FreeBSD/Linux Kernel Cross Reference
sys/compat/linuxkpi/common/src/linux_shrinker.c

     /*-
      * Copyright (c) 2020 Emmanuel Vadot <manu@FreeBSD.org>
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
      * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD$
     */
    
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/queue.h>
    #include <sys/eventhandler.h>
    #include <sys/sx.h>
    
    #include <linux/compat.h>
    #include <linux/shrinker.h>
    
    TAILQ_HEAD(, shrinker) lkpi_shrinkers = TAILQ_HEAD_INITIALIZER(lkpi_shrinkers);
    static struct sx sx_shrinker;
    
    int
    linuxkpi_register_shrinker(struct shrinker *s)
    {
    
            KASSERT(s != NULL, ("NULL shrinker"));
            KASSERT(s->count_objects != NULL, ("NULL shrinker"));
            KASSERT(s->scan_objects != NULL, ("NULL shrinker"));
            sx_xlock(&sx_shrinker);
            TAILQ_INSERT_TAIL(&lkpi_shrinkers, s, next);
            sx_xunlock(&sx_shrinker);
            return (0);
    }
    
    void
    linuxkpi_unregister_shrinker(struct shrinker *s)
    {
    
            sx_xlock(&sx_shrinker);
            TAILQ_REMOVE(&lkpi_shrinkers, s, next);
            sx_xunlock(&sx_shrinker);
    }
    
    #define SHRINKER_BATCH  512
    
    static void
    shrinker_shrink(struct shrinker *s)
    {
            struct shrink_control sc;
            unsigned long can_free;
            unsigned long batch;
            unsigned long scanned = 0;
            unsigned long ret;
    
            can_free = s->count_objects(s, &sc);
            if (can_free <= 0)
                    return;
    
            batch = s->batch ? s->batch : SHRINKER_BATCH;
            while (scanned <= can_free) {
                    sc.nr_to_scan = batch;
                    ret = s->scan_objects(s, &sc);
                    if (ret == SHRINK_STOP)
                            break;
                    scanned += batch;
            }
    }
    
    static void
    linuxkpi_vm_lowmem(void *arg __unused)
    {
            struct shrinker *s;
    
            sx_xlock(&sx_shrinker);
            TAILQ_FOREACH(s, &lkpi_shrinkers, next) {
                    shrinker_shrink(s);
           }
           sx_xunlock(&sx_shrinker);
   }
   
   static eventhandler_tag lowmem_tag;
   
   static void
   linuxkpi_sysinit_shrinker(void *arg __unused)
   {
   
           sx_init(&sx_shrinker, "lkpi-shrinker");
           lowmem_tag = EVENTHANDLER_REGISTER(vm_lowmem, linuxkpi_vm_lowmem,
               NULL, EVENTHANDLER_PRI_FIRST);
   }
   
   static void
   linuxkpi_sysuninit_shrinker(void *arg __unused)
   {
   
           sx_destroy(&sx_shrinker);
           EVENTHANDLER_DEREGISTER(vm_lowmem, lowmem_tag);
   }
   
   SYSINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY,
       linuxkpi_sysinit_shrinker, NULL);
   SYSUNINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY,
       linuxkpi_sysuninit_shrinker, NULL);

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