Re: [PATCH v3 6/6] nbd: add nr_hw_queues module parameter for pre-created devices

在 2026/7/22 11:53, yu kuai 写道:
> Hi,
> 
> 在 2026/7/13 14:56, Yang Erkun 写道:
>> Previous commit can help remove all freeze for netlink newly created nbd
>> device. But for the devices pre-created at module load(nbds_max default
>> as 16), the nr_hw_queues was setting default as 1, then ioctl/netlink
>> path will set the real connection count, and blk_mq_update_nr_hw_queues
>> in nbd_start_device will introduce freeze.
>>
>> Add an nr_hw_queues module parameter so that users who know their
>> expected connection count can pre-created devices with the right queue
>> count to avoid this freeze too.
> 
> I'm fine with this, but this is misleading. Please also add comment to
> emphasize this module parameter is just to avoid queue freeze if user configure
> the exact number of socks as this new module parameter. Otherwise, the real
> nr_hw_queues is still depend on the real number of user configured socks.

OK, will add this comment in next version! Thanks a lot for your careful 
review!

> 
>>
>> Signed-off-by: Yang Erkun <[email protected]>
>> ---
>>    drivers/block/nbd.c | 8 +++++++-
>>    1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
>> index 2c7b09c70da2..f918c9efa9b2 100644
>> --- a/drivers/block/nbd.c
>> +++ b/drivers/block/nbd.c
>> @@ -166,6 +166,7 @@ static struct dentry *nbd_dbg_dir;
>>    
>>    static unsigned int nbds_max = 16;
>>    static int max_part = 16;
>> +static int nr_hw_queues = 1;
>>    static int part_shift;
>>    
>>    static int nbd_dev_dbg_init(struct nbd_device *nbd);
>> @@ -2752,8 +2753,10 @@ static int __init nbd_init(void)
>>    	}
>>    	nbd_dbg_init();
>>    
>> +	if (nr_hw_queues < 1)
>> +		nr_hw_queues = 1;
>>    	for (i = 0; i < nbds_max; i++)
>> -		nbd_dev_add(i, 1, 1);
>> +		nbd_dev_add(i, 1, nr_hw_queues);
>>    	return 0;
>>    }
>>    
>> @@ -2814,3 +2817,6 @@ module_param(nbds_max, int, 0444);
>>    MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
>>    module_param(max_part, int, 0444);
>>    MODULE_PARM_DESC(max_part, "number of partitions per device (default: 16)");
>> +module_param(nr_hw_queues, int, 0444);
>> +MODULE_PARM_DESC(nr_hw_queues,
>> +"number of hardware queues for devices pre-created at module load (default: 1). ");
>