1/*
  2 * Copyright (C) 2007 Oracle.  All rights reserved.
  3 *
  4 * This program is free software; you can redistribute it and/or
  5 * modify it under the terms of the GNU General Public
  6 * License v2 as published by the Free Software Foundation.
  7 *
  8 * This program is distributed in the hope that it will be useful,
  9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 11 * General Public License for more details.
 12 *
 13 * You should have received a copy of the GNU General Public
 14 * License along with this program; if not, write to the
 15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 16 * Boston, MA 021110-1307, USA.
 17 */
 18
 19#include <linux/highmem.h>
 20
 21/* this is some deeply nasty code.  ctree.h has a different
 22 * definition for this BTRFS_SETGET_FUNCS macro, behind a #ifndef
 23 *
 24 * The end result is that anyone who #includes ctree.h gets a
 25 * declaration for the btrfs_set_foo functions and btrfs_foo functions
 26 *
 27 * This file declares the macros and then #includes ctree.h, which results
 28 * in cpp creating the function here based on the template below.
 29 *
 30 * These setget functions do all the extent_buffer related mapping
 31 * required to efficiently read and write specific fields in the extent
 32 * buffers.  Every pointer to metadata items in btrfs is really just
 33 * an unsigned long offset into the extent buffer which has been
 34 * cast to a specific type.  This gives us all the gcc type checking.
 35 *
 36 * The extent buffer api is used to do all the kmapping and page
 37 * spanning work required to get extent buffers in highmem and have
 38 * a metadata blocksize different from the page size.
 39 *
 40 * The macro starts with a simple function prototype declaration so that
 41 * sparse won't complain about it being static.
 42 */
 43
 44#define BTRFS_SETGET_FUNCS(name, type, member, bits)			\
 45u##bits btrfs_##name(struct extent_buffer *eb, type *s);		\
 46void btrfs_set_##name(struct extent_buffer *eb, type *s, u##bits val);	\
 47u##bits btrfs_##name(struct extent_buffer *eb,				\
 48				   type *s)				\
 49{									\
 50	unsigned long part_offset = (unsigned long)s;			\
 51	unsigned long offset = part_offset + offsetof(type, member);	\
 52	type *p;							\
 53	int err;						\
 54	char *kaddr;						\
 55	unsigned long map_start;				\
 56	unsigned long map_len;					\
 57	u##bits res;						\
 58	err = map_private_extent_buffer(eb, offset,		\
 59			sizeof(((type *)0)->member),		\
 60			&kaddr, &map_start, &map_len);		\
 61	if (err) {						\
 62		__le##bits leres;				\
 63		read_eb_member(eb, s, type, member, &leres);	\
 64		return le##bits##_to_cpu(leres);		\
 65	}							\
 66	p = (type *)(kaddr + part_offset - map_start);		\
 67	res = le##bits##_to_cpu(p->member);			\
 68	return res;						\
 69}									\
 70void btrfs_set_##name(struct extent_buffer *eb,				\
 71				    type *s, u##bits val)		\
 72{									\
 73	unsigned long part_offset = (unsigned long)s;			\
 74	unsigned long offset = part_offset + offsetof(type, member);	\
 75	type *p;							\
 76	int err;						\
 77	char *kaddr;						\
 78	unsigned long map_start;				\
 79	unsigned long map_len;					\
 80	err = map_private_extent_buffer(eb, offset,		\
 81			sizeof(((type *)0)->member),		\
 82			&kaddr, &map_start, &map_len);		\
 83	if (err) {						\
 84		__le##bits val2;				\
 85		val2 = cpu_to_le##bits(val);			\
 86		write_eb_member(eb, s, type, member, &val2);	\
 87		return;						\
 88	}							\
 89	p = (type *)(kaddr + part_offset - map_start);		\
 90	p->member = cpu_to_le##bits(val);			\
 91}
 92
 93#include "ctree.h"
 94
 95void btrfs_node_key(struct extent_buffer *eb,
 96		    struct btrfs_disk_key *disk_key, int nr)
 97{
 98	unsigned long ptr = btrfs_node_key_ptr_offset(nr);
 99	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
100		       struct btrfs_key_ptr, key, disk_key);
101}