[PATCHv2] nvme: print out valid arguments when reading from /dev/nvme-fabrics

[Hannes Reinecke]

On 12/13/21 9:06 AM, Chaitanya Kulkarni wrote:
> On 12/7/21 5:55 AM, Hannes Reinecke wrote:
>> Currently applications have a hard time figuring out which
>> nvme-over-fabrics arguments are supported for any given kernel;
>> the ioctl will return an error code on failure, and the application
>> has to guess whether this was due to an invalid argument or due
>> to a connection or controller error.
>> With this patch applications can read a list of supported
>> arguments by simply reading from /dev/nvme-fabrics, allowing
>> them to validate the connection string.
>>
>> Signed-off-by: Hannes Reinecke <hare at suse.de>
>> ---
>>    drivers/nvme/host/fabrics.c | 22 +++++++++++++++++++++-
>>    1 file changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
>> index 282d54117e0a..7ae041e2b3fb 100644
>> --- a/drivers/nvme/host/fabrics.c
>> +++ b/drivers/nvme/host/fabrics.c
>> @@ -1069,6 +1069,26 @@ static ssize_t nvmf_dev_write(struct file *file, const char __user *ubuf,
>>    	return ret ? ret : count;
>>    }
>>    
>> +static void __nvmf_concat_opt_tokens(struct seq_file *seq_file)
>> +{
>> +	const struct match_token *tok;
>> +	int idx;
>> +
>> +	/*
>> +	 * Add dummy entries for instance and cntlid to
>> +	 * signal an invalid/non-existing controller
>> +	 */
>> +	seq_puts(seq_file, "instance=-1,cntlid=-1");
>> +	for (idx = 0; idx < ARRAY_SIZE(opt_tokens); idx++) {
>> +		tok = &opt_tokens[idx];
>> +		if (tok->token == NVMF_OPT_ERR)
>> +			continue;
>> +		seq_puts(seq_file, ",");
> 
> Can we use "\n" instead of "," ?
> with that change it looks :-
> 
> instance=-1,cntlid=-1
> transport=%s
> traddr=%s
> trsvcid=%s
> nqn=%s
> queue_size=%d
> nr_io_queues=%d
> reconnect_delay=%d
> ctrl_loss_tmo=%d
> keep_alive_tmo=%d
> hostnqn=%s
> host_traddr=%s
> host_iface=%s
> hostid=%s
> duplicate_connect
> disable_sqflow
> hdr_digest
> data_digest
> nr_write_queues=%d
> nr_poll_queues=%d
> tos=%d
> fast_io_fail_tmo=%d
> discovery
> 
The ',' format is being used for a successful connect, so I'd rather 
stay with that to make parsing easier.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare at suse.de                              +49 911 74053 688
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