at the same time as CEPH_FEATURE_CRUSH_TUNABLES5
+#define CEPH_FEATURE_NEW_OSDOPREPLY_ENCODING   (1ULL<<58) /* New, v7 encoding */
 
 /*
  * The introduction of CEPH_FEATURE_OSD_SNAPMAPPER caused the feature
@@ -119,7 +121,8 @@ static inline u64 ceph_sanitize_features(u64 features)
 	 CEPH_FEATURE_OSD_PRIMARY_AFFINITY |	\
 	 CEPH_FEATURE_MSGR_KEEPALIVE2 |		\
 	 CEPH_FEATURE_CRUSH_V4 |		\
-	 CEPH_FEATURE_CRUSH_TUNABLES5)
+	 CEPH_FEATURE_CRUSH_TUNABLES5 |		\
+	 CEPH_FEATURE_NEW_OSDOPREPLY_ENCODING)
 
 #define CEPH_FEATURES_REQUIRED_DEFAULT   \
 	(CEPH_FEATURE_NOSRCADDR |	 \

net/ceph/osd_client.c

@@ -1770,6 +1770,7 @@ static void handle_reply(struct ceph_osd_client *osdc, struct ceph_msg *msg)
 	u32 osdmap_epoch;
 	int already_completed;
 	u32 bytes;
+	u8 decode_redir;
 	unsigned int i;
 
 	tid = le64_to_cpu(msg->hdr.tid);
@@ -1841,6 +1842,15 @@ static void handle_reply(struct ceph_osd_client *osdc, struct ceph_msg *msg)
 		p += 8 + 4; /* skip replay_version */
 		p += 8; /* skip user_version */
 
+		if (le16_to_cpu(msg->hdr.version) >= 7)
+			ceph_decode_8_safe(&p, end, decode_redir, bad_put);
+		else
+			decode_redir = 1;
+	} else {
+		decode_redir = 0;
+	}
+
+	if (decode_redir) {
 		err = ceph_redirect_decode(&p, end, &redir);
 		if (err)
 			goto bad_put;