raid5-large-io.patch

lustre 1.6.5 source code

This patch changes max request size to <chunk size> * <disks>
in order to allow Lustre to submit large I/Os and avoid
unnecessary reads.

Index: linux-2.6.9/drivers/md/raid5.c
===================================================================
--- linux-2.6.9.orig/drivers/md/raid5.c	2006-05-22 00:01:30.000000000 +0400
+++ linux-2.6.9/drivers/md/raid5.c	2006-05-22 00:09:56.000000000 +0400
@@ -1609,6 +1609,11 @@ static int run (mddev_t *mddev)
 	mddev->queue->unplug_fn = raid5_unplug_device;
 	mddev->queue->issue_flush_fn = raid5_issue_flush;
 
+	/* in order to support large I/Os */
+	blk_queue_max_sectors(mddev->queue, mddev->chunk_size * mddev->raid_disks >> 9);
+	mddev->queue->max_phys_segments = mddev->chunk_size * mddev->raid_disks >> PAGE_SHIFT;
+	mddev->queue->max_hw_segments = mddev->chunk_size * mddev->raid_disks >> PAGE_SHIFT;;
+
 	PRINTK("raid5: run(%s) called.\n", mdname(mddev));
 
 	ITERATE_RDEV(mddev,rdev,tmp) {