linux-kernel - Re: [PATCH v1 0/3] list: add primitives for private list manipulations

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Message-ID: <CA+CK2bCUBMgnepMzO21+SH6rY7bb2OgRqxkLkUr33UsrPoe_2A@mail.gmail.com>
Date: Fri, 28 Nov 2025 09:45:29 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: corbet@....net, nicolas.frattaroli@...labora.com, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, kees@...nel.org, 
	davidgow@...gle.com, pmladek@...e.com, tamird@...il.com, raemoar63@...il.com, 
	ebiggers@...nel.org, diego.daniel.professional@...il.com, rppt@...nel.org, 
	pratyush@...nel.org, jasonmiu@...gle.com, graf@...zon.com, 
	dmatlack@...gle.com, rientjes@...gle.com
Subject: Re: [PATCH v1 0/3] list: add primitives for private list manipulations

On Wed, Nov 26, 2025 at 2:19 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 26 Nov 2025 13:57:22 -0500 Pasha Tatashin <pasha.tatashin@...een.com> wrote:
>
> > Recently
>
> Well, 2015, in ad315455d396, it seems.
>
> > linux introduced the ability to mark structure members as
> > __private and access them via ACCESS_PRIVATE(). This mechanism ensures
> > that internal implementation details are only accessible by the owning
> > subsystem, enforcing better encapsulation.
>
> Didn't know about this.  It's a thing which requires running sparse
> (which is fine, people run sparse).  It isn't used much at all.
>
> > However, struct list_head is frequently used as an internal linkage
> > mechanism within these private sections. The standard macros in
> > <linux/list.h> (such as list_entry and list_for_each_entry) do not
> > support ACCESS_PRIVATE() natively. Consequently, subsystems using
> > private lists are forced to implement ad-hoc workarounds, verbose
> > casting, or local iterator macros to avoid compiler warnings and access
> > violations.
> >
> > This series introduces <linux/list_private.h>, which provides a set of
> > primitives identical in function to those in <linux/list.h>, but
> > designed specifically for cases where the embedded struct list_head is a
> > private member.
> >
> > The series is structured as follows:
> > Core Implementation: Adds the list_private.h header with support for
> > entry retrieval and iteration (forward, reverse, safe, etc.).
> >
> > Testing: Adds a KUnit test suite to verify that the macros compile
> > correctly and handle pointer offsets/qualifiers as expected.
> >
> > Adoption: Updates the liveupdate subsystem to use the new generic API,
> > replacing its local luo_list_for_each_private implementation.
>
> Fair enough.  Let's push this into the next -rc cycle, OK?

Yes, this works.

Thank you,
Pasha