Commit 2d28ed58 authored by Axel Rasmussen's avatar Axel Rasmussen Committed by Andrew Morton
Browse files

Revert "ptdesc: remove references to folios from __pagetable_ctor() and pagetable_dtor()" 

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: f0c92726 ("ptdesc: remove references to folios from __pagetable_ctor() and pagetable_dtor()")
Signed-off-by: default avatarAxel Rasmussen <axelrasmussen@google.com>
Acked-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarVishal 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f4355d6b

include/linux/mm.h

+6 −11
Original line number Diff line number Diff line
@@ -3514,26 +3514,21 @@ static inline bool ptlock_init(struct ptdesc *ptdesc) { return true; } 
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)