netdev - Re: [PATCH net-next,v4] bonding: return -ENOMEM instead of BUG in alb_upper_dev

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Message-ID: <05108fe1-ab34-6d67-4265-2ec478ce0368@huawei.com>
Date: Tue, 21 Nov 2023 20:25:47 +0800
From: shaozhengchao <shaozhengchao@...wei.com>
To: Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>
CC: <j.vosburgh@...il.com>, <andy@...yhouse.net>, <weiyongjun1@...wei.com>,
	<yuehaibing@...wei.com>
Subject: Re: [PATCH net-next,v4] bonding: return -ENOMEM instead of BUG in
 alb_upper_dev_walk



On 2023/11/21 19:41, Paolo Abeni wrote:
> On Sat, 2023-11-18 at 16:16 +0800, Zhengchao Shao wrote:
>> If failed to allocate "tags" or could not find the final upper device from
>> start_dev's upper list in bond_verify_device_path(), only the loopback
>> detection of the current upper device should be affected, and the system is
>> no need to be panic.
>> So return -ENOMEM in alb_upper_dev_walk to stop walking, print some warn
>> information when failed to allocate memory for vlan tags in
>> bond_verify_device_path.
>>
>> I also think that the following function calls
>> netdev_walk_all_upper_dev_rcu
>> ---->>>alb_upper_dev_walk
>> ---------->>>bond_verify_device_path
>>>  From this way, "end device" can eventually be obtained from "start device"
>> in bond_verify_device_path, IS_ERR(tags) could be instead of
>> IS_ERR_OR_NULL(tags) in alb_upper_dev_walk.
>>
>> Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
>> ---
>> v4: print information instead of warn
>> v3: return -ENOMEM instead of zero to stop walk
>> v2: use WARN_ON_ONCE instead of WARN_ON
>> ---
>>   drivers/net/bonding/bond_alb.c  | 3 ++-
>>   drivers/net/bonding/bond_main.c | 5 ++++-
>>   2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>> index dc2c7b979656..7edf0fd58c34 100644
>> --- a/drivers/net/bonding/bond_alb.c
>> +++ b/drivers/net/bonding/bond_alb.c
>> @@ -985,7 +985,8 @@ static int alb_upper_dev_walk(struct net_device *upper,
>>   	if (netif_is_macvlan(upper) && !strict_match) {
>>   		tags = bond_verify_device_path(bond->dev, upper, 0);
>>   		if (IS_ERR_OR_NULL(tags))
>> -			BUG();
>> +			return -ENOMEM;
>> +
>>   		alb_send_lp_vid(slave, upper->dev_addr,
>>   				tags[0].vlan_proto, tags[0].vlan_id);
>>   		kfree(tags);
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 51d47eda1c87..1a40bd08f984 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -2967,8 +2967,11 @@ struct bond_vlan_tag *bond_verify_device_path(struct net_device *start_dev,
>>   
>>   	if (start_dev == end_dev) {
>>   		tags = kcalloc(level + 1, sizeof(*tags), GFP_ATOMIC);
>> -		if (!tags)
>> +		if (!tags) {
>> +			net_err_ratelimited("%s: %s: Failed to allocate tags\n",
>> +					    __func__, start_dev->name);
> 
> I'm sorry for the repeated back and forth, but checkpatch points out
> that the above warning adds little value: if the memory allocation
> fails, the mm layer will emit a lot warning comprising the backtrace.
> 
> I suggest to drop it, thanks!
Thank you for your advice. And I will send v5 later.

Zhengchao Shao
> 
> Paolo
>