Mike Anderson [andmike@xxxxxxxxxxxxxxxxxx] wrote: > Shi, Harris <Harris.Shi@xxxxxxx> wrote: > > Due to the current timeout management change, our RDAC (failover) driver > > had some difficulties in handling SCSI I/O timeout. The RDAC driver is in > > the similar layer as HBA driver in that it will register into scsi > > mid-layer as scsi_host_template and stays below mid-layer. However, all > > scsi I/Os coming to RDAC stack are routed by a path then dispatched to the > > real HBA driver via mid-layer. We used to rely on the timer in > > scsi_cmnd->eh_timeout to deal with scsi i/o coming into the RDAC stack. > > Basically when I/O is coming to RDAC stack, we need to delete the timer > > for each I/O. Then after selecting a specific path for this I/O, we need > > to send the I/O back to mid-layer with a larger timeout value just to > > avoid the forced failover. When I/O completes successfully, we added the > > original timer back to the I/O and pass it over to upper block layer for > > further process. > > > > > > > > However, with the current timeout management functions moving to block > > layer, it became difficult for us to explicitly control the timeout value > > for specific I/O. > > > > Can you shed some lights on how to handle the I/O based timeout in this > > case? > > > > Since long term mpp capabilities should be handled by dm-mp and the SCSI > RDAC handler exporting functions to allow direct adding and deleting of the > timer may not be something that would be needed long term. It may not be > really clean to add these interfaces in. > > Could similar prior functionality be created by the following? > 1.) To the RDAC vhba add a hostt->eh_timed_out function. In this > timeout function return BLK_EH_RESET_TIMER until it is done with > the command. Since the vhba does not have a transport > scsi_times_out should call this function on every timeout. There is > some overhead here depending on the default timeout value set in > timing out and then resetting the timer. I believe, GDTG driver does this sort of thing for a different purpose. > 2.) For each sdev that is taken over store the previous > rq_timed_out_fn and then use blk_queue_rq_timed_out to set a mpp > specific function for the requests sent to the real HBA drivers. > > 3.) Set the timeout in the real HBA driver requests prior to > sending it to the mid layer. Should work, I guess... -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
