shrinker.h

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    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 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 #ifdef HAVE_REGISTER_SHRINKER_VARARG
   68 #define spl_register_shrinker(x)        register_shrinker(x, "zfs-arc-shrinker")
   69 #else
   70 #define spl_register_shrinker(x)        register_shrinker(x)
   71 #endif
   72 #define spl_unregister_shrinker(x)      unregister_shrinker(x)
   73 
   74 /*
   75  * Linux 3.0 to 3.11 Shrinker API Compatibility.
   76  */
   77 #if defined(HAVE_SINGLE_SHRINKER_CALLBACK)
   78 #define SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost)   \
   79 static int                                                              \
   80 __ ## varname ## _wrapper(struct shrinker *shrink, struct shrink_control *sc)\
   81 {                                                                       \
   82         if (sc->nr_to_scan != 0) {                                      \
   83                 (void) scanfunc(shrink, sc);                            \
   84         }                                                               \
   85         return (countfunc(shrink, sc));                                 \
   86 }                                                                       \
   87                                                                         \
   88 static struct shrinker varname = {                                      \
   89         .shrink = __ ## varname ## _wrapper,                            \
   90         .seeks = seek_cost,                                             \
   91 }
   92 
   93 #define SHRINK_STOP     (-1)
   94 
   95 /*
   96  * Linux 3.12 and later Shrinker API Compatibility.
   97  */
   98 #elif defined(HAVE_SPLIT_SHRINKER_CALLBACK)
   99 #define SPL_SHRINKER_DECLARE(varname, countfunc, scanfunc, seek_cost)   \
  100 static struct shrinker varname = {                                      \
  101         .count_objects = countfunc,                                     \
  102         .scan_objects = scanfunc,                                       \
  103         .seeks = seek_cost,                                             \
  104 }
  105 
  106 #else
  107 /*
  108  * Linux 2.x to 2.6.22, or a newer shrinker API has been introduced.
  109  */
  110 #error "Unknown shrinker callback"
  111 #endif
  112 
  113 #endif /* SPL_SHRINKER_H */

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FreeBSD/Linux Kernel Cross Reference sys/contrib/openzfs/include/os/linux/spl/sys/shrinker.h

FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/include/os/linux/spl/sys/shrinker.h