[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 16:13, 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.
 
>>>>>> +		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);
>>>>>>
>>>>>> .
>>>>>>
>>>>>
>>>> .
>>>>
>>>
>> .
>>
>