s390/qeth: improve completion of pending TX buffers

The current design attaches a pending TX buffer to a custom
single-linked list, which is anchored at the buffer's slot on the
TX ring. The buffer is then checked for final completion whenever
this slot is processed during a subsequent TX NAPI poll cycle.

But if there's insufficient traffic on the ring, we might never make
enough progress to get back to this ring slot and discover the pending
buffer's final TX completion. In particular if this missing TX
completion blocks the application from sending further traffic.

So convert the custom single-linked list code to a per-queue list_head,
and scan this list on every TX NAPI cycle.

Fixes: 0da9581ddb0f ("qeth: exploit asynchronous delivery of storage blocks")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index a1da83b0b0ef..91acff493612 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -436,7 +436,7 @@ struct qeth_qdio_out_buffer {
 	int is_header[QDIO_MAX_ELEMENTS_PER_BUFFER];
 
 	struct qeth_qdio_out_q *q;
-	struct qeth_qdio_out_buffer *next_pending;
+	struct list_head list_entry;
 };
 
 struct qeth_card;
@@ -500,6 +500,7 @@ struct qeth_qdio_out_q {
 	struct qdio_buffer *qdio_bufs[QDIO_MAX_BUFFERS_PER_Q];
 	struct qeth_qdio_out_buffer *bufs[QDIO_MAX_BUFFERS_PER_Q];
 	struct qdio_outbuf_state *bufstates; /* convenience pointer */
+	struct list_head pending_bufs;
 	struct qeth_out_q_stats stats;
 	spinlock_t lock;
 	unsigned int priority;