From: "H. Peter Anvin" <hpa@zytor.com>
This patch merges the latest change (make sure the readahead size is
always a multiple of the stripe size) from raid5.c into raid6main.c.
---
drivers/md/raid6main.c | 12 +++++++++++-
1 files changed, 11 insertions(+), 1 deletion(-)
diff -puN drivers/md/raid6main.c~raid6-readahead-fix drivers/md/raid6main.c
--- 25/drivers/md/raid6main.c~raid6-readahead-fix 2004-01-09 18:31:39.000000000 -0800
+++ 25-akpm/drivers/md/raid6main.c 2004-01-09 18:31:39.000000000 -0800
@@ -5,7 +5,7 @@
* Copyright (C) 2002, 2003 H. Peter Anvin
*
* RAID-6 management functions. This code is derived from raid5.c.
- * Last merge from raid5.c bkcvs version 1.78.
+ * Last merge from raid5.c bkcvs version 1.79 (kernel 2.6.1).
*
* Thanks to Penguin Computing for making the RAID-6 development possible
* by donating a test server!
@@ -1756,6 +1756,16 @@ static int run (mddev_t *mddev)
print_raid6_conf(conf);
+ /* read-ahead size must cover a whole stripe, which is
+ * (n-2) * chunksize where 'n' is the number of raid devices
+ */
+ {
+ int stripe = (mddev->raid_disks-2) * mddev->chunk_size
+ / PAGE_CACHE_SIZE;
+ if (mddev->queue->backing_dev_info.ra_pages < stripe)
+ mddev->queue->backing_dev_info.ra_pages = stripe;
+ }
+
/* Ok, everything is just fine now */
mddev->array_size = mddev->size * (mddev->raid_disks - 2);
return 0;
_