[PATCH 04/22] mm: use mm_is_kernel() in generic page table code

From: Kevin Brodsky <kevin.brodsky@arm.com>
To: linux-mm@kvack.org
Cc: Kevin Brodsky <kevin.brodsky@arm.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
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Subject: [PATCH 04/22] mm: use mm_is_kernel() in generic page table code
Date: Tue, 14 Jul 2026 15:03:53 +0100	[thread overview]
Message-ID: <20260714-remove_pgtable_cdtor-v1-4-44be8a7685d7@arm.com> (raw)
In-Reply-To: <20260714-remove_pgtable_cdtor-v1-0-44be8a7685d7@arm.com>

Generic page-table allocation, constructor and walker code uses
init_mm comparisons to select kernel page table handling. Use
mm_is_kernel() instead so kernel-owned mm's can share that handling
once they are marked with MMF_KERNEL.

No functional change as only init_mm has MMF_KERNEL set for now.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
 include/asm-generic/pgalloc.h | 16 ++++++++--------
 include/linux/mm.h            |  4 ++--
 mm/memory.c                   |  6 +++---
 mm/page_table_check.c         | 14 +++++++-------
 mm/pagewalk.c                 |  4 ++--
 5 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 051aa1331051..a283280e3140 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -138,7 +138,7 @@ static inline pmd_t *pmd_alloc_one_noprof(struct mm_struct *mm, unsigned long ad
 	struct ptdesc *ptdesc;
 	gfp_t gfp = GFP_PGTABLE_USER;
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		gfp = GFP_PGTABLE_KERNEL;
 	ptdesc = pagetable_alloc_noprof(gfp, 0);
 	if (!ptdesc)
@@ -148,7 +148,7 @@ static inline pmd_t *pmd_alloc_one_noprof(struct mm_struct *mm, unsigned long ad
 		return NULL;
 	}
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		ptdesc_set_kernel(ptdesc);
 
 	return ptdesc_address(ptdesc);
@@ -175,7 +175,7 @@ static inline pud_t *__pud_alloc_one_noprof(struct mm_struct *mm, unsigned long
 	gfp_t gfp = GFP_PGTABLE_USER;
 	struct ptdesc *ptdesc;
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		gfp = GFP_PGTABLE_KERNEL;
 
 	ptdesc = pagetable_alloc_noprof(gfp, 0);
@@ -184,7 +184,7 @@ static inline pud_t *__pud_alloc_one_noprof(struct mm_struct *mm, unsigned long
 
 	pagetable_pud_ctor(ptdesc);
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		ptdesc_set_kernel(ptdesc);
 
 	return ptdesc_address(ptdesc);
@@ -232,7 +232,7 @@ static inline p4d_t *__p4d_alloc_one_noprof(struct mm_struct *mm, unsigned long
 	gfp_t gfp = GFP_PGTABLE_USER;
 	struct ptdesc *ptdesc;
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		gfp = GFP_PGTABLE_KERNEL;
 
 	ptdesc = pagetable_alloc_noprof(gfp, 0);
@@ -241,7 +241,7 @@ static inline p4d_t *__p4d_alloc_one_noprof(struct mm_struct *mm, unsigned long
 
 	pagetable_p4d_ctor(ptdesc);
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		ptdesc_set_kernel(ptdesc);
 
 	return ptdesc_address(ptdesc);
@@ -279,7 +279,7 @@ static inline pgd_t *__pgd_alloc_noprof(struct mm_struct *mm, unsigned int order
 	gfp_t gfp = GFP_PGTABLE_USER;
 	struct ptdesc *ptdesc;
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		gfp = GFP_PGTABLE_KERNEL;
 
 	ptdesc = pagetable_alloc_noprof(gfp, order);
@@ -288,7 +288,7 @@ static inline pgd_t *__pgd_alloc_noprof(struct mm_struct *mm, unsigned int order
 
 	pagetable_pgd_ctor(ptdesc);
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		ptdesc_set_kernel(ptdesc);
 
 	return ptdesc_address(ptdesc);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7a4b8e7ac8f4..b336eb32faa0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3818,7 +3818,7 @@ static inline void pagetable_dtor_free(struct ptdesc *ptdesc)
 static inline bool pagetable_pte_ctor(struct mm_struct *mm,
 				      struct ptdesc *ptdesc)
 {
-	if (mm != &init_mm && !ptlock_init(ptdesc))
+	if (!mm_is_kernel(mm) && !ptlock_init(ptdesc))
 		return false;
 	__pagetable_ctor(ptdesc);
 	return true;
@@ -3909,7 +3909,7 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
 static inline bool pagetable_pmd_ctor(struct mm_struct *mm,
 				      struct ptdesc *ptdesc)
 {
-	if (mm != &init_mm && !pmd_ptlock_init(ptdesc))
+	if (!mm_is_kernel(mm) && !pmd_ptlock_init(ptdesc))
 		return false;
 	ptdesc_pmd_pts_init(ptdesc);
 	__pagetable_ctor(ptdesc);
diff --git a/mm/memory.c b/mm/memory.c
index d5e87624f692..c0244c0b0756 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3394,13 +3394,13 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 	spinlock_t *ptl;
 
 	if (create) {
-		mapped_pte = pte = (mm == &init_mm) ?
+		mapped_pte = pte = mm_is_kernel(mm) ?
 			pte_alloc_kernel_track(pmd, addr, mask) :
 			pte_alloc_map_lock(mm, pmd, addr, &ptl);
 		if (!pte)
 			return -ENOMEM;
 	} else {
-		mapped_pte = pte = (mm == &init_mm) ?
+		mapped_pte = pte = mm_is_kernel(mm) ?
 			pte_offset_kernel(pmd, addr) :
 			pte_offset_map_lock(mm, pmd, addr, &ptl);
 		if (!pte)
@@ -3422,7 +3422,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 
 	lazy_mmu_mode_disable();
 
-	if (mm != &init_mm)
+	if (!mm_is_kernel(mm))
 		pte_unmap_unlock(mapped_pte, ptl);
 	return err;
 }
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 3fb995e5d40d..a5382c245b32 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -148,7 +148,7 @@ void __page_table_check_zero(struct page *page, unsigned int order)
 void __page_table_check_pte_clear(struct mm_struct *mm, unsigned long addr,
 				  pte_t pte)
 {
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	if (pte_user_accessible_page(mm, addr, pte))
@@ -159,7 +159,7 @@ EXPORT_SYMBOL(__page_table_check_pte_clear);
 void __page_table_check_pmd_clear(struct mm_struct *mm, unsigned long addr,
 				  pmd_t pmd)
 {
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	if (pmd_user_accessible_page(mm, addr, pmd))
@@ -170,7 +170,7 @@ EXPORT_SYMBOL(__page_table_check_pmd_clear);
 void __page_table_check_pud_clear(struct mm_struct *mm, unsigned long addr,
 				  pud_t pud)
 {
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	if (pud_user_accessible_page(mm, addr, pud))
@@ -201,7 +201,7 @@ void __page_table_check_ptes_set(struct mm_struct *mm, unsigned long addr,
 {
 	unsigned int i;
 
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	page_table_check_pte_flags(pte);
@@ -231,7 +231,7 @@ void __page_table_check_pmds_set(struct mm_struct *mm, unsigned long addr,
 	unsigned long stride = PMD_SIZE >> PAGE_SHIFT;
 	unsigned int i;
 
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	page_table_check_pmd_flags(pmd);
@@ -249,7 +249,7 @@ void __page_table_check_puds_set(struct mm_struct *mm, unsigned long addr,
 	unsigned long stride = PUD_SIZE >> PAGE_SHIFT;
 	unsigned int i;
 
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	for (i = 0; i < nr; i++)
@@ -263,7 +263,7 @@ void __page_table_check_pte_clear_range(struct mm_struct *mm,
 					unsigned long addr,
 					pmd_t pmd)
 {
-	if (&init_mm == mm)
+	if (mm_is_kernel(mm))
 		return;
 
 	if (!pmd_bad(pmd) && !pmd_leaf(pmd)) {
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index ed4860c01936..a3f47d1de3c5 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -72,13 +72,13 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		 * fit its pmd_bad() check (_PAGE_NX set and _PAGE_RW clear),
 		 * and CONFIG_EFI_PGT_DUMP efi_mm goes so far as to walk them.
 		 */
-		if (walk->mm == &init_mm || addr >= TASK_SIZE)
+		if (mm_is_kernel(walk->mm) || addr >= TASK_SIZE)
 			pte = pte_offset_kernel(pmd, addr);
 		else
 			pte = pte_offset_map(pmd, addr);
 		if (pte) {
 			err = walk_pte_range_inner(pte, addr, end, walk);
-			if (walk->mm != &init_mm && addr < TASK_SIZE)
+			if (!mm_is_kernel(walk->mm) && addr < TASK_SIZE)
 				pte_unmap(pte);
 		}
 	} else {

-- 
2.51.2


