linux-kernel - Re: [PATCH] ibmvnic: Use -EBUSY in __ibmvnic

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Date: Tue, 23 Apr 2024 09:55:57 -0500
From: Nick Child <nnac123@...ux.ibm.com>
To: Dan Carpenter <dan.carpenter@...aro.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Markus Elfring <Markus.Elfring@....de>, linuxppc-dev@...ts.ozlabs.org,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Haren Myneni <haren@...ux.ibm.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Rick Lindsley <ricklind@...ux.ibm.com>,
        Thomas Falcon <tlfalcon@...ux.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ibmvnic: Use -EBUSY in __ibmvnic_reset()



On 4/23/24 06:55, Dan Carpenter wrote:
> On Tue, Apr 23, 2024 at 12:54:55PM +0200, Paolo Abeni wrote:
>> On Fri, 2024-04-19 at 16:08 +0200, Markus Elfring wrote:
>>> From: Markus Elfring <elfring@...rs.sourceforge.net>
>>> Date: Fri, 19 Apr 2024 15:46:17 +0200
>>>
>>> Add a minus sign before the error code “EBUSY”
>>> so that a negative value will be used as in other cases.
>>>
>>> This issue was transformed by using the Coccinelle software.
>>>
>>> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
>>> ---
>>>   drivers/net/ethernet/ibm/ibmvnic.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
>>> index 5e9a93bdb518..737ae83a836a 100644
>>> --- a/drivers/net/ethernet/ibm/ibmvnic.c
>>> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
>>> @@ -3212,7 +3212,7 @@ static void __ibmvnic_reset(struct work_struct *work)
>>>   		    adapter->state == VNIC_REMOVED) {
>>>   			spin_unlock_irqrestore(&adapter->state_lock, flags);
>>>   			kfree(rwi);
>>> -			rc = EBUSY;
>>> +			rc = -EBUSY;
>>>   			break;
>>>
>>
>> AFAICS the error is always used as bool, so this will not change any
>> behavior in practice. I tend to think we should not merge this kind of
>> change outside some larger work in the same area, but I'd love a second
>> opinion from the driver owners.
> 
> I missed the original patch due to my procmail filters...
> 
> You're right that it doesn't affect the behavior of the driver except
> for the debug output when we do:
> 
> 	netdev_dbg(adapter->netdev, "Reset failed, rc=%d\n", rc);
> 
> But the - was left off uninitentionally so I think we should apply it.
> 
> I have been trying to look for similar bugs where the - is left off.
> It's a bit challenging because there places where we use positive
> error codes deliberately.  But in this case a static checker could
> easily detect the bug with a low false positive ratio by saying, "We're
> mixing normal negative error codes with positive EBUSY".
> 
> regards,
> dan carpenter

Hello, small clarification, this patch will not effect the debug print 
statement due to the break statement immediately following:
	while () {	
		if () {
			rc = -EBUSY;
			break;
		}
		netdev_dbg(adapter->netdev, "Reset failed, rc=%d\n", rc);
	}
Though this return code can be passed to adapter->reset_done_rc, which 
is only treated as a boolean.

So, the point of the patch not doing any behavioral differences is still 
true.
Personally, I don't have strong opinions on this.
Reviewed-by: Nick Child <nnac123@...ux.ibm.com>