[CRIU] [PATCH v2 03/28] files: Send/receive fds with pointers on their struct fdinfo_list_entry in receiver

[Kirill Tkhai]

On 05.12.2016 16:27, Pavel Emelyanov wrote:
> On 12/05/2016 04:17 PM, Kirill Tkhai wrote:
>> On 05.12.2016 16:13, Pavel Emelyanov wrote:
>>> On 12/05/2016 04:05 PM, Kirill Tkhai wrote:
>>>> On 05.12.2016 15:50, Pavel Emelyanov wrote:
>>>>> On 12/05/2016 01:55 PM, Kirill Tkhai wrote:
>>>>>> On 05.12.2016 12:50, Pavel Emelyanov wrote:
>>>>>>> On 11/30/2016 07:29 PM, Kirill Tkhai wrote:
>>>>>>>> For moving to a single transport socket scheme, we need to be able to differ
>>>>>>>> fds in receive queue from each other. Add a fle pointer as identifier for that.
>>>>>>>>
>>>>>>>> v2: Rebase on compel
>>>>>>>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>>>>>>>> ---
>>>>>>>>  criu/files.c         |   21 +++++++++++++++++++--
>>>>>>>>  criu/include/files.h |    1 +
>>>>>>>>  criu/pipes.c         |    2 +-
>>>>>>>>  criu/sk-unix.c       |    2 +-
>>>>>>>>  criu/tty.c           |    2 +-
>>>>>>>>  5 files changed, 23 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/criu/files.c b/criu/files.c
>>>>>>>> index e691558..c3ea2c4 100644
>>>>>>>> --- a/criu/files.c
>>>>>>>> +++ b/criu/files.c
>>>>>>>> @@ -957,6 +957,23 @@ static int open_transport_fd(int pid, struct fdinfo_list_entry *fle)
>>>>>>>>  	return -1;
>>>>>>>>  }
>>>>>>>>  
>>>>>>>> +int recv_fd_from_peer(struct fdinfo_list_entry *fle)
>>>>>>>> +{
>>>>>>>> +	struct fdinfo_list_entry *tmp;
>>>>>>>> +	int fd, ret;
>>>>>>>> +
>>>>>>>> +	ret = recv_fds(fle->fe->fd, &fd, 1, (void *)&tmp, sizeof(struct fdinfo_list_entry *));
>>>>>>>> +	if (ret)
>>>>>>>> +		return -1;
>>>>>>>> +
>>>>>>>> +	if (tmp != fle) {
>>>>>>>
>>>>>>> Can this patch be applied by its own? I mean each pstree-item allocates its
>>>>>>> own fle-s, their address cannot match to each other.
>>>>>>
>>>>>> Yes, it can be applied by its own. Each fle is related to certain process,
>>>>>> which is specified in fle->pid.
>>>>>
>>>>> So the check for tmp != fle will always be true, will it?
>>>>
>>>> It has to be always false, as we receive the only fd from per-fd transport socket.
>>>
>>> But how will it be false? You call send_fds() passing a pointer to the sender's
>>> fle structure as an argument, then in another task go to this routine and receive
>>> this pointer, then compare it the this other task's local pointer. How can
>>> a != b be false in this scenario?
>>
>> We allocate all fles in shared memory, so the pointers are not local. They are
>> linked to each other in collect_fd(). So all tasks work with the same fles,
>> we do not copy them to task private address space.
> 
> Objects are in shared space, but each task calls collect_fd() which allocates
> a set of fle-s for each pstree_item independently. Thus each task has its own
> set of pointers on shared fle-s.

And we send receiver's fle (not master's):

static int serve_out_fd(int pid, int fd, struct file_desc *d)
{
	...
        list_for_each_entry(fle, &d->fd_info_head, desc_list) {
                if (pid == fle->pid)
                        ret = send_fd_to_self(fd, fle);
                else
                        ret = send_fd_to_peer(fd, fle);
	...
}
 
> -- Pavel
> 
>>>>>>>> +		pr_err("Received wrong fle\n");
>>>>>>>> +		return -1;
>>>>>>>> +	}
>>>>>>>> +
>>>>>>>> +	return fd;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>  int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock)
>>>>>>>>  {
>>>>>>>>  	struct sockaddr_un saddr;
>>>>>>>> @@ -967,7 +984,7 @@ int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock)
>>>>>>>>  	transport_name_gen(&saddr, &len,
>>>>>>>>  			futex_get(&fle->real_pid), fle->fe->fd);
>>>>>>>>  	pr_info("\t\tSend fd %d to %s\n", fd, saddr.sun_path + 1);
>>>>>>>> -	return send_fd(sock, &saddr, len, fd);
>>>>>>>> +	return send_fds(sock, &saddr, len, &fd, 1, (void *)&fle, sizeof(struct fdinfo_list_entry *));
>>>>>>>>  }
>>>>>>>>  
>>>>>>>>  static int send_fd_to_self(int fd, struct fdinfo_list_entry *fle, int sock)
>>>>>>>> @@ -1077,7 +1094,7 @@ static int receive_fd(int pid, struct fdinfo_list_entry *fle)
>>>>>>>>  
>>>>>>>>  	pr_info("\tReceive fd for %d\n", fle->fe->fd);
>>>>>>>>  
>>>>>>>> -	tmp = recv_fd(fle->fe->fd);
>>>>>>>> +	tmp = recv_fd_from_peer(fle);
>>>>>>>>  	if (tmp < 0) {
>>>>>>>>  		pr_err("Can't get fd %d\n", tmp);
>>>>>>>>  		return -1;
>>>>>>>> diff --git a/criu/include/files.h b/criu/include/files.h
>>>>>>>> index 229c0d2..4f40e71 100644
>>>>>>>> --- a/criu/include/files.h
>>>>>>>> +++ b/criu/include/files.h
>>>>>>>> @@ -148,6 +148,7 @@ extern int file_desc_add(struct file_desc *d, u32 id, struct file_desc_ops *ops)
>>>>>>>>  extern struct fdinfo_list_entry *file_master(struct file_desc *d);
>>>>>>>>  extern struct file_desc *find_file_desc_raw(int type, u32 id);
>>>>>>>>  
>>>>>>>> +extern int recv_fd_from_peer(struct fdinfo_list_entry *fle);
>>>>>>>>  extern int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock);
>>>>>>>>  extern int restore_fown(int fd, FownEntry *fown);
>>>>>>>>  extern int rst_file_params(int fd, FownEntry *fown, int flags);
>>>>>>>> diff --git a/criu/pipes.c b/criu/pipes.c
>>>>>>>> index 9fc87bd..31f436e 100644
>>>>>>>> --- a/criu/pipes.c
>>>>>>>> +++ b/criu/pipes.c
>>>>>>>> @@ -237,7 +237,7 @@ static int recv_pipe_fd(struct pipe_info *pi)
>>>>>>>>  
>>>>>>>>  	pr_info("\tWaiting fd for %d\n", fd);
>>>>>>>>  
>>>>>>>> -	tmp = recv_fd(fd);
>>>>>>>> +	tmp = recv_fd_from_peer(fle);
>>>>>>>>  	if (tmp < 0) {
>>>>>>>>  		pr_err("Can't get fd %d\n", tmp);
>>>>>>>>  		return -1;
>>>>>>>> diff --git a/criu/sk-unix.c b/criu/sk-unix.c
>>>>>>>> index 202228d..74bd76d 100644
>>>>>>>> --- a/criu/sk-unix.c
>>>>>>>> +++ b/criu/sk-unix.c
>>>>>>>> @@ -1096,7 +1096,7 @@ static int open_unixsk_pair_slave(struct unix_sk_info *ui)
>>>>>>>>  	pr_info("Opening pair slave (id %#x ino %#x peer %#x) on %d\n",
>>>>>>>>  			ui->ue->id, ui->ue->ino, ui->ue->peer, fle->fe->fd);
>>>>>>>>  
>>>>>>>> -	sk = recv_fd(fle->fe->fd);
>>>>>>>> +	sk = recv_fd_from_peer(fle);
>>>>>>>>  	if (sk < 0) {
>>>>>>>>  		pr_err("Can't recv pair slave\n");
>>>>>>>>  		return -1;
>>>>>>>> diff --git a/criu/tty.c b/criu/tty.c
>>>>>>>> index 7822a4f..6d0c8fa 100644
>>>>>>>> --- a/criu/tty.c
>>>>>>>> +++ b/criu/tty.c
>>>>>>>> @@ -923,7 +923,7 @@ static int receive_tty(struct tty_info *info)
>>>>>>>>  	fle = file_master(&info->d);
>>>>>>>>  	pr_info("\tWaiting tty fd %d (pid %d)\n", fle->fe->fd, fle->pid);
>>>>>>>>  
>>>>>>>> -	fd = recv_fd(fle->fe->fd);
>>>>>>>> +	fd = recv_fd_from_peer(fle);
>>>>>>>>  	close(fle->fe->fd);
>>>>>>>>  	if (fd < 0) {
>>>>>>>>  		pr_err("Can't get fd %d\n", fd);
>>>>>>>>
>>>>>>>> .
>>>>>>>>
>>>>>>>
>>>>>> .
>>>>>>
>>>>>
>>>> .
>>>>
>>>
>> .
>>
>