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3bd94003 | 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
1da177e4 LT |
2 | /* |
3 | * Copyright (C) 2003 Sistina Software. | |
4 | * Copyright (C) 2004 Red Hat, Inc. All rights reserved. | |
5 | * | |
6 | * Module Author: Heinz Mauelshagen | |
7 | * | |
8 | * This file is released under the GPL. | |
9 | * | |
10 | * Path-Selector registration. | |
11 | */ | |
12 | ||
13 | #ifndef DM_PATH_SELECTOR_H | |
14 | #define DM_PATH_SELECTOR_H | |
15 | ||
16 | #include <linux/device-mapper.h> | |
17 | ||
18 | #include "dm-mpath.h" | |
19 | ||
20 | /* | |
21 | * We provide an abstraction for the code that chooses which path | |
22 | * to send some io down. | |
23 | */ | |
24 | struct path_selector_type; | |
25 | struct path_selector { | |
26 | struct path_selector_type *type; | |
27 | void *context; | |
28 | }; | |
29 | ||
c06dfd12 GKB |
30 | /* |
31 | * If a path selector uses this flag, a high resolution timer is used | |
32 | * (via ktime_get_ns) to account for IO start time in BIO-based mpath. | |
33 | * This improves performance of some path selectors (i.e. HST), in | |
34 | * exchange for slightly higher overhead when submitting the BIO. | |
35 | * The extra cost is usually offset by improved path selection for | |
36 | * some benchmarks. | |
37 | * | |
38 | * This has no effect for request-based mpath, since it already uses a | |
39 | * higher precision timer by default. | |
40 | */ | |
41 | #define DM_PS_USE_HR_TIMER 0x00000001 | |
42 | #define dm_ps_use_hr_timer(type) ((type)->features & DM_PS_USE_HR_TIMER) | |
43 | ||
1da177e4 LT |
44 | /* Information about a path selector type */ |
45 | struct path_selector_type { | |
46 | char *name; | |
47 | struct module *module; | |
48 | ||
c06dfd12 | 49 | unsigned int features; |
1da177e4 LT |
50 | unsigned int table_args; |
51 | unsigned int info_args; | |
52 | ||
53 | /* | |
54 | * Constructs a path selector object, takes custom arguments | |
55 | */ | |
8ca817c4 HM |
56 | int (*create)(struct path_selector *ps, unsigned int argc, char **argv); |
57 | void (*destroy)(struct path_selector *ps); | |
1da177e4 LT |
58 | |
59 | /* | |
60 | * Add an opaque path object, along with some selector specific | |
61 | * path args (eg, path priority). | |
62 | */ | |
8ca817c4 HM |
63 | int (*add_path)(struct path_selector *ps, struct dm_path *path, |
64 | int argc, char **argv, char **error); | |
1da177e4 LT |
65 | |
66 | /* | |
67 | * Chooses a path for this io, if no paths are available then | |
68 | * NULL will be returned. | |
1da177e4 | 69 | */ |
8ca817c4 | 70 | struct dm_path *(*select_path)(struct path_selector *ps, size_t nr_bytes); |
1da177e4 LT |
71 | |
72 | /* | |
73 | * Notify the selector that a path has failed. | |
74 | */ | |
8ca817c4 | 75 | void (*fail_path)(struct path_selector *ps, struct dm_path *p); |
1da177e4 LT |
76 | |
77 | /* | |
78 | * Ask selector to reinstate a path. | |
79 | */ | |
8ca817c4 | 80 | int (*reinstate_path)(struct path_selector *ps, struct dm_path *p); |
1da177e4 LT |
81 | |
82 | /* | |
83 | * Table content based on parameters added in ps_add_path_fn | |
84 | * or path selector status | |
85 | */ | |
8ca817c4 HM |
86 | int (*status)(struct path_selector *ps, struct dm_path *path, |
87 | status_type_t type, char *result, unsigned int maxlen); | |
1da177e4 | 88 | |
8ca817c4 HM |
89 | int (*start_io)(struct path_selector *ps, struct dm_path *path, |
90 | size_t nr_bytes); | |
91 | int (*end_io)(struct path_selector *ps, struct dm_path *path, | |
92 | size_t nr_bytes, u64 start_time); | |
1da177e4 LT |
93 | }; |
94 | ||
95 | /* Register a path selector */ | |
96 | int dm_register_path_selector(struct path_selector_type *type); | |
97 | ||
98 | /* Unregister a path selector */ | |
99 | int dm_unregister_path_selector(struct path_selector_type *type); | |
100 | ||
101 | /* Returns a registered path selector type */ | |
102 | struct path_selector_type *dm_get_path_selector(const char *name); | |
103 | ||
104 | /* Releases a path selector */ | |
105 | void dm_put_path_selector(struct path_selector_type *pst); | |
106 | ||
107 | #endif |