netdev - Re: [PATCH v1 03/15] net: generalise net

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b2aa16ac-a5fe-4bab-a047-8f38086f4d43@davidwei.uk>
Date: Fri, 11 Oct 2024 11:44:37 -0700
From: David Wei <dw@...idwei.uk>
To: Stanislav Fomichev <stfomichev@...il.com>,
 Pavel Begunkov <asml.silence@...il.com>
Cc: io-uring@...r.kernel.org, netdev@...r.kernel.org,
 Jens Axboe <axboe@...nel.dk>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jesper Dangaard Brouer
 <hawk@...nel.org>, David Ahern <dsahern@...nel.org>,
 Mina Almasry <almasrymina@...gle.com>, David Wei <dw@...idwei.uk>
Subject: Re: [PATCH v1 03/15] net: generalise net_iov chunk owners

On 2024-10-09 09:28, Stanislav Fomichev wrote:
> On 10/08, Pavel Begunkov wrote:
>> On 10/8/24 16:46, Stanislav Fomichev wrote:
>>> On 10/07, David Wei wrote:
>>>> From: Pavel Begunkov <asml.silence@...il.com>
>>>>
>>>> Currently net_iov stores a pointer to struct dmabuf_genpool_chunk_owner,
>>>> which serves as a useful abstraction to share data and provide a
>>>> context. However, it's too devmem specific, and we want to reuse it for
>>>> other memory providers, and for that we need to decouple net_iov from
>>>> devmem. Make net_iov to point to a new base structure called
>>>> net_iov_area, which dmabuf_genpool_chunk_owner extends.
>>>>
>>>> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
>>>> Signed-off-by: David Wei <dw@...idwei.uk>
>>>> ---
>>>>   include/net/netmem.h | 21 ++++++++++++++++++++-
>>>>   net/core/devmem.c    | 25 +++++++++++++------------
>>>>   net/core/devmem.h    | 25 +++++++++----------------
>>>>   3 files changed, 42 insertions(+), 29 deletions(-)
>>>>
>>>> diff --git a/include/net/netmem.h b/include/net/netmem.h
>>>> index 8a6e20be4b9d..3795ded30d2c 100644
>>>> --- a/include/net/netmem.h
>>>> +++ b/include/net/netmem.h
>>>> @@ -24,11 +24,20 @@ struct net_iov {
>>>>   	unsigned long __unused_padding;
>>>>   	unsigned long pp_magic;
>>>>   	struct page_pool *pp;
>>>> -	struct dmabuf_genpool_chunk_owner *owner;
>>>> +	struct net_iov_area *owner;
>>>
>>> Any reason not to use dmabuf_genpool_chunk_owner as is (or rename it
>>> to net_iov_area to generalize) with the fields that you don't need
>>> set to 0/NULL? container_of makes everything harder to follow :-(
>>
>> It can be that, but then io_uring would have a (null) pointer to
>> struct net_devmem_dmabuf_binding it knows nothing about and other
>> fields devmem might add in the future. Also, it reduces the
>> temptation for the common code to make assumptions about the origin
>> of the area / pp memory provider. IOW, I think it's cleaner
>> when separated like in this patch.
> 
> Ack, let's see whether other people find any issues with this approach.
> For me, it makes the devmem parts harder to read, so my preference
> is on dropping this patch and keeping owner=null on your side.

I don't mind at this point which approach to take right now. I would
prefer keeping dmabuf_genpool_chunk_owner today even if it results in a
nullptr in io_uring's case. Once there are more memory providers in the
future, I think it'll be clearer what sort of abstraction we might need
here.