mm: speculative page references

[linux-2.6] / drivers / net / cassini.c

diff --git a/drivers/net/cassini.c b/drivers/net/cassini.c
index 93e13636f8dda2fef5667cc544b99fb068f2ca17..f1936d51b458e387e3ba0ffef867f1e388bb8a90 100644 (file)
--- a/drivers/net/cassini.c
+++ b/drivers/net/cassini.c
@@ -142,8 +142,8 @@
 
 #define DRV_MODULE_NAME                "cassini"
 #define PFX DRV_MODULE_NAME    ": "
-#define DRV_MODULE_VERSION     "1.5"
-#define DRV_MODULE_RELDATE     "4 Jan 2008"
+#define DRV_MODULE_VERSION     "1.6"
+#define DRV_MODULE_RELDATE     "21 May 2008"
 
 #define CAS_DEF_MSG_ENABLE       \
        (NETIF_MSG_DRV          | \
@@ -576,6 +576,18 @@ static void cas_spare_recover(struct cas *cp, const gfp_t flags)
        list_for_each_safe(elem, tmp, &list) {
                cas_page_t *page = list_entry(elem, cas_page_t, list);
 
+               /*
+                * With the lockless pagecache, cassini buffering scheme gets
+                * slightly less accurate: we might find that a page has an
+                * elevated reference count here, due to a speculative ref,
+                * and skip it as in-use. Ideally we would be able to reclaim
+                * it. However this would be such a rare case, it doesn't
+                * matter too much as we should pick it up the next time round.
+                *
+                * Importantly, if we find that the page has a refcount of 1
+                * here (our refcount), then we know it is definitely not inuse
+                * so we can reuse it.
+                */
                if (page_count(page->buffer) > 1)
                        continue;
 
@@ -2136,9 +2148,12 @@ end_copy_pkt:
                if (addr)
                        cas_page_unmap(addr);
        }
-       skb->csum = csum_unfold(~csum);
-       skb->ip_summed = CHECKSUM_COMPLETE;
        skb->protocol = eth_type_trans(skb, cp->dev);
+       if (skb->protocol == htons(ETH_P_IP)) {
+               skb->csum = csum_unfold(~csum);
+               skb->ip_summed = CHECKSUM_COMPLETE;
+       } else
+               skb->ip_summed = CHECKSUM_NONE;
        return len;
 }