netdev - Re: [PATCH net] bpf: don't trigger OOM killer under pressure with map alloc

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Message-Id: <20170118.171354.1392552826246839853.davem@davemloft.net>
Date:   Wed, 18 Jan 2017 17:13:54 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     daniel@...earbox.net
Cc:     alexei.starovoitov@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: don't trigger OOM killer under pressure with
 map alloc

From: Daniel Borkmann <daniel@...earbox.net>
Date: Wed, 18 Jan 2017 15:14:17 +0100

> This patch adds two helpers, bpf_map_area_alloc() and bpf_map_area_free(),
> that are to be used for map allocations. Using kmalloc() for very large
> allocations can cause excessive work within the page allocator, so i) fall
> back earlier to vmalloc() when the attempt is considered costly anyway,
> and even more importantly ii) don't trigger OOM killer with any of the
> allocators.
> 
> Since this is based on a user space request, for example, when creating
> maps with element pre-allocation, we really want such requests to fail
> instead of killing other user space processes.
> 
> Also, don't spam the kernel log with warnings should any of the allocations
> fail under pressure. Given that, we can make backend selection in
> bpf_map_area_alloc() generic, and convert all maps over to use this API
> for spots with potentially large allocation requests.
> 
> Note, replacing the one kmalloc_array() is fine as overflow checks happen
> earlier in htab_map_alloc(), since it must also protect the multiplication
> for vmalloc() should kmalloc_array() fail.
> 
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Acked-by: Alexei Starovoitov <ast@...nel.org>

Applied, thanks.