Subject: [RFC PATCH RESEND 09/28] mm/mempolicy: mark VMA as locked when changing protection policy

From: Suren Baghdasaryan <[email-masked]>
Date: Thu, 1 Sep 2022 10:34:57 -0700

Protect VMA from concurrent page fault handler while performing VMA
protection policy changes.

Signed-off-by: Suren Baghdasaryan <[email-masked]>
---
 mm/mempolicy.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index b73d3248d976..6be1e5c75556 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -383,8 +383,10 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
 	struct vm_area_struct *vma;
 
 	mmap_write_lock(mm);
-	for (vma = mm->mmap; vma; vma = vma->vm_next)
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		vma_mark_locked(vma);
 		mpol_rebind_policy(vma->vm_policy, new);
+	}
 	mmap_write_unlock(mm);
 }
 
@@ -632,6 +634,7 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
 	struct mmu_gather tlb;
 	int nr_updated;
 
+	vma_mark_locked(vma);
 	tlb_gather_mmu(&tlb, vma->vm_mm);
 
 	nr_updated = change_protection(&tlb, vma, addr, end, PAGE_NONE,
@@ -765,6 +768,7 @@ static int vma_replace_policy(struct vm_area_struct *vma,
 	if (IS_ERR(new))
 		return PTR_ERR(new);
 
+	vma_mark_locked(vma);
 	if (vma->vm_ops && vma->vm_ops->set_policy) {
 		err = vma->vm_ops->set_policy(vma, new);
 		if (err)
-- 
2.37.2.789.g6183377224-goog