[glibc PATCH] fcntl-linux.h: add F_OFD_*32 constants

[Jeff Layton <jlayton@redhat.com>]

The original assumption with OFD lock support was that userland would
always pass in a struct flock that has been set up for large file
support (LFS). It's possible however for someone to build a 32-bit
program without large file support, and still try to use OFD locks. If
that happens then it will send a non-LFS struct flock to the kernel,
which will then try to interpret it as a LFS one, which can cause
unexpected results.

My original idea was to just ensure that the build would fail in this
case by not defining the F_OFD_* constants when LFS support was not
enabled.

Instead though, it's probably better long-term to just go ahead and
support OFD locks with non-LFS struct flock. To do that without breaking
programs that are already working, we add a set of F_OFD_*32 constants,
and add the plumbing to the kernel to make those do the right thing.

This patch adds the same constants to glibc, and has it redefine the
"normal" F_OFD_* constants to their *32 equvalents when LFS support is
not in use.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 ChangeLog                                  |  4 ++++
 sysdeps/unix/sysv/linux/bits/fcntl-linux.h | 17 +++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 59c68d8b9d0d..4a2488b50054 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2016-08-18  Jeff Layton <jlayton@redhat.com>
+	* sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
+	Add F_OFD_GETLK32, F_OFD_SETLK32, F_OFD_SETLKW32
+
 2016-08-18  Stefan Liebler  <stli@linux.vnet.ibm.com>
 
 	* sysdeps/ieee754/dbl-64/k_rem_pio2.c (__kernel_rem_pio2):
diff --git a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
index 7e5b0aecdcb4..9cb1b5f6f3ec 100644
--- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
+++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
@@ -127,11 +127,20 @@
    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. */
+   is put.  */
 #ifdef __USE_GNU
-# define F_OFD_GETLK	36
-# define F_OFD_SETLK	37
-# define F_OFD_SETLKW	38
+# if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
+#  define F_OFD_GETLK		36
+#  define F_OFD_SETLK		37
+#  define F_OFD_SETLKW		38
+# else
+#  define F_OFD_GETLK32		39
+#  define F_OFD_SETLK32		40
+#  define F_OFD_SETLKW32	41
+#  define F_OFD_GETLK		F_OFD_GETLK32
+#  define F_OFD_SETLK		F_OFD_SETLK32
+#  define F_OFD_SETLKW		F_OFD_SETLKW32
+# endif
 #endif
 
 #ifdef __USE_LARGEFILE64
-- 
2.7.4