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  *
  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 wrapper should be used.
  33  *
  34  *   shrinker = spl_register_shrinker(name, countfunc, scanfunc, seek_cost);
  35  *   spl_unregister_shrinker(shrinker);
  36  *
  37  * spl_register_shrinker is used to create and register a shrinker with the
  38  * given name.
  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  * static struct shrinker *my_shrinker;
  62  *
  63  * void my_init_func(void) {
  64  *      my_shrinker = spl_register_shrinker("my-shrinker",
  65  *          my_count, my_scan, DEFAULT_SEEKS);
  66  * }
  67  *
  68  * void my_fini_func(void) {
  69  *      spl_unregister_shrinker(my_shrinker);
  70  * }
  71  */
  72
  73 typedef unsigned long (*spl_shrinker_cb)
  74         (struct shrinker *, struct shrink_control *);
  75
  76 struct shrinker *spl_register_shrinker(const char *name,
  77     spl_shrinker_cb countfunc, spl_shrinker_cb scanfunc, int seek_cost);
  78 void spl_unregister_shrinker(struct shrinker *);
  79
  80 #ifndef SHRINK_STOP
  81 /* 3.0-3.11 compatibility */
  82 #define SHRINK_STOP     (-1)
  83 #endif
  84
  85 #endif /* SPL_SHRINKER_H */