Re: [RFC PATCH 3/3] fb_defio: do not use deprecated page->mapping, index fields

[David Hildenbrand <david@redhat.com>]

On 08.01.25 22:55, Matthew Wilcox wrote:
> On Wed, Jan 08, 2025 at 10:12:36PM +0100, David Hildenbrand wrote:
>> On 08.01.25 21:54, Matthew Wilcox wrote:
>>> Not necessarily!  We already do that (since 2022) for DAX (see
>>> 6a8e0596f004).  rmap lets you find every place that a given range
>>> of a file is mapped into user address spaces; but that file might be a
>>> device file, and so it's not just pagecache but also (in this case)
>>> fb memory, and whatever else device drivers decide to mmap.
>>
>> Yes, that part I remember.
>>
>> I thought we would be passing in a page into rmap_wrprotect_file_page(), and
>> was wondering what we would do to "struct page" that won't be a folio in
>> there.
>>
>> Probably, because the "_page" in rmap_wrprotect_file_page() is misleading :)
>>
>> ... should it be "file_range" ? (but we also pass the pfn ... )
> 
> I don't think it's unprecedented for us to identify a page by its pfn.
> After all, the acronym stands for "page frame number".  That said, for
> the one caller of this, it has the struct page and passes in the result
> from page_to_pfn().  So no harm in passing in the struct page directly.
> 
> I would not like to see this function called "rmap_wrprotect_file_pfn".
> Files don't have pfns, so that's a bad name.

Agreed.

(it's too late in the evening for me to give any good suggestions :) )

-- 
Cheers,

David / dhildenb