zloop testing by randomly assign vdevs as rotational.

The random assignment is a dirty hack.  Reason for this is that it has
to be set before the device open finishes, or the rotor vector index
will be assigned on whatever initial nonrot value the device has.

cmd/ztest/ztest.c

@@ -1001,6 +1001,20 @@ make_vdev_root(char *path, char *aux, char *pool, size_t size, uint64_t ashift,
 	return (root);
 }
 
+boolean_t ztest_vdev_nonrot(void);
+
+boolean_t
+ztest_vdev_nonrot()
+{
+	boolean_t nonrot;
+
+	nonrot = ztest_random(2) == 1 ? B_TRUE : B_FALSE;
+
+	printf("NONROT: %d\n", nonrot);
+
+	return (nonrot);
+}
+
 /*
  * Find a random spa version. Returns back a random spa version in the
  * range [initial_version, SPA_VERSION_FEATURES].
@@ -6541,6 +6555,14 @@ ztest_init(ztest_shared_t *zs)
 		VERIFY3U(0, ==, nvlist_add_uint64(props, buf, 0));
 		free(buf);
 	}
+	{
+		char *buf;
+		VERIFY3S(-1, !=, asprintf(&buf, "ssd<=meta:%d,%d;mixed<=%d;hdd",
+		    32, 4, 64));
+		VERIFY3U(0, ==, nvlist_add_string(props,
+		    ZPOOL_CONFIG_ROTORVECTOR, buf));
+		free(buf);
+	}
 	VERIFY3U(0, ==, spa_create(ztest_opts.zo_pool, nvroot, props, NULL));
 	nvlist_free(nvroot);
 	nvlist_free(props);

module/zfs/metaslab.c

@@ -978,6 +978,10 @@ metaslab_group_set_rotor_category(metaslab_group_t *mg, boolean_t failed_dev)
 		mg->mg_nrot = METASLAB_CLASS_ROTORS-1;
 	else
 		mg->mg_nrot = metaslab_vdev_rotor_category(mc, mg->mg_vd);
+
+#ifndef _KERNEL
+	printf("SET mg->mg_nrot = %d\n", mg->mg_nrot);
+#endif
 }
 
 void

module/zfs/vdev_file.c

@@ -51,6 +51,16 @@ vdev_file_rele(vdev_t *vd)
 	ASSERT(vd->vdev_path != NULL);
 }
 
+#ifndef _KERNEL
+boolean_t ztest_vdev_nonrot(void);
+
+boolean_t
+__attribute__((weak)) ztest_vdev_nonrot()
+{
+	return (B_TRUE);
+}
+#endif
+
 static int
 vdev_file_open(vdev_t *vd, uint64_t *psize, uint64_t *max_psize,
     uint64_t *ashift)
@@ -60,9 +70,14 @@ vdev_file_open(vdev_t *vd, uint64_t *psize, uint64_t *max_psize,
 	vattr_t vattr;
 	int error;
 
+#ifdef _KERNEL
 	/* Rotational optimizations only make sense on block devices */
 	vd->vdev_nonrot = B_TRUE;
 	vd->vdev_nonrot_mix = B_FALSE;
+#else
+	vd->vdev_nonrot = ztest_vdev_nonrot();
+	vd->vdev_nonrot_mix = B_FALSE;
+#endif
 
 	/*
 	 * We must have a pathname, and it must be absolute.