linux-kernel - [RFC v4 12/20] mm/spf Protect vm_policy's changes against speculative pf

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Message-Id: <1497018069-17790-13-git-send-email-ldufour@linux.vnet.ibm.com>
Date:   Fri,  9 Jun 2017 16:21:01 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill@...temov.name,
        ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
        jack@...e.cz, Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com
Subject: [RFC v4 12/20] mm/spf Protect vm_policy's changes against speculative pf

Mark the VMA touched when policy changes are applied to it so that
speculative page fault will be aborted.

Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
---
 mm/mempolicy.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 13d32c25226c..5e44b3e69a0d 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -447,8 +447,11 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
 	struct vm_area_struct *vma;
 
 	down_write(&mm->mmap_sem);
-	for (vma = mm->mmap; vma; vma = vma->vm_next)
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		write_seqcount_begin(&vma->vm_sequence);
 		mpol_rebind_policy(vma->vm_policy, new, MPOL_REBIND_ONCE);
+		write_seqcount_end(&vma->vm_sequence);
+	}
 	up_write(&mm->mmap_sem);
 }
 
@@ -711,6 +714,7 @@ static int vma_replace_policy(struct vm_area_struct *vma,
 	if (IS_ERR(new))
 		return PTR_ERR(new);
 
+	write_seqcount_begin(&vma->vm_sequence);
 	if (vma->vm_ops && vma->vm_ops->set_policy) {
 		err = vma->vm_ops->set_policy(vma, new);
 		if (err)
@@ -719,10 +723,12 @@ static int vma_replace_policy(struct vm_area_struct *vma,
 
 	old = vma->vm_policy;
 	vma->vm_policy = new; /* protected by mmap_sem */
+	write_seqcount_end(&vma->vm_sequence);
 	mpol_put(old);
 
 	return 0;
  err_out:
+	write_seqcount_end(&vma->vm_sequence);
 	mpol_put(new);
 	return err;
 }
-- 
2.7.4