Prune /*NOTREACHED*/

This includes a simplification of mkbusy and format correctness in zhack
and ztest

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #12201

tests/zfs-tests/cmd/mmapwrite/mmapwrite.c

@@ -66,19 +66,15 @@ normal_writer(void *filename)
 		err(1, "failed to open %s", file_path);
 	}
 
-	char *buf = malloc(1);
+	char buf;
 	while (1) {
-		write_num = write(fd, buf, 1);
+		write_num = write(fd, &buf, 1);
 		if (write_num == 0) {
 			err(1, "write failed!");
 			break;
 		}
 		lseek(fd, page_size, SEEK_CUR);
 	}
-
-	if (buf) {
-		free(buf);
-	}
 }
 
 static void *
@@ -140,7 +136,7 @@ main(int argc, char **argv)
 	int i = 0;
 
 	if (argc != 3) {
-		(void) printf("usage: %s <normal write file name>"
+		(void) printf("usage: %s <normal write file name> "
 		    "<map write file name>\n", argv[0]);
 		exit(1);
 	}
@@ -156,7 +152,6 @@ main(int argc, char **argv)
 		err(1, "pthread_create map_writer failed.");
 	}
 
-	/* NOTREACHED */
 	pthread_join(map_write_tid, NULL);
 	return (0);
 }