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-rw-r--r--drivers/md/dm-path-selector.h97
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diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h
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+++ b/drivers/md/dm-path-selector.h
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+/*
+ * Copyright (C) 2003 Sistina Software.
+ * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen
+ *
+ * This file is released under the GPL.
+ *
+ * Path-Selector registration.
+ */
+
+#ifndef DM_PATH_SELECTOR_H
+#define DM_PATH_SELECTOR_H
+
+#include <linux/device-mapper.h>
+
+#include "dm-mpath.h"
+
+/*
+ * We provide an abstraction for the code that chooses which path
+ * to send some io down.
+ */
+struct path_selector_type;
+struct path_selector {
+ struct path_selector_type *type;
+ void *context;
+};
+
+/* Information about a path selector type */
+struct path_selector_type {
+ char *name;
+ struct module *module;
+
+ unsigned int table_args;
+ unsigned int info_args;
+
+ /*
+ * Constructs a path selector object, takes custom arguments
+ */
+ int (*create) (struct path_selector *ps, unsigned argc, char **argv);
+ void (*destroy) (struct path_selector *ps);
+
+ /*
+ * Add an opaque path object, along with some selector specific
+ * path args (eg, path priority).
+ */
+ int (*add_path) (struct path_selector *ps, struct dm_path *path,
+ int argc, char **argv, char **error);
+
+ /*
+ * Chooses a path for this io, if no paths are available then
+ * NULL will be returned.
+ *
+ * repeat_count is the number of times to use the path before
+ * calling the function again. 0 means don't call it again unless
+ * the path fails.
+ */
+ struct dm_path *(*select_path) (struct path_selector *ps,
+ unsigned *repeat_count,
+ size_t nr_bytes);
+
+ /*
+ * Notify the selector that a path has failed.
+ */
+ void (*fail_path) (struct path_selector *ps, struct dm_path *p);
+
+ /*
+ * Ask selector to reinstate a path.
+ */
+ int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);
+
+ /*
+ * Table content based on parameters added in ps_add_path_fn
+ * or path selector status
+ */
+ int (*status) (struct path_selector *ps, struct dm_path *path,
+ status_type_t type, char *result, unsigned int maxlen);
+
+ int (*start_io) (struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes);
+ int (*end_io) (struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes);
+};
+
+/* Register a path selector */
+int dm_register_path_selector(struct path_selector_type *type);
+
+/* Unregister a path selector */
+int dm_unregister_path_selector(struct path_selector_type *type);
+
+/* Returns a registered path selector type */
+struct path_selector_type *dm_get_path_selector(const char *name);
+
+/* Releases a path selector */
+void dm_put_path_selector(struct path_selector_type *pst);
+
+#endif