[v2,2/3] mm: Cleanup apply_to_pte_range() routine

Commit Message

Alexander Gordeev April 8, 2025, 4:07 p.m. UTC

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

Cc: [e-mail]
Fixes: 38e0edb15bd0 ("mm/apply_to_range: call pte function with lazy updates")
Signed-off-by: Alexander Gordeev <[e-mail]>
---
 mm/memory.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

Patch

diff --git a/mm/memory.c b/mm/memory.c
index 2d8c265fc7d6..f0201c8ec1ce 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2915,24 +2915,28 @@  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) {
@@ -2944,12 +2948,14 @@  static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 			}
 		} while (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;
 }