Re: [Xen-devel] [ [PATCH net-next v3] xen-netfront: clean up code in xennet_release_rx_bufs

[Annie <annie.li@xxxxxxxxxx>]

On 01/23/2014 2:55 AM, David Vrabel <david.vrabel@xxxxxxxxxx> wrote

> On 23/01/14 01:36, Annie Li wrote:
>> From: Annie Li <annie.li@xxxxxxxxxx>
>> 
>> This patch removes grant transfer code from netfront, and improves ending
>> grant acess mechanism since gnttab_end_foreign_access_ref may fail when
>> the grant entry is currently used for reading or writing.
>> 
>> * release grant reference and skb for tx/rx path, use get_page/put_page to
>> ensure page is released when grant access is completed successfully.
>> * change corresponding code in xen-blkfront/xen-tpmfront/xen-pcifront because
>> of code change for put_page in gnttab_end_foreign_access.
>> * 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.
>> 
>> V3: Changes as suggestion from David Vrabel, ensure pages are not freed 
>> untill
>> grant acess is ended.
>> 
>> V2: improve patch comments.
>> Signed-off-by: Annie Li <annie.li@xxxxxxxxxx>
>> ---
>> drivers/block/xen-blkfront.c    |   25 ++++++++---
>> drivers/char/tpm/xen-tpmfront.c |    7 +++-
>> drivers/net/xen-netfront.c      |   93 ++++++++++++--------------------------
>> drivers/pci/xen-pcifront.c      |    7 +++-
>> drivers/xen/grant-table.c       |    4 +-
>> 5 files changed, 63 insertions(+), 73 deletions(-)
> 
> I don't understand why you've made all these unnecessary changes to the
> other frontends and grant-table.c.
> 
> The xen-netfront.c changes are fine on their own.

Changes in grant-table.c corresponds to get_page before 
gnttab_end_foreign_access, just keeping consistent in the function name. This 
change does not really change the mechanism, so I can revert it.

For the changes in other frontends, the reason is they also have similar issue 
- grant access probably is not ended successfully when the page is freed.

Thanks
Annie
> 
> David
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