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SubjectRe: [PATCH 1/2] libata: Fix scsi_host can_queue issue in ata_qc_new()
On 07/22/2014 11:42 PM, Tejun Heo wrote:
> Hello,
>
> (cc'ing Dan)
>
> On Tue, Jul 22, 2014 at 10:50:19AM -0400, Mike Qiu wrote:
>> The can_queue in scsi_host can be more than ATA_MAX_QUEUE (32),
>> for example, in ipr, it can be 100 or more.
>>
>> Also, some drivers, like ipr driver, haven't filled the field
>> scsi_host in ata_port, and will lead a call trace, so add
>> check for that.
>>
>> Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
>> ---
>> drivers/ata/libata-core.c | 15 ++++-----------
>> 1 file changed, 4 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
>> index 259d879..a5b9c70 100644
>> --- a/drivers/ata/libata-core.c
>> +++ b/drivers/ata/libata-core.c
>> @@ -4734,7 +4734,10 @@ static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
>> struct ata_queued_cmd *qc = NULL;
>> unsigned int i, tag, max_queue;
>>
>> - max_queue = ap->scsi_host->can_queue;
>> + if (ap->scsi_host && ap->scsi_host->can_queue <= ATA_MAX_QUEUE)
>> + max_queue = ap->scsi_host->can_queue;
>> + else
>> + max_queue = ATA_MAX_QUEUE;
>>
>> /* no command while frozen */
>> if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
>> @@ -6109,16 +6112,6 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
>> {
>> int i, rc;
>>
>> - /*
>> - * The max queue supported by hardware must not be greater than
>> - * ATA_MAX_QUEUE.
>> - */
>> - if (sht->can_queue > ATA_MAX_QUEUE) {
>> - dev_err(host->dev, "BUG: the hardware max queue is too large\n");
>> - WARN_ON(1);
>> - return -EINVAL;
>> - }
>> -
> So, ummm, I really don't like that we're adding the conditionals to
> the hot path (yeah, its implementation is slow but still). Maybe we

Yes, agree ..., not a good idea to do this...

Thanks
Mike
> need to store the chosen queue depth after all? Dan?
>
> Thanks.
>



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