On 12/9/20 4:24 PM, Jason Gunthorpe wrote:
> On Wed, Dec 09, 2020 at 04:02:05PM +0000, Joao Martins wrote:
>
>> Today (without the series) struct pages are not represented the way they
>> are expressed in the page tables, which is what I am hoping to fix in this
>> series thus initializing these as compound pages of a given order. But me
>> introducing PGMAP_COMPOUND was to conservatively keep both old (non-compound)
>> and new (compound pages) co-exist.
>
> Oooh, that I didn't know.. That is kind of horrible to have a PMD
> pointing at an order 0 page only in this one special case.
>
> Still, I think it would be easier to teach record_subpages() that a
> PMD doesn't necessarily point to a high order page, eg do something
> like I suggested for the SGL where it extracts the page order and
> iterates over the contiguous range of pfns.
>
/me nods
> This way it can remain general with no particularly special path for
> devmap or a special PGMAP_COMPOUND check here.
The less special paths the better, indeed.
Joao
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