[CRIU] [RFC PATCH 4/5] autofs: restore procedure introduced

[Pavel Emelyanov]

>>> +struct autofs_info_s {
>>> +	int pipe_fd;
>>> +	const char *mnt_path;
>>> +	struct autofs_info_s *next;
>>> +};
>>> +
>>> +struct autofs_service_s {
>>> +	int pgrp;
>>> +	struct autofs_info_s *mnt_info;
>>> +	struct autofs_service_s *next;
>>> +} *automount;
>>> +
>>> +int autofs_fixup_owner(struct autofs_info_s *info)
>>> +{
>>> +	int autofs_fd, mnt_fd, err = -1;
>>> +	struct autofs_dev_ioctl param;
>>> +
>>> +	autofs_fd = open("/dev/autofs", O_RDONLY);
>>> +	if (autofs_fd == -1) {
>>> +		pr_perror("failed to open /dev/autofs");
>>> +		return -1;
>>> +	}
>>> +
>>> +	mnt_fd = open(info->mnt_path, O_RDONLY | O_DIRECTORY);
>>> +	if (mnt_fd == -1) {
>>> +		pr_perror("failed to open %s", info->mnt_path);
>>> +		goto close_fd;
>>> +	}
>>> +
>>> +	init_autofs_dev_ioctl(&param);
>>> +	err = ioctl(mnt_fd, AUTOFS_IOC_CATATONIC, 0);
>>> +	if (err == -1) {
>>> +		pr_perror("failed to set mount point catatonic");
>>> +		goto close_mnt_fd;
>>> +
>>> +	}
>>> +
>>> +	init_autofs_dev_ioctl(&param);
>>> +	param.ioctlfd = mnt_fd;
>>> +	param.setpipefd.pipefd = info->pipe_fd;
>> The info->pipe_fd is set by autofs_mount() and the fd value is purely
>> parsed from options. Who and when creates this very fd?
> 
> The pipe itself belongs to automount process and restored as any other fd.
> Yes, we are probably lucky, that automount doesn't close write end of 
> the pipe, which is sent to the kernel.

I still don't get it. CRIU would close pipe's write end once ->open is
called, so in ->post_open the kernel part of the pipe should not be
available.

Can you write the sequence of steps that lead to this particular place
in the code and show _where_ the write end of the pipe is (was) created?