/*-
 * Copyright (c) 2011 The FreeBSD Foundation
 * Copyright (c) 2014 François Tigeot
 * All rights reserved.
 *
 * Portions of this software were developed by Konstantin Belousov
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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.
 *
 */

#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_page2.h>
#include <vm/vm_pager.h>

#include <linux/err.h>
#include <linux/shmem_fs.h>

vm_page_t
shmem_read_mapping_page(vm_object_t object, vm_pindex_t pindex)
{
	vm_page_t m;
	int rv;

	VM_OBJECT_LOCK_ASSERT_OWNED(object);
	m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL | VM_ALLOC_RETRY);
	if (m->valid != VM_PAGE_BITS_ALL) {
		if (vm_pager_has_page(object, pindex)) {
			rv = vm_pager_get_page(object, &m, 1);
			m = vm_page_lookup(object, pindex);
			if (m == NULL)
				return ERR_PTR(-ENOMEM);
			if (rv != VM_PAGER_OK) {
				vm_page_free(m);
				return ERR_PTR(-ENOMEM);
			}
		} else {
			pmap_zero_page(VM_PAGE_TO_PHYS(m));
			m->valid = VM_PAGE_BITS_ALL;
			m->dirty = 0;
		}
	}
	vm_page_wire(m);
	vm_page_wakeup(m);
	return (m);
}