files: Kill fd_open_state::receive_fd stage

Since "receive" stage is used only for slave fds
and nobody depends on slave fds receiving is finished,
we may move it functionality in "post_open" stage.
This just makes slave fds to be received a little bit later.

In other words, only masters have post_open stage,
and only slaves have receive stage. So, in the case of
A and B files:

A->open
B->open
A->recv
A->post_open
B->recv
B->post_open

A->post_open can't depend on B->recv. This follows
just from analyzing of all file types post_open methods.

travis-ci: success for Rework file opening scheme to make it asynchronous (rev5)
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/files.c

@@ -865,7 +865,6 @@ static int post_open_fd(int pid, struct fdinfo_list_entry *fle);
 
 static struct fd_open_state states[] = {
 	{ "create",		open_fd,	},
-	{ "receive",		receive_fd,	},
 	{ "post_create",	post_open_fd,	},
 };
 
@@ -971,15 +970,17 @@ static int post_open_fd(int pid, struct fdinfo_list_entry *fle)
 {
 	struct file_desc *d = fle->desc;
 
-	if (!d->ops->post_open)
-		return 0;
-
-	if (is_service_fd(fle->fe->fd, CTL_TTY_OFF))
-		return d->ops->post_open(d, fle->fe->fd);
+	if (fle != file_master(d)) {
+		if (receive_fd(pid, fle) < 0) {
+			pr_err("Can't receive\n");
+			return -1;
+		}
+		if (!is_service_fd(fle->fe->fd, CTL_TTY_OFF))
+			return 0;
+	}
 
-	if (fle != file_master(d))
+	if (!d->ops->post_open)
 		return 0;
-
 	return d->ops->post_open(d, fle->fe->fd);
 }
 
@@ -1034,11 +1035,6 @@ static int open_fd(int pid, struct fdinfo_list_entry *fle)
 static int receive_fd(int pid, struct fdinfo_list_entry *fle)
 {
 	int fd;
-	struct fdinfo_list_entry *flem;
-
-	flem = file_master(fle->desc);
-	if (flem->pid == pid)
-		return 0;
 
 	pr_info("\tReceive fd for %d\n", fle->fe->fd);