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| 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 | * repeat_count is the number of times to use the path before |
| 55 | * calling the function again. 0 means don't call it again unless |
| 56 | * the path fails. |
| 57 | */ |
| 58 | struct dm_path *(*select_path) (struct path_selector *ps, |
| 59 | unsigned *repeat_count, |
| 60 | size_t nr_bytes); |
| 61 | |
| 62 | /* |
| 63 | * Notify the selector that a path has failed. |
| 64 | */ |
| 65 | void (*fail_path) (struct path_selector *ps, struct dm_path *p); |
| 66 | |
| 67 | /* |
| 68 | * Ask selector to reinstate a path. |
| 69 | */ |
| 70 | int (*reinstate_path) (struct path_selector *ps, struct dm_path *p); |
| 71 | |
| 72 | /* |
| 73 | * Table content based on parameters added in ps_add_path_fn |
| 74 | * or path selector status |
| 75 | */ |
| 76 | int (*status) (struct path_selector *ps, struct dm_path *path, |
| 77 | status_type_t type, char *result, unsigned int maxlen); |
| 78 | |
| 79 | int (*start_io) (struct path_selector *ps, struct dm_path *path, |
| 80 | size_t nr_bytes); |
| 81 | int (*end_io) (struct path_selector *ps, struct dm_path *path, |
| 82 | size_t nr_bytes); |
| 83 | }; |
| 84 | |
| 85 | /* Register a path selector */ |
| 86 | int dm_register_path_selector(struct path_selector_type *type); |
| 87 | |
| 88 | /* Unregister a path selector */ |
| 89 | int dm_unregister_path_selector(struct path_selector_type *type); |
| 90 | |
| 91 | /* Returns a registered path selector type */ |
| 92 | struct path_selector_type *dm_get_path_selector(const char *name); |
| 93 | |
| 94 | /* Releases a path selector */ |
| 95 | void dm_put_path_selector(struct path_selector_type *pst); |
| 96 | |
| 97 | #endif |
| 98 |
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