diff --git a/io/Makefile b/io/Makefile
index ec5c6d7a2f..8e4fd8cc19 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -71,7 +71,7 @@ tests		:= test-utime test-stat test-stat2 test-lfs tst-getcwd \
 		   tst-mknodat tst-mkfifoat tst-ttyname_r bug-ftw5 \
 		   tst-posix_fallocate tst-posix_fallocate64 \
 		   tst-fts tst-fts-lfs tst-open-tmpfile \
-		   tst-copy_file_range tst-getcwd-abspath \
+		   tst-copy_file_range tst-getcwd-abspath tst-lockf
 
 # This test includes the compat implementation of copy_file_range,
 # which uses internal, unexported libc functions.
diff --git a/io/lockf.c b/io/lockf.c
index 68a799d54c..df86dd7e92 100644
--- a/io/lockf.c
+++ b/io/lockf.c
@@ -15,34 +15,26 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-/* We need to avoid the header declaration of lockf64, because
-   the types don't match lockf and then the compiler will
-   complain about the mismatch when we do the alias below.  */
-#define lockf64	__renamed_lockf64
+#ifndef __OFF_T_MATCHES_OFF64_T
 
-#include <fcntl.h>
-
-#undef	lockf64
-
-#include <sys/types.h>
 #include <unistd.h>
+#include <fcntl.h>
 #include <errno.h>
-#include <string.h>
 
 /* lockf is a simplified interface to fcntl's locking facilities.  */
-
 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;
+  struct flock fl = {
+    .l_type = F_WRLCK,
+    .l_whence = SEEK_CUR,
+    .l_len = len
+  };
 
+  /* 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.  */
   switch (cmd)
     {
     case F_TEST:
@@ -55,31 +47,15 @@ lockf (int fd, int cmd, off_t len)
 	return 0;
       __set_errno (EACCES);
       return -1;
-
     case F_ULOCK:
       fl.l_type = F_UNLCK;
-      cmd = F_SETLK;
-      break;
+      return __fcntl (fd, F_SETLK, &fl);
     case F_LOCK:
-      fl.l_type = F_WRLCK;
-      cmd = F_SETLKW;
-      break;
+      return __fcntl (fd, F_SETLKW, &fl);
     case F_TLOCK:
-      fl.l_type = F_WRLCK;
-      cmd = F_SETLK;
-      break;
-
-    default:
-      __set_errno (EINVAL);
-      return -1;
+      return __fcntl (fd, F_SETLK, &fl);
     }
-
-  /* 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);
+  __set_errno (EINVAL);
+  return -1;
 }
-
-#ifdef __OFF_T_MATCHES_OFF64_T
-weak_alias (lockf, lockf64)
 #endif
diff --git a/io/lockf64.c b/io/lockf64.c
index 334b8d3180..dd3730f781 100644
--- a/io/lockf64.c
+++ b/io/lockf64.c
@@ -15,69 +15,48 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <sys/types.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
-#include <string.h>
-
-/* lockf.c defines lockf64 as an alias if __OFF_T_MATCHES_OFF64_T.  */
-#ifndef __OFF_T_MATCHES_OFF64_T
 
 /* lockf is a simplified interface to fcntl's locking facilities.  */
-
 int
-lockf64 (int fd, int cmd, off64_t len64)
+__lockf64 (int fd, int cmd, off64_t len64)
 {
-  struct flock fl;
-  off_t len = (off_t) len64;
-
-  if (len64 != (off64_t) len)
-    {
-      /* We can't represent the length.  */
-      __set_errno (EOVERFLOW);
-      return -1;
-    }
-
-  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;
-
+  struct flock64 fl64 = {
+    .l_type = F_WRLCK,
+    .l_whence = SEEK_CUR,
+    .l_len = len64,
+  };
+
+  /* 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.  */
   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)
+      fl64.l_type = F_RDLCK;
+      if (__fcntl (fd, F_GETLK64, &fl64) < 0)
 	return -1;
-      if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
-	return 0;
+      if (fl64.l_type == F_UNLCK || fl64.l_pid == __getpid ())
+        return 0;
       __set_errno (EACCES);
       return -1;
-
     case F_ULOCK:
-      fl.l_type = F_UNLCK;
-      cmd = F_SETLK;
-      break;
+      fl64.l_type = F_UNLCK;
+      return __fcntl64 (fd, F_SETLK64, &fl64);
     case F_LOCK:
-      fl.l_type = F_WRLCK;
-      cmd = F_SETLKW;
-      break;
+      return __fcntl64 (fd, F_SETLKW64, &fl64);
     case F_TLOCK:
-      fl.l_type = F_WRLCK;
-      cmd = F_SETLK;
-      break;
-
-    default:
-      __set_errno (EINVAL);
-      return -1;
+      return __fcntl64 (fd, F_SETLK64, &fl64);
     }
-
-  return __fcntl (fd, cmd, &fl);
+  __set_errno (EINVAL);
+  return -1;
 }
-
+weak_alias (__lockf64, lockf64)
+#ifdef __OFF_T_MATCHES_OFF64_T
+weak_alias (lockf64, lockf)
 #endif
diff --git a/io/tst-lockf.c b/io/tst-lockf.c
new file mode 100644
index 0000000000..ff2af6e312
--- /dev/null
+++ b/io/tst-lockf.c
@@ -0,0 +1,138 @@
+/* Test POSIX lock on an open file (lockf).
+   Copyright (C) 2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <unistd.h>
+#include <stdint.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include <support/temp_file.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+
+static char *temp_filename;
+static int temp_fd;
+
+static void
+do_prepare (int argc, char **argv)
+{
+  temp_fd = create_temp_file ("tst-lockfd.", &temp_filename);
+  TEST_VERIFY_EXIT (temp_fd != -1);
+}
+#define PREPARE do_prepare
+
+static void
+do_test_child_lockf (void *closure)
+{
+  /* Check if parent has [0, 1024) locked.  */
+  TEST_COMPARE (lseek (temp_fd, 0, SEEK_SET), 0);
+  TEST_COMPARE (lockf (temp_fd, F_TLOCK, 1024), -1);
+  TEST_COMPARE (errno, EAGAIN);
+  TEST_COMPARE (lockf (temp_fd, F_TEST, 1024), -1);
+  TEST_COMPARE (errno, EACCES);
+  /* Also Check if parent has last 1024 bytes locked.  */
+  TEST_COMPARE (lseek (temp_fd, INT32_MAX-1024, SEEK_SET), INT32_MAX-1024);
+  TEST_COMPARE (lockf (temp_fd, F_TEST, 1024), -1);
+
+  /* And try to lock [1024, 2048).  */
+  TEST_COMPARE (lseek (temp_fd, 1024, SEEK_SET), 1024);
+  TEST_COMPARE (lockf (temp_fd, F_LOCK, 1024), 0);
+
+  /* Check if non-LFS interface cap access to 32-bif off_t.  */
+  TEST_COMPARE (lseek64 (temp_fd, (off64_t)INT32_MAX, SEEK_SET),
+		(off64_t)INT32_MAX);
+  TEST_COMPARE (lockf64 (temp_fd, F_TEST, 1024), 0);
+}
+
+static void
+do_test_child_lockf64 (void *closure)
+{
+  /* Check if parent has [0, 1024) locked.  */
+  TEST_COMPARE (lseek64 (temp_fd, 0, SEEK_SET), 0);
+  TEST_COMPARE (lockf64 (temp_fd, F_TLOCK, 1024), -1);
+  TEST_COMPARE (errno, EAGAIN);
+  TEST_COMPARE (lockf64 (temp_fd, F_TEST, 1024), -1);
+  TEST_COMPARE (errno, EACCES);
+  /* Also Check if parent has last 1024 bytes locked.  */
+  TEST_COMPARE (lseek64 (temp_fd, INT32_MAX-1024, SEEK_SET), INT32_MAX-1024);
+  TEST_COMPARE (lockf64 (temp_fd, F_TEST, 1024), -1);
+
+  /* And try to lock [1024, 2048).  */
+  TEST_COMPARE (lseek64 (temp_fd, 1024, SEEK_SET), 1024);
+  TEST_COMPARE (lockf64 (temp_fd, F_LOCK, 1024), 0);
+
+  /* And also [INT32_MAX, INT32_MAX+1024).  */
+  {
+    off64_t off = (off64_t)INT32_MAX;
+    TEST_COMPARE (lseek64 (temp_fd, off, SEEK_SET), off);
+    TEST_COMPARE (lockf64 (temp_fd, F_LOCK, 1024), 0);
+  }
+
+  /* Check if [INT32_MAX+1024, INT64_MAX) is locked.  */
+  {
+    off64_t off = (off64_t)INT32_MAX+1024;
+    TEST_COMPARE (lseek64 (temp_fd, off, SEEK_SET), off);
+    TEST_COMPARE (lockf64 (temp_fd, F_TLOCK, 1024), -1);
+    TEST_COMPARE (errno, EAGAIN);
+    TEST_COMPARE (lockf64 (temp_fd, F_TEST, 1024), -1);
+    TEST_COMPARE (errno, EACCES);
+  }
+}
+
+static int
+do_test (void)
+{
+  /* Basic tests to check if a lock can be obtained and checked.  */
+  TEST_COMPARE (lockf (temp_fd, F_LOCK, 1024), 0);
+  TEST_COMPARE (lockf (temp_fd, F_LOCK, INT32_MAX), 0);
+  TEST_COMPARE (lockf (temp_fd, F_TLOCK, 1024), 0);
+  TEST_COMPARE (lockf (temp_fd, F_TEST, 1024), 0);
+  TEST_COMPARE (lseek (temp_fd, 1024, SEEK_SET), 1024);
+  TEST_COMPARE (lockf (temp_fd, F_ULOCK, 1024), 0);
+  /* Parent process should have ([0, 1024), [2048, INT32_MAX)) ranges locked.  */
+
+  {
+    struct support_capture_subprocess result;
+    result = support_capture_subprocess (do_test_child_lockf, NULL);
+    support_capture_subprocess_check (&result, "lockf", 0, sc_allow_none);
+  }
+
+  if (sizeof (off_t) != sizeof (off64_t))
+    {
+      /* Check if previously locked regions with LFS symbol.  */
+      TEST_COMPARE (lseek (temp_fd, 0, SEEK_SET), 0);
+      TEST_COMPARE (lockf64 (temp_fd, F_LOCK, 1024), 0);
+      TEST_COMPARE (lockf64 (temp_fd, F_TLOCK, 1024), 0);
+      TEST_COMPARE (lockf64 (temp_fd, F_TEST, 1024), 0);
+      /* Lock region [INT32_MAX+1024, INT64_MAX).  */
+      off64_t off = (off64_t)INT32_MAX + 1024;
+      TEST_COMPARE (lseek64 (temp_fd, off, SEEK_SET), off);
+      TEST_COMPARE (lockf64 (temp_fd, F_LOCK, 1024), 0);
+      /* Parent process should have ([0, 1024), [2048, INT32_MAX),
+	 [INT32_MAX+1024, INT64_MAX)) ranges locked.  */
+  
+      {
+	struct support_capture_subprocess result;
+	result = support_capture_subprocess (do_test_child_lockf64, NULL);
+	support_capture_subprocess_check (&result, "lockf", 0, sc_allow_none);
+      }
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/mach/hurd/fcntl.c b/sysdeps/mach/hurd/fcntl.c
index 6fa63f2fc7..f7756ec184 100644
--- a/sysdeps/mach/hurd/fcntl.c
+++ b/sysdeps/mach/hurd/fcntl.c
@@ -159,13 +159,13 @@ __libc_fcntl (int fd, int cmd, ...)
 	va_end (ap);
 	switch (cmd)
 	  {
-	  case F_GETLK:
+	  case F_GETLK64:
 	    errno = ENOSYS;
 	    return -1;
-	  case F_SETLKW:
+	  case F_SETLKW64:
 	    wait = 1;
 	    /* FALLTHROUGH */
-	  case F_SETLK:
+	  case F_SETLK64:
 	    result = __f_setlk (fd, fl->l_type, fl->l_whence,
 				fl->l_start, fl->l_len, wait);
 	    break;
diff --git a/sysdeps/unix/sysv/linux/arm/lockf64.c b/sysdeps/unix/sysv/linux/arm/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/arm/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/i386/lockf64.c b/sysdeps/unix/sysv/linux/i386/lockf64.c
deleted file mode 100644
index 8a17c13cbe..0000000000
--- a/sysdeps/unix/sysv/linux/i386/lockf64.c
+++ /dev/null
@@ -1,70 +0,0 @@
-/* Copyright (C) 1994-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <sys/types.h>
-#include <unistd.h>
-#include <fcntl.h>
-#include <errno.h>
-#include <string.h>
-#include <sysdep.h>
-
-/* lockf is a simplified interface to fcntl's locking facilities.  */
-
-int
-lockf64 (int fd, int cmd, off64_t len64)
-{
-  struct flock64 fl64;
-  int cmd64;
-  int result;
-
-  memset ((char *) &fl64, '\0', sizeof (fl64));
-  fl64.l_whence = SEEK_CUR;
-  fl64.l_start = 0;
-  fl64.l_len = len64;
-
-  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.  */
-      fl64.l_type = F_RDLCK;
-      INTERNAL_SYSCALL_DECL (err);
-      result = INTERNAL_SYSCALL (fcntl64, err, 3, fd, F_GETLK64, &fl64);
-      if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err)))
-	return INLINE_SYSCALL_ERROR_RETURN_VALUE (INTERNAL_SYSCALL_ERRNO (result,
-									  err));
-      if (fl64.l_type == F_UNLCK || fl64.l_pid == __getpid ())
-        return 0;
-      return INLINE_SYSCALL_ERROR_RETURN_VALUE (EACCES);
-    case F_ULOCK:
-      fl64.l_type = F_UNLCK;
-      cmd64 = F_SETLK64;
-      break;
-    case F_LOCK:
-      fl64.l_type = F_WRLCK;
-      cmd64 = F_SETLKW64;
-      break;
-    case F_TLOCK:
-      fl64.l_type = F_WRLCK;
-      cmd64 = F_SETLK64;
-      break;
-
-    default:
-      return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
-    }
-  return INLINE_SYSCALL (fcntl64, 3, fd, cmd64, &fl64);
-}
diff --git a/sysdeps/unix/sysv/linux/m68k/lockf64.c b/sysdeps/unix/sysv/linux/m68k/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/m68k/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/lockf64.c b/sysdeps/unix/sysv/linux/mips/mips32/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/mips/mips32/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/lockf64.c b/sysdeps/unix/sysv/linux/mips/mips64/n32/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/lockf64.c b/sysdeps/unix/sysv/linux/powerpc/powerpc32/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/lockf64.c b/sysdeps/unix/sysv/linux/s390/s390-32/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/s390/s390-32/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/sh/lockf64.c b/sysdeps/unix/sysv/linux/sh/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/sh/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/lockf64.c b/sysdeps/unix/sysv/linux/sparc/sparc32/lockf64.c
deleted file mode 100644
index a88f5a784a..0000000000
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/lockf64.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/lockf64.c>
