diff --git a/kernel/mars_if.c b/kernel/mars_if.c
index af7bd0d3..fdf34214 100644
--- a/kernel/mars_if.c
+++ b/kernel/mars_if.c
@@ -966,7 +966,7 @@ loff_t if_get_capacity(struct if_brick *brick)
 	 * e.g. when the size symlink indicates a logically smaller
 	 * device than physically.
 	 */
-	if (brick->dev_size <= 0) {
+	if (brick->real_size <= 0 || brick->max_size != brick->old_max_size) {
 		struct if_input *input = brick->inputs[0];
 		int status;
 
@@ -976,8 +976,14 @@ loff_t if_get_capacity(struct if_brick *brick)
 			return 0;
 		}
 		MARS_INF("determined default capacity: %lld bytes\n", brick->info.current_size);
-		brick->dev_size = brick->info.current_size;
+
+		brick->real_size = brick->info.current_size;
 	}
+	if (brick->max_size > 0 && brick->real_size > brick->max_size)
+		brick->dev_size = brick->max_size;
+	else
+		brick->dev_size = brick->real_size;
+	brick->old_max_size = brick->max_size;
 	return brick->dev_size;
 }
 
diff --git a/kernel/mars_if.h b/kernel/mars_if.h
index 11a5a3fb..11d39409 100644
--- a/kernel/mars_if.h
+++ b/kernel/mars_if.h
@@ -105,6 +105,8 @@ struct if_output {
 struct if_brick {
 	MARS_BRICK(if);
 	// parameters
+	loff_t real_size;
+	loff_t max_size;
 	loff_t dev_size;
 	int max_plugged;
 	int readahead;
@@ -119,6 +121,7 @@ struct if_brick {
 	// private
 	struct semaphore switch_sem;
 	struct say_channel *say_channel;
+	loff_t old_max_size;
 	struct mars_info info;
 };
 
diff --git a/kernel/sy_old/mars_main.c b/kernel/sy_old/mars_main.c
index f4120a69..f5bc2637 100644
--- a/kernel/sy_old/mars_main.c
+++ b/kernel/sy_old/mars_main.c
@@ -1078,19 +1078,8 @@ int _set_if_params(struct mars_brick *_brick, void *private)
 		MARS_ERR("bad brick type\n");
 		return -EINVAL;
 	}
-	if (!rot) {
-		MARS_ERR("too early\n");
-		return -EINVAL;
-	}
-	if (rot->dev_size <= 0) {
-		MARS_ERR("dev_size = %lld\n", rot->dev_size);
-		return -EINVAL;
-	}
-	if (if_brick->dev_size > 0 && rot->dev_size < if_brick->dev_size) {
-		MARS_ERR("new dev size = %lld < old dev_size = %lld\n", rot->dev_size, if_brick->dev_size);
-		return -EINVAL;
-	}
-	if_brick->dev_size = rot->dev_size;
+	if (likely(rot))
+		if_brick->max_size = rot->dev_size;
 	if_brick->max_plugged = IF_MAX_PLUGGED;
 	if_brick->readahead = IF_READAHEAD;
 	if_brick->skip_sync = IF_SKIP_SYNC;