dm thin: update .io_hints methods to not require handling discards last

Removes assumptions about what might follow the discard setup code
(previously the code would return early if discards not enabled).

Makes it possible to add more capabilites to the end of each .io_hints
method (which is the natural thing to do when adding new features).
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

drivers/md/dm-thin.c

@@ -4098,21 +4098,20 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
 	 * They get transferred to the live pool in bind_control_target()
 	 * called from pool_preresume().
 	 */
-	if (!pt->adjusted_pf.discard_enabled) {
+
+	if (pt->adjusted_pf.discard_enabled) {
+		disable_passdown_if_not_supported(pt);
+		/*
+		 * The pool uses the same discard limits as the underlying data
+		 * device.  DM core has already set this up.
+		 */
+	} else {
 		/*
 		 * Must explicitly disallow stacking discard limits otherwise the
 		 * block layer will stack them if pool's data device has support.
 		 */
 		limits->discard_granularity = 0;
-		return;
 	}
-
-	disable_passdown_if_not_supported(pt);
-
-	/*
-	 * The pool uses the same discard limits as the underlying data
-	 * device.  DM core has already set this up.
-	 */
 }
 
 static struct target_type pool_target = {
@@ -4496,11 +4495,10 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
 	struct thin_c *tc = ti->private;
 	struct pool *pool = tc->pool;
 
-	if (!pool->pf.discard_enabled)
-		return;
-
-	limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
-	limits->max_discard_sectors = pool->sectors_per_block * BIO_PRISON_MAX_RANGE;
+	if (pool->pf.discard_enabled) {
+		limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
+		limits->max_discard_sectors = pool->sectors_per_block * BIO_PRISON_MAX_RANGE;
+	}
 }
 
 static struct target_type thin_target = {