netdev - Re: [PATCH iproute2-next v3 5/8] veth,vxcan: Save/reinitialize/restore whole @struct ifinfomsg

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Date:   Mon, 26 Feb 2018 17:57:56 +0200
From:   Serhey Popovych <serhe.popovych@...il.com>
To:     David Ahern <dsahern@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH iproute2-next v3 5/8] veth,vxcan:
 Save/reinitialize/restore whole @struct ifinfomsg

David Ahern wrote:
> On 2/22/18 6:02 AM, Serhey Popovych wrote:
>> Now in iplink_parse() we use ->ifi_change and ->ifi_flags fields and
>> plan to use ->ifi_index with upcoming change.
>>
>> Saving, restoring and reinitializing individual fields is error prone:
>> using new field in iplink_parse() without updating callers in veth and
>> vxcan will overwrite main device ifinfomsg data.
>>
>> Since @struct ifinfomsg is small enough with known sizeof() compiler may
>> inline memcpy()/memset() with few load/store instructions.
>>
>> Signed-off-by: Serhey Popovych <serhe.popovych@...il.com>
>> ---
>>  ip/iplink_vxcan.c |   22 ++++++++--------------
>>  ip/link_veth.c    |   22 ++++++++--------------
>>  2 files changed, 16 insertions(+), 28 deletions(-)
> 
> I don't agree that this change has any benefit. Only the flags and
> change field are wanted; there is no need to save the entire struct,
> 

At the v0 (before submitted) I think so and just add ifi_index
save/restore in addition to ifi_change and ifi_flags. But when
look that memcpy() at 64-bit inlined to just two load/store
instructions I decided to send memcpy()/memset() variant.

If saving/restoring just ifi_index in addition to ifi_change and
ifi_flags instead of full @struct ifinfomsg is preferred I will
get rid of this change and add ifi_index to corresponding patch
within series.



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