common/ompio: correctly position shared fp in append mode

Fixes a bug reported on the mailing list. ompio did only reposition the individual
file pointer when the file was opened in append mode. Set the shared file
pointer also to point to the end of the file, similarly to the individual
file pointer.

Signed-off-by: Edgar Gabriel <egabriel@central.uh.edu>

ompi/mca/common/ompio/common_ompio_file_open.c

@@ -9,7 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2008-2016 University of Houston. All rights reserved.
+ * Copyright (c) 2008-2017 University of Houston. All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
  * Copyright (c) 2016 Cisco Systems, Inc.  All rights reserved.
@@ -204,10 +204,28 @@ int mca_common_ompio_file_open (ompi_communicator_t *comm,
        file pointer of OMPIO to the very end of the file. */
     if ( ompio_fh->f_amode & MPI_MODE_APPEND ) {
         OMPI_MPI_OFFSET_TYPE current_size;
+        mca_sharedfp_base_module_t * shared_fp_base_module;
 
         ompio_fh->f_fs->fs_file_get_size( ompio_fh,
                                           &current_size);
         mca_common_ompio_set_explicit_offset (ompio_fh, current_size);
+        if ( true == use_sharedfp ) {
+            if ( NULL != ompio_fh->f_sharedfp &&
+                 (!mca_io_ompio_sharedfp_lazy_open ||
+                  !strcmp (ompio_fh->f_sharedfp_component->mca_component_name,
+                           "addproc")               )) {
+                
+                shared_fp_base_module = ompio_fh->f_sharedfp;
+                ret = shared_fp_base_module->sharedfp_seek(ompio_fh,current_size, MPI_SEEK_SET);
+            }
+            else {
+                opal_output(1, "mca_common_ompio_file_open: Could not adjust position of "
+                            "shared file pointer whith MPI_MODE_APPEND\n");
+                ret = MPI_ERR_OTHER;
+                goto fn_fail;
+            }
+        }
+
     }