1 /* 2 * Copyright (C) 2003 Sistina Software. 3 * Copyright (C) 2004 Red Hat, Inc. All rights reserved. 4 * 5 * Module Author: Heinz Mauelshagen 6 * 7 * This file is released under the GPL. 8 * 9 * Path-Selector registration. 10 */ 11 12 #ifndef DM_PATH_SELECTOR_H 13 #define DM_PATH_SELECTOR_H 14 15 #include <linux/device-mapper.h> 16 17 #include "dm-mpath.h" 18 19 /* 20 * We provide an abstraction for the code that chooses which path 21 * to send some io down. 22 */ 23 struct path_selector_type; 24 struct path_selector { 25 struct path_selector_type *type; 26 void *context; 27 }; 28 29 /* Information about a path selector type */ 30 struct path_selector_type { 31 char *name; 32 struct module *module; 33 34 unsigned int table_args; 35 unsigned int info_args; 36 37 /* 38 * Constructs a path selector object, takes custom arguments 39 */ 40 int (*create) (struct path_selector *ps, unsigned argc, char **argv); 41 void (*destroy) (struct path_selector *ps); 42 43 /* 44 * Add an opaque path object, along with some selector specific 45 * path args (eg, path priority). 46 */ 47 int (*add_path) (struct path_selector *ps, struct dm_path *path, 48 int argc, char **argv, char **error); 49 50 /* 51 * Chooses a path for this io, if no paths are available then 52 * NULL will be returned. 53 */ 54 struct dm_path *(*select_path) (struct path_selector *ps, 55 size_t nr_bytes); 56 57 /* 58 * Notify the selector that a path has failed. 59 */ 60 void (*fail_path) (struct path_selector *ps, struct dm_path *p); 61 62 /* 63 * Ask selector to reinstate a path. 64 */ 65 int (*reinstate_path) (struct path_selector *ps, struct dm_path *p); 66 67 /* 68 * Table content based on parameters added in ps_add_path_fn 69 * or path selector status 70 */ 71 int (*status) (struct path_selector *ps, struct dm_path *path, 72 status_type_t type, char *result, unsigned int maxlen); 73 74 int (*start_io) (struct path_selector *ps, struct dm_path *path, 75 size_t nr_bytes); 76 int (*end_io) (struct path_selector *ps, struct dm_path *path, 77 size_t nr_bytes); 78 }; 79 80 /* Register a path selector */ 81 int dm_register_path_selector(struct path_selector_type *type); 82 83 /* Unregister a path selector */ 84 int dm_unregister_path_selector(struct path_selector_type *type); 85 86 /* Returns a registered path selector type */ 87 struct path_selector_type *dm_get_path_selector(const char *name); 88 89 /* Releases a path selector */ 90 void dm_put_path_selector(struct path_selector_type *pst); 91 92 #endif 93