[PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Christophe JAILLET]

In idpf_add_del_mac_filters(), filters are chunked up into multiple
messages to avoid sending a control queue message buffer that is too large.

Each chunk has up to IDPF_NUM_FILTERS_PER_MSG entries. So except for the
last iteration which can be smaller, space for exactly
IDPF_NUM_FILTERS_PER_MSG entries is allocated.

There is no need to free and reallocate a smaller array just for the last
iteration.

This slightly simplifies the code and avoid an (unlikely) memory allocation
failure.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
index 70986e12da28..b6f4b58e1094 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
@@ -3669,12 +3669,15 @@ int idpf_add_del_mac_filters(struct idpf_vport *vport,
 		entries_size = sizeof(struct virtchnl2_mac_addr) * num_entries;
 		buf_size = struct_size(ma_list, mac_addr_list, num_entries);
 
-		if (!ma_list || num_entries != IDPF_NUM_FILTERS_PER_MSG) {
-			kfree(ma_list);
+		if (!ma_list) {
 			ma_list = kzalloc(buf_size, GFP_ATOMIC);
 			if (!ma_list)
 				return -ENOMEM;
 		} else {
+			/* ma_list was allocated in the first iteration
+			 * so IDPF_NUM_FILTERS_PER_MSG entries are
+			 * available
+			 */
 			memset(ma_list, 0, buf_size);
 		}
 
-- 
2.46.0

Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Dan Carpenter]

On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:
> In idpf_add_del_mac_filters(), filters are chunked up into multiple
> messages to avoid sending a control queue message buffer that is too large.
> 
> Each chunk has up to IDPF_NUM_FILTERS_PER_MSG entries. So except for the
> last iteration which can be smaller, space for exactly
> IDPF_NUM_FILTERS_PER_MSG entries is allocated.
> 
> There is no need to free and reallocate a smaller array just for the last
> iteration.
> 
> This slightly simplifies the code and avoid an (unlikely) memory allocation
> failure.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> index 70986e12da28..b6f4b58e1094 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> @@ -3669,12 +3669,15 @@ int idpf_add_del_mac_filters(struct idpf_vport *vport,
>  		entries_size = sizeof(struct virtchnl2_mac_addr) * num_entries;
>  		buf_size = struct_size(ma_list, mac_addr_list, num_entries);
>  
> -		if (!ma_list || num_entries != IDPF_NUM_FILTERS_PER_MSG) {
> -			kfree(ma_list);
> +		if (!ma_list) {
>  			ma_list = kzalloc(buf_size, GFP_ATOMIC);
>  			if (!ma_list)
>  				return -ENOMEM;
>  		} else {
> +			/* ma_list was allocated in the first iteration
> +			 * so IDPF_NUM_FILTERS_PER_MSG entries are
> +			 * available
> +			 */
>  			memset(ma_list, 0, buf_size);
>  		}

It would be even nicer to move the ma_list allocation outside the loop:

        buf_size = struct_size(ma_list, mac_addr_list, IDPF_NUM_FILTERS_PER_MSG);
        ma_list = kmalloc(buf_size, GFP_ATOMIC);

regards,
dan carpenter

Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Simon Horman]

On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:
> In idpf_add_del_mac_filters(), filters are chunked up into multiple
> messages to avoid sending a control queue message buffer that is too large.
> 
> Each chunk has up to IDPF_NUM_FILTERS_PER_MSG entries. So except for the
> last iteration which can be smaller, space for exactly
> IDPF_NUM_FILTERS_PER_MSG entries is allocated.
> 
> There is no need to free and reallocate a smaller array just for the last
> iteration.
> 
> This slightly simplifies the code and avoid an (unlikely) memory allocation
> failure.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Przemek Kitszel]

On 8/23/24 11:10, Dan Carpenter wrote:
> On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:
>> In idpf_add_del_mac_filters(), filters are chunked up into multiple
>> messages to avoid sending a control queue message buffer that is too large.
>>
>> Each chunk has up to IDPF_NUM_FILTERS_PER_MSG entries. So except for the
>> last iteration which can be smaller, space for exactly
>> IDPF_NUM_FILTERS_PER_MSG entries is allocated.
>>
>> There is no need to free and reallocate a smaller array just for the last
>> iteration.
>>
>> This slightly simplifies the code and avoid an (unlikely) memory allocation
>> failure.
>>

Thanks, that is indeed an improvement.

>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> ---
>>   drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
>> index 70986e12da28..b6f4b58e1094 100644
>> --- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
>> +++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
>> @@ -3669,12 +3669,15 @@ int idpf_add_del_mac_filters(struct idpf_vport *vport,
>>   		entries_size = sizeof(struct virtchnl2_mac_addr) * num_entries;
>>   		buf_size = struct_size(ma_list, mac_addr_list, num_entries);
>>   
>> -		if (!ma_list || num_entries != IDPF_NUM_FILTERS_PER_MSG) {
>> -			kfree(ma_list);
>> +		if (!ma_list) {
>>   			ma_list = kzalloc(buf_size, GFP_ATOMIC);
>>   			if (!ma_list)
>>   				return -ENOMEM;
>>   		} else {
>> +			/* ma_list was allocated in the first iteration
>> +			 * so IDPF_NUM_FILTERS_PER_MSG entries are
>> +			 * available
>> +			 */
>>   			memset(ma_list, 0, buf_size);
>>   		}
> 
> It would be even nicer to move the ma_list allocation outside the loop:
> 
>          buf_size = struct_size(ma_list, mac_addr_list, IDPF_NUM_FILTERS_PER_MSG);
>          ma_list = kmalloc(buf_size, GFP_ATOMIC);

good point

I've opened whole function for inspection and it asks for even more,
as of now, we allocate an array in atomic context, just to have a copy
of some stuff from the spinlock-protected list.

It would be good to have allocation as pointed by Dan prior to iteration
and fill it on the fly, sending when new message would not fit plus once
at the end. Sending procedure is safe to be called under a spinlock.

CCing author; CCing Olek to ask if there are already some refactors that
would conflict with this.

> 
> regards,
> dan carpenter
> 

Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Christophe JAILLET]

Le 26/08/2024 à 11:15, Przemek Kitszel a écrit :
> On 8/23/24 11:10, Dan Carpenter wrote:
>> On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:
>>> In idpf_add_del_mac_filters(), filters are chunked up into multiple
>>> messages to avoid sending a control queue message buffer that is too 
>>> large.
>>>
>>> Each chunk has up to IDPF_NUM_FILTERS_PER_MSG entries. So except for the
>>> last iteration which can be smaller, space for exactly
>>> IDPF_NUM_FILTERS_PER_MSG entries is allocated.
>>>
>>> There is no need to free and reallocate a smaller array just for the 
>>> last
>>> iteration.
>>>
>>> This slightly simplifies the code and avoid an (unlikely) memory 
>>> allocation
>>> failure.
>>>
> 
> Thanks, that is indeed an improvement.
> 
>>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>>> ---
>>>   drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 7 +++++--
>>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c 
>>> b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
>>> index 70986e12da28..b6f4b58e1094 100644
>>> --- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
>>> +++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
>>> @@ -3669,12 +3669,15 @@ int idpf_add_del_mac_filters(struct 
>>> idpf_vport *vport,
>>>           entries_size = sizeof(struct virtchnl2_mac_addr) * 
>>> num_entries;
>>>           buf_size = struct_size(ma_list, mac_addr_list, num_entries);
>>> -        if (!ma_list || num_entries != IDPF_NUM_FILTERS_PER_MSG) {
>>> -            kfree(ma_list);
>>> +        if (!ma_list) {
>>>               ma_list = kzalloc(buf_size, GFP_ATOMIC);
>>>               if (!ma_list)
>>>                   return -ENOMEM;
>>>           } else {
>>> +            /* ma_list was allocated in the first iteration
>>> +             * so IDPF_NUM_FILTERS_PER_MSG entries are
>>> +             * available
>>> +             */
>>>               memset(ma_list, 0, buf_size);
>>>           }
>>
>> It would be even nicer to move the ma_list allocation outside the loop:
>>
>>          buf_size = struct_size(ma_list, mac_addr_list, 
>> IDPF_NUM_FILTERS_PER_MSG);
>>          ma_list = kmalloc(buf_size, GFP_ATOMIC);
> 
> good point
> 
> I've opened whole function for inspection and it asks for even more,
> as of now, we allocate an array in atomic context, just to have a copy
> of some stuff from the spinlock-protected list.
> 
> It would be good to have allocation as pointed by Dan prior to iteration
> and fill it on the fly, sending when new message would not fit plus once
> at the end. Sending procedure is safe to be called under a spinlock.

If I understand correctly, you propose to remove the initial copy in 
mac_addr and hold &vport_config->mac_filter_list_lock till the end of 
the function?

That's it?

There is a wait_for_completion_timeout() in idpf_vc_xn_exec() and the 
default time-out is IDPF_VC_XN_DEFAULT_TIMEOUT_MSEC	(60 * 1000)

So, should an issue occurs, and the time out run till the end, we could 
hold the 'mac_filter_list_lock' spinlock for up to 60 seconds?
Is that ok?


And if in asynch update mode, idpf_mac_filter_async_handler() also takes 
&vport_config->mac_filter_list_lock;. Could we dead-lock?


So, I'm not sure to understand what you propose, or the code in 
idpf_add_del_mac_filters() and co.

> 
> CCing author; CCing Olek to ask if there are already some refactors that
> would conflict with this.

I'll way a few days for these feedbacks and send a v2.

CJ

> 
>>
>> regards,
>> dan carpenter
>>
> 
> 
> 

Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Przemek Kitszel]

On 8/26/24 19:14, Christophe JAILLET wrote:
> Le 26/08/2024 à 11:15, Przemek Kitszel a écrit :
>> On 8/23/24 11:10, Dan Carpenter wrote:
>>> On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:

>>> It would be even nicer to move the ma_list allocation outside the loop:
>>>
>>>          buf_size = struct_size(ma_list, mac_addr_list, 
>>> IDPF_NUM_FILTERS_PER_MSG);
>>>          ma_list = kmalloc(buf_size, GFP_ATOMIC);
>>
>> good point
>>
>> I've opened whole function for inspection and it asks for even more,
>> as of now, we allocate an array in atomic context, just to have a copy
>> of some stuff from the spinlock-protected list.
>>
>> It would be good to have allocation as pointed by Dan prior to iteration
>> and fill it on the fly, sending when new message would not fit plus once
>> at the end. Sending procedure is safe to be called under a spinlock.
> 
> If I understand correctly, you propose to remove the initial copy in 
> mac_addr and hold &vport_config->mac_filter_list_lock till the end of 
> the function?
> 
> That's it?

You got it right. Thanks for your further analysis below.

> 
> There is a wait_for_completion_timeout() in idpf_vc_xn_exec() and the 
> default time-out is IDPF_VC_XN_DEFAULT_TIMEOUT_MSEC    (60 * 1000)
> 
> So, should an issue occurs, and the time out run till the end, we could 
> hold the 'mac_filter_list_lock' spinlock for up to 60 seconds?
> Is that ok?

Messing with this list while we are not done processing does not sound
right either.
But the most concerning part for me with my proposition is that it could
be very slow to just "abort and unload the driver".

> 
> 
> And if in asynch update mode, idpf_mac_filter_async_handler() also takes 
> &vport_config->mac_filter_list_lock;. Could we dead-lock?

indeed looks so :( sorry

> 
> 
> So, I'm not sure to understand what you propose, or the code in 
> idpf_add_del_mac_filters() and co.
> 
>>
>> CCing author; CCing Olek to ask if there are already some refactors that
>> would conflict with this.
> 
> I'll way a few days for these feedbacks and send a v2.

Would be good to have simple memory cleanup first, and later (if at all)
to untangle our locks a bit.

Re: [PATCH net-next] idpf: Slightly simplify memory management in idpf_add_del_mac_filters()

[Alexander Lobakin]

From: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Date: Tue, 27 Aug 2024 08:58:33 +0200

> On 8/26/24 19:14, Christophe JAILLET wrote:
>> Le 26/08/2024 à 11:15, Przemek Kitszel a écrit :
>>> On 8/23/24 11:10, Dan Carpenter wrote:
>>>> On Fri, Aug 23, 2024 at 08:23:29AM +0200, Christophe JAILLET wrote:
> 
>>>> It would be even nicer to move the ma_list allocation outside the loop:
>>>>
>>>>          buf_size = struct_size(ma_list, mac_addr_list,
>>>> IDPF_NUM_FILTERS_PER_MSG);
>>>>          ma_list = kmalloc(buf_size, GFP_ATOMIC);

[...]

>> So, I'm not sure to understand what you propose, or the code in
>> idpf_add_del_mac_filters() and co.
>>
>>>
>>> CCing author; CCing Olek to ask if there are already some refactors that
>>> would conflict with this.

I'm not aware of any MAC filter code refactors.

>>
>> I'll way a few days for these feedbacks and send a v2.
> 
> Would be good to have simple memory cleanup first, and later (if at all)
> to untangle our locks a bit.

Thanks,
Olek