files: Do not close PROC_PID_FD_OFF sfd in prepare_fds()

Here we need to close proc self fd only, as it's not
a service fd, and it can occupy real task fd number.
Closing of PROC_PID_FD_OFF is useless action here,
because it's already occupy a service fd number.

So, we skip this excess syscall, and leave PROC_PID_FD_OFF
open.

v4: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/files.c

@@ -1248,7 +1248,7 @@ int prepare_fds(struct pstree_item *me)
 	 * set than its parent
 	 */
 	close_service_fd(CGROUP_YARD);
-	close_pid_proc(); /* flush any proc cached fds we may have */
+	set_proc_self_fd(-1); /* flush any proc cached fds we may have */
 
 	if (rsti(me)->fdt) {
 		struct fdt *fdt = rsti(me)->fdt;

criu/include/servicefd.h

@@ -28,6 +28,7 @@ enum sfd_type {
 
 struct pstree_item;
 
+extern void set_proc_self_fd(int fd);
 extern int clone_service_fd(int id);
 extern int init_service_fd(void);
 extern int get_service_fd(enum sfd_type type);

criu/util.c

@@ -296,7 +296,7 @@ static pid_t open_proc_pid = PROC_NONE;
 static pid_t open_proc_self_pid;
 static int open_proc_self_fd = -1;
 
-static inline void set_proc_self_fd(int fd)
+void set_proc_self_fd(int fd)
 {
 	if (open_proc_self_fd >= 0)
 		close(open_proc_self_fd);