Date:   Wed, 15 Feb 2023 21:17:37 -0800
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Subject: [PATCH v3 22/35] kernel/fork: assert no VMA readers during its destruction
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,
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        michalechner92@googlemail.com, linux-mm@kvack.org,
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        Suren Baghdasaryan <surenb@google.com>
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Assert there are no holders of VMA lock for reading when it is about to be
destroyed.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 kernel/fork.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/fork.c b/kernel/fork.c
index 9141427a98b2..a08cc0e2bfde 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -491,6 +491,9 @@ static void vm_area_free_rcu_cb(struct rcu_head *head)
 {
 	struct vm_area_struct *vma = container_of(head, struct vm_area_struct,
 						  vm_rcu);
+
+	/* The vma should not be locked while being destroyed. */
+	VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock), vma);
 	__vm_area_free(vma);
 }
 #endif
-- 
2.39.1