Make sync_file_range() usage optional

Under uClibc, sync_file_range() is not available under all
architectures, so we fall back to fdatasync() in this case.

Inspired by the patch done by Thomas Petazzoni for the
2.0-pre25 version.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
---
 configure.ac              |    2 +-
 src/common/compat/fcntl.h |    5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 5808c79..065b9cf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -120,7 +120,7 @@ AS_IF([test "x$lttng_ust_support" = "xyes"], [

 AM_CONDITIONAL([HAVE_LIBLTTNG_UST_CTL], [ test "x$ac_cv_lib_lttng_ust_ctl_ustctl_create_session" = "xyes" ])

-AC_CHECK_FUNCS([sched_getcpu sysconf])
+AC_CHECK_FUNCS([sched_getcpu sysconf sync_file_range])

 # check for dlopen
 AC_CHECK_LIB([dl], [dlopen],
diff --git a/src/common/compat/fcntl.h b/src/common/compat/fcntl.h
index 58c1579..dafb33e 100644
--- a/src/common/compat/fcntl.h
+++ b/src/common/compat/fcntl.h
@@ -23,10 +23,15 @@

 #ifdef __linux__

+#if defined(HAVE_SYNC_FILE_RANGE)
 extern int compat_sync_file_range(int fd, off64_t offset, off64_t nbytes,
 		unsigned int flags);
 #define lttng_sync_file_range(fd, offset, nbytes, flags) \
 	compat_sync_file_range(fd, offset, nbytes, flags)
+#else
+#define lttng_sync_file_range(fd, offset, nbytes, flags) \
+	fdatasync(fd);
+#endif

 #elif defined(__FreeBSD__)

--
1.7.10