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Re: [Xen-devel] [PATCH net-next v4] xen-netfront: clean up code in xennet_release_rx_bufs




On 2014/1/24 18:48, David Vrabel wrote:
On 24/01/14 03:28, Annie Li wrote:
From: Annie Li <annie.li@xxxxxxxxxx>

This patch removes grant transfer releasing code from netfront, and uses
gnttab_end_foreign_access to end grant access since
gnttab_end_foreign_access_ref may fail when the grant entry is
currently used for reading or writing.

* 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.

* release grant access (through gnttab_end_foreign_access) and skb for tx/rx 
path,
use get_page to ensure page is released when grant access is completed 
successfully.

Xen-blkfront/xen-tpmfront/xen-pcifront also have similar issue, but patches
for them will be created separately.
...
@@ -1439,8 +1403,11 @@ static int netfront_probe(struct xenbus_device *dev,
  static void xennet_end_access(int ref, void *page)
  {
        /* This frees the page as a side-effect */
-       if (ref != GRANT_INVALID_REF)
+       if (ref != GRANT_INVALID_REF) {
+               get_page(virt_to_page(page));
                gnttab_end_foreign_access(ref, 0, (unsigned long)page);
+               free_page((unsigned long)page);
+       }
  }

Oh, these code were kept from my debug, will remove it.

Thanks
Annie
Please drop this hunk.

Otherwise,

Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

David

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