[PATCH net 2/2] net: atlantic: free RX pages of consumed but not refilled buffers

[Yangyu Chen <cyy@cyyself.name>]

aq_ring_rx_deinit() only walks [sw_head, sw_tail), the region posted to
hardware. Since the page reuse strategy was added, a cleaned RX buffer
keeps its page (and its DMA mapping) in the ring for reuse, and refill
is batched: aq_ring_rx_fill() returns early until AQ_CFG_RX_REFILL_THRES
slots are free. Slots that were consumed but not yet reposted therefore
sit in the complementary [sw_tail, sw_head) gap with a live page, and
the deinit walk never visits them: up to a refill batch worth of pages
and DMA mappings leak on every interface down.

Walk the whole ring instead and release whatever is still there. Also
bail out if the buffer ring is already gone: a partial
aq_ptp_ring_alloc() failure frees the ring but leaves aq_nic set, so
aq_ptp_ring_deinit() still gets here on the unwind path.

Fixes: 46f4c29d9de6 ("net: aquantia: optimize rx performance by page reuse strategy")
Cc: stable@vger.kernel.org # v5.2+
Reviewed-by: Sukhdeep Singh <sukhdeeps@marvell.com>
Assisted-by: Claude:claude-fable-5
Signed-off-by: Yangyu Chen <cyy@cyyself.name>
---

Notes:
    Without this fix, the page_pool conversion posted for net-next turns the missed
    pages into fragments that page_pool_destroy() waits for forever.
    Reproduced on an AQC100 with the conversion applied and this fix
    reverted -- ordinary small received frames (<= 256 byte header-only
    packets, e.g. ping replies or pure TCP ACKs) are enough to populate
    the [sw_tail, sw_head) gap:
    
      ping -c 200 -i 0.005 <peer>%enp99s0
      ip link set enp99s0 down
    
    One short ping flow left three of the eight RX rings' pools with
    stranded fragments, and page_pool_release_retry() warns for each of
    them every 60 seconds, indefinitely:
    
      [278084.929092] page_pool_release_retry() stalled pool shutdown: id 123, 1 inflight 60 sec
      [278084.961064] page_pool_release_retry() stalled pool shutdown: id 126, 1 inflight 60 sec
      [278084.961087] page_pool_release_retry() stalled pool shutdown: id 125, 6 inflight 60 sec
      [278145.346737] page_pool_release_retry() stalled pool shutdown: id 123, 1 inflight 120 sec
      [278145.378745] page_pool_release_retry() stalled pool shutdown: id 125, 6 inflight 120 sec
      [278145.378759] page_pool_release_retry() stalled pool shutdown: id 126, 1 inflight 120 sec
    
    With this patch the whole ring is walked at deinit, the pages are
    released, and the pools drain immediately. On the current code the
    same gap leaks the pages and their DMA mappings silently.
    
    Applies and was build- and runtime-tested independently of the
    page_pool conversion, against the current page reuse scheme.

 .../net/ethernet/aquantia/atlantic/aq_ring.c  | 22 +++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
index 81685a4dc5a6..e1193c6719d9 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
@@ -950,15 +950,29 @@ int aq_ring_rx_fill(struct aq_ring_s *self)
 
 void aq_ring_rx_deinit(struct aq_ring_s *self)
 {
-	if (!self)
+	unsigned int i;
+
+	if (!self || !self->buff_ring)
 		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];
+	/* Release every page still owned by the ring.
+	 *
+	 * Walking [sw_head, sw_tail) is not enough: refill is batched
+	 * (aq_ring_rx_fill() waits for AQ_CFG_RX_REFILL_THRES free slots),
+	 * so slots that were cleaned but not yet reposted accumulate in the
+	 * [sw_tail, sw_head) gap, and they keep their page for reuse. Walk
+	 * the whole ring and release whatever is left.
+	 */
+	for (i = 0; i < self->size; i++) {
+		struct aq_ring_buff_s *buff = &self->buff_ring[i];
+
+		if (!buff->rxdata.page)
+			continue;
 
 		aq_free_rxpage(&buff->rxdata, aq_nic_get_dev(self->aq_nic));
 	}
+
+	self->sw_head = self->sw_tail;
 }
 
 void aq_ring_free(struct aq_ring_s *self)
-- 
2.47.3