Le 03/08/2026 à 18:43, Pedro Falcato a écrit :
Since forever, MM code has thrown pte_t * around with no concern for const
safety, or typesafety of any kind. This is confusing. Attempt to address it
by:
What do you mean by "typesafety of any kind" ?
On powerpc64, pte_t is a struct so you can't play-up too much with it.
On powerpc32, pte_t is a long int because having it as a struct is
counter-performant, but we have it as a struct when __CHECKER__ is
defined, ie when doing a sparse check with 'make C=2'.
1) Making sure pte_get*() helpers can cope with const pte_t * arguments
2) Constifying the pte_offset_map_ro_nolock() return type, which by definition
already pledges that users will not write to it.
These two simple steps were already able to uncover code smell from
khugepaged + do_swap_page().
Separate steps could include introducing pte_offset_map_ro_lock() for more
widespread usage of this.
Benefits of this include less confusion and better type-safety. It could also
futurely aid in efforts such as [0] which may want semantic annotation of these
accesses.
Based on mm-unstable and compile-tested on a handful of architectures.
No functional changes intended.
For the series,
Reviewed-by: Christophe Leroy (CS GROUP) <[email protected]>
[CC list editorially trimmed for brevity reasons; apologies if you're not on it]
Link:
https://lore.kernel.org/linux-mm/[email protected]/#t
[0]
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: "Liam R. Howlett" <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Nico Pache <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Muhammad Usama Anjum <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
v2:
- Small fixups on the arm64 side
- Re-order patches in a way such that bisection is preserved
- Pick up Helge's patch dropping parisc ptep_get()
- Constify s390's ptep_get() as well
Helge Deller (1):
parisc: Drop own implementations for ptep_get() and
ptep_test_and_clear_young()
Pedro Falcato (5):
mm/arm64: constify pte_get*() and contpte get logic
mm/powerpc/8xx: constify ptep_get() argument
mm/s390: constify ptep_get() argument
mm: constify generic pte_get*()
mm: constify the pte_offset_map_ro_nolock() return value
arch/arm64/include/asm/pgtable.h | 10 +++++-----
arch/arm64/mm/contpte.c | 11 ++++++++---
arch/parisc/include/asm/pgtable.h | 20 --------------------
arch/powerpc/include/asm/nohash/32/pte-8xx.h | 2 +-
arch/powerpc/mm/pgtable.c | 2 +-
arch/s390/include/asm/pgtable.h | 2 +-
include/linux/mm.h | 4 ++--
include/linux/pgtable.h | 8 ++++----
mm/filemap.c | 2 +-
mm/khugepaged.c | 2 +-
mm/pgtable-generic.c | 4 ++--
11 files changed, 26 insertions(+), 41 deletions(-)
