On 7/2/18 2:28 PM, Douglas Gilbert wrote:
> On 2018-07-02 07:06 AM, Ming Lei wrote:
>> With the introduced module parameter of 'use_blk_mq', it is easy
>> to switch between 'blk_mq' and 'non_blk_mq' by reloading scsi_debug
>> module, so that we can test scsi_mq/blk_mq related regressions easily.
>>
>> Cc: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
>> Cc: Bart Van Assche <bart.vanassche@xxxxxxx>
>> Cc: Jens Axboe <axboe@xxxxxxxxx>
>> Cc: Omar Sandoval <osandov@xxxxxx>
>> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
>> ---
>> drivers/scsi/scsi_debug.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
>> index 24d7496cd9e2..236cfb669df3 100644
>> --- a/drivers/scsi/scsi_debug.c
>> +++ b/drivers/scsi/scsi_debug.c
>> @@ -144,6 +144,7 @@ static const char *sdebug_version_date = "20180128";
>> #define DEF_SUBMIT_QUEUES 1
>> #define DEF_UUID_CTL 0
>> #define JDELAY_OVERRIDDEN -9999
>> +#define DEF_USE_BLK_MQ 0
>>
>> #define SDEBUG_LUN_0_VAL 0
>>
>> @@ -671,6 +672,7 @@ static bool sdebug_verbose;
>> static bool have_dif_prot;
>> static bool write_since_sync;
>> static bool sdebug_statistics = DEF_STATISTICS;
>> +static bool sdebug_use_blk_mq = DEF_USE_BLK_MQ;
>>
>> static unsigned int sdebug_store_sectors;
>> static sector_t sdebug_capacity; /* in sectors */
>> @@ -4537,6 +4539,7 @@ module_param_named(vpd_use_hostno, sdebug_vpd_use_hostno, int,
>> S_IRUGO | S_IWUSR);
>> module_param_named(write_same_length, sdebug_write_same_length, int,
>> S_IRUGO | S_IWUSR);
>> +module_param_named(use_blk_mq, sdebug_use_blk_mq, bool, S_IRUGO | S_IWUSR);
>>
>> MODULE_AUTHOR("Eric Youngdale + Douglas Gilbert");
>> MODULE_DESCRIPTION("SCSI debug adapter driver");
>> @@ -5849,6 +5852,8 @@ static int sdebug_driver_probe(struct device *dev)
>> sdebug_driver_template.can_queue = sdebug_max_queue;
>> if (sdebug_clustering)
>> sdebug_driver_template.use_clustering = ENABLE_CLUSTERING;
>> + if (sdebug_use_blk_mq)
>> + sdebug_driver_template.force_blk_mq = 1;
>> hpnt = scsi_host_alloc(&sdebug_driver_template, sizeof(sdbg_host));
>> if (NULL == hpnt) {
>> pr_err("scsi_host_alloc failed\n");
>>
>
> Hi,
> It is up to others whether this patch goes through. It seems the default
> associated with blk_mq may soon change. So two things:
> - I'd like to see a MODULE_PARM_DESC(use_blk_mq, ...) entry in patch
> - perhaps a 3 valued use_blk_mq: 1 --> force blk_mq; 0 (def) --> accept
> default mq setting; -1 --> turn off mq (if possible, if not it's a
> NOP)
The point is that the parameter is going to be short lived, since the
non-mq path will be going away. We don't want drivers exposing this
sort of thing, just to remove the option shortly again. Once we're
happy with scsi-mq for a release or two, the old code should be
deleted. Once that happens, then the option will have no purpose.
--
Jens Axboe
