From: Dmitry V. Levin <ldv@altlinux.org>
Date: Feb. 22, 2017, 2:29 a.m.
Subject: uapi: add a compatibility layer between linux/uio.h and glibc
References: bsc#1053501
Patch-mainline: Not yet, submitted 2/22/2017 to lkml <jeffm: and largely ignored, lduncan will follow up, Oct 4, 2017>

Do not define struct iovec in linux/uio.h when <sys/uio.h> or <fcntl.h>
is already included and provides these definitions.

This fixes the following compilation error when <sys/uio.h> or <fcntl.h>
is included before <linux/uio.h>:

/usr/include/linux/uio.h:16:8: error: redefinition of 'struct iovec'

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Acked-by: Lee Duncan <lduncan@suse.com>
---
 include/uapi/linux/libc-compat.h |   10 ++++++++++
 include/uapi/linux/uio.h         |    3 +++
 2 files changed, 13 insertions(+)

--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -158,6 +158,13 @@
 
 #endif /* defined(__NETIPX_IPX_H) */
 
+/* Coordinate with glibc bits/uio.h header. */
+#if defined(_SYS_UIO_H) || defined(_FCNTL_H)
+#define __UAPI_DEF_IOVEC		0
+#else
+#define __UAPI_DEF_IOVEC		1
+#endif
+
 /* Definitions for xattr.h */
 #if defined(_SYS_XATTR_H)
 #define __UAPI_DEF_XATTR		0
@@ -205,6 +212,9 @@
 #define __UAPI_DEF_IPX_ROUTE_DEF		1
 #endif
 
+/* Definitions for uio.h */
+#define __UAPI_DEF_IOVEC		1
+
 /* Definitions for xattr.h */
 #ifndef __UAPI_DEF_XATTR
 #define __UAPI_DEF_XATTR		1
--- a/include/uapi/linux/uio.h
+++ b/include/uapi/linux/uio.h
@@ -9,15 +9,18 @@
 #ifndef _UAPI__LINUX_UIO_H
 #define _UAPI__LINUX_UIO_H
 
+#include <linux/libc-compat.h>
 #include <linux/compiler.h>
 #include <linux/types.h>
 
 
+#if __UAPI_DEF_IOVEC
 struct iovec
 {
 	void __user *iov_base;	/* BSD uses caddr_t (1003.1g requires void *) */
 	__kernel_size_t iov_len; /* Must be size_t (1003.1g) */
 };
+#endif /* __UAPI_DEF_IOVEC */
 
 /*
  *	UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)