blkid: add new return code 8 for ambivalent low-level probing result

Signed-off-by: Karel Zak <kzak@redhat.com>

misc-utils/blkid.8

@@ -253,9 +253,15 @@ appear in
 are shown, if they are recognized.
 .SH "RETURN CODE"
 If the specified token was found, or if any tags were shown from (specified)
-devices, 0 is returned.  If the specified token was not found, or no
-(specified) devices could be identified, an exit code of 2 is returned.
+devices, 0 is returned.
+
+If the specified token was not found, or no (specified) devices could be
+identified an exit code of 2 is returned.
+
 For usage or other errors, an exit code of 4 is returned.
+
+If the ambivalent low-level probing result was detected an exit code of 8 is
+returned.
 .SH AUTHOR
 .B blkid
 was written by Andreas Dilger for libblkid and improved by Theodore Ts'o

misc-utils/blkid.c

@@ -565,7 +565,13 @@ done:
 				devname);
 	}
 	close(fd);
-	return !nvals ? 2 : 0;
+
+	if (rc == -2)
+		return 8;	/* ambivalent probing result */
+	if (!nvals)
+		return 2;	/* nothing detected */
+
+	return 0;		/* sucess */
 }
 
 /* converts comma separated list to BLKID_USAGE_* mask */