file-posix: Implement bdrv_co_copy_range

With copy_file_range(2), we can implement the bdrv_co_copy_range
semantics.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 20180601092648.24614-6-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/configure b/configure
index be6edc7..8c6ea9b 100755
--- a/configure
+++ b/configure
@@ -5183,6 +5183,20 @@
   fi
 fi
 
+###############################################
+# Check if copy_file_range is provided by glibc
+have_copy_file_range=no
+cat > $TMPC << EOF
+#include <unistd.h>
+int main(void) {
+  copy_file_range(0, NULL, 0, NULL, 0, 0);
+  return 0;
+}
+EOF
+if compile_prog "" "" ; then
+    have_copy_file_range=yes
+fi
+
 ##########################################
 # check if struct fsxattr is available via linux/fs.h
 
@@ -6286,6 +6300,9 @@
 if test "$have_fsxattr" = "yes" ; then
     echo "HAVE_FSXATTR=y" >> $config_host_mak
 fi
+if test "$have_copy_file_range" = "yes" ; then
+    echo "HAVE_COPY_FILE_RANGE=y" >> $config_host_mak
+fi
 if test "$vte" = "yes" ; then
   echo "CONFIG_VTE=y" >> $config_host_mak
   echo "VTE_CFLAGS=$vte_cflags" >> $config_host_mak