linux-kernel - [PATCH v4 16/33] mm/mmap: write-lock VMAs in vma

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Message-ID: <20230227173632.3292573-17-surenb@google.com>
Date:   Mon, 27 Feb 2023 09:36:15 -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,
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        peterz@...radead.org, ldufour@...ux.ibm.com, paulmck@...nel.org,
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        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 v4 16/33] mm/mmap: write-lock VMAs in vma_prepare before
 modifying them

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@...gle.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