diff -uNr qemu-3.1.0/lockf_implementation.h qemu-3.1.0.mod/lockf_implementation.h
--- qemu-3.1.0/lockf_implementation.h	1970-01-01 03:00:00.000000000 +0300
+++ qemu-3.1.0.mod/lockf_implementation.h	2019-02-14 00:17:12.137667319 +0200
@@ -0,0 +1,56 @@
+#ifndef LOCKF_IMPLEMENTATION_H
+#define LOCKF_IMPLEMENTATION_H
+
+//
+// lockf() implementation from GNU Libc
+//
+
+static int lockf (int fd, int cmd, off_t len)
+{
+  struct flock fl;
+
+  memset ((char *) &fl, '\0', sizeof (fl));
+
+  /* lockf is always relative to the current file position.  */
+  fl.l_whence = SEEK_CUR;
+  fl.l_start = 0;
+  fl.l_len = len;
+
+  switch (cmd)
+    {
+    case F_TEST:
+      /* Test the lock: return 0 if FD is unlocked or locked by this process;
+     return -1, set errno to EACCES, if another process holds the lock.  */
+      fl.l_type = F_RDLCK;
+      if (fcntl (fd, F_GETLK, &fl) < 0)
+    return -1;
+      if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
+    return 0;
+      errno = EACCES;
+      return -1;
+
+    case F_ULOCK:
+      fl.l_type = F_UNLCK;
+      cmd = F_SETLK;
+      break;
+    case F_LOCK:
+      fl.l_type = F_WRLCK;
+      cmd = F_SETLKW;
+      break;
+    case F_TLOCK:
+      fl.l_type = F_WRLCK;
+      cmd = F_SETLK;
+      break;
+
+    default:
+      errno = EINVAL;
+      return -1;
+    }
+
+  /* lockf() is a cancellation point but so is fcntl() if F_SETLKW is
+     used.  Therefore we don't have to care about cancellation here,
+     the fcntl() function will take care of it.  */
+  return fcntl (fd, cmd, &fl);
+}
+
+#endif
diff -uNr qemu-3.1.0/os-posix.c qemu-3.1.0.mod/os-posix.c
--- qemu-3.1.0/os-posix.c	2018-12-11 19:44:34.000000000 +0200
+++ qemu-3.1.0.mod/os-posix.c	2019-02-14 00:17:05.354295183 +0200
@@ -36,6 +36,7 @@
 #include "qemu/error-report.h"
 #include "qemu/log.h"
 #include "qemu/cutils.h"
+#include "lockf_implementation.h"
 
 #ifdef CONFIG_LINUX
 #include <sys/prctl.h>
diff -uNr qemu-3.1.0/qga/main.c qemu-3.1.0.mod/qga/main.c
--- qemu-3.1.0/qga/main.c	2018-12-11 19:44:34.000000000 +0200
+++ qemu-3.1.0.mod/qga/main.c	2019-02-14 00:17:18.731038388 +0200
@@ -45,6 +45,8 @@
 #endif
 #endif
 
+#include "lockf_implementation.h"
+
 #ifndef _WIN32
 #define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent.0"
 #define QGA_STATE_RELATIVE_DIR  "run"
diff -uNr qemu-3.1.0/scsi/qemu-pr-helper.c qemu-3.1.0.mod/scsi/qemu-pr-helper.c
--- qemu-3.1.0/scsi/qemu-pr-helper.c	2018-12-11 19:44:34.000000000 +0200
+++ qemu-3.1.0.mod/scsi/qemu-pr-helper.c	2019-02-14 00:17:24.634405524 +0200
@@ -24,6 +24,8 @@
 #include <linux/dm-ioctl.h>
 #include <scsi/sg.h>
 
+#include "lockf_implementation.h"
+
 #ifdef CONFIG_LIBCAP
 #include <cap-ng.h>
 #endif