Re: [PATCH] scsi: core: Cap initial sdev queue depth at shost.can_queue

From: John Garry
Date: Tue Apr 20 2021 - 04:16:57 EST

On 20/04/2021 01:02, Ming Lei wrote:
On Tue, Apr 20, 2021 at 12:06:24AM +0800, John Garry wrote:
Function sdev_store_queue_depth() enforces that the sdev queue depth cannot
exceed shost.can_queue.

However, the LLDD may still set cmd_per_lun > can_queue, which leads to an
initial sdev queue depth greater than can_queue.

Stop this happened by capping initial sdev queue depth at can_queue.

Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
Topic originally discussed at:

Last idea there was to error/warn in scsi_add_host() for cmd_per_lun >

Hi Ming,

No, that isn't my suggestion.

Right, it was what I mentioned.

can_queue. However, such a shost driver could still configure the sdev
queue depth to be sound value at .slave_configure callback, so now thinking
the orig patch better.

As I mentioned last time, why can't we fix ->cmd_per_lun in
scsi_add_host() using .can_queue?

I would rather not change the values which are provided from the driver. I would rather take the original values and try to use them in a sane way.

I have not seen other places where driver shost config values are modified by the core code.