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

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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