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

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Date:	Thu, 31 Mar 2016 14:49:18 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	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: Re: [PATCH] mm/rmap: replace BUG_ON(anon_vma->degree) with VM_WARN_ON

On 03/31/2016 10:57 AM, Konstantin Khlebnikov wrote:
> 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>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>   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);
>
> --
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