Return a plugin_err_t from plugin_load_from_file in order to allow

callers to better handle and report errors from this function. Also
update all callers to use new calling style. Update call site in
plugstack.c to report error using plugin_strerror(). Other callers
ignore errors as before.

src/common/plugin.c

@@ -140,12 +140,25 @@ plugin_peek( const char *fq_path,
 	return SLURM_SUCCESS;
 }
 
-plugin_handle_t
-plugin_load_from_file(const char *fq_path)
+plugin_err_t
+plugin_load_from_file(plugin_handle_t *p, const char *fq_path)
 {
+	struct stat st;
 	plugin_handle_t plug;
 	int (*init)(void);
 
+	*p = PLUGIN_INVALID_HANDLE;
+
+	/*
+	 *  Check for file existence and access permissions
+	 */
+	if (access(fq_path, R_OK) < 0) {
+		if (errno == ENOENT)
+			return EPLUGIN_NOTFOUND;
+		else
+			return EPLUGIN_ACCESS_ERROR;
+	}
+
 	/*
 	 * Try to open the shared object.
 	 *
@@ -161,16 +174,15 @@ plugin_load_from_file(const char *fq_path)
 		error("plugin_load_from_file: dlopen(%s): %s",
 		      fq_path,
 		      _dlerror());
-		return PLUGIN_INVALID_HANDLE;
+		return EPLUGIN_DLOPEN_FAILED;
 	}
 
 	/* Now see if our required symbols are defined. */
 	if ((dlsym(plug, PLUGIN_NAME) == NULL) ||
 	    (dlsym(plug, PLUGIN_TYPE) == NULL) ||
 	    (dlsym(plug, PLUGIN_VERSION) == NULL)) {
-		debug("plugin_load_from_file: invalid symbol");
-		/* slurm_seterrno( SLURM_PLUGIN_SYMBOLS ); */
-		return PLUGIN_INVALID_HANDLE;
+		dlclose (plug);
+		return EPLUGIN_MISSING_SYMBOL;
 	}
 
 	/*
@@ -179,14 +191,13 @@ plugin_load_from_file(const char *fq_path)
 	 */
 	if ((init = dlsym(plug, "init")) != NULL) {
 		if ((*init)() != 0) {
-			error("plugin_load_from_file(%s): init() returned SLURM_ERROR",
-			      fq_path);
-			(void) dlclose(plug);
-			return PLUGIN_INVALID_HANDLE;
+			dlclose(plug);
+			return EPLUGIN_INIT_FAILED;
 		}
 	}
 
-	return plug;
+	*p = plug;
+	return EPLUGIN_SUCCESS;
 }
 
 plugin_handle_t
@@ -230,7 +241,7 @@ plugin_load_and_link(const char *type_name, int n_syms,
 			debug4("No Good.");
 			xfree(file_name);
 		} else {
-			plug = plugin_load_from_file(file_name);
+			plugin_load_from_file(&plug, file_name);
 			xfree(file_name);
 			if (plugin_get_syms(plug, n_syms, names, ptrs) >= 
 			    n_syms) {

src/common/plugin.h

@@ -119,15 +119,17 @@ int plugin_peek( const char *fq_path,
 /*
  * Simplest way to get a plugin -- load it from a file.
  *
+ * pph     - Pointer to a plugin handle
  * fq_path - the fully-qualified pathname (i.e., from root) to
  * the plugin to load.
  *
- * Returns a handle if successful, or NULL if not.
+ * Returns EPLUGIN_SUCCESS on success, and an plugin_err_t error
+ * code on failure.
  *
  * The plugin's initialization code will be executed prior
  * to this function's return.
  */
-plugin_handle_t plugin_load_from_file( const char *fq_path );
+plugin_err_t plugin_load_from_file(plugin_handle_t *pph, const char *fq_path);
 
 /*
  * load plugin and link hooks.

src/common/plugrack.c

@@ -548,7 +548,7 @@ plugrack_load_all( plugrack_t rack )
         it = list_iterator_create( rack->entries );
         while ( ( e = list_next( it ) ) != NULL ) {
                 if ( e->plug == PLUGIN_INVALID_HANDLE ) {
-                        e->plug = plugin_load_from_file( e->fq_path );
+                        plugin_load_from_file(&e->plug, e->fq_path);
                 }
         }
 
@@ -585,7 +585,7 @@ plugrack_use_by_type( plugrack_t rack,
 		
                 /* See if plugin is loaded. */
                 if ( e->plug == PLUGIN_INVALID_HANDLE ) 
-			e->plug = plugin_load_from_file( e->fq_path );
+                        plugin_load_from_file(&e->plug, e->fq_path);
 
                 /* If load was successful, increment the reference count. */
                 if ( e->plug == PLUGIN_INVALID_HANDLE )

src/common/plugstack.c

@@ -260,10 +260,13 @@ static struct spank_plugin *_spank_plugin_create(char *path, int ac,
 {
 	struct spank_plugin *plugin;
 	plugin_handle_t p;
+	plugin_err_t e;
 	struct spank_plugin_operations ops;
 
-	if (!(p = plugin_load_from_file(path)))
+	if ((e = plugin_load_from_file(&p, path)) != EPLUGIN_SUCCESS) {
+		error ("spank: %s: %s\n", path, plugin_strerror(e));
 		return NULL;
+	}
 
 	if (plugin_get_syms(p, n_spank_syms, spank_syms, (void **)&ops) == 0) {
 		error("spank: \"%s\" exports 0 symbols\n", path);