Re: [PATCH] null_blk: add zoned config support information

[Jens Axboe <axboe@kernel.dk>]

On 1/4/19 1:37 PM, John Pittman wrote:
> Thanks Bart; I made the changes and sent them in as a v2, I'm sure you
> already saw.  I have a quick, unrelated question if you have a moment.
> In testing the null_blk driver, I found that trim commands sent by fio
> were rejected due to lack of support.  Tracking down Shaohua's commit
> 306eb6b4a ("nullb: support discard"), he mentions that "discard makes
> sense for memory backed disk".  Just to see what would happen, I
> edited the source to make discard a configurable parameter at
> modprobe, and after the edit & build, the trim commands submitted
> fine.  Does this sort of change make sense?  I mean the ability to do
> discard to null_blk without it being memory backed;  solely for
> testing/benchmarking purposes.  I haven't found any good instructions
> on creating a memory backed or discard enabled null_blk device from
> the command line, so I assume a higher level driver would have to hook
> in and enable these features manually.  Thanks for your time and any
> information.

I think that would be fine, no option needed. It's really no different
than reads/writes being completed without having a memory backing.

-- 
Jens Axboe