[PATCH 6.18 180/333] Revert "ptdesc: remove references to folios from __pagetable_ctor() and pagetable_dtor()"

Greg Kroah-Hartman
2026-03-17T17:20:15Z

From: Axel Rasmussen <axelrasmussen@google.com>

commit 2d28ed588f8d7d0d41b0a4fad7f0d05e4bbf1797 upstream.

This change swapped out mod_node_page_state for lruvec_stat_add_folio.
But, these two APIs are not interchangeable: the lruvec version also
increments memcg stats, in addition to "global" pgdat stats.

So after this change, the "pagetables" memcg stat in memory.stat always
yields "0", which is a userspace visible regression.

I tried to look for a refactor where we add a variant of
lruvec_stat_mod_folio which takes a pgdat and a memcg instead of a folio,
to try to adhere to the spirit of the original patch. But at the end of
the day this just means we have to call folio_memcg(ptdesc_folio(ptdesc))
anyway, which doesn't really accomplish much.

This regression is visible in master as well as 6.18 stable, so CC stable
too.

Link: https://lkml.kernel.org/r/20260225002434.2953895-1-axelrasmussen@google.com
Fixes: f0c92726e89f ("ptdesc: remove references to folios from __pagetable_ctor() and pagetable_dtor()")
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/mm.h | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3138,26 +3138,21 @@ static inline bool ptlock_init(struct pt
static inline void ptlock_free(struct ptdesc *ptdesc) {}
#endif /* defined(CONFIG_SPLIT_PTE_PTLOCKS) */

-static inline unsigned long ptdesc_nr_pages(const struct ptdesc *ptdesc)
-{
- return compound_nr(ptdesc_page(ptdesc));
-}
-
static inline void __pagetable_ctor(struct ptdesc *ptdesc)
{
- pg_data_t *pgdat = NODE_DATA(memdesc_nid(ptdesc->pt_flags));
+ struct folio *folio = ptdesc_folio(ptdesc);

- __SetPageTable(ptdesc_page(ptdesc));
- mod_node_page_state(pgdat, NR_PAGETABLE, ptdesc_nr_pages(ptdesc));
+ __folio_set_pgtable(folio);
+ lruvec_stat_add_folio(folio, NR_PAGETABLE);
}

static inline void pagetable_dtor(struct ptdesc *ptdesc)
{
- pg_data_t *pgdat = NODE_DATA(memdesc_nid(ptdesc->pt_flags));
+ struct folio *folio = ptdesc_folio(ptdesc);

ptlock_free(ptdesc);
- __ClearPageTable(ptdesc_page(ptdesc));
- mod_node_page_state(pgdat, NR_PAGETABLE, -ptdesc_nr_pages(ptdesc));
+ __folio_clear_pgtable(folio);
+ lruvec_stat_sub_folio(folio, NR_PAGETABLE);
}

static inline void pagetable_dtor_free(struct ptdesc *ptdesc)