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Date: Wed, 25 Jun 2014 15:03:18 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: linux-mm@kvack.org, Hugh Dickins <hughd@google.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm: catch memory commitment underflow
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On Wed, 25 Jun 2014 00:16:14 +0400 Konstantin Khlebnikov <koct9i@gmail.com> wrote:

> This patch prints warning (if CONFIG_DEBUG_VM=y) when
> memory commitment becomes too negative.
> 
> ...
>
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -134,6 +134,12 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
>  {
>  	unsigned long free, allowed, reserve;
>  
> +#ifdef CONFIG_DEBUG_VM
> +	WARN_ONCE(percpu_counter_read(&vm_committed_as) <
> +			-(s64)vm_committed_as_batch * num_online_cpus(),
> +			"memory commitment underflow");
> +#endif
> +
>  	vm_acct_memory(pages);

The changelog doesn't describe the reasons for making the change.

I assume this warning will detect the situation which the previous two
patches just fixed?