[PATCH 07/10] mm: Introduce ctor/dtor at P4D level

Kevin Brodsky
2024-12-19T16:55:47Z

Commit 55d2a0bd5ead ("mm: add statistics for PUD level pagetable")
added accounting for PUD-level page tables. This patch does exactly
the same thing for P4D-level page tables, introducing
pagetable_p4d_[cd]tor with the same implementation as the PUD
ctor/dtor and calling them on all alloc/free paths.

Besides the small improvement in accounting accuracy, this also
enables adding construction/destruction hooks in just one generic
place for page tables at P4D level (like lower levels).

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
arch/riscv/include/asm/pgalloc.h | 8 ++++++--
arch/s390/include/asm/pgalloc.h | 12 ++++++++----
arch/x86/mm/pgtable.c | 3 +++
include/asm-generic/pgalloc.h | 2 ++
include/linux/mm.h | 10 ++++++++++
5 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index 551d614d3369..3c364ecc3100 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h
@@ -108,8 +108,12 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
static inline void __p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d,
unsigned long addr)
{
- if (pgtable_l5_enabled)
- riscv_tlb_remove_ptdesc(tlb, virt_to_ptdesc(p4d));
+ if (pgtable_l5_enabled) {
+ struct ptdesc *ptdesc = virt_to_ptdesc(p4d);
+
+ pagetable_p4d_dtor(ptdesc);
+ riscv_tlb_remove_ptdesc(tlb, ptdesc);
+ }
}
#endif /* __PAGETABLE_PMD_FOLDED */

diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h
index 97db66ae06b9..85a5d07365aa 100644
--- a/arch/s390/include/asm/pgalloc.h
+++ b/arch/s390/include/asm/pgalloc.h
@@ -53,15 +53,19 @@ static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long address)
{
unsigned long *table = crst_table_alloc(mm);

- if (table)
- crst_table_init(table, _REGION2_ENTRY_EMPTY);
+ if (!table)
+ return NULL;
+ crst_table_init(table, _REGION2_ENTRY_EMPTY);
+ pagetable_p4d_ctor(virt_to_ptdesc(table));
return (p4d_t *) table;
}

static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
{
- if (!mm_p4d_folded(mm))
- crst_table_free(mm, (unsigned long *) p4d);
+ if (mm_p4d_folded(mm))
+ return;
+ pagetable_p4d_dtor(virt_to_ptdesc(p4d));
+ crst_table_free(mm, (unsigned long *) p4d);
}

static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 5745a354a241..c1bfdf7b4767 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -86,6 +86,9 @@ void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
#if CONFIG_PGTABLE_LEVELS > 4
void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d)
{
+ struct ptdesc *ptdesc = virt_to_ptdesc(p4d);
+
+ pagetable_p4d_dtor(ptdesc);
paravirt_release_p4d(__pa(p4d) >> PAGE_SHIFT);
paravirt_tlb_remove_table(tlb, virt_to_page(p4d));
}
diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 59131629ac9c..bb482eeca0c3 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -230,6 +230,7 @@ static inline p4d_t *__p4d_alloc_one_noprof(struct mm_struct *mm, unsigned long
if (!ptdesc)
return NULL;

+ pagetable_p4d_ctor(ptdesc);
return ptdesc_address(ptdesc);
}
#define __p4d_alloc_one(...) alloc_hooks(__p4d_alloc_one_noprof(__VA_ARGS__))
@@ -247,6 +248,7 @@ static inline void __p4d_free(struct mm_struct *mm, p4d_t *p4d)
struct ptdesc *ptdesc = virt_to_ptdesc(p4d);

BUG_ON((unsigned long)p4d & (PAGE_SIZE-1));
+ pagetable_p4d_dtor(ptdesc);
pagetable_free(ptdesc);
}

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a5b482362792..e8b92f4bf3f1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3161,6 +3161,16 @@ static inline void pagetable_pud_dtor(struct ptdesc *ptdesc)
__pagetable_dtor(ptdesc);
}

+static inline void pagetable_p4d_ctor(struct ptdesc *ptdesc)
+{
+ __pagetable_ctor(ptdesc);
+}
+
+static inline void pagetable_p4d_dtor(struct ptdesc *ptdesc)
+{
+ __pagetable_dtor(ptdesc);
+}
+
extern void __init pagecache_init(void);
extern void free_initmem(void);

--
2.47.0