netdev - Re: [PATCH RFC net-next 2/2] net: skbuff: do not allocate emergency memory if flags is not __GFP

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Date:	Sat, 23 Aug 2014 16:53:49 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Govindarajulu Varadarajan <_govind@....com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	mgorman@...e.de
Subject: Re: [PATCH RFC net-next 2/2] net: skbuff: do not allocate emergency
 memory if flags is not __GFP_MEMALLOC

On Sun, 2014-08-24 at 03:07 +0530, Govindarajulu Varadarajan wrote:
> It is possible that nc->frag.page is previously allocated from emergency memory.
> For new alloc call, if the flags does not contain __GFP_MEMALLOC, do not
> return pfmemalloc memory.
> 
> Signed-off-by: Govindarajulu Varadarajan <_govind@....com>
> ---
>  net/core/skbuff.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 51a3328..792ce89 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -364,6 +364,13 @@ recycle:
>  		atomic_set(&nc->frag.page->_count, NETDEV_PAGECNT_MAX_BIAS);
>  		nc->pagecnt_bias = NETDEV_PAGECNT_MAX_BIAS;
>  		nc->frag.offset = 0;
> +	} else if (nc->frag.page->pfmemalloc && !(gfp_mask & __GFP_MEMALLOC)) {
> +		if (atomic_sub_and_test(nc->pagecnt_bias,
> +					&nc->frag.page->_count)) {
> +			atomic_set(&nc->frag.page->_count, 1);
> +			kfree(page_address(nc->frag.page));

No idea of what you think you do.

How have you tested this patch ?

> +		}
> +		goto refill;
>  	}
>  
>  	if (nc->frag.offset + fragsz > nc->frag.size) {


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