[CRIU] [PATCH v4 11/15] files: Add file_desc_ops::receive method

[Pavel Emelyanov]

On 06/09/2016 04:31 PM, Kirill Tkhai wrote:
> 
> 
> On 09.06.2016 16:15, Pavel Emelyanov wrote:
>> On 06/01/2016 07:03 PM, Kirill Tkhai wrote:
>>> Currently, nothing is done for master files in receive_fd().
>>> Add a receive method, which may be useful for subsystems,
>>> which need it (for queuer-less dgram sockets, going in following
>>> patches).
>>>
>>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>>> ---
>>>  criu/files.c         |    3 ++-
>>>  criu/include/files.h |   10 +++++++++-
>>>  2 files changed, 11 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/criu/files.c b/criu/files.c
>>> index bb3b142..22668ec 100644
>>> --- a/criu/files.c
>>> +++ b/criu/files.c
>>> @@ -1053,12 +1053,13 @@ static int open_fd(int pid, struct fdinfo_list_entry *fle)
>>>  
>>>  static int receive_fd(int pid, struct fdinfo_list_entry *fle)
>>>  {
>>> +	struct file_desc *d = fle->desc;
>>>  	int tmp;
>>>  	struct fdinfo_list_entry *flem;
>>>  
>>>  	flem = file_master(fle->desc);
>>>  	if (flem->pid == pid)
>>> -		return 0;
>>> +		return d->ops->receive ? d->ops->receive(d, fle->fe->fd) : 0;
>>
>> Erm... This path is not receiving an fd, it's just us who's the
>> file master.
> 
> I don't understand your comment. Could you please explain what you mean?

The "return 0" you've removed doesn't mean "receive descriptor". It means "OK,
the descriptor is already at the place we want it to". And renaming this
into "go ahead and to fd-specific receiving" is confusing.

Describe what operation you plan to "virtualize" with this callback.

>>>  
>>>  	pr_info("\tReceive fd for %d\n", fle->fe->fd);
>>>  
>>> diff --git a/criu/include/files.h b/criu/include/files.h
>>> index 5e3d6dc..f0d5f23 100644
>>> --- a/criu/include/files.h
>>> +++ b/criu/include/files.h
>>> @@ -90,7 +90,15 @@ struct file_desc_ops {
>>>  	int			(*open)(struct file_desc *d);
>>>  	/*
>>>  	 * Called on a file when all files of that type are opened
>>> -	 * and with the fd being the "restored" one.
>>> +	 * and with the fd being the "restored" one. This may be used
>>> +	 * to receive some additional file descriptors that are needed
>>> +	 * at post_open stage.
>>> +	 */
>>> +	int			(*receive)(struct file_desc *d, int fd);
>>> +	/*
>>> +	 * Called on a file when all files of that type are opened
>>> +	 * and with the fd being the "restored" one and all data need
>>> +	 * to complete restore is received.
>>>  	 */
>>>  	int			(*post_open)(struct file_desc *d, int fd);
>>>  	/*
>>>
>>> _______________________________________________
>>> CRIU mailing list
>>> CRIU at openvz.org
>>> https://lists.openvz.org/mailman/listinfo/criu
>>> .
>>>
>>
> .
>