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

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

[Thorsten Blum]

Move offset_in_page() out of linux/mm.h so users that only need page
offset calculations can include this lightweight header instead of
pulling in all of linux/mm.h.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 include/linux/mm.h           |  2 +-
 include/linux/page_helpers.h | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/page_helpers.h

diff --git a/include/linux/mm.h b/include/linux/mm.h
index af23453e9dbd..bf49e52f749a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -17,6 +17,7 @@
 #include <linux/mm_types.h>
 #include <linux/mmap_lock.h>
 #include <linux/range.h>
+#include <linux/page_helpers.h>
 #include <linux/pfn.h>
 #include <linux/percpu-refcount.h>
 #include <linux/bit_spinlock.h>
@@ -3033,7 +3034,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
  */
 extern void pagefault_out_of_memory(void);
 
-#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
 #define offset_in_folio(folio, p) ((unsigned long)(p) & (folio_size(folio) - 1))
 
 /*
diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
new file mode 100644
index 000000000000..102a4f3c3868
--- /dev/null
+++ b/include/linux/page_helpers.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_PAGE_HELPERS_H
+#define _LINUX_PAGE_HELPERS_H
+
+#include <asm/page.h>
+
+#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
+
+#endif /* _LINUX_PAGE_HELPERS_H */

[PATCH 2/3] mm: add bytes_to_page_end() helper

[Thorsten Blum]

Add bytes_to_page_end() for the common PAGE_SIZE - offset_in_page()
calculation.

Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 include/linux/page_helpers.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
index 102a4f3c3868..981731faa1fc 100644
--- a/include/linux/page_helpers.h
+++ b/include/linux/page_helpers.h
@@ -6,5 +6,6 @@
 #include <asm/page.h>
 
 #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
+#define bytes_to_page_end(p)	(PAGE_SIZE - offset_in_page(p))
 
 #endif /* _LINUX_PAGE_HELPERS_H */

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[Yury Norov]

On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
> Add bytes_to_page_end() for the common PAGE_SIZE - offset_in_page()
> calculation.
> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  include/linux/page_helpers.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
> index 102a4f3c3868..981731faa1fc 100644
> --- a/include/linux/page_helpers.h
> +++ b/include/linux/page_helpers.h
> @@ -6,5 +6,6 @@
>  #include <asm/page.h>
>  
>  #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
> +#define bytes_to_page_end(p)	(PAGE_SIZE - offset_in_page(p))
>  
>  #endif /* _LINUX_PAGE_HELPERS_H */

I've got a series for this

https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/

The feedback is surprisingly negative. Please add people from that
thread. Maybe you'll be more successful convincing them.

Thanks,
Yury

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[Andy Shevchenko]

On Sun, May 17, 2026 at 11:28:05AM -0400, Yury Norov wrote:
> On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:

...

> I've got a series for this
> 
> https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/
> 
> The feedback is surprisingly negative. Please add people from that
> thread. Maybe you'll be more successful convincing them.

We always can simply fork, but I truly do not understand the pushback.
These are simple macros that are way spread in the kernel, "include everything"
kinda linux/mm.h is not needed in vast majority of the users, hence the
split is logical step.

I'm in favour of this series.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[Lorenzo Stoakes]

On Mon, May 18, 2026 at 09:48:32AM +0300, Andy Shevchenko wrote:
> On Sun, May 17, 2026 at 11:28:05AM -0400, Yury Norov wrote:
> > On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
>
> ...
>
> > I've got a series for this
> >
> > https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/
> >
> > The feedback is surprisingly negative. Please add people from that
> > thread. Maybe you'll be more successful convincing them.

There's a cost to adding yet more super-specific headers where stuff gets hidden
and people don't know where to put what, things quickly become a mess and header
dependencies are already a nightmare.

Also in the case of this helper, I don't see the value in adding a vague,
untyped, confusingly-named macro when PAGE_SIZE - offset_in_page() is perfectly
cromulent and clear in what it's doing?

>
> We always can simply fork, but I truly do not understand the pushback.

Well, be my guest? This isn't a hugely helpful or friendly comment.

> These are simple macros that are way spread in the kernel, "include everything"
> kinda linux/mm.h is not needed in vast majority of the users, hence the
> split is logical step.

Right but that's completely orthogonal to adding this macro?

I'm fine with moving offset_in_page() to e.g. mm_types.h.

But a series that doesn't even give any actual motivation for the change is not
convicing, and we aren't required to just accept any change.

>
> I'm in favour of this series.

OK, I'm not :)

>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Thanks, Lorenzo

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[William Kucharski]

[-- Attachment #1: Type: text/plain, Size: 2269 bytes --]

As with Lorenzo's concerns, my biggest issue with this change is that it becomes unclear what "page" means in this context.

Is it a base PAGE_SIZE page? A 2 MB "large" page? A 1 GB "huge" page on architectures that support it?

The "rest_of_page()" macro masks that distinction, where the current code’s explicit reference to PAGE_SIZE makes the basis of the calculation obvious.

I don’t see why we would want to obscure that behind a macro, especially when it makes the code harder to follow.


> On May 18, 2026, at 04:28, Lorenzo Stoakes <ljs@kernel.org> wrote:
> 
> On Mon, May 18, 2026 at 09:48:32AM +0300, Andy Shevchenko wrote:
>>> On Sun, May 17, 2026 at 11:28:05AM -0400, Yury Norov wrote:
>>> On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
>> 
>> ...
>> 
>>> I've got a series for this
>>> 
>>> https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/
>>> 
>>> The feedback is surprisingly negative. Please add people from that
>>> thread. Maybe you'll be more successful convincing them.
> 
> There's a cost to adding yet more super-specific headers where stuff gets hidden
> and people don't know where to put what, things quickly become a mess and header
> dependencies are already a nightmare.
> 
> Also in the case of this helper, I don't see the value in adding a vague,
> untyped, confusingly-named macro when PAGE_SIZE - offset_in_page() is perfectly
> cromulent and clear in what it's doing?
> 
>> 
>> We always can simply fork, but I truly do not understand the pushback.
> 
> Well, be my guest? This isn't a hugely helpful or friendly comment.
> 
>> These are simple macros that are way spread in the kernel, "include everything"
>> kinda linux/mm.h is not needed in vast majority of the users, hence the
>> split is logical step.
> 
> Right but that's completely orthogonal to adding this macro?
> 
> I'm fine with moving offset_in_page() to e.g. mm_types.h.
> 
> But a series that doesn't even give any actual motivation for the change is not
> convicing, and we aren't required to just accept any change.
> 
>> 
>> I'm in favour of this series.
> 
> OK, I'm not :)
> 
>> 
>> --
>> With Best Regards,
>> Andy Shevchenko
>> 
>> 
> 
> Thanks, Lorenzo
> 

[-- Attachment #2: Type: text/html, Size: 4738 bytes --]

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[William Kucharski]

(My apologies for the earlier HTML encoding.)

As with Lorenzo's concerns, my biggest issue with this change is that it
becomes unclear what "page" means in this context.

Is it a base PAGE_SIZE page? A 2 MB "large" page? A 1 GB "huge" page on
architectures that support it?

The "rest_of_page()" macro masks that distinction, where the current code’s
explicit reference to PAGE_SIZE makes the basis of the calculation obvious.

I don’t see why we would want to obscure that behind a macro, especially
when it makes the code harder to follow.

Thanks,
    Bill

> On May 18, 2026, at 04:23, Lorenzo Stoakes <ljs@kernel.org> wrote:
> 
> On Mon, May 18, 2026 at 09:48:32AM +0300, Andy Shevchenko wrote:
>> On Sun, May 17, 2026 at 11:28:05AM -0400, Yury Norov wrote:
>>> On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
>> 
>> ...
>> 
>>> I've got a series for this
>>> 
>>> https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/
>>> 
>>> The feedback is surprisingly negative. Please add people from that
>>> thread. Maybe you'll be more successful convincing them.
> 
> There's a cost to adding yet more super-specific headers where stuff gets hidden
> and people don't know where to put what, things quickly become a mess and header
> dependencies are already a nightmare.
> 
> Also in the case of this helper, I don't see the value in adding a vague,
> untyped, confusingly-named macro when PAGE_SIZE - offset_in_page() is perfectly
> cromulent and clear in what it's doing?
> 
>> 
>> We always can simply fork, but I truly do not understand the pushback.
> 
> Well, be my guest? This isn't a hugely helpful or friendly comment.
> 
>> These are simple macros that are way spread in the kernel, "include everything"
>> kinda linux/mm.h is not needed in vast majority of the users, hence the
>> split is logical step.
> 
> Right but that's completely orthogonal to adding this macro?
> 
> I'm fine with moving offset_in_page() to e.g. mm_types.h.
> 
> But a series that doesn't even give any actual motivation for the change is not
> convicing, and we aren't required to just accept any change.
> 
>> 
>> I'm in favour of this series.
> 
> OK, I'm not :)
> 
>> 
>> --
>> With Best Regards,
>> Andy Shevchenko
>> 
>> 
> 
> Thanks, Lorenzo
> 

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[David Laight]

On Sun, 17 May 2026 11:28:05 -0400
Yury Norov <ynorov@nvidia.com> wrote:

> On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
> > Add bytes_to_page_end() for the common PAGE_SIZE - offset_in_page()
> > calculation.
> > 
> > Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> > Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> > ---
> >  include/linux/page_helpers.h | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
> > index 102a4f3c3868..981731faa1fc 100644
> > --- a/include/linux/page_helpers.h
> > +++ b/include/linux/page_helpers.h
> > @@ -6,5 +6,6 @@
> >  #include <asm/page.h>
> >  
> >  #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
> > +#define bytes_to_page_end(p)	(PAGE_SIZE - offset_in_page(p))
> >  
> >  #endif /* _LINUX_PAGE_HELPERS_H */  
> 
> I've got a series for this
> 
> https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/
> 
> The feedback is surprisingly negative. Please add people from that
> thread. Maybe you'll be more successful convincing them.

I don't think you need a another new header.
There is already vdso/page.h which is where PAGE_MASK comes from.

-- David

> 
> Thanks,
> Yury
> 

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[Lorenzo Stoakes]

On Mon, May 18, 2026 at 10:09:33AM +0100, David Laight wrote:
> On Sun, 17 May 2026 11:28:05 -0400
> Yury Norov <ynorov@nvidia.com> wrote:
>
> > On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
> > > Add bytes_to_page_end() for the common PAGE_SIZE - offset_in_page()
> > > calculation.
> > >
> > > Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> > > Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> > > ---
> > >  include/linux/page_helpers.h | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
> > > index 102a4f3c3868..981731faa1fc 100644
> > > --- a/include/linux/page_helpers.h
> > > +++ b/include/linux/page_helpers.h
> > > @@ -6,5 +6,6 @@
> > >  #include <asm/page.h>
> > >
> > >  #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
> > > +#define bytes_to_page_end(p)	(PAGE_SIZE - offset_in_page(p))
> > >
> > >  #endif /* _LINUX_PAGE_HELPERS_H */
> >
> > I've got a series for this
> >
> > https://lore.kernel.org/all/20260303182845.250bb2de@kernel.org/
> >
> > The feedback is surprisingly negative. Please add people from that
> > thread. Maybe you'll be more successful convincing them.
>
> I don't think you need a another new header.
> There is already vdso/page.h which is where PAGE_MASK comes from.

Yeah please don't, that's already a weird situation I don't really love the idea
of extending that.

mm_types.h seems the more appropriate place.

>
> -- David
>
> >
> > Thanks,
> > Yury
> >
>

Thanks, Lorenzo

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[Andy Shevchenko]

On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
> Add bytes_to_page_end() for the common PAGE_SIZE - offset_in_page()
> calculation.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/3] mm: add bytes_to_page_end() helper

[Lorenzo Stoakes]

Why is this a separate commit? It's tiny, I don't think it needs to be separated
at all.

On Sun, May 17, 2026 at 02:34:30PM +0200, Thorsten Blum wrote:
> Add bytes_to_page_end() for the common PAGE_SIZE - offset_in_page()
> calculation.

This is a totally useless commit message. Again you're not indicating why it's
needed. Please look around mm to get a sense of how commit messages should look.

Also it's so common that you have exactly zero callers updated here or
elsewhere?

I see uses which are all pretty specific. I wonder if it's really useful to make
this its own thing?

And it's untyped and etc. etc. yeah, it's a no really to this.

>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>

Was there a previous discussion that led to this series? You should really give
some background somewhere (like a cover letter, and if previous revisions were
sent, a history of them below the ---)

> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>

Again I'm really unconvinced you need to do any of this.

> ---
>  include/linux/page_helpers.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
> index 102a4f3c3868..981731faa1fc 100644
> --- a/include/linux/page_helpers.h
> +++ b/include/linux/page_helpers.h
> @@ -6,5 +6,6 @@
>  #include <asm/page.h>
>
>  #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)

I mean another thing about this (and yes this was existing but since you're
proposing making this rather special it's worth raising) is that it's enormously
un-typesafe and 'p' is vague, what if somebody put a (struct page *) here?

It'd be better if it was a static inline function, maybe there's places which
use this already that require it to be a macro but perhaps not.

> +#define bytes_to_page_end(p)	(PAGE_SIZE - offset_in_page(p))

Here, since, you're adding it, there's no excuse at all for it being a
macro. And you're implementing something just as horribly vague as the other
form, it's not obvious 'p' is meant to be a pointer. Page begins with p too :)

Anyway I'm not really convinced this is useful.

>
>  #endif /* _LINUX_PAGE_HELPERS_H */

Thanks, Lorenzo

[PATCH 3/3] lib/bitmap: use bytes_to_page_end() helper

[Thorsten Blum]

bitmap-str.c includes linux/mm.h for offset_in_page() and kfree().
Instead, include linux/page_helpers.h and linux/slab.h directly, and
use bytes_to_page_end() to simplify the code.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 lib/bitmap-str.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/bitmap-str.c b/lib/bitmap-str.c
index be745209507a..bf245a3eae4a 100644
--- a/lib/bitmap-str.c
+++ b/lib/bitmap-str.c
@@ -7,7 +7,8 @@
 #include <linux/export.h>
 #include <linux/hex.h>
 #include <linux/kernel.h>
-#include <linux/mm.h>
+#include <linux/page_helpers.h>
+#include <linux/slab.h>
 #include <linux/string.h>
 
 #include "kstrtox.h"
@@ -58,7 +59,7 @@ EXPORT_SYMBOL(bitmap_parse_user);
 int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
 			    int nmaskbits)
 {
-	ptrdiff_t len = PAGE_SIZE - offset_in_page(buf);
+	ptrdiff_t len = bytes_to_page_end(buf);
 
 	return list ? scnprintf(buf, len, "%*pbl\n", nmaskbits, maskp) :
 		      scnprintf(buf, len, "%*pb\n", nmaskbits, maskp);

Re: [PATCH 3/3] lib/bitmap: use bytes_to_page_end() helper

[Lorenzo Stoakes]

On Sun, May 17, 2026 at 02:34:31PM +0200, Thorsten Blum wrote:
> bitmap-str.c includes linux/mm.h for offset_in_page() and kfree().

I'd specifically say that it's including linux/mm.h which in turn includes
linux/slab.h and that you're fixing this, because saying you include mm.h for
kfree() is a little confusing.

> Instead, include linux/page_helpers.h and linux/slab.h directly, and
> use bytes_to_page_end() to simplify the code.

This is again, a useless commit message. You're not explaining why what for, how
etc., you're putting in words what the code is doing.

And I'm still very confused as to what the motive is here overall. What's so
problematic about including that header? Longer compile times, somehow? If so,
what are the measurements before/after this change? What was the problem that
led to it? Etc.

We could end up with hundreds of super specific headers files for things, so
there really has to be a good reason for it.


>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  lib/bitmap-str.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/bitmap-str.c b/lib/bitmap-str.c
> index be745209507a..bf245a3eae4a 100644
> --- a/lib/bitmap-str.c
> +++ b/lib/bitmap-str.c
> @@ -7,7 +7,8 @@
>  #include <linux/export.h>
>  #include <linux/hex.h>
>  #include <linux/kernel.h>
> -#include <linux/mm.h>
> +#include <linux/page_helpers.h>
> +#include <linux/slab.h>
>  #include <linux/string.h>
>
>  #include "kstrtox.h"
> @@ -58,7 +59,7 @@ EXPORT_SYMBOL(bitmap_parse_user);
>  int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
>  			    int nmaskbits)
>  {
> -	ptrdiff_t len = PAGE_SIZE - offset_in_page(buf);
> +	ptrdiff_t len = bytes_to_page_end(buf);

yeah this is kind of nasty, going from a clear thing to a 'I wonder how that is
implemented' mystery meat function. I think the original is better.

>
>  	return list ? scnprintf(buf, len, "%*pbl\n", nmaskbits, maskp) :
>  		      scnprintf(buf, len, "%*pb\n", nmaskbits, maskp);

Thanks, Lorenzo

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

[Andy Shevchenko]

On Sun, May 17, 2026 at 02:34:29PM +0200, Thorsten Blum wrote:
> Move offset_in_page() out of linux/mm.h so users that only need page
> offset calculations can include this lightweight header instead of
> pulling in all of linux/mm.h.

Yep, the whole mm.h is rarely used in the cases where this and a new one
(next patch) are being (going to be) used.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

(Do we need to update MAINTAINERS / Documentation parts anywhere?)

-- 
With Best Regards,
Andy Shevchenko

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

[Lorenzo Stoakes]

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.

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

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?

On Sun, May 17, 2026 at 02:34:29PM +0200, Thorsten Blum wrote:
> Move offset_in_page() out of linux/mm.h so users that only need page
> offset calculations can include this lightweight header instead of
> pulling in all of linux/mm.h.

What's the motivation? What caused you to want to do this? Why should we have a
new tiny header with only this define? What makes that important?

Why is pulling in a 'big' header file such an issue?

This commit message is pretty useless right now, you're just saying what you're
doing, yeah I can see that from the diff.

You should use the commit message to explain why and what for etc.

>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  include/linux/mm.h           |  2 +-
>  include/linux/page_helpers.h | 10 ++++++++++

You've added a new file and not updated MAINTAINERS, nor indicated that it will
be caught by a glob?

Also super super restrictive to have 'page helpers', that's likely to be tiny
forever, why not just move this macro to mm_types.h and import that instead?
It's highly likely it's already imported wherever you need it, anyway.

>  2 files changed, 11 insertions(+), 1 deletion(-)
>  create mode 100644 include/linux/page_helpers.h
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index af23453e9dbd..bf49e52f749a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -17,6 +17,7 @@
>  #include <linux/mm_types.h>
>  #include <linux/mmap_lock.h>
>  #include <linux/range.h>
> +#include <linux/page_helpers.h>
>  #include <linux/pfn.h>
>  #include <linux/percpu-refcount.h>
>  #include <linux/bit_spinlock.h>
> @@ -3033,7 +3034,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
>   */
>  extern void pagefault_out_of_memory(void);
>
> -#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
>  #define offset_in_folio(folio, p) ((unsigned long)(p) & (folio_size(folio) - 1))
>
>  /*
> diff --git a/include/linux/page_helpers.h b/include/linux/page_helpers.h
> new file mode 100644
> index 000000000000..102a4f3c3868
> --- /dev/null
> +++ b/include/linux/page_helpers.h
> @@ -0,0 +1,10 @@
> +/* SPDX-License-Identifier: GPL-2.0 */

No description of what this is for?

> +
> +#ifndef _LINUX_PAGE_HELPERS_H
> +#define _LINUX_PAGE_HELPERS_H
> +
> +#include <asm/page.h>
> +
> +#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)

Why are you only porting the page version when ostensibly folios are more likely
to be the unit-of-operation in future?

> +
> +#endif /* _LINUX_PAGE_HELPERS_H */

Thanks, Lorenzo