openfs.c revision 39c47ce6417b81aa74596fd0d4d98d542525a444 
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#include "ext2_fs.h"
27
28
29#include "ext2fs.h"
30#include "e2image.h"
31
32blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
33{
34	int	bg;
35	int	has_super = 0;
36	int	ret_blk;
37
38	if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) ||
39	    (i < fs->super->s_first_meta_bg))
40		return (group_block + i + 1);
41
42	bg = (fs->blocksize / sizeof (struct ext2_group_desc)) * i;
43	if (ext2fs_bg_has_super(fs, bg))
44		has_super = 1;
45	ret_blk = (fs->super->s_first_data_block + has_super +
46		   (bg * fs->super->s_blocks_per_group));
47	/*
48	 * If group_block is not the normal value, we're trying to use
49	 * the backup group descriptors and superblock --- so use the
50	 * alternate location of the second block group in the
51	 * metablock group.  Ideally we should be testing each bg
52	 * descriptor block individually for correctness, but we don't
53	 * have the infrastructure in place to do that.
54	 */
55	if (group_block != fs->super->s_first_data_block &&
56	    ((ret_blk + fs->super->s_blocks_per_group) <
57	     fs->super->s_blocks_count))
58		ret_blk += fs->super->s_blocks_per_group;
59	return ret_blk;
60}
61
62errcode_t ext2fs_open(const char *name, int flags, int superblock,
63		      unsigned int block_size, io_manager manager,
64		      ext2_filsys *ret_fs)
65{
66	return ext2fs_open2(name, 0, flags, superblock, block_size,
67			    manager, ret_fs);
68}
69
70/*
71 *  Note: if superblock is non-zero, block-size must also be non-zero.
72 * 	Superblock and block_size can be zero to use the default size.
73 *
74 * Valid flags for ext2fs_open()
75 *
76 * 	EXT2_FLAG_RW	- Open the filesystem for read/write.
77 * 	EXT2_FLAG_FORCE - Open the filesystem even if some of the
78 *				features aren't supported.
79 *	EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device
80 */
81errcode_t ext2fs_open2(const char *name, const char *io_options,
82		       int flags, int superblock,
83		       unsigned int block_size, io_manager manager,
84		       ext2_filsys *ret_fs)
85{
86	ext2_filsys	fs;
87	errcode_t	retval;
88	unsigned long	i;
89	int		j, groups_per_block, blocks_per_group, io_flags;
90	blk_t		group_block, blk;
91	char		*dest, *cp;
92	struct ext2_group_desc *gdp;
93
94	EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
95
96	retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs);
97	if (retval)
98		return retval;
99
100	memset(fs, 0, sizeof(struct struct_ext2_filsys));
101	fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
102	fs->flags = flags;
103	fs->umask = 022;
104	retval = ext2fs_get_mem(strlen(name)+1, &fs->device_name);
105	if (retval)
106		goto cleanup;
107	strcpy(fs->device_name, name);
108	cp = strchr(fs->device_name, '?');
109	if (!io_options && cp) {
110		*cp++ = 0;
111		io_options = cp;
112	}
113
114	io_flags = 0;
115	if (flags & EXT2_FLAG_RW)
116		io_flags |= IO_FLAG_RW;
117	if (flags & EXT2_FLAG_EXCLUSIVE)
118		io_flags |= IO_FLAG_EXCLUSIVE;
119	retval = manager->open(fs->device_name, io_flags, &fs->io);
120	if (retval)
121		goto cleanup;
122	if (io_options &&
123	    (retval = io_channel_set_options(fs->io, io_options)))
124		goto cleanup;
125	fs->image_io = fs->io;
126	fs->io->app_data = fs;
127	retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->super);
128	if (retval)
129		goto cleanup;
130	if (flags & EXT2_FLAG_IMAGE_FILE) {
131		retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
132					&fs->image_header);
133		if (retval)
134			goto cleanup;
135		retval = io_channel_read_blk(fs->io, 0,
136					     -sizeof(struct ext2_image_hdr),
137					     fs->image_header);
138		if (retval)
139			goto cleanup;
140		if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
141			return EXT2_ET_MAGIC_E2IMAGE;
142		superblock = 1;
143		block_size = fs->image_header->fs_blocksize;
144	}
145
146	/*
147	 * If the user specifies a specific block # for the
148	 * superblock, then he/she must also specify the block size!
149	 * Otherwise, read the master superblock located at offset
150	 * SUPERBLOCK_OFFSET from the start of the partition.
151	 *
152	 * Note: we only save a backup copy of the superblock if we
153	 * are reading the superblock from the primary superblock location.
154	 */
155	if (superblock) {
156		if (!block_size) {
157			retval = EXT2_ET_INVALID_ARGUMENT;
158			goto cleanup;
159		}
160		io_channel_set_blksize(fs->io, block_size);
161		group_block = superblock;
162		fs->orig_super = 0;
163	} else {
164		io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
165		superblock = 1;
166		group_block = 0;
167		retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super);
168		if (retval)
169			goto cleanup;
170	}
171	retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
172				     fs->super);
173	if (retval)
174		goto cleanup;
175	if (fs->orig_super)
176		memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);
177
178#ifdef EXT2FS_ENABLE_SWAPFS
179	if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
180	    (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
181		fs->flags |= EXT2_FLAG_SWAP_BYTES;
182
183		ext2fs_swap_super(fs->super);
184	}
185#endif
186
187	if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
188		retval = EXT2_ET_BAD_MAGIC;
189		goto cleanup;
190	}
191	if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
192		retval = EXT2_ET_REV_TOO_HIGH;
193		goto cleanup;
194	}
195
196	/*
197	 * Check for feature set incompatibility
198	 */
199	if (!(flags & EXT2_FLAG_FORCE)) {
200		if (fs->super->s_feature_incompat &
201		    ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
202			retval = EXT2_ET_UNSUPP_FEATURE;
203			goto cleanup;
204		}
205		if ((flags & EXT2_FLAG_RW) &&
206		    (fs->super->s_feature_ro_compat &
207		     ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
208			retval = EXT2_ET_RO_UNSUPP_FEATURE;
209			goto cleanup;
210		}
211		if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
212		    (fs->super->s_feature_incompat &
213		     EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
214			retval = EXT2_ET_UNSUPP_FEATURE;
215			goto cleanup;
216		}
217	}
218
219	fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
220	if (fs->blocksize == 0) {
221		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
222		goto cleanup;
223	}
224	fs->fragsize = EXT2_FRAG_SIZE(fs->super);
225	fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
226				       EXT2_INODE_SIZE(fs->super) +
227				       EXT2_BLOCK_SIZE(fs->super) - 1) /
228				      EXT2_BLOCK_SIZE(fs->super));
229	if (block_size) {
230		if (block_size != fs->blocksize) {
231			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
232			goto cleanup;
233		}
234	}
235	/*
236	 * Set the blocksize to the filesystem's blocksize.
237	 */
238	io_channel_set_blksize(fs->io, fs->blocksize);
239
240	/*
241	 * If this is an external journal device, don't try to read
242	 * the group descriptors, because they're not there.
243	 */
244	if (fs->super->s_feature_incompat &
245	    EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
246		fs->group_desc_count = 0;
247		*ret_fs = fs;
248		return 0;
249	}
250
251	/*
252	 * Read group descriptors
253	 */
254	blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);
255	if (blocks_per_group == 0 ||
256	    blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||
257	    fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super)) {
258		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
259		goto cleanup;
260	}
261	fs->group_desc_count = (fs->super->s_blocks_count -
262				fs->super->s_first_data_block +
263				blocks_per_group - 1) / blocks_per_group;
264	fs->desc_blocks = (fs->group_desc_count +
265			   EXT2_DESC_PER_BLOCK(fs->super) - 1)
266		/ EXT2_DESC_PER_BLOCK(fs->super);
267	retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
268				&fs->group_desc);
269	if (retval)
270		goto cleanup;
271	if (!group_block)
272		group_block = fs->super->s_first_data_block;
273	dest = (char *) fs->group_desc;
274	groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc);
275	for (i=0 ; i < fs->desc_blocks; i++) {
276		blk = ext2fs_descriptor_block_loc(fs, group_block, i);
277		retval = io_channel_read_blk(fs->io, blk, 1, dest);
278		if (retval)
279			goto cleanup;
280#ifdef EXT2FS_ENABLE_SWAPFS
281		if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
282			gdp = (struct ext2_group_desc *) dest;
283			for (j=0; j < groups_per_block; j++)
284				ext2fs_swap_group_desc(gdp++);
285		}
286#endif
287		dest += fs->blocksize;
288	}
289
290	*ret_fs = fs;
291	return 0;
292cleanup:
293	ext2fs_free(fs);
294	return retval;
295}
296
297/*
298 * Set/get the filesystem data I/O channel.
299 *
300 * These functions are only valid if EXT2_FLAG_IMAGE_FILE is true.
301 */
302errcode_t ext2fs_get_data_io(ext2_filsys fs, io_channel *old_io)
303{
304	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
305		return EXT2_ET_NOT_IMAGE_FILE;
306	if (old_io) {
307		*old_io = (fs->image_io == fs->io) ? 0 : fs->io;
308	}
309	return 0;
310}
311
312errcode_t ext2fs_set_data_io(ext2_filsys fs, io_channel new_io)
313{
314	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
315		return EXT2_ET_NOT_IMAGE_FILE;
316	fs->io = new_io ? new_io : fs->image_io;
317	return 0;
318}
319
320errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io)
321{
322	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
323		return EXT2_ET_NOT_IMAGE_FILE;
324	fs->io = fs->image_io = new_io;
325	fs->flags |= EXT2_FLAG_DIRTY | EXT2_FLAG_RW |
326		EXT2_FLAG_BB_DIRTY | EXT2_FLAG_IB_DIRTY;
327	fs->flags &= ~EXT2_FLAG_IMAGE_FILE;
328	return 0;
329}
330