[PATCH 2/3] mm: generalize PMD page table allocation
From: Muchun Song
Date: Wed Oct 14 2026 - 00:00:20 EST
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@xxxxxxxxxxxxx>
---
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