From cf8fd1a70884db0b31e312d0780611f262bb9b45 Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba@suse.com>
Date: Fri, 14 Oct 2016 18:39:40 +0200
Subject: [PATCH] btrfs-progs: build: detect fiemap shared flag but don't fail
 build

The FIEMAP_EXTENT_SHARED fiemap flag was introduced in 2.6.33. If the
headers do not provide the definition, the build will fail. The support
of the fiemap sharing depends on the running kernel. There are still
systems with 2.6.32 kernel headers but running newer versions.

To support such environment, don't fail build, provide own defintion of
the structure and detect if there's an old kernel in use in the relevant
command (btrfs fi du).

Reported-by: Abhay Sachan <lkp.abhay@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 cmds-fi-du.c | 14 ++++++++++++++
 configure.ac | 10 +++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/cmds-fi-du.c b/cmds-fi-du.c
index a5b66e6f..895c242e 100644
--- a/cmds-fi-du.c
+++ b/cmds-fi-du.c
@@ -27,8 +27,13 @@
 
 #include <sys/ioctl.h>
 #include <linux/fs.h>
+#include <linux/version.h>
 #include <linux/fiemap.h>
 
+#if !defined(FIEMAP_EXTENT_SHARED) && (HAVE_OWN_FIEMAP_EXTENT_SHARED_DEFINE == 1)
+#define FIEMAP_EXTENT_SHARED           0x00002000
+#endif
+
 #include "utils.h"
 #include "commands.h"
 #include "kerncompat.h"
@@ -546,6 +551,7 @@ int cmd_filesystem_du(int argc, char **argv)
 {
 	int ret = 0, err = 0;
 	int i;
+	u32 kernel_version;
 
 	unit_mode = get_unit_mode_from_arg(&argc, argv, 1);
 
@@ -570,6 +576,14 @@ int cmd_filesystem_du(int argc, char **argv)
 	if (check_argc_min(argc - optind, 1))
 		usage(cmd_filesystem_du_usage);
 
+	kernel_version = get_running_kernel_version();
+
+	if (kernel_version < KERNEL_VERSION(2,6,33)) {
+		warning(
+"old kernel version detected, shared space will be reported as exclusive\n"
+"due to missing support for FIEMAP_EXTENT_SHARED flag");
+	}
+
 	printf("%10s  %10s  %10s  %s\n", "Total", "Exclusive", "Set shared",
 			"Filename");
 
diff --git a/configure.ac b/configure.ac
index 8fd8f425..9c6df3b9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -144,8 +144,16 @@ if test "$DISABLE_BTRFSCONVERT" = 0 && test "x$convertfs" = "x"; then
 	AC_MSG_ERROR([no filesystems for convert, use --disable-convert instead])
 fi
 
+HAVE_OWN_FIEMAP_EXTENT_SHARED_DEFINE=0
 AX_CHECK_DEFINE([linux/fiemap.h], [FIEMAP_EXTENT_SHARED], [],
-		[AC_MSG_ERROR([no definition of FIEMAP_EXTENT_SHARED found])])
+		[HAVE_OWN_FIEMAP_EXTENT_SHARED_DEFINE=1
+		 AC_MSG_WARN([no definition of FIEMAP_EXTENT_SHARED found, probably old kernel, will use own defintion, 'btrfs fi du' might report wrong numbers])])
+
+if test "x$HAVE_OWN_FIEMAP_EXTENT_SHARED_DEFINE" == "x1"; then
+AC_DEFINE([HAVE_OWN_FIEMAP_EXTENT_SHARED_DEFINE], [1], [We defined FIEMAP_EXTENT_SHARED])
+else
+AC_DEFINE([HAVE_OWN_FIEMAP_EXTENT_SHARED_DEFINE], [0], [We did not define FIEMAP_EXTENT_SHARED])
+fi
 
 dnl Define <NAME>_LIBS= and <NAME>_CFLAGS= by pkg-config
 dnl