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

[Muchun Song <songmuchun@bytedance.com>]

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