Re: [PATCH 1/2] engines/io_uring: support r/w with metadata

[Jens Axboe <axboe@kernel.dk>]

>> +	if (!strcmp(td->io_ops->name, "io_uring") && o->md_per_io_size) {
>> +		struct nvme_data *data = FILE_ENG_DATA(io_u->file);
>> +		struct nvme_cmd_ext_io_opts ext_opts = {0};
>> +
>> +		if (data->pi_type) {
>> +			if (o->pi_act)
>> +				ext_opts.io_flags |= NVME_IO_PRINFO_PRACT;
>> +
>> +			ext_opts.io_flags |= o->prchk;
>> +			ext_opts.apptag = o->apptag;
>> +			ext_opts.apptag_mask = o->apptag_mask;
>> +		}
>> +		fio_nvme_generate_guard(io_u, &ext_opts);
>> +	}
> 
> Ehh a strcmp() in the hot path?! First of all, that's a big no-no.
> Secondly, if this really was required, you'd add something to put that
> strcmp() in the slow path and flag it. Lastly, thankfully this should be
> much better as:
> 
> 	if (td->io_ops == &ioengine_uring ...)
> 
> instead.

Eh I guess dynamically loaded engines would need special treatment. I'll
take a look. In any case, strcmp() is just too ugly to live, actually
quite a few in there and the io_uring engine is the only one that thinks
this is necessary.

-- 
Jens Axboe