Re: [PATCH v2 2/2] mm: Extract non-swap page handling to do_non_swap_page()

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Mon, Jul 27, 2026 at 02:16:40PM +0200, David Hildenbrand (Arm) wrote:
> On 7/27/26 14:10, Hongfu Li wrote:
> >>>  mm/memory.c | 120 ++++++++++++++++++++++++++++++----------------------
> >>>  1 file changed, 69 insertions(+), 51 deletions(-)
> >>>
> >>> diff --git a/mm/memory.c b/mm/memory.c
> >>> index ae521baa8c84..50d8e92aef91 100644
> >>> --- a/mm/memory.c
> >>> +++ b/mm/memory.c
> >>> @@ -4815,6 +4815,74 @@ static void check_swap_exclusive(struct folio *folio, swp_entry_t entry,
> >>>  	} while (--nr_pages);
> >>>  }
> >>>
> >>> +static vm_fault_t do_non_swap_page(struct vm_fault *vmf)
> >>
> >> We're handling softleaf entries that are not swap entries.
> >>
> >> do_nonswap_softleaf() or sth like that would be better than talking about "page"
> >> if there is not even a page.
> >>
> >> But actually it should be the other way around:
> >>
> >> do_softleaf_entry() [currently do_swap_page]
> >>    ... non-swap entries
> >>    do_swap_entry()
> >>
> >> Or sth like that. Then, maybe in the future, we can just move do_swap_entry()
> >> out of memory.c
> >>
> >> So we're factoring the wrong thing out in this patch.
> >
> > Thank you very much for the detailed review, your analysis makes perfect sense to me.
> >
> > I'm glad to send out v3 shortly for your further review, with
> > do_non_swap_page renamed to do_nonswap_softleaf.
>
> Read again, that's not what I meant.

Yeah please do NOT introduce 'nonswap' we already had fun with the nonswap swap
entry before :)

Quoting David:

	do_softleaf_entry() [currently do_swap_page]
		... non-swap entries
		do_swap_entry()

Also, swap entries _are_ softleaf entries.

The whole point of the softleaf change/renaming was to differentiate page
table entries that are purely there for mapping stuff from the hardware's
point of view (non-present because nothing is mapped there, present if
mapping something) vs. something non-present because the entry is
software-defined (hence SOFT-leaf).

Swap entries are software-defined and thus fall into category.

You can see all of the softleaf types trivially in include/linux/leafops.h
in enum softleaf_type:

enum softleaf_type {
	/* Fundamental types. */
	SOFTLEAF_NONE,
	SOFTLEAF_SWAP,
	/* Migration types. */
	SOFTLEAF_MIGRATION_READ,
	SOFTLEAF_MIGRATION_READ_EXCLUSIVE,
	SOFTLEAF_MIGRATION_WRITE,
	/* Device types. */
	SOFTLEAF_DEVICE_PRIVATE_READ,
	SOFTLEAF_DEVICE_PRIVATE_WRITE,
	SOFTLEAF_DEVICE_EXCLUSIVE,
	/* H/W posion types. */
	SOFTLEAF_HWPOISON,
	/* Marker types. */
	SOFTLEAF_MARKER,
};

>
> --
> Cheers,
>
> David

Cheers, Lorenzo

P.S. I do remember suggesting that you _slow down_ :) we are into the quiet
period now so let's maybe reduce the pace of series + respins, thanks.