gluster: Handle changed glfs_ftruncate signature

New versions of Glusters libgfapi.so have an updated glfs_ftruncate()
function that returns additional 'struct stat' structures to enable
advanced caching of attributes. This is useful for file servers, not so
much for QEMU. Nevertheless, the API has changed and needs to be
adopted.

Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

configure

@@ -456,6 +456,7 @@ glusterfs_xlator_opt="no"
 glusterfs_discard="no"
 glusterfs_fallocate="no"
 glusterfs_zerofill="no"
+glusterfs_ftruncate_has_stat="no"
 gtk=""
 gtk_gl="no"
 tls_priority="NORMAL"
@@ -4091,6 +4092,19 @@ if test "$glusterfs" != "no" ; then
       glusterfs_fallocate="yes"
       glusterfs_zerofill="yes"
     fi
+    cat > $TMPC << EOF
+#include <glusterfs/api/glfs.h>
+
+int
+main(void)
+{
+	/* new glfs_ftruncate() passes two additional args */
+	return glfs_ftruncate(NULL, 0, NULL, NULL);
+}
+EOF
+    if compile_prog "$glusterfs_cflags" "$glusterfs_libs" ; then
+      glusterfs_ftruncate_has_stat="yes"
+    fi
   else
     if test "$glusterfs" = "yes" ; then
       feature_not_found "GlusterFS backend support" \
@@ -6976,6 +6990,10 @@ if test "$glusterfs_zerofill" = "yes" ; then
   echo "CONFIG_GLUSTERFS_ZEROFILL=y" >> $config_host_mak
 fi
 
+if test "$glusterfs_ftruncate_has_stat" = "yes" ; then
+  echo "CONFIG_GLUSTERFS_FTRUNCATE_HAS_STAT=y" >> $config_host_mak
+fi
+
 if test "$libssh2" = "yes" ; then
   echo "CONFIG_LIBSSH2=m" >> $config_host_mak
   echo "LIBSSH2_CFLAGS=$libssh2_cflags" >> $config_host_mak