linux-kernel - Re: [PATCH v2 28/40] mm/memory: page_remove_rmap() -> folio_remove_rmap

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Message-ID: <c8763420-69c8-4e22-ab87-ad702d5abb34@arm.com>
Date: Mon, 22 Jan 2024 17:26:00 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Matthew Wilcox <willy@...radead.org>, David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>,
 Yin Fengwei <fengwei.yin@...el.com>, Mike Kravetz <mike.kravetz@...cle.com>,
 Muchun Song <muchun.song@...ux.dev>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH v2 28/40] mm/memory: page_remove_rmap() ->
 folio_remove_rmap_pte()

On 22/01/2024 17:20, Matthew Wilcox wrote:
> On Mon, Jan 22, 2024 at 06:01:58PM +0100, David Hildenbrand wrote:
>>> And folio_mark_dirty() is doing more than just setting teh PG_dirty bit. In my
>>> equivalent change, as part of the contpte series, I've swapped set_page_dirty()
>>> for folio_mark_dirty().
>>
>> Good catch, that should be folio_mark_dirty(). Let me send a fixup.
>>
>> (the difference in naming for both functions really is bad)
> 
> It really is, and I don't know what to do about it.
> 
> We need a function that literally just sets the flag.  For every other
> flag, that's folio_set_FLAG.  We can't use __folio_set_flag because that
> means "set the flag non-atomically".
> 
> We need a function that does all of the work involved with tracking
> dirty folios.  I chose folio_mark_dirty() to align with
> folio_mark_uptodate() (ie mark is not just 'set" but also "do some extra
> work").
> 
> But because we're converting from set_page_dirty(), the OBVIOUS rename
> is to folio_set_dirty(), which is WRONG.
> 
> So we're in the part of the design space where the consistent naming and
> the-obvious-thing-to-do-is-wrong are in collision, and I do not have a
> good answer.
> 
> Maybe we can call the first function _folio_set_dirty(), and we don't
> have a folio_set_dirty() at all?  We don't have a folio_set_uptodate(),
> so there's some precedent there.

Is there anything stopping us from renaming set_page_dirty() to
mark_page_dirty() (or page_mark_dirty())? For me the folio naming is consistent,
but the page names suck; presumably PageSetDirty() and set_page_dirty()... yuk.