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Date: Tue, 24 Mar 2015 15:00:54 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Roman Pen <r.peniaev@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>, David Rientjes <rientjes@google.com>,
        WANG Chao <chaowang@redhat.com>, Fabian Frederick <fabf@skynet.be>,
        Christoph Lameter <cl@linux.com>, Gioh Kim <gioh.kim@lge.com>,
        Rob Jones <rob.jones@codethink.co.uk>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [RFC v2 1/3] mm/vmalloc: fix possible exhaustion of vmalloc
 space caused by vm_map_ram allocator
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On Thu, 19 Mar 2015 23:04:39 +0900 Roman Pen <r.peniaev@gmail.com> wrote:

> If suitable block can't be found, new block is allocated and put into a head
> of a free list, so on next iteration this new block will be found first.
> 
> ...
>
> Cc: stable@vger.kernel.org
>
> ...
>
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -837,7 +837,7 @@ static struct vmap_block *new_vmap_block(gfp_t gfp_mask)
>  
>  	vbq = &get_cpu_var(vmap_block_queue);
>  	spin_lock(&vbq->lock);
> -	list_add_rcu(&vb->free_list, &vbq->free);
> +	list_add_tail_rcu(&vb->free_list, &vbq->free);
>  	spin_unlock(&vbq->lock);
>  	put_cpu_var(vmap_block_queue);
>  

I'm not sure about the cc:stable here.  There is potential for
unexpected side-effects and I don't *think* people are hurting from
this issue in real life.  Or maybe I'm wrong about that?