FAILED: patch "[PATCH] net: atlantic: free stranded TX buffers on ring deinit" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 452636ea5410a96e02ebaaf80b21e3620b98e0dd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026081728-ounce-implicit-0ec5@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 452636ea5410a96e02ebaaf80b21e3620b98e0dd Mon Sep 17 00:00:00 2001
From: Yangyu Chen <[email protected]>
Date: Sun, 2 Aug 2026 23:46:00 +0800
Subject: [PATCH] net: atlantic: free stranded TX buffers on ring deinit

aq_vec_deinit() drains the TX rings with a single aq_ring_tx_clean() call, which frees at most AQ_CFG_TX_CLEAN_BUDGET (256) descriptors and stops at hw_head, which no longer moves once aq_vec_stop() has stopped the hardware and NAPI. Completed descriptors beyond the budget and everything still posted in [hw_head, sw_tail) keep their skb or xdp_frame when the interface goes down: aq_vec_ring_free() then frees the buffer ring and the references are lost for good.

Today this is a silent memory leak on every interface down under TX/XDP_TX load. With the conversion of the RX path to page_pool posted for net-next it becomes much more visible: XDP_TX frames carry fragment references on the RX ring's page_pool, so a single stranded frame keeps the pool's inflight count above zero forever. page_pool_destroy() then never completes, the pool is leaked together with its pages, and "page_pool_release_retry() stalled pool shutdown" is warned every 60 seconds from that point on, on every ifdown, XDP detach or ring resize under XDP_TX load.

Bring back aq_ring_tx_deinit() as it was before the removal and use it for teardown again, with one extension: TX rings can hold xdp_frames nowadays, so release those too. They are returned with xdp_return_frame() since this runs in process context.

index 8ff07de2bd52..81685a4dc5a6 100644
@@ -360,6 +360,35 @@ bool aq_ring_tx_clean(struct aq_ring_s *self)
 	return !!budget;
 }
 
+void aq_ring_tx_deinit(struct aq_ring_s *self)
+{
+	if (!self)
+		return;
+
+	for (; self->sw_head != self->sw_tail;
+		self->sw_head = aq_ring_next_dx(self, self->sw_head)) {
+		struct aq_ring_buff_s *buff = &self->buff_ring[self->sw_head];
+		struct device *ndev = aq_nic_get_dev(self->aq_nic);
+
+		if (buff->is_mapped) {
+			if (buff->is_sop) {
+				dma_unmap_single(ndev, buff->pa, buff->len,
+						 DMA_TO_DEVICE);
+			} else {
+				dma_unmap_page(ndev, buff->pa, buff->len,
+					       DMA_TO_DEVICE);
+			}
+		}
+
+		if (buff->is_eop) {
+			if (buff->skb)
+				dev_kfree_skb_any(buff->skb);
+			else if (buff->xdpf)
+				xdp_return_frame(buff->xdpf);
+		}
+	}
+}
+
 static void aq_rx_checksum(struct aq_ring_s *self,
 			   struct aq_ring_buff_s *buff,
 			   struct sk_buff *skb)

index a70b880ada67..6431cc62962f 100644
@@ -202,6 +202,7 @@ void aq_ring_update_queue_state(struct aq_ring_s *ring);
 void aq_ring_queue_wake(struct aq_ring_s *ring);
 void aq_ring_queue_stop(struct aq_ring_s *ring);
 bool aq_ring_tx_clean(struct aq_ring_s *self);
+void aq_ring_tx_deinit(struct aq_ring_s *self);
 int aq_xdp_xmit(struct net_device *dev, int num_frames,
 		struct xdp_frame **frames, u32 flags);
 int aq_ring_rx_clean(struct aq_ring_s *self,

index 2f9033ceed8c..05814fea0f5f 100644
@@ -275,7 +275,7 @@ void aq_vec_deinit(struct aq_vec_s *self)
 
 	for (i = 0U; self->tx_rings > i; ++i) {
 		ring = self->ring[i];
-		aq_ring_tx_clean(&ring[AQ_VEC_TX_ID]);
+		aq_ring_tx_deinit(&ring[AQ_VEC_TX_ID]);
 		aq_ring_rx_deinit(&ring[AQ_VEC_RX_ID]);
 	}
 

From: Yangyu Chen <[email protected]>

[ Upstream commit 452636ea5410a96e02ebaaf80b21e3620b98e0dd ]

aq_vec_deinit() drains the TX rings with a single aq_ring_tx_clean() call, which frees at most AQ_CFG_TX_CLEAN_BUDGET (256) descriptors and stops at hw_head, which no longer moves once aq_vec_stop() has stopped the hardware and NAPI. Completed descriptors beyond the budget and everything still posted in [hw_head, sw_tail) keep their skb or xdp_frame when the interface goes down: aq_vec_ring_free() then frees the buffer ring and the references are lost for good.

Today this is a silent memory leak on every interface down under TX/XDP_TX load. With the conversion of the RX path to page_pool posted for net-next it becomes much more visible: XDP_TX frames carry fragment references on the RX ring's page_pool, so a single stranded frame keeps the pool's inflight count above zero forever. page_pool_destroy() then never completes, the pool is leaked together with its pages, and "page_pool_release_retry() stalled pool shutdown" is warned every 60 seconds from that point on, on every ifdown, XDP detach or ring resize under XDP_TX load.

Bring back aq_ring_tx_deinit() as it was before the removal and use it for teardown again, with one extension: TX rings can hold xdp_frames nowadays, so release those too. They are returned with xdp_return_frame() since this runs in process context.

---
 .../net/ethernet/aquantia/atlantic/aq_ring.c  | 25 +++++++++++++++++++
 .../net/ethernet/aquantia/atlantic/aq_ring.h  |  1 +
 .../net/ethernet/aquantia/atlantic/aq_vec.c   |  2 +-
 3 files changed, 27 insertions(+), 1 deletion(-)

index 4063d4a6f47e1..685fb78846c66 100644
@@ -314,6 +314,31 @@ bool aq_ring_tx_clean(struct aq_ring_s *self)
 	return !!budget;
 }
 
+void aq_ring_tx_deinit(struct aq_ring_s *self)
+{
+	if (!self)
+		return;
+
+	for (; self->sw_head != self->sw_tail;
+		self->sw_head = aq_ring_next_dx(self, self->sw_head)) {
+		struct aq_ring_buff_s *buff = &self->buff_ring[self->sw_head];
+		struct device *ndev = aq_nic_get_dev(self->aq_nic);
+
+		if (buff->is_mapped) {
+			if (buff->is_sop) {
+				dma_unmap_single(ndev, buff->pa, buff->len,
+						 DMA_TO_DEVICE);
+			} else {
+				dma_unmap_page(ndev, buff->pa, buff->len,
+					       DMA_TO_DEVICE);
+			}
+		}
+
+		if (buff->is_eop && buff->skb)
+			dev_kfree_skb_any(buff->skb);
+	}
+}
+
 static void aq_rx_checksum(struct aq_ring_s *self,
 			   struct aq_ring_buff_s *buff,
 			   struct sk_buff *skb)

index 93659e58f1ce1..3be56a4fc5bb0 100644
@@ -182,6 +182,7 @@ void aq_ring_update_queue_state(struct aq_ring_s *ring);
 void aq_ring_queue_wake(struct aq_ring_s *ring);
 void aq_ring_queue_stop(struct aq_ring_s *ring);
 bool aq_ring_tx_clean(struct aq_ring_s *self);
+void aq_ring_tx_deinit(struct aq_ring_s *self);
 int aq_ring_rx_clean(struct aq_ring_s *self,
 		     struct napi_struct *napi,
 		     int *work_done,

index 6ab1f3212d246..2d77554d1b819 100644
@@ -270,7 +270,7 @@ void aq_vec_deinit(struct aq_vec_s *self)
 
 	for (i = 0U; self->tx_rings > i; ++i) {
 		ring = self->ring[i];
-		aq_ring_tx_clean(&ring[AQ_VEC_TX_ID]);
+		aq_ring_tx_deinit(&ring[AQ_VEC_TX_ID]);
 		aq_ring_rx_deinit(&ring[AQ_VEC_RX_ID]);
 	}
 

2.53.0