Since [1], constructors/destructors are expected to be called for all page table pages, at all levels and for both user and kernel pgtables. There is however one glaring exception: kernel PTEs are managed via separate helpers (pte_alloc_kernel/pte_free_kernel), which do not call the [cd]tor, at least not in the generic implementation. The most obvious reason for this anomaly is that init_mm is special-cased not to use split page table locks. As a result calling ptlock_init() for PTEs associated with init_mm would be wasteful, potentially resulting in dynamic memory allocation. However, pgtable [cd]tors perform other actions - currently related to accounting/statistics, and potentially more functionally significant in the future. Now that pagetable_pte_ctor() is passed the associated mm, we can make it skip the call to ptlock_init() for init_mm; this allows us to call the ctor from pte_alloc_one_kernel() too. This is matched by a call to the pgtable destructor in pte_free_kernel(); no special-casing is needed on that path, as ptlock_free() is already called unconditionally. (ptlock_free() is a no-op unless a ptlock was allocated for the given PTP.) This patch ensures that all architectures that rely on <asm-generic/pgalloc.h> call the [cd]tor for kernel PTEs. pte_free_kernel() cannot be overridden so changing the generic implementation is sufficient. pte_alloc_one_kernel() can be overridden using __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL, and a few architectures implement it by calling the page allocator directly. We amend those so that they call the generic __pte_alloc_one_kernel() instead, if possible, ensuring that the ctor is called. A few architectures do not use <asm-generic/pgalloc.h>; those will be taken care of separately. [1] https://lore.kernel.org/linux-mm/20250103184415.2744423-1-kevin.brodsky@xxxxxxx/ Signed-off-by: Kevin Brodsky <kevin.brodsky@xxxxxxx> --- arch/csky/include/asm/pgalloc.h | 2 +- arch/microblaze/mm/pgtable.c | 2 +- arch/openrisc/mm/ioremap.c | 2 +- include/asm-generic/pgalloc.h | 7 ++++++- include/linux/mm.h | 2 +- 5 files changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/csky/include/asm/pgalloc.h b/arch/csky/include/asm/pgalloc.h index bf8400c28b5a..288dca0d160a 100644 --- a/arch/csky/include/asm/pgalloc.h +++ b/arch/csky/include/asm/pgalloc.h @@ -29,7 +29,7 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm) pte_t *pte; unsigned long i; - pte = (pte_t *) __get_free_page(GFP_KERNEL); + pte = __pte_alloc_one_kernel(mm); if (!pte) return NULL; diff --git a/arch/microblaze/mm/pgtable.c b/arch/microblaze/mm/pgtable.c index 9f73265aad4e..e96dd1b7aba4 100644 --- a/arch/microblaze/mm/pgtable.c +++ b/arch/microblaze/mm/pgtable.c @@ -245,7 +245,7 @@ unsigned long iopa(unsigned long addr) __ref pte_t *pte_alloc_one_kernel(struct mm_struct *mm) { if (mem_init_done) - return (pte_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO); + return __pte_alloc_one_kernel(mm); else return memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE, MEMBLOCK_LOW_LIMIT, diff --git a/arch/openrisc/mm/ioremap.c b/arch/openrisc/mm/ioremap.c index 8e63e86251ca..3b352f97fecb 100644 --- a/arch/openrisc/mm/ioremap.c +++ b/arch/openrisc/mm/ioremap.c @@ -36,7 +36,7 @@ pte_t __ref *pte_alloc_one_kernel(struct mm_struct *mm) pte_t *pte; if (likely(mem_init_done)) { - pte = (pte_t *)get_zeroed_page(GFP_KERNEL); + pte = __pte_alloc_one_kernel(mm); } else { pte = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE); } diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h index e164ca66f0f6..3c8ec3bfea44 100644 --- a/include/asm-generic/pgalloc.h +++ b/include/asm-generic/pgalloc.h @@ -23,6 +23,11 @@ static inline pte_t *__pte_alloc_one_kernel_noprof(struct mm_struct *mm) if (!ptdesc) return NULL; + if (!pagetable_pte_ctor(mm, ptdesc)) { + pagetable_free(ptdesc); + return NULL; + } + return ptdesc_address(ptdesc); } #define __pte_alloc_one_kernel(...) alloc_hooks(__pte_alloc_one_kernel_noprof(__VA_ARGS__)) @@ -48,7 +53,7 @@ static inline pte_t *pte_alloc_one_kernel_noprof(struct mm_struct *mm) */ static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte) { - pagetable_free(virt_to_ptdesc(pte)); + pagetable_dtor_free(virt_to_ptdesc(pte)); } /** diff --git a/include/linux/mm.h b/include/linux/mm.h index d92c16f6cfa2..ee31ffd7ead2 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3018,7 +3018,7 @@ static inline void pagetable_dtor_free(struct ptdesc *ptdesc) static inline bool pagetable_pte_ctor(struct mm_struct *mm, struct ptdesc *ptdesc) { - if (!ptlock_init(ptdesc)) + if (mm != &init_mm && !ptlock_init(ptdesc)) return false; __pagetable_ctor(ptdesc); return true; -- 2.47.0
