Re: [PATCH 1/3] mm: move offset_in_page() to page_helpers.h

[Thorsten Blum <thorsten.blum@linux.dev>]

Hi Lorenzo,

On Mon, May 18, 2026 at 11:02:10AM +0100, Lorenzo Stoakes wrote:
> Seriously, please resend this.
> 
> This is 3 patches with 2 in-reply-to 1/3, that's not how we do series in mm,
> take a look around :)
> 
> Write a cover letter, and have all the patches in-reply-to that.

A cover letter seemed unnecessary for such a seemingly trivial 3-patch
series, but this thread [1] might have been helpful for context.

[1] https://lore.kernel.org/lkml/CAHp75VfQNkqEYsO4Uup0c-uiYuVyAWit=tmCz2BsYLp-sjXsZw@mail.gmail.com/

> Was there not previous versions of this? I _seem_ to remember that, but might be
> misremembering :)

I only know about the one Yury mentioned. This is v1 of my series.

> Also I'm really questioning the value of this, you've not sold why we should
> take this whatsoever.
> 
> 'Add a random new header file we have to maintain because it's smaller' is not
> really hugely compelling.
> 
> Also a _lot_ of stuff in the kernel ultimately pulls in mm.h. So what exactly
> has the specific requirement of both needing this define and (somehow) doesn't
> use mm?

Patch 3/3 is one of many examples that pulls in all of mm.h just for
offset_in_page(). lib/string.c from the same thread [1] is another
example that would need to include mm.h just for offset_in_page().

Many other files (hundreds) don't use offset_in_page(), but open-code it
in many different ways instead:

	(unsigned long)p & ~PAGE_MASK
	(unsigned long)p & (PAGE_SIZE - 1)
	(long)p & (PAGE_SIZE - 1)
	...

I can't tell whether they didn't know about offset_in_page(), or
deliberately chose not to include mm.h.

Thanks,
Thorsten