[Xen-devel] [PATCH net-next] xen-netback: Follow-up patch for grant mapping series

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

Ian made some late comments about the grant mapping series, I incorporated the
outcomes into this patch. Additional comments, refactoring etc.

Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
---
diff --git a/drivers/net/xen-netback/interface.c 
b/drivers/net/xen-netback/interface.c
index 6837bfc..fa19538 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -576,15 +576,15 @@ void xenvif_disconnect(struct xenvif *vif)
 void xenvif_free(struct xenvif *vif)
 {
        int i, unmap_timeout = 0;
-       /* Here we want to avoid timeout messages if an skb can be legitimatly
-        * stucked somewhere else. Realisticly this could be an another vif's
+       /* Here we want to avoid timeout messages if an skb can be legitimately
+        * stuck somewhere else. Realistically this could be an another vif's
         * internal or QDisc queue. That another vif also has this
         * rx_drain_timeout_msecs timeout, but the timer only ditches the
         * internal queue. After that, the QDisc queue can put in worst case
         * XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS skbs into that another vif's
         * internal queue, so we need several rounds of such timeouts until we
         * can be sure that no another vif should have skb's from us. We are
-        * not sending more skb's, so newly stucked packets are not interesting
+        * not sending more skb's, so newly stuck packets are not interesting
         * for us here.
         */
        unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000) *
@@ -599,6 +599,13 @@ void xenvif_free(struct xenvif *vif)
                                netdev_err(vif->dev,
                                           "Page still granted! Index: %x\n",
                                           i);
+                       /* If there are still unmapped pages, reset the loop to
+                        * start mchecking again. We shouldn't exit here until
+                        * dealloc thread and NAPI instance release all the
+                        * pages. If a kernel bug cause the skbs stall
+                        * somewhere, the interface couldn't be brought down
+                        * properly.
+                        */
                        i = -1;
                }
        }
diff --git a/drivers/net/xen-netback/netback.c 
b/drivers/net/xen-netback/netback.c
index 1c336f6..0e46184b 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -56,7 +56,7 @@ bool separate_tx_rx_irq = 1;
 module_param(separate_tx_rx_irq, bool, 0644);
 
 /* When guest ring is filled up, qdisc queues the packets for us, but we have
- * to timeout them, otherwise other guests' packets can get stucked there
+ * to timeout them, otherwise other guests' packets can get stuck there
  */
 unsigned int rx_drain_timeout_msecs = 10000;
 module_param(rx_drain_timeout_msecs, uint, 0444);
@@ -99,6 +99,9 @@ static inline unsigned long idx_to_kaddr(struct xenvif *vif,
        return (unsigned long)pfn_to_kaddr(idx_to_pfn(vif, idx));
 }
 
+#define callback_param(vif, pending_idx) \
+       (vif->pending_tx_info[pending_idx].callback_struct)
+
 /* Find the containing VIF's structure from a pointer in pending_tx_info array
  */
 static inline struct xenvif* ubuf_to_vif(struct ubuf_info *ubuf)
@@ -1025,12 +1028,12 @@ static void xenvif_fill_frags(struct xenvif *vif, 
struct sk_buff *skb)
                /* If this is not the first frag, chain it to the previous*/
                if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
                        skb_shinfo(skb)->destructor_arg =
-                               
&vif->pending_tx_info[pending_idx].callback_struct;
+                               &callback_param(vif, pending_idx);
                else if (likely(pending_idx != prev_pending_idx))
-                       
vif->pending_tx_info[prev_pending_idx].callback_struct.ctx =
-                               
&(vif->pending_tx_info[pending_idx].callback_struct);
+                       callback_param(vif, prev_pending_idx).ctx =
+                               &callback_param(vif, pending_idx);
 
-               vif->pending_tx_info[pending_idx].callback_struct.ctx = NULL;
+               callback_param(vif, pending_idx).ctx = NULL;
                prev_pending_idx = pending_idx;
 
                txp = &vif->pending_tx_info[pending_idx].req;
@@ -1400,13 +1403,13 @@ static int xenvif_tx_submit(struct xenvif *vif)
                memcpy(skb->data,
                       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
                       data_len);
-               vif->pending_tx_info[pending_idx].callback_struct.ctx = NULL;
+               callback_param(vif, pending_idx).ctx = NULL;
                if (data_len < txp->size) {
                        /* Append the packet payload as a fragment. */
                        txp->offset += data_len;
                        txp->size -= data_len;
                        skb_shinfo(skb)->destructor_arg =
-                               
&vif->pending_tx_info[pending_idx].callback_struct;
+                               &callback_param(vif, pending_idx);
                } else {
                        /* Schedule a response immediately. */
                        xenvif_idx_unmap(vif, pending_idx);
@@ -1550,7 +1553,6 @@ static inline void xenvif_tx_dealloc_action(struct xenvif 
*vif)
                                            idx_to_kaddr(vif, pending_idx),
                                            GNTMAP_host_map,
                                            vif->grant_tx_handle[pending_idx]);
-                       /* Btw. already unmapped? */
                        xenvif_grant_handle_reset(vif, pending_idx);
                        ++gop;
                }
@@ -1683,12 +1685,20 @@ void xenvif_idx_unmap(struct xenvif *vif, u16 
pending_idx)
                            idx_to_kaddr(vif, pending_idx),
                            GNTMAP_host_map,
                            vif->grant_tx_handle[pending_idx]);
-       /* Btw. already unmapped? */
        xenvif_grant_handle_reset(vif, pending_idx);
 
        ret = gnttab_unmap_refs(&tx_unmap_op, NULL,
                                &vif->mmap_pages[pending_idx], 1);
-       BUG_ON(ret);
+       if (ret) {
+               netdev_err(vif->dev,
+                          "Unmap fail: ret: %d pending_idx: %d host_addr: %llx 
handle: %x status: %d\n",
+                          ret,
+                          pending_idx,
+                          tx_unmap_op.host_addr,
+                          tx_unmap_op.handle,
+                          tx_unmap_op.status);
+               BUG();
+       }
 
        xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
 }

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