I2O subsystem has been broken in mainstream several months ago (after 2.6.18).
The following patch from Jens Axboe splits struct request ->flags into two
parts: cmd_type and cmd_flags
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=4aff5e2333c9a1609662f2091f55c3f6fffdad36

In i2o layer this patch has replaced flag REQ_SPECIAL by the according cmd_type.
However i2o has used REQ_SPECIAL not as command type but as driver-specific flag
for the debug purposes. As result all i2o requests have type "special" now, are
not processed to the hardware and fail with I/O error:

 i2o/hda:<3>Buffer I/O error on device i2o/hda, logical block 0
Buffer I/O error on device i2o/hda, logical block 0
Buffer I/O error on device i2o/hda, logical block 0
 unable to read partition table
block-osm: device added (TID: 207): i2o/hda

The following patch removes the extra debug checks without any drawbacks and
restores the normal driver's work.

Signed-off-by:  Vasily Averin <[EMAIL PROTECTED]>

--- 2.6.21-rc5/drivers/message/i2o/i2o_block.c  2007-02-04 21:44:54.000000000 
+0300
+++ 2.6.21-rc5/drivers/message/i2o/i2o_block.c  2007-03-26 11:03:52.000000000 
+0400
@@ -390,13 +390,6 @@ static int i2o_block_prep_req_fn(struct
                return BLKPREP_KILL;
        }

-       /* request is already processed by us, so return */
-       if (blk_special_request(req)) {
-               osm_debug("REQ_SPECIAL already set!\n");
-               req->cmd_flags |= REQ_DONTPREP;
-               return BLKPREP_OK;
-       }
-
        /* connect the i2o_block_request to the request */
        if (!req->special) {
                ireq = i2o_block_request_alloc();
@@ -408,11 +401,8 @@ static int i2o_block_prep_req_fn(struct
                ireq->i2o_blk_dev = i2o_blk_dev;
                req->special = ireq;
                ireq->req = req;
-       } else
-               ireq = req->special;
-
+       }
        /* do not come back here */
-       req->cmd_type = REQ_TYPE_SPECIAL;
        req->cmd_flags |= REQ_DONTPREP;

        return BLKPREP_OK;

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