From mboxrd@z Thu Jan  1 00:00:00 1970
From: ajit4mail@gmail.com (ajit jain)
Date: Tue, 26 Apr 2011 22:42:06 +0530
Subject: block request execution failing on RHEL6.0 (2.6.32-71.el6.x86_64)
In-Reply-To: <BANLkTimpWXJtcH03Dc3uyddAQLeDkT6cfw@mail.gmail.com>
References: <BANLkTimpWXJtcH03Dc3uyddAQLeDkT6cfw@mail.gmail.com>
Message-ID: <BANLkTi=LLZnKod1M3DubXjqVCroOjmf3gw@mail.gmail.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Hi All,

I have found the issue.

in kernel prior to RHEL 6.0 blk_pc_request(rq) is define as:
#define blk_pc_request(rq)      ((rq)->flags & REQ_BLOCK_PC)
while in RHEL 6.0 it is define as:
#define blk_pc_request(rq)      ((rq)->cmd_type == REQ_TYPE_BLOCK_PC)

So, the issue was adding I was REQ_NOMERGE flag in cmd_type field of the
request. This was making blk_pc_request(rq) to return false and thats why
IOs were not going to scsi layer.

thanks,
ajit

On Wed, Apr 20, 2011 at 6:06 PM, ajit jain <ajit4mail@gmail.com> wrote:

> Hi All,
>
> I have written a func to send a CDB on a scsi device from the kernel. For
> that I am getting a request and queueing for execution.
> But blk_execute_rq() func is setting errors field of request to 65536 and
> sense length is set but all the fields in sense header is
> 0.
>
> I dont know what I am missing, any suggestion would be great help.
>
>
> snippet of the code
> ===========================
>     rq = blk_get_request(q, rw, __GFP_WAIT);
>     if(!rq){
>          goto out;
>     }
>     if (buflen &&  blk_rq_map_kern(q, rq, buf, buflen, __GFP_WAIT)){
>          goto out;
>     }
>     rq->cmd_len = cmdlen;
>     memcpy(rq->cmd, cmd, cmdlen);
>     memset(sense, 0, sizeof(sense));
>     rq->sense_len = 0;
>     rq->sense = sense;
>     rq->cmd_type |= REQ_TYPE_BLOCK_PC;
>     rq->cmd_type |= REQ_NOMERGE;
>     rq->timeout = WRITE_SCSI_TIMEOUT;              //WRITE_SCSI_TIMEOUT is
> set to 60 sec
>     blk_execute_rq(q, bd_disk, rq, 0);
>     error = rq->errors;
>     if( error ){
>         dbg("error in blk_execute_rq error %d",error);
>     }
>     if(rq->sense_len){
>             process_sense_info(rq->sense);
>     } else {
>             info("no sense available");
>      }
> ==========================================
>
>
> thanks,
> ajit
>
> PS:We can not use sg_ioctl interface because code expects user space
> application only to invoke sg_ioctl that the reason it does a copyin.
>
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