Re: [PATCH V2 11/20] tap: support enabling or disabling a queue

From: Jason Wang <jasowang@redhat.com>
To: Blue Swirl <blauwirbel@gmail.com>
Cc: krkumar2@in.ibm.com, aliguori@us.ibm.com, kvm@vger.kernel.org,
	mst@redhat.com, mprivozn@redhat.com, rusty@rustcorp.com.au,
	qemu-devel@nongnu.org, shajnocz@redhat.com,
	gaowanlong@cn.fujitsu.com, jwhan@filewood.snu.ac.kr,
	shiyer@redhat.com
Subject: Re: [PATCH V2 11/20] tap: support enabling or disabling a queue
Date: Tue, 29 Jan 2013 21:50:45 +0800	[thread overview]
Message-ID: <5107D3B5.8050506@redhat.com> (raw)
In-Reply-To: <CAAu8pHu4XXtbyt5ZXE2pXjeupgRz=K=fxYJU_iy6UUG3FrSS-w@mail.gmail.com>

On 01/26/2013 03:13 AM, Blue Swirl wrote:
> On Fri, Jan 25, 2013 at 10:35 AM, Jason Wang <jasowang@redhat.com> wrote:
>> This patch introduce a new bit - enabled in TAPState which tracks whether a
>> specific queue/fd is enabled. The tap/fd is enabled during initialization and
>> could be enabled/disabled by tap_enalbe() and tap_disable() which calls platform
>> specific helpers to do the real work. Polling of a tap fd can only done when
>> the tap was enabled.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>  include/net/tap.h |    2 ++
>>  net/tap-win32.c   |   10 ++++++++++
>>  net/tap.c         |   43 ++++++++++++++++++++++++++++++++++++++++---
>>  3 files changed, 52 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/net/tap.h b/include/net/tap.h
>> index bb7efb5..0caf8c4 100644
>> --- a/include/net/tap.h
>> +++ b/include/net/tap.h
>> @@ -35,6 +35,8 @@ int tap_has_vnet_hdr_len(NetClientState *nc, int len);
>>  void tap_using_vnet_hdr(NetClientState *nc, int using_vnet_hdr);
>>  void tap_set_offload(NetClientState *nc, int csum, int tso4, int tso6, int ecn, int ufo);
>>  void tap_set_vnet_hdr_len(NetClientState *nc, int len);
>> +int tap_enable(NetClientState *nc);
>> +int tap_disable(NetClientState *nc);
>>
>>  int tap_get_fd(NetClientState *nc);
>>
>> diff --git a/net/tap-win32.c b/net/tap-win32.c
>> index 265369c..a2cd94b 100644
>> --- a/net/tap-win32.c
>> +++ b/net/tap-win32.c
>> @@ -764,3 +764,13 @@ void tap_set_vnet_hdr_len(NetClientState *nc, int len)
>>  {
>>      assert(0);
>>  }
>> +
>> +int tap_enable(NetClientState *nc)
>> +{
>> +    assert(0);
> abort()

This is just to be consistent with the reset of the helpers in this file.
>
>> +}
>> +
>> +int tap_disable(NetClientState *nc)
>> +{
>> +    assert(0);
>> +}
>> diff --git a/net/tap.c b/net/tap.c
>> index 67080f1..95e557b 100644
>> --- a/net/tap.c
>> +++ b/net/tap.c
>> @@ -59,6 +59,7 @@ typedef struct TAPState {
>>      unsigned int write_poll : 1;
>>      unsigned int using_vnet_hdr : 1;
>>      unsigned int has_ufo: 1;
>> +    unsigned int enabled : 1;
> bool without bit field?

Also to be consistent with other field. If you wish I can send patches
to convert all those bit field to bool on top of this series.

Thanks
>>      VHostNetState *vhost_net;
>>      unsigned host_vnet_hdr_len;
>>  } TAPState;
>> @@ -72,9 +73,9 @@ static void tap_writable(void *opaque);
>>  static void tap_update_fd_handler(TAPState *s)
>>  {
>>      qemu_set_fd_handler2(s->fd,
>> -                         s->read_poll  ? tap_can_send : NULL,
>> -                         s->read_poll  ? tap_send     : NULL,
>> -                         s->write_poll ? tap_writable : NULL,
>> +                         s->read_poll && s->enabled ? tap_can_send : NULL,
>> +                         s->read_poll && s->enabled ? tap_send     : NULL,
>> +                         s->write_poll && s->enabled ? tap_writable : NULL,
>>                           s);
>>  }
>>
>> @@ -339,6 +340,7 @@ static TAPState *net_tap_fd_init(NetClientState *peer,
>>      s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
>>      s->using_vnet_hdr = 0;
>>      s->has_ufo = tap_probe_has_ufo(s->fd);
>> +    s->enabled = 1;
>>      tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
>>      /*
>>       * Make sure host header length is set correctly in tap:
>> @@ -737,3 +739,38 @@ VHostNetState *tap_get_vhost_net(NetClientState *nc)
>>      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
>>      return s->vhost_net;
>>  }
>> +
>> +int tap_enable(NetClientState *nc)
>> +{
>> +    TAPState *s = DO_UPCAST(TAPState, nc, nc);
>> +    int ret;
>> +
>> +    if (s->enabled) {
>> +        return 0;
>> +    } else {
>> +        ret = tap_fd_enable(s->fd);
>> +        if (ret == 0) {
>> +            s->enabled = 1;
>> +            tap_update_fd_handler(s);
>> +        }
>> +        return ret;
>> +    }
>> +}
>> +
>> +int tap_disable(NetClientState *nc)
>> +{
>> +    TAPState *s = DO_UPCAST(TAPState, nc, nc);
>> +    int ret;
>> +
>> +    if (s->enabled == 0) {
>> +        return 0;
>> +    } else {
>> +        ret = tap_fd_disable(s->fd);
>> +        if (ret == 0) {
>> +            qemu_purge_queued_packets(nc);
>> +            s->enabled = 0;
>> +            tap_update_fd_handler(s);
>> +        }
>> +        return ret;
>> +    }
>> +}
>> --
>> 1.7.1
>>
>>