netdev - [PATCH net-next v3 2/3] page_pool: Turn dma

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Message-Id: <20250326-page-pool-track-dma-v3-2-8e464016e0ac@redhat.com>
Date: Wed, 26 Mar 2025 09:18:39 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: "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, 
 Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH net-next v3 2/3] page_pool: Turn dma_sync into a full-width
 bool field

Change the single-bit boolean for dma_sync into a full-width bool, so we
can read it as volatile with READ_ONCE(). A subsequent patch will add
writing with WRITE_ONCE() on teardown.

Reviewed-by: Mina Almasry <almasrymina@...gle.com>
Tested-by: Yonglong Liu <liuyonglong@...wei.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 include/net/page_pool/types.h | 6 +++---
 net/core/page_pool.c          | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index df0d3c1608929605224feb26173135ff37951ef8..d6c93150384fbc4579bb0d0afb357ebb26c564a3 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -173,10 +173,10 @@ struct page_pool {
 	int cpuid;
 	u32 pages_state_hold_cnt;

-	bool has_init_callback:1;	/* slow::init_callback is set */
+	bool dma_sync;				/* Perform DMA sync for device */
+	bool dma_sync_for_cpu:1;		/* Perform DMA sync for cpu */
 	bool dma_map:1;			/* Perform DMA mapping */
-	bool dma_sync:1;		/* Perform DMA sync for device */
-	bool dma_sync_for_cpu:1;	/* Perform DMA sync for cpu */
+	bool has_init_callback:1;	/* slow::init_callback is set */
 #ifdef CONFIG_PAGE_POOL_STATS
 	bool system:1;			/* This is a global percpu pool */
 #endif
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index acef1fcd8ddcfd1853a6f2055c1f1820ab248e8d..fb32768a97765aacc7f1103bfee38000c988b0de 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -466,7 +466,7 @@ page_pool_dma_sync_for_device(const struct page_pool *pool,
 			      netmem_ref netmem,
 			      u32 dma_sync_size)
 {
-	if (pool->dma_sync && dma_dev_need_sync(pool->p.dev))
+	if (READ_ONCE(pool->dma_sync) && dma_dev_need_sync(pool->p.dev))
 		__page_pool_dma_sync_for_device(pool, netmem, dma_sync_size);
 }

-- 
2.48.1