1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2007 Oracle.  All rights reserved.
  4 */
  5
  6#include <linux/highmem.h>
  7#include <asm/unaligned.h>
  8
  9#include "ctree.h"
 10
 11static inline u8 get_unaligned_le8(const void *p)
 12{
 13       return *(u8 *)p;
 14}
 15
 16static inline void put_unaligned_le8(u8 val, void *p)
 17{
 18       *(u8 *)p = val;
 19}
 20
 21/*
 22 * this is some deeply nasty code.
 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 * which are wrappers of btrfs_set_token_#bits functions and
 27 * btrfs_get_token_#bits functions, which are defined in this file.
 28 *
 29 * These setget functions do all the extent_buffer related mapping
 30 * required to efficiently read and write specific fields in the extent
 31 * buffers.  Every pointer to metadata items in btrfs is really just
 32 * an unsigned long offset into the extent buffer which has been
 33 * cast to a specific type.  This gives us all the gcc type checking.
 34 *
 35 * The extent buffer api is used to do the page spanning work required to
 36 * have a metadata blocksize different from the page size.
 37 */
 38
 39#define DEFINE_BTRFS_SETGET_BITS(bits)					\
 40u##bits btrfs_get_token_##bits(const struct extent_buffer *eb,		\
 41			       const void *ptr, unsigned long off,	\
 42			       struct btrfs_map_token *token)		\
 43{									\
 44	unsigned long part_offset = (unsigned long)ptr;			\
 45	unsigned long offset = part_offset + off;			\
 46	void *p;							\
 47	int err;							\
 48	char *kaddr;							\
 49	unsigned long map_start;					\
 50	unsigned long map_len;						\
 51	int size = sizeof(u##bits);					\
 52	u##bits res;							\
 53									\
 54	if (token && token->kaddr && token->offset <= offset &&		\
 55	    token->eb == eb &&						\
 56	   (token->offset + PAGE_SIZE >= offset + size)) {	\
 57		kaddr = token->kaddr;					\
 58		p = kaddr + part_offset - token->offset;		\
 59		res = get_unaligned_le##bits(p + off);			\
 60		return res;						\
 61	}								\
 62	err = map_private_extent_buffer(eb, offset, size,		\
 63					&kaddr, &map_start, &map_len);	\
 64	if (err) {							\
 65		__le##bits leres;					\
 66									\
 67		read_extent_buffer(eb, &leres, offset, size);		\
 68		return le##bits##_to_cpu(leres);			\
 69	}								\
 70	p = kaddr + part_offset - map_start;				\
 71	res = get_unaligned_le##bits(p + off);				\
 72	if (token) {							\
 73		token->kaddr = kaddr;					\
 74		token->offset = map_start;				\
 75		token->eb = eb;						\
 76	}								\
 77	return res;							\
 78}									\
 79void btrfs_set_token_##bits(struct extent_buffer *eb,			\
 80			    const void *ptr, unsigned long off,		\
 81			    u##bits val,				\
 82			    struct btrfs_map_token *token)		\
 83{									\
 84	unsigned long part_offset = (unsigned long)ptr;			\
 85	unsigned long offset = part_offset + off;			\
 86	void *p;							\
 87	int err;							\
 88	char *kaddr;							\
 89	unsigned long map_start;					\
 90	unsigned long map_len;						\
 91	int size = sizeof(u##bits);					\
 92									\
 93	if (token && token->kaddr && token->offset <= offset &&		\
 94	    token->eb == eb &&						\
 95	   (token->offset + PAGE_SIZE >= offset + size)) {	\
 96		kaddr = token->kaddr;					\
 97		p = kaddr + part_offset - token->offset;		\
 98		put_unaligned_le##bits(val, p + off);			\
 99		return;							\
100	}								\
101	err = map_private_extent_buffer(eb, offset, size,		\
102			&kaddr, &map_start, &map_len);			\
103	if (err) {							\
104		__le##bits val2;					\
105									\
106		val2 = cpu_to_le##bits(val);				\
107		write_extent_buffer(eb, &val2, offset, size);		\
108		return;							\
109	}								\
110	p = kaddr + part_offset - map_start;				\
111	put_unaligned_le##bits(val, p + off);				\
112	if (token) {							\
113		token->kaddr = kaddr;					\
114		token->offset = map_start;				\
115		token->eb = eb;						\
116	}								\
117}
118
119DEFINE_BTRFS_SETGET_BITS(8)
120DEFINE_BTRFS_SETGET_BITS(16)
121DEFINE_BTRFS_SETGET_BITS(32)
122DEFINE_BTRFS_SETGET_BITS(64)
123
124void btrfs_node_key(const struct extent_buffer *eb,
125		    struct btrfs_disk_key *disk_key, int nr)
126{
127	unsigned long ptr = btrfs_node_key_ptr_offset(nr);
128	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
129		       struct btrfs_key_ptr, key, disk_key);
130}