linux-kernel - [PATCH] mm/rmap: replace BUG_ON(anon_vma->degree) with VM_WARN

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Date:	Thu, 31 Mar 2016 11:57:10 +0300
From:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH] mm/rmap: replace BUG_ON(anon_vma->degree) with VM_WARN_ON

This check effectively catches anon vma hierarchy inconsistence and some
vma corruptions. It was effective for catching corner cases in anon vma
reusing logic. For now this code seems stable so check could be hidden
under CONFIG_DEBUG_VM and replaced with WARN because it's not so fatal.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Suggested-by: Vasily Averin <vvs@...tuozzo.com>
---
 mm/rmap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 395e314b7996..a8d52d3f40ed 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -409,7 +409,7 @@ void unlink_anon_vmas(struct vm_area_struct *vma)
 	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
 		struct anon_vma *anon_vma = avc->anon_vma;
 
-		BUG_ON(anon_vma->degree);
+		VM_WARN_ON(anon_vma->degree);
 		put_anon_vma(anon_vma);
 
 		list_del(&avc->same_vma);