netdev - Re: [PATCH net-next 2/8] bonding: Check return of dev_set

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Message-ID: <485EFE06.7040104@cn.fujitsu.com>
Date:	Mon, 23 Jun 2008 09:36:06 +0800
From:	Wang Chen <wangchen@...fujitsu.com>
To:	Joe Eykholt <jeykholt@...co.com>
CC:	David Miller <davem@...emloft.net>, jgarzik@...ox.com,
	netdev@...r.kernel.org, fubar@...ibm.com, kaber@...sh.net
Subject: Re: [PATCH net-next 2/8] bonding: Check return of dev_set_promiscuity/allmulti

Joe Eykholt said the following on 2008-6-22 2:19:
> David Miller wrote:
>> From: Wang Chen <wangchen@...fujitsu.com>
>> Date: Fri, 20 Jun 2008 08:54:42 +0800
>>
>>> @@ -419,8 +419,11 @@ static void rlb_teach_disabled_mac_on_primary(struct bonding *bond, u8 addr[])
>>>  	}
>>>  
>>>  	if (!bond->alb_info.primary_is_promisc) {
>>> -		bond->alb_info.primary_is_promisc = 1;
>>> -		dev_set_promiscuity(bond->curr_active_slave->dev, 1);
>>> +		/* dev_set_promiscuity might overflow, check it here */
>>> +		if (!dev_set_promiscuity(bond->curr_active_slave->dev, 1))
>> Like the first patch, please don't add such comments.
>>
>>> @@ -955,6 +965,9 @@ static void bond_mc_swap(struct bonding *bond, struct slave *new_active, struct
>>>  	}
>>>  
>>>  	if (new_active) {
>>> +		/* FIXME: promiscuity and allmulti might overflow,
>>> +		 * but bond_mc_swap's caller likes quiet handle.
>>> +		 */
>>>  		if (bond->dev->flags & IFF_PROMISC) {
>>>  			dev_set_promiscuity(new_active->dev, 1);
>>>  		}
>> Please reword this comment.  The issue is that this code path has no
>> mechanism to signal errors upstream.  It isn't about a specific type
>> of error condition in particular, it's about error handling capabilites
>> in general.
> 
> If netdev->promiscuity overflows, shouldn't there be a WARN_ON or BUG_ON
> that catches that?  Either someone forgot to clean up, or much less likely,
> the counter needs to be widened.  It isn't necessarily the current caller's
> fault, but some indication of the problem is better than nothing.
> 

If promiscuity overflows, dev_set_promiscuity will printk(KERN_WARNING) now.
Compare to that, WARN_ON has more information about modules info and dump stack.
But I think printk has enough information to indicate the problem and we
don't need WARN_ON.
How do you think?

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