freebsd-dev/sys/vm/phys_pager.c

/*
 * Copyright (c) 2000 Peter Wemm
 *
 * 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 AUTHORS 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 AUTHORS 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/param.h>
#include <sys/systm.h>
#include <sys/linker_set.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/mman.h>
#include <sys/sysctl.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_zone.h>

/* prevent concurrant creation races */
static int phys_pager_alloc_lock;
/* list of device pager objects */
static struct pagerlst phys_pager_object_list;
/* protect access to phys_pager_object_list */
static struct mtx phys_pager_mtx;

static void
phys_pager_init(void)
{

	TAILQ_INIT(&phys_pager_object_list);
	mtx_init(&phys_pager_mtx, "phys_pager list", MTX_DEF);
}

static vm_object_t
phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
		 vm_ooffset_t foff)
{
	vm_object_t object;

	/*
	 * Offset should be page aligned.
	 */
	if (foff & PAGE_MASK)
		return (NULL);

	size = round_page(size);

	if (handle != NULL) {
		/*
		 * Lock to prevent object creation race condition.
		 */
		while (phys_pager_alloc_lock) {
			phys_pager_alloc_lock = -1;
			msleep(&phys_pager_alloc_lock, &vm_mtx, PVM, "swpalc", 0);
		}

		/*
		 * Look up pager, creating as necessary.
		 */
		object = vm_pager_object_lookup(&phys_pager_object_list, handle);
		if (object == NULL) {
			/*
			 * Allocate object and associate it with the pager.
			 */
			object = vm_object_allocate(OBJT_PHYS,
				OFF_TO_IDX(foff + size));
			object->handle = handle;
			mtx_lock(&phys_pager_mtx);
			TAILQ_INSERT_TAIL(&phys_pager_object_list, object,
			    pager_object_list);
			mtx_unlock(&phys_pager_mtx);
		} else {
			/*
			 * Gain a reference to the object.
			 */
			vm_object_reference(object);
			if (OFF_TO_IDX(foff + size) > object->size)
				object->size = OFF_TO_IDX(foff + size);
		}
		if (phys_pager_alloc_lock)
			wakeup(&phys_pager_alloc_lock);
		phys_pager_alloc_lock = 0;

	} else {
		object = vm_object_allocate(OBJT_PHYS,
			OFF_TO_IDX(foff + size));
	}

	return (object);
}

static void
phys_pager_dealloc(vm_object_t object)
{

	if (object->handle != NULL) {
		mtx_lock(&phys_pager_mtx);
		TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
		mtx_unlock(&phys_pager_mtx);
	}
}

static int
phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
{
	int i, s;

	s = splvm();
	/*
	 * Fill as many pages as vm_fault has allocated for us.
	 */
	for (i = 0; i < count; i++) {
		if ((m[i]->flags & PG_ZERO) == 0)
			vm_page_zero_fill(m[i]);
		vm_page_flag_set(m[i], PG_ZERO);
		/* Switch off pv_entries */
		vm_page_unmanage(m[i]);
		m[i]->valid = VM_PAGE_BITS_ALL;
		m[i]->dirty = 0;
		/* The requested page must remain busy, the others not. */
		if (reqpage != i) {
			vm_page_flag_clear(m[i], PG_BUSY);
			m[i]->busy = 0;
		}
	}
	splx(s);

	return (VM_PAGER_OK);
}

static void
phys_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync,
		    int *rtvals)
{

	panic("phys_pager_putpage called");
}

/*
 * Implement a pretty aggressive clustered getpages strategy.  Hint that
 * everything in an entire 4MB window should be prefaulted at once.
 *
 * XXX 4MB (1024 slots per page table page) is convenient for x86,
 * but may not be for other arches.
 */
#ifndef PHYSCLUSTER
#define PHYSCLUSTER 1024
#endif
static boolean_t
phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
		   int *after)
{
	vm_pindex_t base, end;

	base = pindex & (~(PHYSCLUSTER - 1));
	end = base + (PHYSCLUSTER - 1);
	if (before != NULL)
		*before = pindex - base;
	if (after != NULL)
		*after = end - pindex;
	return (TRUE);
}

struct pagerops physpagerops = {
	phys_pager_init,
	phys_pager_alloc,
	phys_pager_dealloc,
	phys_pager_getpages,
	phys_pager_putpages,
	phys_pager_haspage,
	NULL
};