Re: [PATCH v5 5/8] nbd: skip queue freeze when setting size at device startup

[yangerkun <yangerkun@huawei.com>]

在 2026/8/2 19:45, yu kuai 写道:
> Hi,
> 
> 在 2026/7/30 16:20, Yang Erkun 写道:
>> Commit 242a49e5c878 ("nbd: freeze the queue for queue limits updates")
>> added the freeze to keep in-flight commands from seeing torn
>> queue_limits.  But at startup the capacity is still 0
>> (invalidate_disk cleared it) and the write cache is off (the previous
>> patch cleared it on disconnect, and nbd_set_size sets it back only after
>> the commit), so submit_bio_noacct() rejects any bio before it reaches
>> the driver and no I/O is in flight.  Drop the freeze there.
>>
>> Split nbd_set_size() with a bool: nbd_start_device() passes false, the
>> runtime resize/reconfigure paths (ioctls and nbd_genl_size_set) keep
>> passing true.  nbd->pid is still 0 when nbd_genl_connect calls
>> nbd_genl_size_set, so the early return in nbd_set_size keeps that path
>> from applying limits before startup; the true covers the reconnect path
>> on a live device.
>>
>> Signed-off-by: Yang Erkun <yangerkun@huawei.com>
>> ---
>>    drivers/block/nbd.c | 21 ++++++++++++++-------
>>    1 file changed, 14 insertions(+), 7 deletions(-)
> 
> Can you just checking if size is 0 and write cache is disabled first, and just
> skip freeze in this case. I think this is simpler and straightforward, as you
> don't have to modify all the callers.

OK, it seems simple and clear, I will try it next version!

> 
>>
>> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
>> index ce25c254e5fb..3b7363b11d0b 100644
>> --- a/drivers/block/nbd.c
>> +++ b/drivers/block/nbd.c
>> @@ -331,7 +331,8 @@ static void nbd_mark_nsock_dead(struct nbd_device *nbd, struct nbd_sock *nsock,
>>    	nsock->sent = 0;
>>    }
>>    
>> -static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, loff_t blksize)
>> +static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, loff_t blksize,
>> +			bool freeze)
>>    {
>>    	struct queue_limits lim;
>>    	int error;
>> @@ -371,7 +372,13 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, loff_t blksize)
>>    
>>    	lim.logical_block_size = blksize;
>>    	lim.physical_block_size = blksize;
>> -	error = queue_limits_commit_update_frozen(nbd->disk->queue, &lim);
>> +
>> +	if (freeze)
>> +		error = queue_limits_commit_update_frozen(nbd->disk->queue,
>> +				&lim);
>> +	else
>> +		error = queue_limits_commit_update(nbd->disk->queue, &lim);
>> +
>>    	if (error)
>>    		return error;
>>    
>> @@ -1568,7 +1575,7 @@ static int nbd_start_device(struct nbd_device *nbd)
>>    		args->index = i;
>>    		queue_work(nbd->recv_workq, &args->work);
>>    	}
>> -	return nbd_set_size(nbd, config->bytesize, nbd_blksize(config));
>> +	return nbd_set_size(nbd, config->bytesize, nbd_blksize(config), false);
>>    }
>>    
>>    static int nbd_start_device_ioctl(struct nbd_device *nbd)
>> @@ -1636,13 +1643,13 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
>>    	case NBD_SET_SOCK:
>>    		return nbd_add_socket(nbd, arg, false);
>>    	case NBD_SET_BLKSIZE:
>> -		return nbd_set_size(nbd, config->bytesize, arg);
>> +		return nbd_set_size(nbd, config->bytesize, arg, true);
>>    	case NBD_SET_SIZE:
>> -		return nbd_set_size(nbd, arg, nbd_blksize(config));
>> +		return nbd_set_size(nbd, arg, nbd_blksize(config), true);
>>    	case NBD_SET_SIZE_BLOCKS:
>>    		if (check_shl_overflow(arg, config->blksize_bits, &bytesize))
>>    			return -EINVAL;
>> -		return nbd_set_size(nbd, bytesize, nbd_blksize(config));
>> +		return nbd_set_size(nbd, bytesize, nbd_blksize(config), true);
>>    	case NBD_SET_TIMEOUT:
>>    		nbd_set_cmd_timeout(nbd, arg);
>>    		return 0;
>> @@ -2097,7 +2104,7 @@ static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd)
>>    		bsize = nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]);
>>    
>>    	if (bytes != config->bytesize || bsize != nbd_blksize(config))
>> -		return nbd_set_size(nbd, bytes, bsize);
>> +		return nbd_set_size(nbd, bytes, bsize, true);
>>    	return 0;
>>    }
>>    
>