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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 | /* SPDX-License-Identifier: GPL-2.0-only */ /* * 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; }; /* * If a path selector uses this flag, a high resolution timer is used * (via ktime_get_ns) to account for IO start time in BIO-based mpath. * This improves performance of some path selectors (i.e. HST), in * exchange for slightly higher overhead when submitting the BIO. * The extra cost is usually offset by improved path selection for * some benchmarks. * * This has no effect for request-based mpath, since it already uses a * higher precision timer by default. */ #define DM_PS_USE_HR_TIMER 0x00000001 #define dm_ps_use_hr_timer(type) ((type)->features & DM_PS_USE_HR_TIMER) /* Information about a path selector type */ struct path_selector_type { char *name; struct module *module; unsigned int features; unsigned int table_args; unsigned int info_args; /* * Constructs a path selector object, takes custom arguments */ int (*create)(struct path_selector *ps, unsigned int 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. */ struct dm_path *(*select_path)(struct path_selector *ps, 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, u64 start_time); }; /* 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 |