csum.c revision 5711ed297b1a3d94086256b5b3b891d4f77b21ca 
1/*
2 * csum.c --- checksumming of ext3 structures
3 *
4 * Copyright (C) 2006 Cluster File Systems, Inc.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Public
8 * License.
9 * %End-Header%
10 */
11
12#include "ext2_fs.h"
13#include "ext2fs.h"
14#include "crc16.h"
15#include <assert.h>
16
17#ifndef offsetof
18#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
19#endif
20
21#ifdef DEBUG
22#define STATIC
23#else
24#define STATIC static
25#endif
26
27STATIC __u16 ext2fs_group_desc_csum(ext2_filsys fs, dgrp_t group)
28{
29	__u16 crc = 0;
30	struct ext2_group_desc *desc;
31
32	desc = &fs->group_desc[group];
33
34	if (fs->super->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_GDT_CSUM) {
35		int offset = offsetof(struct ext2_group_desc, bg_checksum);
36
37#ifdef WORDS_BIGENDIAN
38		struct ext2_group_desc swabdesc = *desc;
39
40		/* Have to swab back to little-endian to do the checksum */
41		ext2fs_swap_group_desc(&swabdesc);
42		desc = &swabdesc;
43
44		group = ext2fs_swab32(group);
45#endif
46		crc = crc16(~0, fs->super->s_uuid, sizeof(fs->super->s_uuid));
47		crc = crc16(crc, &group, sizeof(group));
48		crc = crc16(crc, desc, offset);
49		offset += sizeof(desc->bg_checksum); /* skip checksum */
50		assert(offset == sizeof(*desc));
51		/* for checksum of struct ext4_group_desc do the rest...*/
52		if (offset < fs->super->s_desc_size) {
53			crc = crc16(crc, (char *)desc + offset,
54				    fs->super->s_desc_size - offset);
55		}
56	}
57
58	return crc;
59}
60
61int ext2fs_group_desc_csum_verify(ext2_filsys fs, dgrp_t group)
62{
63	if (fs->group_desc[group].bg_checksum !=
64	    ext2fs_group_desc_csum(fs, group))
65		return 0;
66
67	return 1;
68}
69
70void ext2fs_group_desc_csum_set(ext2_filsys fs, dgrp_t group)
71{
72	if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
73				       EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
74		fs->group_desc[group].bg_checksum =
75			ext2fs_group_desc_csum(fs, group);
76}
77
78static __u32 find_last_inode_ingrp(ext2fs_inode_bitmap bitmap,
79				   __u32 inodes_per_grp, dgrp_t grp_no)
80{
81	ext2_ino_t i, start_ino, end_ino;
82
83	start_ino = grp_no * inodes_per_grp + 1;
84	end_ino = start_ino + inodes_per_grp - 1;
85
86	for (i = end_ino; i >= start_ino; i--) {
87		if (ext2fs_fast_test_inode_bitmap(bitmap, i))
88			return i - start_ino + 1;
89	}
90	return inodes_per_grp;
91}
92
93/* update the bitmap flags, set the itable high watermark, and calculate
94 * checksums for the group descriptors */
95errcode_t ext2fs_set_gdt_csum(ext2_filsys fs)
96{
97	struct ext2_super_block *sb = fs->super;
98	struct ext2_group_desc *bg = fs->group_desc;
99	int blks, dirty = 0;
100	dgrp_t i;
101
102	if (!fs->inode_map)
103		return EXT2_ET_NO_INODE_BITMAP;
104
105	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
106					EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
107		return 0;
108
109	for (i = 0; i < fs->group_desc_count; i++, bg++) {
110		int old_csum = bg->bg_checksum;
111		int old_unused = bg->bg_itable_unused;
112		int old_flags = bg->bg_flags;
113
114		if (bg->bg_free_inodes_count == sb->s_inodes_per_group) {
115			bg->bg_flags |= EXT2_BG_INODE_UNINIT;
116			bg->bg_itable_unused = sb->s_inodes_per_group;
117		} else {
118			bg->bg_flags &= ~EXT2_BG_INODE_UNINIT;
119			bg->bg_itable_unused = sb->s_inodes_per_group -
120				find_last_inode_ingrp(fs->inode_map,
121						      sb->s_inodes_per_group,i);
122		}
123
124		ext2fs_group_desc_csum_set(fs, i);
125		if (old_flags != bg->bg_flags)
126			dirty = 1;
127		if (old_unused != bg->bg_itable_unused)
128			dirty = 1;
129		if (old_csum != bg->bg_checksum)
130			dirty = 1;
131	}
132	if (dirty)
133		ext2fs_mark_super_dirty(fs);
134	return 0;
135}
136