openfs.c revision e5b38a5fafe4807b54d90a2e70bddf4b41b1695b 
1/*
2 * openfs.c --- open an ext2 filesystem
3 *
4 * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
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 <stdio.h>
13#include <string.h>
14#if HAVE_UNISTD_H
15#include <unistd.h>
16#endif
17#include <fcntl.h>
18#include <time.h>
19#if HAVE_SYS_STAT_H
20#include <sys/stat.h>
21#endif
22#if HAVE_SYS_TYPES_H
23#include <sys/types.h>
24#endif
25
26#if EXT2_FLAT_INCLUDES
27#include "ext2_fs.h"
28#else
29#include <linux/ext2_fs.h>
30#endif
31
32#include "ext2fs.h"
33
34/*
35 *  Note: if superblock is non-zero, block-size must also be non-zero.
36 * 	Superblock and block_size can be zero to use the default size.
37 *
38 * Valid flags for ext2fs_open()
39 *
40 * 	EXT2_FLAG_RW	- Open the filesystem for read/write.
41 * 	EXT2_FLAG_FORCE - Open the filesystem even if some of the
42 *  				features aren't supported.
43 */
44errcode_t ext2fs_open(const char *name, int flags, int superblock,
45		      int block_size, io_manager manager, ext2_filsys *ret_fs)
46{
47	ext2_filsys	fs;
48	errcode_t	retval;
49	int		i, j, groups_per_block;
50	blk_t		group_block;
51	char		*dest;
52	struct ext2_group_desc *gdp;
53
54	EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
55
56	retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys),
57				(void **) &fs);
58	if (retval)
59		return retval;
60
61	memset(fs, 0, sizeof(struct struct_ext2_filsys));
62	fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
63	fs->flags = flags;
64	retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
65			       &fs->io);
66	if (retval)
67		goto cleanup;
68	fs->io->app_data = fs;
69	retval = ext2fs_get_mem(strlen(name)+1, (void **) &fs->device_name);
70	if (retval)
71		goto cleanup;
72	strcpy(fs->device_name, name);
73	retval = ext2fs_get_mem(SUPERBLOCK_SIZE, (void **) &fs->super);
74	if (retval)
75		goto cleanup;
76
77	/*
78	 * If the user specifies a specific block # for the
79	 * superblock, then he/she must also specify the block size!
80	 * Otherwise, read the master superblock located at offset
81	 * SUPERBLOCK_OFFSET from the start of the partition.
82	 *
83	 * Note: we only save a backup copy of the superblock if we
84	 * are reading the superblock from the primary superblock location.
85	 */
86	if (superblock) {
87		if (!block_size) {
88			retval = EXT2_ET_INVALID_ARGUMENT;
89			goto cleanup;
90		}
91		io_channel_set_blksize(fs->io, block_size);
92		group_block = superblock + 1;
93		fs->orig_super = 0;
94	} else {
95		io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
96		superblock = 1;
97		group_block = 0;
98		retval = ext2fs_get_mem(SUPERBLOCK_SIZE,
99					(void **) &fs->orig_super);
100		if (retval)
101			goto cleanup;
102	}
103	retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
104				     fs->super);
105	if (retval)
106		goto cleanup;
107	if (fs->orig_super)
108		memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);
109
110	if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
111	    (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
112		fs->flags |= EXT2_FLAG_SWAP_BYTES;
113
114		ext2fs_swap_super(fs->super);
115	}
116
117	if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
118		retval = EXT2_ET_BAD_MAGIC;
119		goto cleanup;
120	}
121	if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
122		retval = EXT2_ET_REV_TOO_HIGH;
123		goto cleanup;
124	}
125
126	/*
127	 * Check for feature set incompatibility
128	 */
129	if (!(flags & EXT2_FLAG_FORCE)) {
130		if (fs->super->s_feature_incompat &
131		    ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
132			retval = EXT2_ET_UNSUPP_FEATURE;
133			goto cleanup;
134		}
135		if ((flags & EXT2_FLAG_RW) &&
136		    (fs->super->s_feature_ro_compat &
137		     ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
138			retval = EXT2_ET_RO_UNSUPP_FEATURE;
139			goto cleanup;
140		}
141	}
142
143	fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
144	if (fs->blocksize == 0) {
145		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
146		goto cleanup;
147	}
148	fs->fragsize = EXT2_FRAG_SIZE(fs->super);
149	fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
150				       EXT2_INODE_SIZE(fs->super) +
151				       EXT2_BLOCK_SIZE(fs->super) - 1) /
152				      EXT2_BLOCK_SIZE(fs->super));
153	if (block_size) {
154		if (block_size != fs->blocksize) {
155			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
156			goto cleanup;
157		}
158	}
159	/*
160	 * Set the blocksize to the filesystem's blocksize.
161	 */
162	io_channel_set_blksize(fs->io, fs->blocksize);
163
164	/*
165	 * Read group descriptors
166	 */
167	if ((EXT2_BLOCKS_PER_GROUP(fs->super)) == 0) {
168		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
169		goto cleanup;
170	}
171	fs->group_desc_count = (fs->super->s_blocks_count -
172				fs->super->s_first_data_block +
173				EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
174		/ EXT2_BLOCKS_PER_GROUP(fs->super);
175	fs->desc_blocks = (fs->group_desc_count +
176			   EXT2_DESC_PER_BLOCK(fs->super) - 1)
177		/ EXT2_DESC_PER_BLOCK(fs->super);
178	retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
179				(void **) &fs->group_desc);
180	if (retval)
181		goto cleanup;
182	if (!group_block)
183		group_block = fs->super->s_first_data_block + 1;
184	dest = (char *) fs->group_desc;
185	for (i=0 ; i < fs->desc_blocks; i++) {
186		retval = io_channel_read_blk(fs->io, group_block, 1, dest);
187		if (retval)
188			goto cleanup;
189		group_block++;
190		if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
191			gdp = (struct ext2_group_desc *) dest;
192			groups_per_block = fs->blocksize /
193				sizeof(struct ext2_group_desc);
194			for (j=0; j < groups_per_block; j++)
195				ext2fs_swap_group_desc(gdp++);
196		}
197		dest += fs->blocksize;
198	}
199
200	*ret_fs = fs;
201	return 0;
202cleanup:
203	ext2fs_free(fs);
204	return retval;
205}
206
207