Re: [PATCH v5 17/21] libnvdimm: infrastructure for btt devices

Jeff Moyer
2015-06-17T16:57:44Z

Dan Williams <dan.j.williams@intel.com> writes:

> On Wed, Jun 17, 2015 at 9:47 AM, Jeff Moyer <jmoyer@redhat.com> wrote:
>> Christoph Hellwig <hch@lst.de> writes:
>>
>>> On Wed, Jun 10, 2015 at 02:46:16PM -0400, Matthew Wilcox wrote:
>>>> Don't screw up rw_page. The point of rw_page is to read or write a page
>>>> cache page. It can sleep, and it indicates success by using the page
>>>> flags. Don't try and scqueeze rw_bytes into it. If you want rw_bytes
>>>> to be a queue operation, that's one thing, but don't mess with rw_page.
>>>
>>> Oh, I forgot about the page manipulating nature. Yes, we'll need a different
>>> operation in this case.
>>
>> I didn't see this addressed in the new patch set. I'm also concerned
>> about the layering, but I haven't put enough time into it to really make
>> a better suggestion. I really dislike the idea of yet another device
>> stacking model in the kernel and I'm worried the code will go in, and the
>> sysfs interface will end up as a "user abi" and we won't be able to
>> change it in the future.
>>
>> Dan, have you made any progress on this, or do you have plans to?
>
> ? in v6 ->rw_bytes() moved from libnvdimm local hackery to a top-level
> block device operation. Is that your concern or something else?

Hmm, I guess I was conflating two things. I see now that you did move
the rw_bytes into the block device operations, that looks good. I'll
table my concerns over yet another stacking model until I can say
something intelligent about it.

Cheers,
Jeff