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Subject: Re: [PATCH v2 07/11] mm/hmm: add default fault flags to avoid the
 need to pre-fill pfns arrays.
To:     Jerome Glisse <jglisse@redhat.com>, Ira Weiny <ira.weiny@intel.com>
CC:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
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From:   John Hubbard <jhubbard@nvidia.com>
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On 3/28/19 6:17 PM, Jerome Glisse wrote:
> On Thu, Mar 28, 2019 at 09:42:31AM -0700, Ira Weiny wrote:
>> On Thu, Mar 28, 2019 at 04:28:47PM -0700, John Hubbard wrote:
>>> On 3/28/19 4:21 PM, Jerome Glisse wrote:
>>>> On Thu, Mar 28, 2019 at 03:40:42PM -0700, John Hubbard wrote:
>>>>> On 3/28/19 3:31 PM, Jerome Glisse wrote:
>>>>>> On Thu, Mar 28, 2019 at 03:19:06PM -0700, John Hubbard wrote:
>>>>>>> On 3/28/19 3:12 PM, Jerome Glisse wrote:
>>>>>>>> On Thu, Mar 28, 2019 at 02:59:50PM -0700, John Hubbard wrote:
>>>>>>>>> On 3/25/19 7:40 AM, jglisse@redhat.com wrote:
>>>>>>>>>> From: J=C3=A9r=C3=B4me Glisse <jglisse@redhat.com>
>>> [...]
>> Indeed I did not realize there is an hmm "pfn" until I saw this function=
:
>>
>> /*
>>  * hmm_pfn_from_pfn() - create a valid HMM pfn value from pfn
>>  * @range: range use to encode HMM pfn value
>>  * @pfn: pfn value for which to create the HMM pfn
>>  * Returns: valid HMM pfn for the pfn
>>  */
>> static inline uint64_t hmm_pfn_from_pfn(const struct hmm_range *range,
>>                                         unsigned long pfn)
>>
>> So should this patch contain some sort of helper like this... maybe?
>>
>> I'm assuming the "hmm_pfn" being returned above is the device pfn being
>> discussed here?
>>
>> I'm also thinking calling it pfn is confusing.  I'm not advocating a new=
 type
>> but calling the "device pfn's" "hmm_pfn" or "device_pfn" seems like it w=
ould
>> have shortened the discussion here.
>>
>=20
> That helper is also use today by nouveau so changing that name is not tha=
t
> easy it does require the multi-release dance. So i am not sure how much
> value there is in a name change.
>=20

Once the dust settles, I would expect that a name change for this could go
via Andrew's tree, right? It seems incredible to claim that we've built som=
ething
that effectively does not allow any minor changes!

I do think it's worth some *minor* trouble to improve the name, assuming th=
at we
can do it in a simple patch, rather than some huge maintainer-level effort.

This field name not a large thing, but the cumulative effect of having a nu=
mber of
naming glitches within HMM is significant. The size and complexity of HMM h=
as
always made it hard to attract code reviewers, so let's improve what we can=
, to
counteract that.

thanks,
--=20
John Hubbard
NVIDIA