openfs.c revision 3839e65723771b85975f4263102dd3ceec4523c0 
1/*
2 * openfs.c --- open an ext2 filesystem
3 *
4 * Copyright (C) 1993, 1994 Theodore Ts'o.  This file may be redistributed
5 * under the terms of the GNU Public License.
6 */
7
8#include <stdio.h>
9#include <string.h>
10#include <unistd.h>
11#include <stdlib.h>
12#include <fcntl.h>
13#include <time.h>
14#include <sys/stat.h>
15#include <sys/types.h>
16
17#include <linux/fs.h>
18#include <linux/ext2_fs.h>
19
20#include "ext2fs.h"
21
22/*
23 *  Note: if superblock is non-zero, block-size must also be non-zero.
24 * 	Superblock and block_size can be zero to use the default size.
25 */
26errcode_t ext2fs_open(const char *name, int flags, int superblock,
27		      int block_size, io_manager manager, ext2_filsys *ret_fs)
28{
29	ext2_filsys	fs;
30	errcode_t	retval;
31	int		i, group_block;
32	char		*dest;
33
34	fs = (ext2_filsys) malloc(sizeof(struct struct_ext2_filsys));
35	if (!fs)
36		return ENOMEM;
37
38	memset(fs, 0, sizeof(struct struct_ext2_filsys));
39	fs->flags = flags;
40	retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
41			       &fs->io);
42	if (retval)
43		goto cleanup;
44	fs->device_name = malloc(strlen(name)+1);
45	if (!fs->device_name) {
46		retval = ENOMEM;
47		goto cleanup;
48	}
49	strcpy(fs->device_name, name);
50	fs->super = malloc(SUPERBLOCK_SIZE);
51	if (!fs->super) {
52		retval = ENOMEM;
53		goto cleanup;
54	}
55
56	/*
57	 * If the user specifies a specific block # for the
58	 * superblock, then he/she must also specify the block size!
59	 * Otherwise, read the master superblock located at offset
60	 * SUPERBLOCK_OFFSET from the start of the partition.
61	 */
62	if (superblock) {
63		if (!block_size) {
64			retval = EINVAL;
65			goto cleanup;
66		}
67		io_channel_set_blksize(fs->io, block_size);
68	} else {
69		io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
70		superblock = 1;
71	}
72	retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
73				     fs->super);
74	if (retval)
75		goto cleanup;
76
77	if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
78		retval = EXT2_ET_BAD_MAGIC;
79		goto cleanup;
80	}
81	fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
82	fs->fragsize = EXT2_FRAG_SIZE(fs->super);
83	fs->inode_blocks_per_group = (fs->super->s_inodes_per_group /
84				      EXT2_INODES_PER_BLOCK(fs->super));
85	if (block_size) {
86		if (block_size != fs->blocksize) {
87			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
88			goto cleanup;
89		}
90	}
91	/*
92	 * Set the blocksize to the filesystem's blocksize.
93	 */
94	io_channel_set_blksize(fs->io, fs->blocksize);
95
96	/*
97	 * Read group descriptors
98	 */
99	fs->group_desc_count = (fs->super->s_blocks_count -
100				fs->super->s_first_data_block +
101				EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
102		/ EXT2_BLOCKS_PER_GROUP(fs->super);
103	fs->desc_blocks = (fs->group_desc_count +
104			   EXT2_DESC_PER_BLOCK(fs->super) - 1)
105		/ EXT2_DESC_PER_BLOCK(fs->super);
106	fs->group_desc = malloc(fs->desc_blocks * fs->blocksize);
107	if (!fs->group_desc) {
108		retval = ENOMEM;
109		goto cleanup;
110	}
111	group_block = fs->super->s_first_data_block + 1;
112	dest = (char *) fs->group_desc;
113	for (i=0 ; i < fs->desc_blocks; i++) {
114		retval = io_channel_read_blk(fs->io, group_block, 1, dest);
115		if (retval)
116			goto cleanup;
117		group_block++;
118		dest += fs->blocksize;
119	}
120
121	*ret_fs = fs;
122	return 0;
123cleanup:
124	ext2fs_free(fs);
125	return retval;
126}
127
128/*
129 * This routine sanity checks the group descriptors
130 */
131errcode_t ext2fs_check_desc(ext2_filsys fs)
132{
133	int i;
134	int block = fs->super->s_first_data_block;
135	int next, inode_blocks_per_group;
136
137	inode_blocks_per_group = fs->super->s_inodes_per_group /
138		EXT2_INODES_PER_BLOCK (fs->super);
139
140	for (i = 0; i < fs->group_desc_count; i++) {
141		next = block + fs->super->s_blocks_per_group;
142		/*
143		 * Check to make sure block bitmap for group is
144		 * located within the group.
145		 */
146		if (fs->group_desc[i].bg_block_bitmap < block ||
147		    fs->group_desc[i].bg_block_bitmap >= next)
148			return EXT2_ET_GDESC_BAD_BLOCK_MAP;
149		/*
150		 * Check to make sure inode bitmap for group is
151		 * located within the group
152		 */
153		if (fs->group_desc[i].bg_inode_bitmap < block ||
154		    fs->group_desc[i].bg_inode_bitmap >= next)
155			return EXT2_ET_GDESC_BAD_INODE_MAP;
156		/*
157		 * Check to make sure inode table for group is located
158		 * within the group
159		 */
160		if (fs->group_desc[i].bg_inode_table < block ||
161		    fs->group_desc[i].bg_inode_table+inode_blocks_per_group >=
162		    next)
163			return EXT2_ET_GDESC_BAD_INODE_TABLE;
164
165		block = next;
166	}
167	return 0;
168}
169
170