linux-kernel - Re: Removing page->index

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Message-ID: <1a02554d-d7c1-4925-8180-a39bd6ecdd32@redhat.com>
Date: Tue, 10 Dec 2024 13:16:24 +0100
From: David Hildenbrand <david@...hat.com>
To: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
 linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-s390@...r.kernel.org
Subject: Re: Removing page->index

On 10.12.24 13:04, Claudio Imbrenda wrote:
> On Tue, 10 Dec 2024 12:05:25 +0100
> David Hildenbrand <david@...hat.com> wrote:
> 
>> On 09.12.24 18:36, Claudio Imbrenda wrote:
>>> On Wed, 4 Dec 2024 16:58:52 +0100
>>> David Hildenbrand <david@...hat.com> wrote:
> 
> [...]
> 
>>>> I know that Claudio is working on some changes, but not sure how that
>>>> would affect gmap's usage of page->index.
>>>
>>> After I'm done, we won't use page->index anymore.
>>>
>>> The changes I'm working on are massive, it's very impractical to push
>>> everything at once, so I'm refactoring and splitting smaller and more
>>> manageable (and reviewable) series.
>>>
>>> This means that it will take some time before I'm done (I'm *hoping*
>>> to be done for 6.15)
>>
>> Thanks for the information. So for the time being, we could likely
>> switch to page->private.
>>
>> One question may be whether these (not-user-space) page tables should at
>> some point deserve a dedicated memdesc. But likely the question is what
> 
> maybe? but given that everything is changing all the time, I'm avoiding
> any magic logic in struct page / struct folio.

I think Willy wants to get rid of page->index in the next release, so 
any way to avoid the page->index usage in s390x is appreciated. 
page->private might be the low hanging fruit. If your approach is 
feasible in that time frame, it would also be great.

-- 
Cheers,

David / dhildenb