From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pete Zaitcev <zaitcev@redhat.com>
Subject: Bug in RAID1 in 2.4
Date: Sat, 20 Dec 2003 03:25:47 -0500
Sender: linux-raid-owner@vger.kernel.org
Message-ID: <20031220082547.GB18118@devserv.devel.redhat.com>
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To: neilb@cse.unsw.edu.au
Cc: linux-raid@vger.kernel.org, Ingo Molnar <mingo@redhat.com>, Pete Zaitcev <zaitcev@redhat.com>
List-Id: linux-raid.ids

In drivers/md/raid1.c, raid1_sync_request contains the following:
  
        block_nr = sector_nr;
        bsize = 512;
        while (!(block_nr & 1) && bsize < PAGE_SIZE
                        && (block_nr+2)*(bsize>>9) < (mddev->sb->size *2)) {
                block_nr >>= 1;
                bsize <<= 1;
        }

Suppose that a mirror is 4K in size. The code above produces
reads (and writes) of the following offsets and sizes:
 0K[2K], 2K[1K], 3K[0.5K], 3.5K[0.5K]

The above is correct, but it makes the RAID1 completely unuseable
on s390, because I/O with sizes less than 4K is not supported.
I would like the attached patch applied to correct the issue.

-- Pete

--- linux-2.4.23/drivers/md/raid1.c	2003-06-13 07:51:34.000000000 -0700
+++ linux-2.4.23-nip/drivers/md/raid1.c	2003-12-19 23:57:57.000000000 -0800
@@ -1436,7 +1436,7 @@
 	block_nr = sector_nr;
 	bsize = 512;
 	while (!(block_nr & 1) && bsize < PAGE_SIZE
-			&& (block_nr+2)*(bsize>>9) < (mddev->sb->size *2)) {
+			&& (block_nr+2)*(bsize>>9) <= (mddev->sb->size *2)) {
 		block_nr >>= 1;
 		bsize <<= 1;
 	}