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

[yangerkun <yangerkun@huawei.com>]

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 <yangerkun@huawei.com>
> > ---
> >    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). ");