linux-kernel - Re: [PATCH net v3] igb: cope with large MAX_SKB

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Message-ID: <d33c7174-733a-bc70-78cd-dfcfe666f263@intel.com>
Date: Tue, 23 Jul 2024 10:16:27 -0700
From: Tony Nguyen <anthony.l.nguyen@...el.com>
To: Paolo Abeni <pabeni@...hat.com>, Corinna Vinschen <vinschen@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<intel-wired-lan@...ts.osuosl.org>, Nikolay Aleksandrov
	<razor@...ckwall.org>, Jason Xing <kerneljasonxing@...il.com>, Jakub Kicinski
	<kuba@...nel.org>, "David S . Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH net v3] igb: cope with large MAX_SKB_FRAGS.



On 7/23/2024 1:27 AM, Paolo Abeni wrote:
> On 7/18/24 10:56, Corinna Vinschen wrote:
>> From: Paolo Abeni <pabeni@...hat.com>
>>
>> Sabrina reports that the igb driver does not cope well with large
>> MAX_SKB_FRAG values: setting MAX_SKB_FRAG to 45 causes payload
>> corruption on TX.
>>
>> An easy reproducer is to run ssh to connect to the machine.  With
>> MAX_SKB_FRAGS=17 it works, with MAX_SKB_FRAGS=45 it fails.
>>
>> The root cause of the issue is that the driver does not take into
>> account properly the (possibly large) shared info size when selecting
>> the ring layout, and will try to fit two packets inside the same 4K
>> page even when the 1st fraglist will trump over the 2nd head.
>>
>> Address the issue forcing the driver to fit a single packet per page,
>> leaving there enough room to store the (currently) largest possible
>> skb_shared_info.
>>
>> Fixes: 3948b05950fd ("net: introduce a config option to tweak 
>> MAX_SKB_FRAGS")
>> Reported-by: Jan Tluka <jtluka@...hat.com>
>> Reported-by: Jirka Hladky <jhladky@...hat.com>
>> Reported-by: Sabrina Dubroca <sd@...asysnail.net>
>> Tested-by: Sabrina Dubroca <sd@...asysnail.net>
>> Tested-by: Corinna Vinschen <vinschen@...hat.com>
>> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> 
> @Tony: would you like to take this one in your tree first, or we can 
> merge it directly?

Hi Paolo,

I can take it through IWL unless you need to get it in sooner, in which 
case, feel free to take it directly. If so...

Reviewed-by: Tony Nguyen <anthony.l.nguyen@...el.com>

Thanks,
Tony