Differential D27728 Diff 81067 sys/compat/linuxkpi/common/src/linux_shrinker.c

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sys/compat/linuxkpi/common/src/linux_shrinker.c

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				/*-
				* 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/mutex.h>

				#include <linux/shrinker.h>

				TAILQ_HEAD(, shrinker) lkpi_shrinkers = TAILQ_HEAD_INITIALIZER(lkpi_shrinkers);
				static struct mtx mtx_shrinker;

				int
				linuxkpi_register_shrinker(struct shrinker *s)
				{

				bzUnsubmitted Done Inline Actions I always wonder if we should document that fields are initialised by at least adding KASSERT()s? I guess I've been calling too many NULL function pointers lately elsewhere which were never initialised or checked on registration. bz: I always wonder if we should document that fields are initialised by at least adding KASSERT()s?
				manuAuthorUnsubmitted Done Inline Actions you mean adding something like KASSERT(s->count_objects == NULL, ...) ? Anyway yeah I think that I should check that both function pointer are not NULL here. manu: you mean adding something like KASSERT(s->count_objects == NULL, ...) ? Anyway yeah I think…
				mtx_lock(&mtx_shrinker);
				TAILQ_INSERT_TAIL(&lkpi_shrinkers, s, next);
				mtx_unlock(&mtx_shrinker);
				return (0);
				}

				void
				linuxkpi_unregister_shrinker(struct shrinker *s)
				{

				mtx_lock(&mtx_shrinker);
				TAILQ_REMOVE(&lkpi_shrinkers, s, next);
				mtx_unlock(&mtx_shrinker);
				}

				#define SHRINKER_BATCH 512

				static void
				shrinker_shrink(struct shrinker *s)
				{
				struct shrink_control sc;
				unsigned long can_free;
				unsigned long batch = s->batch ? s->batch : SHRINKER_BATCH;
				bzUnsubmitted Done Inline Actions batch is not needed until line 79; can it be initialised after the initial return? bz: batch is not needed until line 79; can it be initialised after the initial return?
				manuAuthorUnsubmitted Done Inline Actions Will change. manu: Will change.
				unsigned long freeed = 0;
				unsigned long ret;

				can_free = s->count_objects(s, &sc);
				if (can_free <= 0) {
				return;
				}
				bzUnsubmitted Done Inline Actions No { } needed. bz: No { } needed.
				manuAuthorUnsubmitted Done Inline Actions printf debugging leftover :) I'll change that. manu: printf debugging leftover :) I'll change that.

				while (freeed <= can_free) {
				sc.nr_to_scan = batch;
				ret = s->scan_objects(s, &sc);
				if (ret == SHRINK_STOP)
				break;
				freeed += ret;
				}
				}

				static void
				linuxkpi_vm_lowmem(void *arg __unused)
				{
				struct shrinker *s;

				mtx_lock(&mtx_shrinker);
				TAILQ_FOREACH(s, &lkpi_shrinkers, next) {
				shrinker_shrink(s);
				}
				mtx_unlock(&mtx_shrinker);
				}

				static eventhandler_tag lowmem_tag;

				static void
				linuxkpi_sysinit_shrinker(void *arg __unused)
				{

				mtx_init(&mtx_shrinker, "lkpi-shrinker", NULL, MTX_DEF);
				lowmem_tag = EVENTHANDLER_REGISTER(vm_lowmem, linuxkpi_vm_lowmem, NULL, EVENTHANDLER_PRI_FIRST);
				bzUnsubmitted Done Inline Actions Long line. bz: Long line.
				manuAuthorUnsubmitted Done Inline Actions Will change. manu: Will change.
				}

				static void
				linuxkpi_sysuninit_shrinker(void *arg __unused)
				{

				mtx_destroy(&mtx_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);