netdev - Re: [PATCH net-next v6 2/2] page_pool: Track DMA-mapped pages and unmap them when destroying the pool

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Message-ID: <20250403153129.013a7bdd@kernel.org>
Date: Thu, 3 Apr 2025 15:31:29 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jesper Dangaard Brouer
 <hawk@...nel.org>, Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky
 <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, Simon
 Horman <horms@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Mina
 Almasry <almasrymina@...gle.com>, Yonglong Liu <liuyonglong@...wei.com>,
 Yunsheng Lin <linyunsheng@...wei.com>, Pavel Begunkov
 <asml.silence@...il.com>, Matthew Wilcox <willy@...radead.org>,
 netdev@...r.kernel.org, bpf@...r.kernel.org, linux-rdma@...r.kernel.org,
 linux-mm@...ck.org, Qiuling Ren <qren@...hat.com>, Yuying Ma
 <yuma@...hat.com>
Subject: Re: [PATCH net-next v6 2/2] page_pool: Track DMA-mapped pages and
 unmap them when destroying the pool

On Tue, 01 Apr 2025 11:27:19 +0200 Toke Høiland-Jørgensen wrote:
> +	if (err) {
> +		WARN_ONCE(1, "couldn't track DMA mapping, please report to netdev@");
>  		goto unmap_failed;

FWIW I second Pavel's concern about the warning being too drastic.
I have the feeling Meta's fleet will hit this.
How about WARN_ONCE(err != -ENOMEM, ... ? I presume you care mostly
about the array filling up so -EBUSY

> +	}
>  
> +	if (page_pool_set_dma_addr_netmem(netmem, dma)) {
> +		WARN_ONCE(1, "unexpected DMA address, please report to netdev@");
> +		goto unmap_failed;
> +	}

I think this is ever so slightly leaking the id, if it ever happens?