[Xen-devel] [PATCH net-next v2] xen-netfront: clean up code in xennet_release_rx_bufs

[Annie Li <Annie.li@xxxxxxxxxx>]

This patch implements two things:

* release grant reference and skb for rx path, this fixex resource leaking.
* clean up grant transfer code kept from old netfront(2.6.18) which grants
pages for access/map and transfer. But grant transfer is deprecated in current
netfront, so remove corresponding release code for transfer.

gnttab_end_foreign_access_ref may fail when the grant entry is currently used
for reading or writing. But this patch does not cover this and improvement for
this failure may be implemented in a separate patch.

Test has been run with this patch.

V2: improve patch comments.

Signed-off-by: Annie Li <Annie.li@xxxxxxxxxx>
---
 drivers/net/xen-netfront.c |   60 ++-----------------------------------------
 1 files changed, 3 insertions(+), 57 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index e59acb1..692589e 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1134,78 +1134,24 @@ static void xennet_release_tx_bufs(struct netfront_info 
*np)
 
 static void xennet_release_rx_bufs(struct netfront_info *np)
 {
-       struct mmu_update      *mmu = np->rx_mmu;
-       struct multicall_entry *mcl = np->rx_mcl;
-       struct sk_buff_head free_list;
        struct sk_buff *skb;
-       unsigned long mfn;
-       int xfer = 0, noxfer = 0, unused = 0;
        int id, ref;
 
-       dev_warn(&np->netdev->dev, "%s: fix me for copying receiver.\n",
-                        __func__);
-       return;
-
-       skb_queue_head_init(&free_list);
-
        spin_lock_bh(&np->rx_lock);
 
        for (id = 0; id < NET_RX_RING_SIZE; id++) {
                ref = np->grant_rx_ref[id];
-               if (ref == GRANT_INVALID_REF) {
-                       unused++;
+               if (ref == GRANT_INVALID_REF)
                        continue;
-               }
 
                skb = np->rx_skbs[id];
-               mfn = gnttab_end_foreign_transfer_ref(ref);
+               gnttab_end_foreign_access_ref(ref, 0);
                gnttab_release_grant_reference(&np->gref_rx_head, ref);
                np->grant_rx_ref[id] = GRANT_INVALID_REF;
 
-               if (0 == mfn) {
-                       skb_shinfo(skb)->nr_frags = 0;
-                       dev_kfree_skb(skb);
-                       noxfer++;
-                       continue;
-               }
-
-               if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-                       /* Remap the page. */
-                       const struct page *page =
-                               skb_frag_page(&skb_shinfo(skb)->frags[0]);
-                       unsigned long pfn = page_to_pfn(page);
-                       void *vaddr = page_address(page);
-
-                       MULTI_update_va_mapping(mcl, (unsigned long)vaddr,
-                                               mfn_pte(mfn, PAGE_KERNEL),
-                                               0);
-                       mcl++;
-                       mmu->ptr = ((u64)mfn << PAGE_SHIFT)
-                               | MMU_MACHPHYS_UPDATE;
-                       mmu->val = pfn;
-                       mmu++;
-
-                       set_phys_to_machine(pfn, mfn);
-               }
-               __skb_queue_tail(&free_list, skb);
-               xfer++;
-       }
-
-       dev_info(&np->netdev->dev, "%s: %d xfer, %d noxfer, %d unused\n",
-                __func__, xfer, noxfer, unused);
-
-       if (xfer) {
-               if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-                       /* Do all the remapping work and M2P updates. */
-                       MULTI_mmu_update(mcl, np->rx_mmu, mmu - np->rx_mmu,
-                                        NULL, DOMID_SELF);
-                       mcl++;
-                       HYPERVISOR_multicall(np->rx_mcl, mcl - np->rx_mcl);
-               }
+               kfree_skb(skb);
        }
 
-       __skb_queue_purge(&free_list);
-
        spin_unlock_bh(&np->rx_lock);
 }
 
-- 
1.7.6.5


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