1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
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 | |
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 | |
44 | /* Information about a path selector type */ |
45 | struct path_selector_type { |
46 | char *name; |
47 | struct module *module; |
48 | |
49 | unsigned int features; |
50 | unsigned int table_args; |
51 | unsigned int info_args; |
52 | |
53 | /* |
54 | * Constructs a path selector object, takes custom arguments |
55 | */ |
56 | int (*create)(struct path_selector *ps, unsigned int argc, char **argv); |
57 | void (*destroy)(struct path_selector *ps); |
58 | |
59 | /* |
60 | * Add an opaque path object, along with some selector specific |
61 | * path args (eg, path priority). |
62 | */ |
63 | int (*add_path)(struct path_selector *ps, struct dm_path *path, |
64 | int argc, char **argv, char **error); |
65 | |
66 | /* |
67 | * Chooses a path for this io, if no paths are available then |
68 | * NULL will be returned. |
69 | */ |
70 | struct dm_path *(*select_path)(struct path_selector *ps, size_t nr_bytes); |
71 | |
72 | /* |
73 | * Notify the selector that a path has failed. |
74 | */ |
75 | void (*fail_path)(struct path_selector *ps, struct dm_path *p); |
76 | |
77 | /* |
78 | * Ask selector to reinstate a path. |
79 | */ |
80 | int (*reinstate_path)(struct path_selector *ps, struct dm_path *p); |
81 | |
82 | /* |
83 | * Table content based on parameters added in ps_add_path_fn |
84 | * or path selector status |
85 | */ |
86 | int (*status)(struct path_selector *ps, struct dm_path *path, |
87 | status_type_t type, char *result, unsigned int maxlen); |
88 | |
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); |
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 |
108 | |