A better solution than r6672. If the caller passes in a data segment

alignment of 0, then assume there will be no data segment and don't do
the checks to see if it will be beyond the end of the file.

This commit was SVN r6773.

The following SVN revision numbers were found above:
  r6672 --> open-mpi/ompi@8b56769307

ompi/mca/btl/sm/btl_sm.c

@@ -279,15 +279,12 @@ int mca_btl_sm_add_procs_same_base_addr(
             goto CLEANUP;
         }
 
-        /* Need to add in padding at end of size to account for a data
-           segment in the mmap file (even though we're not going to
-           use it; mca_common_sm_mmap_init() assumes that we will use
-           it and will error if we don't allocate enough space to at
-           least start a data segment) */
-        size = sizeof(mca_btl_sm_module_resource_t) + 8;
+        /* Pass in a data segment alignment of 0 to get no data
+           segment (only the shared control structure */
+        size = sizeof(mca_btl_sm_module_resource_t);
         if(NULL==(mca_btl_sm_component.mmap_file=mca_common_sm_mmap_init(size,
                         mca_btl_sm_component.sm_resouce_ctl_file,
-                        sizeof(mca_btl_sm_module_resource_t), 8 ))) 
+                        sizeof(mca_btl_sm_module_resource_t), 0))) 
         {
             opal_output(0, "mca_btl_sm_add_procs: unable to create shared memory BTL coordinating strucure :: size %ld \n",
                     size);

ompi/mca/common/sm/common_sm_mmap.c

@@ -75,24 +75,6 @@ static int mca_common_sm_mmap_open(char* path)
 
 }
 
-/**
- *  This routine is used to set up a shared memory file, backed
- *  by a specified file.  It is assumed that the file does not
- *  exist before any of the current set of processes try and open
- *  it.
- *
- *  @param size - size of the file, in bytes (IN)
- *
- *  @param file_name  name of file to be opened. (IN)
- *
- *  @param size_ctl_structure  size of the control structure at
- *                             the head of the file. The control structure 
- *                             is assumed to have mca_common_sm_file_header_t
- *                             as its first segment (IN)
- *
- *  @param data_seg_alignment  alignment of the data segment.  this
- *                             follows the control structure (IN)
- */
 
 mca_common_sm_mmap_t* mca_common_sm_mmap_init(size_t size, char *file_name, 
         size_t size_ctl_structure, size_t data_seg_alignment)
@@ -109,8 +91,7 @@ mca_common_sm_mmap_t* mca_common_sm_mmap_init(size_t size, char *file_name,
     if( (size < sizeof(mca_common_sm_file_header_t) ) ||
                 ( file_name == NULL ) || 
                 ( size_ctl_structure <
-                  sizeof(mca_common_sm_file_header_t ) ) ||
-                ( data_seg_alignment == 0 ) ) {
+                  sizeof(mca_common_sm_file_header_t ) )) {
         return NULL;
     }
 
@@ -166,27 +147,33 @@ mca_common_sm_mmap_t* mca_common_sm_mmap_init(size_t size, char *file_name,
        element */
     map->map_seg = seg;
 
-    /* allign start of data segment */
-    addr = ((unsigned char *) seg) + size_ctl_structure;
-    /* calculate how far off alignment we are */
-    tmp = ((size_t) addr) % data_seg_alignment;
-    /* if we're off alignment, then move up to the next alignment */
-    if (tmp > 0) {
-        addr += (data_seg_alignment - tmp);
-    }
+    /* If we have a data segment (i.e., if 0 != data_seg_alignment),
+       then make it the first aligned address after the control
+       structure. */
+    if (0 != data_seg_alignment) {
+        addr = ((unsigned char *) seg) + size_ctl_structure;
+        /* calculate how far off alignment we are */
+        tmp = ((size_t) addr) % data_seg_alignment;
+        /* if we're off alignment, then move up to the next alignment */
+        if (tmp > 0) {
+            addr += (data_seg_alignment - tmp);
+        }
 
-    /* is addr past end of file ? */
-    if( (unsigned char*)seg+size < addr ){
-        opal_output(0, "mca_common_sm_mmap_init: memory region too small len %d  addr %p\n",
-                size,addr);
-        fchmod(fd, 0600);
-        close(fd);
-        munmap(seg,size);
-        return NULL;
+        /* is addr past end of file ? */
+        if( (unsigned char*)seg+size < addr ){
+            opal_output(0, "mca_common_sm_mmap_init: memory region too small len %d  addr %p\n",
+                        size,addr);
+            fchmod(fd, 0600);
+            close(fd);
+            munmap(seg,size);
+            return NULL;
+        }
+        map->data_addr = addr;
+    } else {
+        map->data_addr = NULL;
     }
     mem_offset=addr-(unsigned char *)seg;
     map->map_addr = (unsigned char *)seg;
-    map->data_addr = addr;
     map->map_size = size;
 
     /* initialize the segment - only the first process to open the file */

ompi/mca/common/sm/common_sm_mmap.h

@@ -86,7 +86,10 @@ OBJ_CLASS_DECLARATION(mca_common_sm_mmap_t);
  *                             as its first segment (IN)
  *
  *  @param data_set_alignment  alignment of the data segment.  this
- *                             follows the control structure (IN)
+ *                             follows the control structure.  If this 
+ *                             value if 0, then assume that there will 
+ *                             be no data segment following the control 
+ *                             structure. (IN)
  *
  *  @returnvalue pointer to control structure at head of file.
  */