netdev - [RFC net-next v1 6/6] io_uring/zcrx: avoid netmem casts with nmdesc

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Message-ID: <7468b556ab5f9ac79f00a530464590e65f65e712.1754929026.git.asml.silence@gmail.com>
Date: Mon, 11 Aug 2025 17:29:43 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	davem@...emloft.net,
	sdf@...ichev.me,
	almasrymina@...gle.com,
	dw@...idwei.uk,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Byungchul Park <byungchul@...com>,
	asml.silence@...il.com
Subject: [RFC net-next v1 6/6] io_uring/zcrx: avoid netmem casts with nmdesc

There is a bunch of hot path places where zcrx casts a net_iov to a
netmem just to pass it to a generic helper, which will immediately
remove NET_IOV from it. It's messy, and compilers can't completely
optimise it. Use newly introduced netmem_desc based helpers to avoid the
overhead.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 io_uring/zcrx.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index e5ff49f3425e..9c733a490122 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -301,7 +301,7 @@ static void io_zcrx_sync_for_device(const struct page_pool *pool,
 	if (!dma_dev_need_sync(pool->p.dev))
 		return;
 
-	dma_addr = page_pool_get_dma_addr_netmem(net_iov_to_netmem(niov));
+	dma_addr = page_pool_get_dma_addr_nmdesc(&niov->desc);
 	__dma_sync_single_for_device(pool->p.dev, dma_addr + pool->p.offset,
 				     PAGE_SIZE, pool->p.dma_dir);
 #endif
@@ -752,7 +752,6 @@ static void io_zcrx_ring_refill(struct page_pool *pp,
 {
 	unsigned int mask = ifq->rq_entries - 1;
 	unsigned int entries;
-	netmem_ref netmem;
 
 	spin_lock_bh(&ifq->rq_lock);
 
@@ -784,8 +783,7 @@ static void io_zcrx_ring_refill(struct page_pool *pp,
 		if (!io_zcrx_put_niov_uref(niov))
 			continue;
 
-		netmem = net_iov_to_netmem(niov);
-		if (page_pool_unref_netmem(netmem, 1) != 0)
+		if (page_pool_unref_nmdesc(&niov->desc, 1) != 0)
 			continue;
 
 		if (unlikely(niov->pp != pp)) {
@@ -794,7 +792,7 @@ static void io_zcrx_ring_refill(struct page_pool *pp,
 		}
 
 		io_zcrx_sync_for_device(pp, niov);
-		net_mp_netmem_place_in_cache(pp, netmem);
+		net_mp_netmem_place_in_cache(pp, net_iov_to_netmem(niov));
 	} while (--entries);
 
 	smp_store_release(&ifq->rq_ring->head, ifq->cached_rq_head);
@@ -950,7 +948,7 @@ static struct net_iov *io_zcrx_alloc_fallback(struct io_zcrx_area *area)
 	spin_unlock_bh(&area->freelist_lock);
 
 	if (niov)
-		page_pool_fragment_netmem(net_iov_to_netmem(niov), 1);
+		page_pool_fragment_nmdesc(&niov->desc, 1);
 	return niov;
 }
 
@@ -1070,7 +1068,7 @@ static int io_zcrx_recv_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
 	 * Prevent it from being recycled while user is accessing it.
 	 * It has to be done before grabbing a user reference.
 	 */
-	page_pool_ref_netmem(net_iov_to_netmem(niov));
+	page_pool_ref_nmdesc(&niov->desc);
 	io_zcrx_get_niov_uref(niov);
 	return len;
 }
-- 
2.49.0