1 /* 2 * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. 3 * Copyright (C) 2007 The Regents of the University of California. 4 * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). 5 * Written by Brian Behlendorf <[email protected]>. 6 * UCRL-CODE-235197 7 * 8 * This file is part of the SPL, Solaris Porting Layer. 9 * 10 * The SPL is free software; you can redistribute it and/or modify it 11 * under the terms of the GNU General Public License as published by the 12 * Free Software Foundation; either version 2 of the License, or (at your 13 * option) any later version. 14 * 15 * The SPL is distributed in the hope that it will be useful, but WITHOUT 16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 18 * for more details. 19 * 20 * You should have received a copy of the GNU General Public License along 21 * with the SPL. If not, see <http://www.gnu.org/licenses/>. 22 */ 23 24 #ifndef _SPL_SHRINKER_H 25 #define _SPL_SHRINKER_H 26 27 #include <linux/mm.h> 28 #include <linux/fs.h> 29 30 /* 31 * Due to frequent changes in the shrinker API the following 32 * compatibility wrappers should be used. They are as follows: 33 * 34 * SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost); 35 * 36 * SPL_SHRINKER_DECLARE is used to declare a shrinker with the name varname, 37 * which is passed to spl_register_shrinker()/spl_unregister_shrinker(). 38 * The countfunc returns the number of free-able objects. 39 * The scanfunc returns the number of objects that were freed. 40 * The callbacks can return SHRINK_STOP if further calls can't make any more 41 * progress. Note that a return value of SHRINK_EMPTY is currently not 42 * supported. 43 * 44 * Example: 45 * 46 * static unsigned long 47 * my_count(struct shrinker *shrink, struct shrink_control *sc) 48 * { 49 * ...calculate number of objects in the cache... 50 * 51 * return (number of objects in the cache); 52 * } 53 * 54 * static unsigned long 55 * my_scan(struct shrinker *shrink, struct shrink_control *sc) 56 * { 57 * ...scan objects in the cache and reclaim them... 58 * } 59 * 60 * SPL_SHRINKER_DECLARE(my_shrinker, my_count, my_scan, DEFAULT_SEEKS); 61 * 62 * void my_init_func(void) { 63 * spl_register_shrinker(&my_shrinker); 64 * } 65 */ 66 67 #define spl_register_shrinker(x) register_shrinker(x) 68 #define spl_unregister_shrinker(x) unregister_shrinker(x) 69 70 /* 71 * Linux 3.0 to 3.11 Shrinker API Compatibility. 72 */ 73 #if defined(HAVE_SINGLE_SHRINKER_CALLBACK) 74 #define SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost) \ 75 static int \ 76 __ ## varname ## _wrapper(struct shrinker *shrink, struct shrink_control *sc)\ 77 { \ 78 if (sc->nr_to_scan != 0) { \ 79 (void) scanfunc(shrink, sc); \ 80 } \ 81 return (countfunc(shrink, sc)); \ 82 } \ 83 \ 84 static struct shrinker varname = { \ 85 .shrink = __ ## varname ## _wrapper, \ 86 .seeks = seek_cost, \ 87 } 88 89 #define SHRINK_STOP (-1) 90 91 /* 92 * Linux 3.12 and later Shrinker API Compatibility. 93 */ 94 #elif defined(HAVE_SPLIT_SHRINKER_CALLBACK) 95 #define SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost) \ 96 static struct shrinker varname = { \ 97 .count_objects = countfunc, \ 98 .scan_objects = scanfunc, \ 99 .seeks = seek_cost, \ 100 } 101 102 #else 103 /* 104 * Linux 2.x to 2.6.22, or a newer shrinker API has been introduced. 105 */ 106 #error "Unknown shrinker callback" 107 #endif 108 109 #endif /* SPL_SHRINKER_H */ 110