raidz_test: Set io_offset reasonably

 - io_offset of 1 makes no sense.  Set default to 0.
 - Initialize io_offset in all cases.

Signed-off-by: Alexander Motin <alexander.motin@TrueNAS.com>

Author: amotin

cmd/raidz_test/raidz_test.c

@@ -374,7 +374,7 @@ init_raidz_map(raidz_test_opts_t *opts, zio_t **zio, const int parity)
 
 	*zio = umem_zalloc(sizeof (zio_t), UMEM_NOFAIL);
 
-	(*zio)->io_offset = 0;
+	(*zio)->io_offset = opts->rto_offset;
 	(*zio)->io_size = alloc_dsize;
 	(*zio)->io_abd = raidz_alloc(alloc_dsize);
 	init_zio_abd(*zio);

cmd/raidz_test/raidz_test.h

@@ -72,7 +72,7 @@ typedef struct raidz_test_opts {
 
 static const raidz_test_opts_t rto_opts_defaults = {
 	.rto_ashift = 9,
-	.rto_offset = 1ULL << 0,
+	.rto_offset = 0,
 	.rto_dcols = 8,
 	.rto_dsize = 1<<19,
 	.rto_v = D_ALL,