dm: add support for REQ_NOWAIT to various targets

commit 021a24460dc2 ("block: add QUEUE_FLAG_NOWAIT") added a new queue
flag QUEUE_FLAG_NOWAIT to advertise if the bdev supports handling of
REQ_NOWAIT or not. DM core supports stacking QUEUE_FLAG_NOWAIT since
commit 6abc49468eea ("dm: add support for REQ_NOWAIT and enable it for
linear target"), in which only dm-linear enabled it.

Update others DM targets, which just do simple remapping, to enable
support for REQ_NOWAIT.

Signed-off-by: Jeffle Xu <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-stripe.c

···
 static struct target_type stripe_target = {
 	.name   = "striped",
 	.version = {1, 6, 0},
-	.features = DM_TARGET_PASSES_INTEGRITY,
+	.features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_NOWAIT,
 	.module = THIS_MODULE,
 	.ctr    = stripe_ctr,
 	.dtr    = stripe_dtr,

drivers/md/dm-switch.c

···
 static struct target_type switch_target = {
 	.name = "switch",
 	.version = {1, 1, 0},
+	.features = DM_TARGET_NOWAIT,
 	.module = THIS_MODULE,
 	.ctr = switch_ctr,
 	.dtr = switch_dtr,

drivers/md/dm-unstripe.c

···
 static struct target_type unstripe_target = {
 	.name = "unstriped",
 	.version = {1, 1, 0},
+	.features = DM_TARGET_NOWAIT,
 	.module = THIS_MODULE,
 	.ctr = unstripe_ctr,
 	.dtr = unstripe_dtr,

drivers/md/dm-zero.c

···
 static struct target_type zero_target = {
 	.name   = "zero",
 	.version = {1, 1, 0},
+	.features = DM_TARGET_NOWAIT,
 	.module = THIS_MODULE,
 	.ctr    = zero_ctr,
 	.map    = zero_map,