From: Melanie Plageman (Microsoft) <melanieplage...@gmail.com> Sent: Friday, March 5, 2021 3:22 PM > > The scsi_device->queue_depth is set to Scsi_Host->cmd_per_lun during > allocation. > > Cap cmd_per_lun at can_queue to avoid dispatch errors. > > Signed-off-by: Melanie Plageman (Microsoft) <melanieplage...@gmail.com> > --- > drivers/scsi/storvsc_drv.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c > index 6bc5453cea8a..d7953a6e00e6 100644 > --- a/drivers/scsi/storvsc_drv.c > +++ b/drivers/scsi/storvsc_drv.c > @@ -1946,6 +1946,8 @@ static int storvsc_probe(struct hv_device *device, > (max_sub_channels + 1) * > (100 - ring_avail_percent_lowater) / 100; > > + scsi_driver.cmd_per_lun = min_t(u32, scsi_driver.cmd_per_lun, > scsi_driver.can_queue); > +
I'm not sure what you mean by "avoid dispatch errors". Can you elaborate? Be aware that the calculation of "can_queue" in this driver is somewhat flawed -- it should not be based on the size of the ring buffer, but instead on the maximum number of requests Hyper-V will queue. And even then, can_queue doesn't provide the cap you might expect because the blk-mq layer allocates can_queue tags for each HW queue, not as a total. I agree that the cmd_per_lun setting is also too big, but we should fix that in the context of getting all of these different settings working together correctly, and not piecemeal. Michael > host = scsi_host_alloc(&scsi_driver, > sizeof(struct hv_host_device)); > if (!host) > -- > 2.20.1
