netdev - Re: [RFC PATCH net-next] page_pool: Track DMA-mapped pages and unmap them when destroying the pool

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Message-ID: <52f4e8b1-527a-42fb-9297-2689ba7c7516@kernel.org>
Date: Wed, 12 Mar 2025 12:35:03 -0600
From: Shuah <shuah@...nel.org>
To: Yunsheng Lin <linyunsheng@...wei.com>,
 Matthew Wilcox <willy@...radead.org>
Cc: Toke Høiland-Jørgensen <toke@...hat.com>,
 Yunsheng Lin <yunshenglin0825@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 Ilias Apalodimas <ilias.apalodimas@...aro.org>,
 "David S. Miller" <davem@...emloft.net>,
 Yonglong Liu <liuyonglong@...wei.com>, Mina Almasry
 <almasrymina@...gle.com>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, linux-mm@...ck.org, netdev@...r.kernel.org,
 conduct@...nel.org
Subject: Re: [RFC PATCH net-next] page_pool: Track DMA-mapped pages and unmap
 them when destroying the pool

On 3/12/25 06:05, Yunsheng Lin wrote:
> On 2025/3/11 23:11, Matthew Wilcox wrote:
>> On Tue, Mar 11, 2025 at 08:25:25PM +0800, Yunsheng Lin wrote:
>>>> struct page {
>>>> 	unsigned long flags;
>>>> 	unsigned long memdesc;
>>>
>>> It seems there may be memory behind the above 'memdesc' with different size
>>> and layout for different subsystem?
>>
>> Yes.
>>
>>> I am not sure if I understand the case of the same page might be handle in
>>> two subsystems concurrently or a page is allocated in one subsystem and
>>> then passed to be handled in other subsystem, for examlpe:
>>> page_pool owned page is mmap'ed into user space through tcp zero copy,
>>> see tcp_zerocopy_vm_insert_batch(), it seems the same page is handled in
>>> both networking/page_pool and vm subsystem?
>>
>> It's not that arbitrary.  I mean, you could read all the documentation
>> I've written about this concept, listen to the talks I've given.

You can't point to talk given on the concept - people don't have to go
find your talks to understand the concept. You are expected to answer
the question and explain it to us here in this thread.

But
>> sure, you're a special fucking snowflake and deserve your own unique
>> explanation.

Yunsheng Lin, This message is a rude personal attack. This isn't the
way to treat your peers in the community. Apology is warranted.

> 
> If you don't like responding to the above question/comment, I would rather
> you strip out them like the other question/comment or just ignore it:(
> 
> I am not sure how to interpret the comment, but I am sure it is not a kind
> one, so CC 'Code of Conduct Committee' in case there is more coming.
> 

Thank you Mathew for letting us know about this.

thanks,
-- Shuah ((on behalf of the CoC committee)