4.4-stable review patch. If anyone has any objections, please let me know.
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From: Igor Druzhinin igor.druzhinin@citrix.com
[ Upstream commit 99e87f56b48f490fb16b6e0f74691c1e664dea95 ]
Zero-copy callback flag is not yet set on frag list skb at the moment xenvif_handle_frag_list() returns -ENOMEM. This eventually results in leaking grant ref mappings since xenvif_zerocopy_callback() is never called for these fragments. Those eventually build up and cause Xen to kill Dom0 as the slots get reused for new mappings:
"d0v0 Attempt to implicitly unmap a granted PTE c010000329fce005"
That behavior is observed under certain workloads where sudden spikes of page cache writes coexist with active atomic skb allocations from network traffic. Additionally, rework the logic to deal with frag_list deallocation in a single place.
Signed-off-by: Paul Durrant paul.durrant@citrix.com Signed-off-by: Igor Druzhinin igor.druzhinin@citrix.com Acked-by: Wei Liu wei.liu2@citrix.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/xen-netback/netback.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
--- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1538,11 +1538,6 @@ static int xenvif_handle_frag_list(struc skb_frag_size_set(&frags[i], len); }
- /* Copied all the bits from the frag list -- free it. */ - skb_frag_list_init(skb); - xenvif_skb_zerocopy_prepare(queue, nskb); - kfree_skb(nskb); - /* Release all the original (foreign) frags. */ for (f = 0; f < skb_shinfo(skb)->nr_frags; f++) skb_frag_unref(skb, f); @@ -1611,6 +1606,8 @@ static int xenvif_tx_submit(struct xenvi xenvif_fill_frags(queue, skb);
if (unlikely(skb_has_frag_list(skb))) { + struct sk_buff *nskb = skb_shinfo(skb)->frag_list; + xenvif_skb_zerocopy_prepare(queue, nskb); if (xenvif_handle_frag_list(queue, skb)) { if (net_ratelimit()) netdev_err(queue->vif->dev, @@ -1619,6 +1616,9 @@ static int xenvif_tx_submit(struct xenvi kfree_skb(skb); continue; } + /* Copied all the bits from the frag list -- free it. */ + skb_frag_list_init(skb); + kfree_skb(nskb); }
skb->dev = queue->vif->dev;