[PATCH 0/3] mm: Generalize page table allocation helpers

[PATCH 0/3] mm: Generalize page table allocation helpers

[Muchun Song]

A subsequent series will switch runtime vmemmap population to the
generic page-table allocators. Since vmemmap tables belong to init_mm,
the allocators must select GFP_PGTABLE_KERNEL and mark the ptdesc as a
kernel page table.

Some architecture-specific allocators do not preserve both semantics.
LoongArch and MIPS choose PMD/PUD GFP flags without checking the mm,
which can charge kernel PMD tables to a memcg and leave user PUD tables
unaccounted. The private PMD/PUD allocators also omit kernel ptdesc
marking.

Rather than duplicate this handling in each architecture, extend the
generic PTE, PMD and PUD allocators to support architecture
initialization hooks and non-zero table orders. LoongArch, MIPS and
parisc can then drop their private allocators and inherit the generic
GFP selection and ptdesc handling.

This series only prepares the allocation interfaces; the runtime
vmemmap conversion will be submitted separately.

Muchun Song (3):
  mm: generalize kernel PTE table allocation
  mm: generalize PMD page table allocation
  mm: generalize PUD page table allocation

 arch/loongarch/include/asm/pgalloc.h | 48 ----------------------------
 arch/mips/include/asm/pgalloc.h      | 40 -----------------------
 arch/parisc/include/asm/pgalloc.h    | 17 ----------
 include/asm-generic/pgalloc.h        | 29 ++++++++++++++---
 4 files changed, 24 insertions(+), 110 deletions(-)


base-commit: ad9f2d463666c64e94b04be5263c9bf8f9f96fb7
-- 
2.54.0

[PATCH 1/3] mm: generalize kernel PTE table allocation

[Muchun Song]

Architectures whose empty kernel PTE representation is not all zero must
initialize new kernel PTE tables. LoongArch therefore wraps
__pte_alloc_one_kernel() solely to call kernel_pte_init().

Call the architecture initialization hook from the generic allocator so
LoongArch can use it directly. The default hook is empty, so this does not
change other architectures.

Assisted-by: LLM
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 arch/loongarch/include/asm/pgalloc.h | 11 -----------
 include/asm-generic/pgalloc.h        |  6 +++++-
 2 files changed, 5 insertions(+), 12 deletions(-)

diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
index 248f62d0b590..a3f93a8b58be 100644
--- a/arch/loongarch/include/asm/pgalloc.h
+++ b/arch/loongarch/include/asm/pgalloc.h
@@ -10,7 +10,6 @@
 
 #define __HAVE_ARCH_PMD_ALLOC_ONE
 #define __HAVE_ARCH_PUD_ALLOC_ONE
-#define __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
 #include <asm-generic/pgalloc.h>
 
 static inline void pmd_populate_kernel(struct mm_struct *mm,
@@ -45,16 +44,6 @@ extern void pagetable_init(void);
 
 extern pgd_t *pgd_alloc(struct mm_struct *mm);
 
-static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
-{
-	pte_t *pte = __pte_alloc_one_kernel(mm);
-
-	if (pte)
-		kernel_pte_init(pte);
-
-	return pte;
-}
-
 #define __pte_free_tlb(tlb, pte, address)	tlb_remove_ptdesc((tlb), page_ptdesc(pte))
 
 #ifndef __PAGETABLE_PMD_FOLDED
diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 051aa1331051..a1de7d246754 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -19,6 +19,7 @@
 static inline pte_t *__pte_alloc_one_kernel_noprof(struct mm_struct *mm)
 {
 	struct ptdesc *ptdesc = pagetable_alloc_noprof(GFP_PGTABLE_KERNEL, 0);
+	pte_t *pte;
 
 	if (!ptdesc)
 		return NULL;
@@ -29,7 +30,10 @@ static inline pte_t *__pte_alloc_one_kernel_noprof(struct mm_struct *mm)
 
 	ptdesc_set_kernel(ptdesc);
 
-	return ptdesc_address(ptdesc);
+	pte = ptdesc_address(ptdesc);
+	kernel_pte_init(pte);
+
+	return pte;
 }
 #define __pte_alloc_one_kernel(...)	alloc_hooks(__pte_alloc_one_kernel_noprof(__VA_ARGS__))
 
-- 
2.54.0

[PATCH 2/3] mm: generalize PMD page table allocation

[Muchun Song]

The generic PMD allocator assumes order-0 page tables and zero-valued
empty entries. MIPS and LoongArch need pmd_init() to install their invalid
entries, while MIPS and parisc use PMD_TABLE_ORDER to describe the
allocation size.

Default PMD_TABLE_ORDER to zero, honor architecture overrides, and invoke
pmd_init() from the generic allocator. MIPS, LoongArch, and parisc can then
use the generic GFP selection, constructor handling, and kernel ptdesc
marking instead of duplicating most of the helper.

Assisted-by: LLM
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 arch/loongarch/include/asm/pgalloc.h | 21 ---------------------
 arch/mips/include/asm/pgalloc.h      | 25 -------------------------
 arch/parisc/include/asm/pgalloc.h    | 17 -----------------
 include/asm-generic/pgalloc.h        | 12 ++++++++++--
 4 files changed, 10 insertions(+), 65 deletions(-)

diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
index a3f93a8b58be..1fc9a0751f19 100644
--- a/arch/loongarch/include/asm/pgalloc.h
+++ b/arch/loongarch/include/asm/pgalloc.h
@@ -8,7 +8,6 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 
-#define __HAVE_ARCH_PMD_ALLOC_ONE
 #define __HAVE_ARCH_PUD_ALLOC_ONE
 #include <asm-generic/pgalloc.h>
 
@@ -47,26 +46,6 @@ extern pgd_t *pgd_alloc(struct mm_struct *mm);
 #define __pte_free_tlb(tlb, pte, address)	tlb_remove_ptdesc((tlb), page_ptdesc(pte))
 
 #ifndef __PAGETABLE_PMD_FOLDED
-
-static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
-{
-	pmd_t *pmd;
-	struct ptdesc *ptdesc;
-
-	ptdesc = pagetable_alloc(GFP_KERNEL_ACCOUNT, 0);
-	if (!ptdesc)
-		return NULL;
-
-	if (!pagetable_pmd_ctor(mm, ptdesc)) {
-		pagetable_free(ptdesc);
-		return NULL;
-	}
-
-	pmd = ptdesc_address(ptdesc);
-	pmd_init(pmd);
-	return pmd;
-}
-
 #define __pmd_free_tlb(tlb, x, addr)	tlb_remove_ptdesc((tlb), virt_to_ptdesc(x))
 
 #endif
diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
index 9ec9cf01e92e..2f123455e363 100644
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -13,7 +13,6 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 
-#define __HAVE_ARCH_PMD_ALLOC_ONE
 #define __HAVE_ARCH_PUD_ALLOC_ONE
 #include <asm-generic/pgalloc.h>
 
@@ -29,11 +28,6 @@ static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd,
 	set_pmd(pmd, __pmd((unsigned long)page_address(pte)));
 }
 
-/*
- * Initialize a new pmd table with invalid pointers.
- */
-extern void pmd_init(void *addr);
-
 #ifndef __PAGETABLE_PMD_FOLDED
 
 static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
@@ -52,25 +46,6 @@ extern pgd_t *pgd_alloc(struct mm_struct *mm);
 
 #ifndef __PAGETABLE_PMD_FOLDED
 
-static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
-{
-	pmd_t *pmd;
-	struct ptdesc *ptdesc;
-
-	ptdesc = pagetable_alloc(GFP_KERNEL_ACCOUNT, PMD_TABLE_ORDER);
-	if (!ptdesc)
-		return NULL;
-
-	if (!pagetable_pmd_ctor(mm, ptdesc)) {
-		pagetable_free(ptdesc);
-		return NULL;
-	}
-
-	pmd = ptdesc_address(ptdesc);
-	pmd_init(pmd);
-	return pmd;
-}
-
 #define __pmd_free_tlb(tlb, x, addr)	tlb_remove_ptdesc((tlb), virt_to_ptdesc(x))
 
 #endif
diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
index 3b84ee93edaa..880a3e9ad0cb 100644
--- a/arch/parisc/include/asm/pgalloc.h
+++ b/arch/parisc/include/asm/pgalloc.h
@@ -10,7 +10,6 @@
 
 #include <asm/cache.h>
 
-#define __HAVE_ARCH_PMD_ALLOC_ONE
 #include <asm-generic/pgalloc.h>
 
 /* Allocate the top level pgd (page directory) */
@@ -29,22 +28,6 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
 			(__u32)(__pa((unsigned long)pmd) >> PxD_VALUE_SHIFT)));
 }
 
-static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
-{
-	struct ptdesc *ptdesc;
-	gfp_t gfp = GFP_PGTABLE_USER;
-
-	if (mm == &init_mm)
-		gfp = GFP_PGTABLE_KERNEL;
-	ptdesc = pagetable_alloc(gfp, PMD_TABLE_ORDER);
-	if (!ptdesc)
-		return NULL;
-	if (!pagetable_pmd_ctor(mm, ptdesc)) {
-		pagetable_free(ptdesc);
-		return NULL;
-	}
-	return ptdesc_address(ptdesc);
-}
 #endif
 
 static inline void
diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index a1de7d246754..68e473908758 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -125,6 +125,10 @@ static inline void pte_free(struct mm_struct *mm, struct page *pte_page)
 
 #if CONFIG_PGTABLE_LEVELS > 2
 
+#ifndef PMD_TABLE_ORDER
+#define PMD_TABLE_ORDER	0
+#endif
+
 #ifndef __HAVE_ARCH_PMD_ALLOC_ONE
 /**
  * pmd_alloc_one - allocate memory for a PMD-level page table
@@ -140,11 +144,12 @@ static inline void pte_free(struct mm_struct *mm, struct page *pte_page)
 static inline pmd_t *pmd_alloc_one_noprof(struct mm_struct *mm, unsigned long addr)
 {
 	struct ptdesc *ptdesc;
+	pmd_t *pmd;
 	gfp_t gfp = GFP_PGTABLE_USER;
 
 	if (mm == &init_mm)
 		gfp = GFP_PGTABLE_KERNEL;
-	ptdesc = pagetable_alloc_noprof(gfp, 0);
+	ptdesc = pagetable_alloc_noprof(gfp, PMD_TABLE_ORDER);
 	if (!ptdesc)
 		return NULL;
 	if (!pagetable_pmd_ctor(mm, ptdesc)) {
@@ -152,10 +157,13 @@ static inline pmd_t *pmd_alloc_one_noprof(struct mm_struct *mm, unsigned long ad
 		return NULL;
 	}
 
+	pmd = ptdesc_address(ptdesc);
+	pmd_init(pmd);
+
 	if (mm == &init_mm)
 		ptdesc_set_kernel(ptdesc);
 
-	return ptdesc_address(ptdesc);
+	return pmd;
 }
 #define pmd_alloc_one(...)	alloc_hooks(pmd_alloc_one_noprof(__VA_ARGS__))
 #endif
-- 
2.54.0

[PATCH 3/3] mm: generalize PUD page table allocation

[Muchun Song]

The generic PUD allocator assumes order-0 page tables and zero-valued empty
entries. MIPS and LoongArch need pud_init() to install their invalid
entries. MIPS also uses PUD_TABLE_ORDER to describe the allocation size.

Default PUD_TABLE_ORDER to zero, honor architecture overrides, and invoke
pud_init() from the generic allocator. MIPS and LoongArch can then drop
their duplicate helpers and use the generic constructor handling and kernel
ptdesc marking.

This also switches their user PUD allocations from GFP_KERNEL to
GFP_PGTABLE_USER, so they are accounted to the active memory cgroup
context. Allocations for init_mm continue to use GFP_PGTABLE_KERNEL.

Assisted-by: LLM
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 arch/loongarch/include/asm/pgalloc.h | 16 ----------------
 arch/mips/include/asm/pgalloc.h      | 15 ---------------
 include/asm-generic/pgalloc.h        | 11 +++++++++--
 3 files changed, 9 insertions(+), 33 deletions(-)

diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
index 1fc9a0751f19..06a36da302d3 100644
--- a/arch/loongarch/include/asm/pgalloc.h
+++ b/arch/loongarch/include/asm/pgalloc.h
@@ -8,7 +8,6 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 
-#define __HAVE_ARCH_PUD_ALLOC_ONE
 #include <asm-generic/pgalloc.h>
 
 static inline void pmd_populate_kernel(struct mm_struct *mm,
@@ -51,21 +50,6 @@ extern pgd_t *pgd_alloc(struct mm_struct *mm);
 #endif
 
 #ifndef __PAGETABLE_PUD_FOLDED
-
-static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
-{
-	pud_t *pud;
-	struct ptdesc *ptdesc = pagetable_alloc(GFP_KERNEL, 0);
-
-	if (!ptdesc)
-		return NULL;
-	pagetable_pud_ctor(ptdesc);
-	pud = ptdesc_address(ptdesc);
-
-	pud_init(pud);
-	return pud;
-}
-
 #define __pud_free_tlb(tlb, x, addr)	tlb_remove_ptdesc((tlb), virt_to_ptdesc(x))
 
 #endif /* __PAGETABLE_PUD_FOLDED */
diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
index 2f123455e363..4346802e283f 100644
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -13,7 +13,6 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 
-#define __HAVE_ARCH_PUD_ALLOC_ONE
 #include <asm-generic/pgalloc.h>
 
 static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd,
@@ -52,20 +51,6 @@ extern pgd_t *pgd_alloc(struct mm_struct *mm);
 
 #ifndef __PAGETABLE_PUD_FOLDED
 
-static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
-{
-	pud_t *pud;
-	struct ptdesc *ptdesc = pagetable_alloc(GFP_KERNEL, PUD_TABLE_ORDER);
-
-	if (!ptdesc)
-		return NULL;
-	pagetable_pud_ctor(ptdesc);
-	pud = ptdesc_address(ptdesc);
-
-	pud_init(pud);
-	return pud;
-}
-
 static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4d, pud_t *pud)
 {
 	set_p4d(p4d, __p4d((unsigned long)pud));
diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 68e473908758..cc8445e6078d 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -182,24 +182,31 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
 
 #if CONFIG_PGTABLE_LEVELS > 3
 
+#ifndef PUD_TABLE_ORDER
+#define PUD_TABLE_ORDER	0
+#endif
+
 static inline pud_t *__pud_alloc_one_noprof(struct mm_struct *mm, unsigned long addr)
 {
 	gfp_t gfp = GFP_PGTABLE_USER;
 	struct ptdesc *ptdesc;
+	pud_t *pud;
 
 	if (mm == &init_mm)
 		gfp = GFP_PGTABLE_KERNEL;
 
-	ptdesc = pagetable_alloc_noprof(gfp, 0);
+	ptdesc = pagetable_alloc_noprof(gfp, PUD_TABLE_ORDER);
 	if (!ptdesc)
 		return NULL;
 
 	pagetable_pud_ctor(ptdesc);
+	pud = ptdesc_address(ptdesc);
+	pud_init(pud);
 
 	if (mm == &init_mm)
 		ptdesc_set_kernel(ptdesc);
 
-	return ptdesc_address(ptdesc);
+	return pud;
 }
 #define __pud_alloc_one(...)	alloc_hooks(__pud_alloc_one_noprof(__VA_ARGS__))
 
-- 
2.54.0

Re: [PATCH 0/3] mm: Generalize page table allocation helpers

[Mike Rapoport]

On Wed, Oct 14, 2026 at 11:59:07AM +0800, Muchun Song wrote:
> A subsequent series will switch runtime vmemmap population to the
> generic page-table allocators. Since vmemmap tables belong to init_mm,
> the allocators must select GFP_PGTABLE_KERNEL and mark the ptdesc as a
> kernel page table.
> 
> Some architecture-specific allocators do not preserve both semantics.
> LoongArch and MIPS choose PMD/PUD GFP flags without checking the mm,
> which can charge kernel PMD tables to a memcg and leave user PUD tables
> unaccounted. The private PMD/PUD allocators also omit kernel ptdesc
> marking.
> 
> Rather than duplicate this handling in each architecture, extend the
> generic PTE, PMD and PUD allocators to support architecture
> initialization hooks and non-zero table orders. LoongArch, MIPS and
> parisc can then drop their private allocators and inherit the generic
> GFP selection and ptdesc handling.
> 
> This series only prepares the allocation interfaces; the runtime
> vmemmap conversion will be submitted separately.
> 
> Muchun Song (3):
>   mm: generalize kernel PTE table allocation
>   mm: generalize PMD page table allocation
>   mm: generalize PUD page table allocation

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

>  arch/loongarch/include/asm/pgalloc.h | 48 ----------------------------
>  arch/mips/include/asm/pgalloc.h      | 40 -----------------------
>  arch/parisc/include/asm/pgalloc.h    | 17 ----------
>  include/asm-generic/pgalloc.h        | 29 ++++++++++++++---
>  4 files changed, 24 insertions(+), 110 deletions(-)
> 
> 
> base-commit: ad9f2d463666c64e94b04be5263c9bf8f9f96fb7
> -- 
> 2.54.0
> 

-- 
Sincerely yours,
Mike.