[dm-devel] multipath_busy() stalls IO due to scsi_host_is_busy()

[James Bottomley]

On Wed, 2012-05-16 at 14:28 +0200, Bernd Schubert wrote:
> shost->can_queue -> 62 here
> shost->host_busy -> 62 when one of the multipath groups does IO, further 
> multipath groups then seem to get stalled.
> 
> I'm not sure yet why multipath_busy() does not stall IO when there is a 
> passive path in the prio group.
> 
> Any idea how to properly address this problem?

shost->can_queue is supposed to represent the maximum number of possible
outstanding commands per HBA (i.e. the HBA hardware limit).  Assuming
the driver got it right, the only way of increasing this is to buy a
better HBA.

James