[Lustre-discuss] blk_rq_check_limits errors

[Frank Heckes]

Hi Bernd,

On Thu, 2010-09-02 at 23:41 +0200, Bernd Schubert wrote:
> On Thursday, September 02, 2010, Frank Heckes wrote:
> > Hi all,
> >
> > for some of our OSSes a massive amount of errors like:
> >
> > Sep  2 20:28:15 jf61o02 kernel: blk_rq_check_limits: over max size
> > limit.
> >
> > appearing in /var/log/messages (and dmesg). Does anyone have got a clue
> > how-to get of the root cause? Many thanks in advance.
>
> linux/block/blk-core.c
>
> int blk_rq_check_limits(struct request_queue *q, struct request *rq)
> {
>         if (rq->cmd_flags & REQ_DISCARD)
>                 return 0;
>
>         if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
>             blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
>                 printk(KERN_ERR "%s: over max size limit.\n", __func__);
>                 return -EIO;
>         }
>
>
> I haven't seen that before, but if I should guess, I would guess that dm-* has
> a larger queue than your underlying block device. If that is with your DDN
> storage, can you verify if all those devices are have max_sec_kb tuned to
> maximum?
>
Yes, we're using multipath to access the 'disks' (luns). Indeed the
setting for 'max_sec_kb' was different for the multipath device and disk
devices file, due to an obsolete udev-rule. We changed the values
consistently and the error messages stopped almost immediately. Many
thanks for the help.

> Also, does that come up with 1.8.4 only? (I have SG_ALL in my mind which was
> increased from 255 to 256, which might not be supported by all scsi host
> adapters).
>
We use version 1.8.1.1 still, but good to know about this.

>
> Cheers,
> Bernd
>
Cheers

-Frank


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