linux-kernel - Re: [RFC v2 1/3] mm/vmalloc: fix possible exhaustion of vmalloc space caused by vm_map

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Message-Id: <20150324150054.a9050b7814860790e1d9b0d0@linux-foundation.org>
Date:	Tue, 24 Mar 2015 15:00:54 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Roman Pen <r.peniaev@...il.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	WANG Chao <chaowang@...hat.com>,
	Fabian Frederick <fabf@...net.be>,
	Christoph Lameter <cl@...ux.com>, Gioh Kim <gioh.kim@....com>,
	Rob Jones <rob.jones@...ethink.co.uk>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [RFC v2 1/3] mm/vmalloc: fix possible exhaustion of vmalloc
 space caused by vm_map_ram allocator

On Thu, 19 Mar 2015 23:04:39 +0900 Roman Pen <r.peniaev@...il.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@...r.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?

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