linux-kernel - [PATCH 1/6] mm: Cleanup apply_to_pte

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Message-ID: <b687f16961eaa285960d6b2c5e84360f1c3269df.1749747752.git.agordeev@linux.ibm.com>
Date: Thu, 12 Jun 2025 19:36:08 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        sparclinux@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>, Nicholas Piggin <npiggin@...il.com>,
        Guenter Roeck <linux@...ck-us.net>, Juergen Gross <jgross@...e.com>,
        Jeremy Fitzhardinge <jeremy@...p.org>,
        Ryan Roberts <ryan.roberts@....com>
Subject: [PATCH 1/6] mm: Cleanup apply_to_pte_range() routine

Reverse 'create' vs 'mm == &init_mm' conditions and move
page table mask modification out of the atomic context.
This is a prerequisite for locking kernel page tables.

Reviewed-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
---
 mm/memory.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 8eba595056fe..71b3d3f98999 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3006,24 +3006,28 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 				     pte_fn_t fn, void *data, bool create,
 				     pgtbl_mod_mask *mask)
 {
+	int err = create ? -ENOMEM : -EINVAL;
 	pte_t *pte, *mapped_pte;
-	int err = 0;
 	spinlock_t *ptl;
 
-	if (create) {
-		mapped_pte = pte = (mm == &init_mm) ?
-			pte_alloc_kernel_track(pmd, addr, mask) :
-			pte_alloc_map_lock(mm, pmd, addr, &ptl);
+	if (mm == &init_mm) {
+		if (create)
+			pte = pte_alloc_kernel_track(pmd, addr, mask);
+		else
+			pte = pte_offset_kernel(pmd, addr);
 		if (!pte)
-			return -ENOMEM;
+			return err;
 	} else {
-		mapped_pte = pte = (mm == &init_mm) ?
-			pte_offset_kernel(pmd, addr) :
-			pte_offset_map_lock(mm, pmd, addr, &ptl);
+		if (create)
+			pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
+		else
+			pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 		if (!pte)
-			return -EINVAL;
+			return err;
+		mapped_pte = pte;
 	}
 
+	err = 0;
 	arch_enter_lazy_mmu_mode();
 
 	if (fn) {
@@ -3035,12 +3039,14 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 			}
 		} while (pte++, addr += PAGE_SIZE, addr != end);
 	}
-	*mask |= PGTBL_PTE_MODIFIED;
 
 	arch_leave_lazy_mmu_mode();
 
 	if (mm != &init_mm)
 		pte_unmap_unlock(mapped_pte, ptl);
+
+	*mask |= PGTBL_PTE_MODIFIED;
+
 	return err;
 }
 
-- 
2.48.1