[PATCH 2.6.35-rc1] net: vmxnet3 fixes [0/5] Spare skb to avoid starvation

* [PATCH 2.6.35-rc1] net: vmxnet3 fixes [0/5] Spare skb to avoid starvation
@ 2010-07-07  9:00 Shreyas Bhatewara
  2010-07-07  9:24 ` [PATCH 2.6.35-rc1] net: vmxnet3 fixes [2/5] Interrupt control bitmap Shreyas Bhatewara
                   ` (2 more replies)
  0 siblings, 3 replies; 32+ messages in thread
From: Shreyas Bhatewara @ 2010-07-07  9:00 UTC (permalink / raw)
  To: netdev-devel; +Cc: linux-kernel, pv-drivers, stolarchuk


From: Shreyas Bhatewara <sbhatewara@vmware.com>

skb_alloc() failure can cause the recv ring to loose all packet reception.
Avoid this by introducing a spare buffer.

Signed-off-by: Michael Stolarchuk <stolarchuk@vmware.com>
Signed-off-by: Shreyas Bhatewara <sbhatewara@vmware.com>

---

diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
index 989b742..5a50d10 100644
--- a/drivers/net/vmxnet3/vmxnet3_drv.c
+++ b/drivers/net/vmxnet3/vmxnet3_drv.c
@@ -541,7 +541,12 @@ vmxnet3_rq_alloc_rx_buf(struct vmxnet3_rx_queue *rq, u32 ring_idx,
 							 NET_IP_ALIGN);
 				if (unlikely(rbi->skb == NULL)) {
 					rq->stats.rx_buf_alloc_failure++;
-					break;
+					/* starvation prevention */
+					if (vmxnet3_cmd_ring_desc_empty(
+							rq->rx_ring + ring_idx))
+						rbi->skb = rq->spare_skb;
+					else
+						break;
 				}
 				rbi->skb->dev = adapter->netdev;
 
@@ -611,6 +616,29 @@ vmxnet3_append_frag(struct sk_buff *skb, struct Vmxnet3_RxCompDesc *rcd,
 }
 
 
+/*
+ * Free any pages which were attached to the frags of the spare skb.  This can
+ * happen when the spare skb is attached to the rx ring to prevent starvation,
+ * but there was no issue with page allocation.
+ */
+
+static void
+vmxnet3_rx_spare_skb_free_frags(struct vmxnet3_adapter *adapter)
+{
+	struct sk_buff *skb = adapter->rx_queue.spare_skb;
+	int i;
+	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+		struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i];
+		BUG_ON(frag->page != 0);
+		put_page(frag->page);
+		frag->page = 0;
+		frag->size = 0;
+	}
+	skb_shinfo(skb)->nr_frags = 0;
+	skb->data_len = 0;
+}
+
+
 static void
 vmxnet3_map_pkt(struct sk_buff *skb, struct vmxnet3_tx_ctx *ctx,
 		struct vmxnet3_tx_queue *tq, struct pci_dev *pdev,
@@ -1060,8 +1088,12 @@ vmxnet3_rx_error(struct vmxnet3_rx_queue *rq, struct Vmxnet3_RxCompDesc *rcd,
 	 * ctx->skb may be NULL if this is the first and the only one
 	 * desc for the pkt
 	 */
-	if (ctx->skb)
-		dev_kfree_skb_irq(ctx->skb);
+	if (ctx->skb) {
+		if (ctx->skb == rq->spare_skb)
+			vmxnet3_rx_spare_skb_free_frags(adapter);
+		else
+			dev_kfree_skb_irq(ctx->skb);
+	}
 
 	ctx->skb = NULL;
 }
@@ -1159,6 +1191,12 @@ vmxnet3_rq_rx_complete(struct vmxnet3_rx_queue *rq,
 
 		skb = ctx->skb;
 		if (rcd->eop) {
+			if (skb == rq->spare_skb) {
+				rq->stats.drop_total++;
+				vmxnet3_rx_spare_skb_free_frags(adapter);
+				ctx->skb = NULL;
+				goto rcd_done;
+			}
 			skb->len += skb->data_len;
 			skb->truesize += skb->data_len;
 
@@ -1244,6 +1282,14 @@ vmxnet3_rq_cleanup(struct vmxnet3_rx_queue *rq,
 		rq->uncommitted[ring_idx] = 0;
 	}
 
+	/* free starvation prevention skb if allocated */
+	if (rq->spare_skb) {
+		vmxnet3_rx_spare_skb_free_frags(adapter);
+		dev_kfree_skb(rq->spare_skb);
+		rq->spare_skb = NULL;
+	}
+
+
 	rq->comp_ring.gen = VMXNET3_INIT_GEN;
 	rq->comp_ring.next2proc = 0;
 }
@@ -1325,6 +1371,15 @@ vmxnet3_rq_init(struct vmxnet3_rx_queue *rq,
 	}
 	vmxnet3_rq_alloc_rx_buf(rq, 1, rq->rx_ring[1].size - 1, adapter);
 
+	/* allocate ring starvation protection */
+	rq->spare_skb = dev_alloc_skb(PAGE_SIZE);
+	if (rq->spare_skb == NULL) {
+		vmxnet3_rq_cleanup(rq, adapter);
+		return -ENOMEM;
+	}
+
+
+
 	/* reset the comp ring */
 	rq->comp_ring.next2proc = 0;
 	memset(rq->comp_ring.base, 0, rq->comp_ring.size *
diff --git a/drivers/net/vmxnet3/vmxnet3_int.h b/drivers/net/vmxnet3/vmxnet3_int.h
index 34f392f..7985ba4 100644
--- a/drivers/net/vmxnet3/vmxnet3_int.h
+++ b/drivers/net/vmxnet3/vmxnet3_int.h
@@ -68,10 +68,10 @@
 /*
  * Version numbers
  */
-#define VMXNET3_DRIVER_VERSION_STRING   "1.0.5.0-k"
+#define VMXNET3_DRIVER_VERSION_STRING   "1.0.6.0-k"
 
 /* a 32-bit int, each byte encode a verion number in VMXNET3_DRIVER_VERSION */
-#define VMXNET3_DRIVER_VERSION_NUM      0x01000500
+#define VMXNET3_DRIVER_VERSION_NUM      0x01000600
 
 
 /*
@@ -149,6 +149,13 @@ vmxnet3_cmd_ring_desc_avail(struct vmxnet3_cmd_ring *ring)
 		ring->next2comp - ring->next2fill - 1;
 }
 
+static inline bool
+vmxnet3_cmd_ring_desc_empty(struct vmxnet3_cmd_ring *ring)
+{
+	return (ring->next2comp == ring->next2fill);
+}
+
+
 struct vmxnet3_comp_ring {
 	union Vmxnet3_GenericDesc *base;
 	u32               size;
@@ -266,9 +273,10 @@ struct vmxnet3_rx_queue {
 	u32 qid2;           /* rqID in RCD for buffer from 2nd ring */
 	u32 uncommitted[2]; /* # of buffers allocated since last RXPROD
 				* update */
-	struct vmxnet3_rx_buf_info     *buf_info[2];
-	struct Vmxnet3_RxQueueCtrl            *shared;
+	struct vmxnet3_rx_buf_info	*buf_info[2];
+	struct Vmxnet3_RxQueueCtrl	*shared;
 	struct vmxnet3_rq_driver_stats  stats;
+	struct sk_buff			*spare_skb;      /* starvation skb */
 } __attribute__((__aligned__(SMP_CACHE_BYTES)));
 
 #define VMXNET3_LINUX_MAX_MSIX_VECT     1

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