netdev - Re: [PATCH v2 net] tcp: md5: do not use alloc

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Message-ID: <5449CB58.40100@gmail.com>
Date:	Thu, 23 Oct 2014 21:45:28 -0600
From:	David Ahern <dsahern@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
CC:	Crestez Dan Leonard <cdleonard@...il.com>, netdev@...r.kernel.org,
	Jonathan Toppins <jtoppins@...ulusnetworks.com>
Subject: Re: [PATCH v2 net] tcp: md5: do not use alloc_percpu()

On 10/23/14, 1:58 PM, Eric Dumazet wrote:
> From: Eric Dumazet<edumazet@...gle.com>
>
> percpu tcp_md5sig_pool contains memory blobs that ultimately
> go through sg_set_buf().
>
> -> sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
>
> This requires that whole area is in a physically contiguous portion
> of memory. And that @buf is not backed by vmalloc().
>
> Given that alloc_percpu() can use vmalloc() areas, this does not
> fit the requirements.
>
> Replace alloc_percpu() by a static DEFINE_PER_CPU() as tcp_md5sig_pool
> is small anyway, there is no gain to dynamically allocate it.
>
> Signed-off-by: Eric Dumazet<edumazet@...gle.com>
> Fixes: 765cf9976e93 ("tcp: md5: remove one indirection level in tcp_md5sig_pool")
> Reported-by: Crestez Dan Leonard<cdleonard@...il.com>

Too much time (and too many changes) has passed for this to apply easily 
to v3.4 kernels.

David
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