linux-kernel - [PATCH] mm: add access/dirty bit on numa page fault

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Date:   Tue, 15 Mar 2022 21:08:36 -0400
From:   Bibo Mao <maobibo@...ngson.cn>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mm: add access/dirty bit on numa page fault

During numa page fault, dirty bit can be added for old pte if
fail to migrate on write fault. And if it succeeds to migrate,
access bit can be added for migrated new pte, also dirty bit
can be added for write fault.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 mm/memory.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index c125c4969913..65813bec9c06 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4404,6 +4404,22 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	if (migrate_misplaced_page(page, vma, target_nid)) {
 		page_nid = target_nid;
 		flags |= TNF_MIGRATED;
+
+		/*
+		 * update pte entry with access bit, and dirty bit for
+		 * write fault
+		 */
+		spin_lock(vmf->ptl);
+		pte = *vmf->pte;
+		pte = pte_mkyoung(pte);
+		if (was_writable) {
+			pte = pte_mkwrite(pte);
+			if (vmf->flags & FAULT_FLAG_WRITE)
+				pte = pte_mkdirty(pte);
+		}
+		set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
+		update_mmu_cache(vma, vmf->address, vmf->pte);
+		pte_unmap_unlock(vmf->pte, vmf->ptl);
 	} else {
 		flags |= TNF_MIGRATE_FAIL;
 		vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
@@ -4427,8 +4443,11 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
 	pte = pte_modify(old_pte, vma->vm_page_prot);
 	pte = pte_mkyoung(pte);
-	if (was_writable)
+	if (was_writable) {
 		pte = pte_mkwrite(pte);
+		if (vmf->flags & FAULT_FLAG_WRITE)
+			pte = pte_mkdirty(pte);
+	}
 	ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
 	update_mmu_cache(vma, vmf->address, vmf->pte);
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
-- 
2.31.1