sys/contrib/openzfs/include/os/linux/spl/sys/shrinker.h

   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 <behlendorf1@llnl.gov>.
   6  *  UCRL-CODE-235197
   7  *
   8  *  This file is part of the SPL, Solaris Porting Layer.
   9  *  For details, see <http://zfsonlinux.org/>.
  10  *
  11  *  The SPL is free software; you can redistribute it and/or modify it
  12  *  under the terms of the GNU General Public License as published by the
  13  *  Free Software Foundation; either version 2 of the License, or (at your
  14  *  option) any later version.
  15  *
  16  *  The SPL is distributed in the hope that it will be useful, but WITHOUT
  17  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  19  *  for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License along
  22  *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
  23  */
  24
  25 #ifndef _SPL_SHRINKER_H
  26 #define _SPL_SHRINKER_H
  27
  28 #include <linux/mm.h>
  29 #include <linux/fs.h>
  30
  31 /*
  32  * Due to frequent changes in the shrinker API the following
  33  * compatibility wrappers should be used.  They are as follows:
  34  *
  35  *   SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost);
  36  *
  37  * SPL_SHRINKER_DECLARE is used to declare a shrinker with the name varname,
  38  * which is passed to spl_register_shrinker()/spl_unregister_shrinker().
  39  * The countfunc returns the number of free-able objects.
  40  * The scanfunc returns the number of objects that were freed.
  41  * The callbacks can return SHRINK_STOP if further calls can't make any more
  42  * progress.  Note that a return value of SHRINK_EMPTY is currently not
  43  * supported.
  44  *
  45  * Example:
  46  *
  47  * static unsigned long
  48  * my_count(struct shrinker *shrink, struct shrink_control *sc)
  49  * {
  50  *      ...calculate number of objects in the cache...
  51  *
  52  *      return (number of objects in the cache);
  53  * }
  54  *
  55  * static unsigned long
  56  * my_scan(struct shrinker *shrink, struct shrink_control *sc)
  57  * {
  58  *      ...scan objects in the cache and reclaim them...
  59  * }
  60  *
  61  * SPL_SHRINKER_DECLARE(my_shrinker, my_count, my_scan, DEFAULT_SEEKS);
  62  *
  63  * void my_init_func(void) {
  64  *      spl_register_shrinker(&my_shrinker);
  65  * }
  66  */
  67
  68 #define spl_register_shrinker(x)        register_shrinker(x)
  69 #define spl_unregister_shrinker(x)      unregister_shrinker(x)
  70
  71 /*
  72  * Linux 3.0 to 3.11 Shrinker API Compatibility.
  73  */
  74 #if defined(HAVE_SINGLE_SHRINKER_CALLBACK)
  75 #define SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost)   \
  76 static int                                                              \
  77 __ ## varname ## _wrapper(struct shrinker *shrink, struct shrink_control *sc)\
  78 {                                                                       \
  79         if (sc->nr_to_scan != 0) {                                      \
  80                 (void) scanfunc(shrink, sc);                            \
  81         }                                                               \
  82         return (countfunc(shrink, sc));                                 \
  83 }                                                                       \
  84                                                                         \
  85 static struct shrinker varname = {                                      \
  86         .shrink = __ ## varname ## _wrapper,                            \
  87         .seeks = seek_cost,                                             \
  88 }
  89
  90 #define SHRINK_STOP     (-1)
  91
  92 /*
  93  * Linux 3.12 and later Shrinker API Compatibility.
  94  */
  95 #elif defined(HAVE_SPLIT_SHRINKER_CALLBACK)
  96 #define SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost)   \
  97 static struct shrinker varname = {                                      \
  98         .count_objects = countfunc,                                     \
  99         .scan_objects = scanfunc,                                       \
 100         .seeks = seek_cost,                                             \
 101 }
 102
 103 #else
 104 /*
 105  * Linux 2.x to 2.6.22, or a newer shrinker API has been introduced.
 106  */
 107 #error "Unknown shrinker callback"
 108 #endif
 109
 110 #endif /* SPL_SHRINKER_H */