accessors.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2007 Oracle.  All rights reserved.
  4 */
  5
  6#include <linux/unaligned.h>
  7#include "messages.h"
  8#include "extent_io.h"
  9#include "fs.h"
 10#include "accessors.h"
 11
 12static void __cold report_setget_bounds(const struct extent_buffer *eb,
 13					const void *ptr, unsigned off, int size)
 14{
 15	unsigned long member_offset = (unsigned long)ptr + off;
 16
 17	btrfs_warn(eb->fs_info,
 18		   "bad eb member %s: ptr 0x%lx start %llu member offset %lu size %d",
 19		   (member_offset > eb->len ? "start" : "end"),
 20		   (unsigned long)ptr, eb->start, member_offset, size);
 21}
 22
 23/* Copy bytes from @src1 and @src2 to @dest. */
 24static __always_inline void memcpy_split_src(char *dest, const char *src1,
 25					     const char *src2, const size_t len1,
 26					     const size_t total)
 27{
 28	memcpy(dest, src1, len1);
 29	memcpy(dest + len1, src2, total - len1);
 30}
 31
 32/*
 33 * Macro templates that define helpers to read/write extent buffer data of a
 34 * given size, that are also used via ctree.h for access to item members by
 35 * specialized helpers.
 36 *
 37 * Generic helpers:
 38 * - btrfs_set_8 (for 8/16/32/64)
 39 * - btrfs_get_8 (for 8/16/32/64)
 40 *
 41 * The set/get functions handle data spanning two pages transparently, in case
 42 * metadata block size is larger than page.  Every pointer to metadata items is
 43 * an offset into the extent buffer page array, cast to a specific type.  This
 44 * gives us all the type checking.
 45 *
 46 * The extent buffer pages stored in the array folios may not form a contiguous
 47 * physical range, but the API functions assume the linear offset to the range
 48 * from 0 to metadata node size.
 49 */
 50
 51#define DEFINE_BTRFS_SETGET_BITS(bits)					\
 52u##bits btrfs_get_##bits(const struct extent_buffer *eb,		\
 53			 const void *ptr, unsigned long off)		\
 54{									\
 55	const unsigned long member_offset = (unsigned long)ptr + off;	\
 56	const unsigned long idx = get_eb_folio_index(eb, member_offset);\
 57	const unsigned long oif = get_eb_offset_in_folio(eb,		\
 58							 member_offset);\
 59	char *kaddr = folio_address(eb->folios[idx]) + oif;		\
 60	const int part = eb->folio_size - oif;				\
 61	u8 lebytes[sizeof(u##bits)];					\
 62									\
 63	if (unlikely(member_offset + sizeof(u##bits) > eb->len)) {	\
 64		report_setget_bounds(eb, ptr, off, sizeof(u##bits));	\
 65		return 0;						\
 66	}								\
 67	if (INLINE_EXTENT_BUFFER_PAGES == 1 || sizeof(u##bits) == 1 ||	\
 68	    likely(sizeof(u##bits) <= part))				\
 69		return get_unaligned_le##bits(kaddr);			\
 70									\
 71	if (sizeof(u##bits) == 2) {					\
 72		lebytes[0] = *kaddr;					\
 73		kaddr = folio_address(eb->folios[idx + 1]);		\
 74		lebytes[1] = *kaddr;					\
 75	} else {							\
 76		memcpy_split_src(lebytes, kaddr,			\
 77				 folio_address(eb->folios[idx + 1]),	\
 78				 part, sizeof(u##bits));		\
 79	}								\
 80	return get_unaligned_le##bits(lebytes);				\
 81}									\
 82void btrfs_set_##bits(const struct extent_buffer *eb, void *ptr,	\
 83		      unsigned long off, u##bits val)			\
 84{									\
 85	const unsigned long member_offset = (unsigned long)ptr + off;	\
 86	const unsigned long idx = get_eb_folio_index(eb, member_offset);\
 87	const unsigned long oif = get_eb_offset_in_folio(eb,		\
 88							 member_offset);\
 89	char *kaddr = folio_address(eb->folios[idx]) + oif;		\
 90	const int part = eb->folio_size - oif;				\
 91	u8 lebytes[sizeof(u##bits)];					\
 92									\
 93	if (unlikely(member_offset + sizeof(u##bits) > eb->len)) {	\
 94		report_setget_bounds(eb, ptr, off, sizeof(u##bits));	\
 95		return;							\
 96	}								\
 97	if (INLINE_EXTENT_BUFFER_PAGES == 1 || sizeof(u##bits) == 1 ||	\
 98	    likely(sizeof(u##bits) <= part)) {				\
 99		put_unaligned_le##bits(val, kaddr);			\
100		return;							\
101	}								\
102	put_unaligned_le##bits(val, lebytes);				\
103	if (sizeof(u##bits) == 2) {					\
104		*kaddr = lebytes[0];					\
105		kaddr = folio_address(eb->folios[idx + 1]);		\
106		*kaddr = lebytes[1];					\
107	} else {							\
108		memcpy(kaddr, lebytes, part);				\
109		kaddr = folio_address(eb->folios[idx + 1]);		\
110		memcpy(kaddr, lebytes + part, sizeof(u##bits) - part);	\
111	}								\
112}
113
114DEFINE_BTRFS_SETGET_BITS(8)
115DEFINE_BTRFS_SETGET_BITS(16)
116DEFINE_BTRFS_SETGET_BITS(32)
117DEFINE_BTRFS_SETGET_BITS(64)
118
119void btrfs_node_key(const struct extent_buffer *eb,
120		    struct btrfs_disk_key *disk_key, int nr)
121{
122	unsigned long ptr = btrfs_node_key_ptr_offset(eb, nr);
123	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
124		       struct btrfs_key_ptr, key, disk_key);
125}