Date:   Mon, 27 Feb 2023 09:36:15 -0800
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Subject: [PATCH v4 16/33] mm/mmap: write-lock VMAs in vma_prepare before
 modifying them
From:   Suren Baghdasaryan <surenb@google.com>
To:     akpm@linux-foundation.org
Cc:     michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
        vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
        dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
        peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org,
        mingo@redhat.com, will@kernel.org, luto@kernel.org,
        songliubraving@fb.com, peterx@redhat.com, david@redhat.com,
        dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de,
        kent.overstreet@linux.dev, punit.agrawal@bytedance.com,
        lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com,
        chriscli@google.com, axelrasmussen@google.com, joelaf@google.com,
        minchan@google.com, rppt@kernel.org, jannh@google.com,
        shakeelb@google.com, tatashin@google.com, edumazet@google.com,
        gthelen@google.com, gurua@google.com, arjunroy@google.com,
        soheil@google.com, leewalsh@google.com, posk@google.com,
        michalechner92@googlemail.com, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, kernel-team@android.com,
        Suren Baghdasaryan <surenb@google.com>
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Precedence: bulk

Write-lock all VMAs which might be affected by a merge, split, expand
or shrink operations. All these operations use vma_prepare() before
making the modifications, therefore it provides a centralized place to
perform VMA locking.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 mm/mmap.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 92893d86c0af..e73fbb84ce12 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -502,6 +502,16 @@ static inline void init_vma_prep(struct vma_prepare *vp,
  */
 static inline void vma_prepare(struct vma_prepare *vp)
 {
+	if (vp->vma)
+		vma_start_write(vp->vma);
+	if (vp->adj_next)
+		vma_start_write(vp->adj_next);
+	/* vp->insert is always a newly created VMA, no need for locking */
+	if (vp->remove)
+		vma_start_write(vp->remove);
+	if (vp->remove2)
+		vma_start_write(vp->remove2);
+
 	if (vp->file) {
 		uprobe_munmap(vp->vma, vp->vma->vm_start, vp->vma->vm_end);
 
-- 
2.39.2.722.g9855ee24e9-goog