netdev - Re: [PATCH net-next 2/3] page_pool: Turn dma_sync and dma_sync

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Message-ID: <b0636b00-e721-4f21-b1c5-74391a36a3be@gmail.com>
Date: Sat, 15 Mar 2025 17:31:29 +0800
From: Yunsheng Lin <yunshenglin0825@...il.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 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>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, linux-rdma@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH net-next 2/3] page_pool: Turn dma_sync and dma_sync_cpu
 fields into a bitmap

On 3/14/2025 6:10 PM, Toke Høiland-Jørgensen wrote:
> Change the single-bit booleans for dma_sync into an unsigned long with
> BIT() definitions so that a subsequent patch can write them both with a
> singe WRITE_ONCE() on teardown. Also move the check for the sync_cpu
> side into __page_pool_dma_sync_for_cpu() so it can be disabled for
> non-netmem providers as well.

I guess this patch is for the preparation of disabling the
page_pool_dma_sync_for_cpu() related API on teardown?

It seems unnecessary that page_pool_dma_sync_for_cpu() related API need
to be disabled on teardown as page_pool_dma_sync_for_cpu() has the same
calling assumption as the alloc API, which is not supposed to be called
by the drivers when page_pool_destroy() is called.