linux-kernel - Re: [PATCH] scsi: core: Cap initial sdev queue depth at shost.can

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Date:   Tue, 20 Apr 2021 08:02:40 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     John Garry <john.garry@...wei.com>
Cc:     jejb@...ux.ibm.com, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        kashyap.desai@...adcom.com, dgilbert@...erlog.com
Subject: Re: [PATCH] scsi: core: Cap initial sdev queue depth at
 shost.can_queue

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@...wei.com>
> ---
> Topic originally discussed at:
> https://lore.kernel.org/linux-scsi/85dec8eb-8eab-c7d6-b0fb-5622747c5499@interlog.com/T/#m5663d0cac657d843b93d0c9a2374f98fc04384b9
> 
> Last idea there was to error/warn in scsi_add_host() for cmd_per_lun >

No, that isn't my suggestion.

> 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?

-- 
Ming