Re: [PATCH v8 8/8] nbd: add pre_defined_connections module parameter for pre-created devices

[yangerkun <yangerkun@huawei.com>]

Hi Kuai,

Thanks for your careful review during this period.

Thanks,
Erkun.

在 2026/8/7 16:12, yu kuai 写道:
> 在 2026/8/5 20:29, Yang Erkun 写道:
> 
>> blk_mq_update_nr_hw_queues() in nbd_start_device() may cause a queue
>> freeze.  The previous commit addressed this for newly created nbd
>> devices by setting the expected nr_hw_queues in nbd_dev_add().  However,
>> when reusing an old inactive nbd device, the queue freeze can still
>> occur if the old nbd->tag_set->nr_hw_queues does not match the new
>> socket connection count.  Inactive nbd devices can originate from two
>> sources: loading the nbd module with nbds_max, which sets the default
>> nr_hw_queues to 1, and the netlink method, which sets nr_hw_queues
>> according to the expected number of socket connections.  For the first
>> case, add a module parameter so the default nr_hw_queues can be
>> changed.  Users who know their expected number of connections can then
>> prevent queue freezes on pre-created devices via nbds_max.
>>
>> Before this patchset:
>> real    0m2.195s
>> user    0m0.005s
>> sys     0m0.022s
>>
>> After this patchset:
>> real    0m0.090s
>> user    0m0.004s
>> sys     0m0.018s
>>
>> Signed-off-by: Yang Erkun<yangerkun@huawei.com>
>> ---
>>    drivers/block/nbd.c | 16 +++++++++++++++-
>>    1 file changed, 15 insertions(+), 1 deletion(-)
> Reviewed-by: Yu Kuai <yukuai@fygo.io>
>