[PATCH RFC net-next v4 10/14] xsk: extend xsk_cq_reserve_locked() to reserve n slots

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

Previously it only reserves one slot. The patch extends it to n to cover
the batch mode.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 net/xdp/xsk.c       | 12 ++++++++----
 net/xdp/xsk_queue.h | 12 +++++++-----
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 6cd2e58e170c..c26e26cb4dda 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -546,12 +546,17 @@ static int xsk_wakeup(struct xdp_sock *xs, u8 flags)
 	return dev->netdev_ops->ndo_xsk_wakeup(dev, xs->queue_id, flags);
 }
 
-static int xsk_cq_reserve_locked(struct xsk_buff_pool *pool)
+/* The function tries to reserve as many descs as possible. If there
+ * is no single slot to allocate, return zero. Otherwise, return how
+ * many slots are available, even though it might stop reserving at
+ * certain point.
+ */
+static int xsk_cq_reserve_locked(struct xsk_buff_pool *pool, u32 n)
 {
 	int ret;
 
 	spin_lock(&pool->cq->cq_cached_prod_lock);
-	ret = xskq_prod_reserve(pool->cq);
+	ret = xskq_prod_reserve(pool->cq, n);
 	spin_unlock(&pool->cq->cq_cached_prod_lock);
 
 	return ret;
@@ -947,8 +952,7 @@ static int __xsk_generic_xmit(struct sock *sk)
 		 * if there is space in it. This avoids having to implement
 		 * any buffering in the Tx path.
 		 */
-		err = xsk_cq_reserve_locked(xs->pool);
-		if (err) {
+		if (!xsk_cq_reserve_locked(xs->pool, 1)) {
 			err = -EAGAIN;
 			goto out;
 		}
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 354f6fe86893..34cc07d6115e 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -413,14 +413,16 @@ static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt)
 	q->cached_prod -= cnt;
 }
 
-static inline int xskq_prod_reserve(struct xsk_queue *q)
+static inline int xskq_prod_reserve(struct xsk_queue *q, u32 n)
 {
-	if (xskq_prod_is_full(q))
-		return -ENOSPC;
+	u32 nr_free = xskq_prod_nb_free(q, n);
+
+	if (!nr_free)
+		return 0;
 
 	/* A, matches D */
-	q->cached_prod++;
-	return 0;
+	q->cached_prod += nr_free;
+	return nr_free;
 }
 
 static inline int xskq_prod_reserve_addr(struct xsk_queue *q, u64 addr)
-- 
2.41.3