commit 0961f7e1e300ef633b0c1ad95d0999fb5c169f4e
Author: Jeff Layton <jlayton@poochiereds.net>
Date:   Wed Jul 23 14:21:05 2014 -0400

    fcntl-linux.h: add new definitions and manual updates for open file description locks
    
    Open file description locks have been merged into the Linux kernel for
    v3.15.  Add the appropriate command-value definitions and an update to
    the manual that describes their usage.

Note by DJ: the implementation doesn't work correctly for 32-bit file
offsets.  Upstream changed the ABI to compensate but RHEL can't, so we
enable these only for when file offsets are 64 bits.

diff -rup a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
--- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h	2018-04-13 18:38:24.000000000 -0400
+++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h	2018-04-13 20:05:21.743234360 -0400
@@ -117,6 +117,25 @@
 # define F_SETLKW64	14	/* Set record locking info (blocking).	*/
 #endif
 
+#ifdef __USE_FILE_OFFSET64
+/* open file description locks.
+
+   Usually record locks held by a process are released on *any* close and are
+   not inherited across a fork.
+
+   These cmd values will set locks that conflict with process-associated record
+   locks, but are "owned" by the opened file description, not the process.
+   This means that they are inherited across fork or clone with CLONE_FILES
+   like BSD (flock) locks, and they are only released automatically when the
+   last reference to the the file description against which they were acquired
+   is put. */
+#ifdef __USE_GNU
+# define F_OFD_GETLK	36
+# define F_OFD_SETLK	37
+# define F_OFD_SETLKW	38
+#endif
+#endif
+
 #ifdef __USE_LARGEFILE64
 # define O_LARGEFILE __O_LARGEFILE
 #endif