[PATCH] md: define backing_dev_info.congested_fn for raid0 and linear

Each backing_dev needs to be able to report whether it is congested, either by
modulating BDI_*_congested in ->state, or by defining a ->congested_fn.
md/raid did neither of these. This patch add a congested_fn which simply
checks all component devices to see if they are congested.

Signed-off-by: Neil Brown <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/md/linear.c

···
 	return ret;
 }
 
+static int linear_congested(void *data, int bits)
+{
+	mddev_t *mddev = data;
+	linear_conf_t *conf = mddev_to_conf(mddev);
+	int i, ret = 0;
+
+	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
+		request_queue_t *q = bdev_get_queue(conf->disks[i].rdev->bdev);
+		ret |= bdi_congested(&q->backing_dev_info, bits);
+	}
+	return ret;
+}
+
 static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
 {
 	linear_conf_t *conf;
···
 	blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 	mddev->queue->unplug_fn = linear_unplug;
 	mddev->queue->issue_flush_fn = linear_issue_flush;
+	mddev->queue->backing_dev_info.congested_fn = linear_congested;
+	mddev->queue->backing_dev_info.congested_data = mddev;
 	return 0;
 }
 

drivers/md/raid0.c

···
 	return ret;
 }
 
+static int raid0_congested(void *data, int bits)
+{
+	mddev_t *mddev = data;
+	raid0_conf_t *conf = mddev_to_conf(mddev);
+	mdk_rdev_t **devlist = conf->strip_zone[0].dev;
+	int i, ret = 0;
+
+	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
+		request_queue_t *q = bdev_get_queue(devlist[i]->bdev);
+
+		ret |= bdi_congested(&q->backing_dev_info, bits);
+	}
+	return ret;
+}
+
 
 static int create_strip_zones (mddev_t *mddev)
 {
···
 	mddev->queue->unplug_fn = raid0_unplug;
 
 	mddev->queue->issue_flush_fn = raid0_issue_flush;
+	mddev->queue->backing_dev_info.congested_fn = raid0_congested;
+	mddev->queue->backing_dev_info.congested_data = mddev;
 
 	printk("raid0: done.\n");
 	return 0;