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

Mulyadi Santosa mulyadi.santosa at
Tue Apr 26 13:22:55 EDT 2011

On Wed, Apr 27, 2011 at 00:12, ajit jain <ajit4mail at> wrote:
> 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.

Wow, great research! May I suggest something? I think you need to
inform this bug to RHEL kernel team.... quite likely it's a serious

Mulyadi Santosa
Freelance Linux trainer and consultant


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