linux-kernel - [PATCH v3 17/35] mm/mmap: write-lock VMA before shrinking or expanding it

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Date:   Wed, 15 Feb 2023 21:17:32 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
        vbabka@...e.cz, hannes@...xchg.org, mgorman@...hsingularity.net,
        dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com,
        peterz@...radead.org, ldufour@...ux.ibm.com, paulmck@...nel.org,
        mingo@...hat.com, will@...nel.org, luto@...nel.org,
        songliubraving@...com, peterx@...hat.com, david@...hat.com,
        dhowells@...hat.com, hughd@...gle.com, bigeasy@...utronix.de,
        kent.overstreet@...ux.dev, punit.agrawal@...edance.com,
        lstoakes@...il.com, peterjung1337@...il.com, rientjes@...gle.com,
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        gthelen@...gle.com, gurua@...gle.com, arjunroy@...gle.com,
        soheil@...gle.com, leewalsh@...gle.com, posk@...gle.com,
        michalechner92@...glemail.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH v3 17/35] mm/mmap: write-lock VMA before shrinking or
 expanding it

vma_expand and vma_shrink change VMA boundaries. Expansion might also
result in freeing of an adjacent VMA. Write-lock affected VMAs to prevent
concurrent page faults.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 mm/mmap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index ec2f8d0af280..f079e5bbcd57 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -674,6 +674,9 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		ret = dup_anon_vma(vma, next);
 		if (ret)
 			return ret;
+
+		/* Lock the VMA  before removing it */
+		vma_start_write(next);
 	}
 
 	init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
@@ -686,6 +689,7 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	if (vma_iter_prealloc(vmi))
 		goto nomem;
 
+	vma_start_write(vma);
 	vma_adjust_trans_huge(vma, start, end, 0);
 	/* VMA iterator points to previous, so set to start if necessary */
 	if (vma_iter_addr(vmi) != start)
@@ -725,6 +729,7 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	if (vma_iter_prealloc(vmi))
 		return -ENOMEM;
 
+	vma_start_write(vma);
 	init_vma_prep(&vp, vma);
 	vma_adjust_trans_huge(vma, start, end, 0);
 	vma_prepare(&vp);
-- 
2.39.1