From: John Garry <john.garry@huawei.com>
To: Bart Van Assche <bvanassche@acm.org>, <jejb@linux.ibm.com>,
<martin.petersen@oracle.com>
Cc: <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<ming.lei@redhat.com>
Subject: Re: [PATCH] scsi: core: Cap shost cmd_per_lun at can_queue
Date: Thu, 20 May 2021 17:41:15 +0100 [thread overview]
Message-ID: <a838c8e2-6513-a266-f145-5bcaed0a4f96@huawei.com> (raw)
In-Reply-To: <988856ad-8e89-97e4-f8fe-54c1ca1b4a93@acm.org>
On 20/05/2021 16:57, Bart Van Assche wrote:
> On 5/19/21 7:31 AM, John Garry wrote:
>> Function sdev_store_queue_depth() enforces that the sdev queue depth cannot
>> exceed Shost.can_queue.
>>
>> The sdev initial value comes from shost cmd_per_lun.
>>
>> However, the LLDD may still set cmd_per_lun > can_queue, which leads to an
>> initial sdev queue depth greater than can_queue.
>>
>> Such an issue was reported in [0], which caused a hang. That has since
>> been fixed in commit fc09acb7de31 ("scsi: scsi_debug: Fix cmd_per_lun,
>> set to max_queue").
>>
>> Stop this possibly happening for other drivers by capping
>> shost.cmd_per_lun at shost.can_queue.
>>
>> [0] https://lore.kernel.org/linux-scsi/YHaez6iN2HHYxYOh@T590/
>>
>> Signed-off-by: John Garry <john.garry@huawei.com>
>> ---
>> Earlier patch was in https://lore.kernel.org/linux-scsi/1618848384-204144-1-git-send-email-john.garry@huawei.com/
>>
>> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
>> index ba72bd4202a2..624e2582c3df 100644
>> --- a/drivers/scsi/hosts.c
>> +++ b/drivers/scsi/hosts.c
>> @@ -220,6 +220,9 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>> goto fail;
>> }
>>
>> + shost->cmd_per_lun = min_t(short, shost->cmd_per_lun,
>> + shost->can_queue);
>> +
>> error = scsi_init_sense_cache(shost);
>> if (error)
>> goto fail;
>
>
Hi Bart,
> In SCSI header files a mix of int, short and unsigned int is used for
> cmd_per_lun and can_queue. How about changing the types of these two
> member variables in include/scsi/*h into u16?
I don't mind doing that, but is there any requirement for can_queue to
not be limited to 16b?
It seems intentional that can_queue is int and cmd_per_lun is short.
As an aside, if short is 16b, it does not even seem to have efficient
packing on Scsi_host today (although we can move things around):
int can_queue;
short cmd_per_lun;
short unsigned int sg_tablesize;
short unsigned int sg_prot_tablesize;
/* 16b hole */
unsigned int max_sectors;
>
> Anyway:
>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
>
thanks!
>
>
> .
>
next prev parent reply other threads:[~2021-05-20 16:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 14:31 [PATCH] scsi: core: Cap shost cmd_per_lun at can_queue John Garry
2021-05-20 1:24 ` Ming Lei
2021-05-20 15:57 ` Bart Van Assche
2021-05-20 16:41 ` John Garry [this message]
2021-05-20 16:57 ` Bart Van Assche
2021-05-20 17:24 ` John Garry
2021-05-22 4:28 ` Martin K. Petersen
2021-05-22 4:35 ` Martin K. Petersen
2021-05-26 4:07 ` Martin K. Petersen
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