Re: [PATCH v1 1/2] mm: move pte table reclaim code to memory.c

[David Hildenbrand (Red Hat)]

On 1/20/26 12:19, Kiryl Shutsemau wrote:
> On Mon, Jan 19, 2026 at 11:07:07PM +0100, David Hildenbrand (Red Hat) wrote:
> > The pte-table reclaim code is only called from memory.c, while zapping
> > pages, and it better also stays that way in the long run. If we ever
> > have to call it from other files, we should expose proper high-level
> > helpers for zapping if the existing helpers are not good enough.
> >
> > So, let's move the code over (it's not a lot) and slightly clean it up a
> > bit by:
> > - Renaming the functions.
> > - Dropping the "Check if it is empty PTE page" comment, which is now
> >    self-explaining given the function name.
> > - Making zap_pte_table_if_empty() return whether zapping worked so the
> >    caller can free it.
> > - Adding a comment in pte_table_reclaim_possible().
> > - Inlining free_pte() in the last remaining user.
> > - In zap_empty_pte_table(), switch from pmdp_get_lcokless() to
> >    pmd_clear(), we are holding the PMD PT lock.
> >
> > By moving the code over, compilers can also easily figure out when
> > zap_empty_pte_table() does not initialize the pmdval variable, avoiding
> > false-positive warnings about the variable possibly not being
> > initialized.
>
> mm/memory.c is a kitchen sink as it is.
>
> I think you miss opportunity to introduce mm/zap.c and move all zap
> code.
>
> It can be done for code from both mm/memory.c and mm/huge_memory.c.
> Line between THP and non-THP code gets more and more blurry over time.
>
> The same can be done for copy and fault code. I think it is going to be
> more maintainable this way.

While agree that memory.c contains too much stuff, I don't think zap.c 
is the right abstraction either. And actually, I think basic page table 
handling is well kept in memory.c, or moved along with other stuff 
(fork()) handling somewhere else.

So I won't do any of that as part of this patch.

--
Cheers

David