linux-kernel - Re: [PATCH net-next] hyperv: Add support for physically discontinuous receive buffer

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Message-Id: <20140114.143133.1863157816134006560.davem@davemloft.net>
Date:	Tue, 14 Jan 2014 14:31:33 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	haiyangz@...rosoft.com
Cc:	netdev@...r.kernel.org, kys@...rosoft.com, olaf@...fle.de,
	jasowang@...hat.com, linux-kernel@...r.kernel.org,
	driverdev-devel@...uxdriverproject.org
Subject: Re: [PATCH net-next] hyperv: Add support for physically
 discontinuous receive buffer

From: Haiyang Zhang <haiyangz@...rosoft.com>
Date: Thu,  9 Jan 2014 14:24:47 -0800

> This will allow us to use bigger receive buffer, and prevent allocation failure
> due to fragmented memory.
> 
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> Reviewed-by: K. Y. Srinivasan <kys@...rosoft.com>

Not until you start using paged SKBs in netvsc_recv_callback.

Whatever fragmention you think you're avoiding in the hyperv layer,
you're still going to get from the:

	skb = netdev_alloc_skb_ip_align(net, packet->total_data_buflen);

call there.

This change makes no sense in isolation, therefore I'm not applying it
until you also include the appropriate changes to avoid the same
exact fragmentation issue in netvsc_drv.c as stated above.
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