bcache-tools: check incompatible feature set

When bcache-tools is not updated with kernel driver (or on the versus),
we need to make sure the feature set conflict can be detected to avoid
unexpected data operation.

This patch checks whether there is unsupported {compatc, ro_compat,
incompat} features detected in detail_dev(). If there is, prints out
error message and return error to its caller.

Signed-off-by: Coly Li <colyli@suse.de>
diff --git a/lib.c b/lib.c
index 29172f5..a529ad3 100644
--- a/lib.c
+++ b/lib.c
@@ -442,6 +442,33 @@
 		goto Fail;
 	}
 
+	/* Check for incompat feature set */
+	if (sb.version >= BCACHE_SB_VERSION_BDEV_WITH_FEATURES ||
+	    sb.version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES) {
+		uint64_t features;
+
+		features = sb.feature_compat & ~BCH_FEATURE_COMPAT_SUPP;
+		if (features) {
+			fprintf(stderr,
+				"Unsupported compatible feature found\n");
+			goto Fail;
+		}
+
+		features = sb.feature_ro_compat & ~BCH_FEATURE_RO_COMPAT_SUPP;
+		if (features) {
+			fprintf(stderr,
+				"Unsupported read-only compatible feature found\n");
+			goto Fail;
+		}
+
+		features = sb.feature_incompat & ~BCH_FEATURE_INCOMPAT_SUPP;
+		if (features) {
+			fprintf(stderr,
+				"Unsupported incompatible feature found\n");
+			goto Fail;
+		}
+	}
+
 	*type = sb.version;
 	if (sb.version == BCACHE_SB_VERSION_BDEV ||
 	    sb.version == BCACHE_SB_VERSION_BDEV_WITH_OFFSET ||