netdev - Re: [PATCH net-next] mlxsw: spectrum_router: fix xa

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Message-ID: <107fb00f-1dac-4a13-b444-af2649901ae4@huawei.com>
Date: Wed, 16 Oct 2024 10:19:19 +0800
From: Yuan Can <yuancan@...wei.com>
To: Petr Machata <petrm@...dia.com>
CC: <idosch@...dia.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] mlxsw: spectrum_router: fix xa_store() error
 checking

On 2024/10/15 16:06, Petr Machata wrote:
> Yuan Can <yuancan@...wei.com> writes:
>
>> It is meant to use xa_err() to extract the error encoded in the return
>> value of xa_store().
>>
>> Fixes: 44c2fbebe18a ("mlxsw: spectrum_router: Share nexthop counters in resilient groups")
>> Signed-off-by: Yuan Can <yuancan@...wei.com>
> Reviewed-by: Petr Machata <petrm@...dia.com>
>
> What's the consequence of using IS_ERR()/PTR_ERR() vs. xa_err()? From
> the documentation it looks like IS_ERR() might interpret some valid
> pointers as errors[0]. Which would then show as leaks, because we bail
> out early and never clean up?

At least the PRT_ERR() will return a wrong error number, though the 
error number

seems not used nor printed.

>
> I.e. should this aim at net rather than net-next? It looks like it's not
> just semantics, but has actual observable impact.
Ok, do I need to send a V2 patch to net branch?
>
> [0] "The XArray does not support storing IS_ERR() pointers as some
>      conflict with value entries or internal entries."
>
>> ---
>>   drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c | 9 +++------
>>   1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
>> index 800dfb64ec83..7d6d859cef3f 100644
>> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
>> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
>> @@ -3197,7 +3197,6 @@ mlxsw_sp_nexthop_sh_counter_get(struct mlxsw_sp *mlxsw_sp,
>>   {
>>   	struct mlxsw_sp_nexthop_group *nh_grp = nh->nhgi->nh_grp;
>>   	struct mlxsw_sp_nexthop_counter *nhct;
>> -	void *ptr;
>>   	int err;
>>   
>>   	nhct = xa_load(&nh_grp->nhgi->nexthop_counters, nh->id);
>> @@ -3210,12 +3209,10 @@ mlxsw_sp_nexthop_sh_counter_get(struct mlxsw_sp *mlxsw_sp,
>>   	if (IS_ERR(nhct))
>>   		return nhct;
>>   
>> -	ptr = xa_store(&nh_grp->nhgi->nexthop_counters, nh->id, nhct,
>> -		       GFP_KERNEL);
>> -	if (IS_ERR(ptr)) {
>> -		err = PTR_ERR(ptr);
>> +	err = xa_err(xa_store(&nh_grp->nhgi->nexthop_counters, nh->id, nhct,
>> +			      GFP_KERNEL));
>> +	if (err)
>>   		goto err_store;
>> -	}

-- 
Best regards,
Yuan Can