Re: block request execution failing on RHEL6.0 (2.6.32-71.el6.x86_64)

April 26, 2011

      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.