openfs.c revision cf8272e1081f69d898d5182ed516e28807135dea 
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	__u32		features;
90	int		j, groups_per_block, blocks_per_group, io_flags;
91	blk_t		group_block, blk;
92	char		*dest, *cp;
93	struct ext2_group_desc *gdp;
94
95	EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
96
97	retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs);
98	if (retval)
99		return retval;
100
101	memset(fs, 0, sizeof(struct struct_ext2_filsys));
102	fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
103	fs->flags = flags;
104	fs->umask = 022;
105	retval = ext2fs_get_mem(strlen(name)+1, &fs->device_name);
106	if (retval)
107		goto cleanup;
108	strcpy(fs->device_name, name);
109	cp = strchr(fs->device_name, '?');
110	if (!io_options && cp) {
111		*cp++ = 0;
112		io_options = cp;
113	}
114
115	io_flags = 0;
116	if (flags & EXT2_FLAG_RW)
117		io_flags |= IO_FLAG_RW;
118	if (flags & EXT2_FLAG_EXCLUSIVE)
119		io_flags |= IO_FLAG_EXCLUSIVE;
120	retval = manager->open(fs->device_name, io_flags, &fs->io);
121	if (retval)
122		goto cleanup;
123	if (io_options &&
124	    (retval = io_channel_set_options(fs->io, io_options)))
125		goto cleanup;
126	fs->image_io = fs->io;
127	fs->io->app_data = fs;
128	retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->super);
129	if (retval)
130		goto cleanup;
131	if (flags & EXT2_FLAG_IMAGE_FILE) {
132		retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
133					&fs->image_header);
134		if (retval)
135			goto cleanup;
136		retval = io_channel_read_blk(fs->io, 0,
137					     -(int)sizeof(struct ext2_image_hdr),
138					     fs->image_header);
139		if (retval)
140			goto cleanup;
141		if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
142			return EXT2_ET_MAGIC_E2IMAGE;
143		superblock = 1;
144		block_size = fs->image_header->fs_blocksize;
145	}
146
147	/*
148	 * If the user specifies a specific block # for the
149	 * superblock, then he/she must also specify the block size!
150	 * Otherwise, read the master superblock located at offset
151	 * SUPERBLOCK_OFFSET from the start of the partition.
152	 *
153	 * Note: we only save a backup copy of the superblock if we
154	 * are reading the superblock from the primary superblock location.
155	 */
156	if (superblock) {
157		if (!block_size) {
158			retval = EXT2_ET_INVALID_ARGUMENT;
159			goto cleanup;
160		}
161		io_channel_set_blksize(fs->io, block_size);
162		group_block = superblock;
163		fs->orig_super = 0;
164	} else {
165		io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
166		superblock = 1;
167		group_block = 0;
168		retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super);
169		if (retval)
170			goto cleanup;
171	}
172	retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
173				     fs->super);
174	if (retval)
175		goto cleanup;
176	if (fs->orig_super)
177		memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);
178
179#ifdef EXT2FS_ENABLE_SWAPFS
180	if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
181	    (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
182		fs->flags |= EXT2_FLAG_SWAP_BYTES;
183
184		ext2fs_swap_super(fs->super);
185	}
186#endif
187
188	if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
189		retval = EXT2_ET_BAD_MAGIC;
190		goto cleanup;
191	}
192	if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
193		retval = EXT2_ET_REV_TOO_HIGH;
194		goto cleanup;
195	}
196
197	/*
198	 * Check for feature set incompatibility
199	 */
200	if (!(flags & EXT2_FLAG_FORCE)) {
201		features = fs->super->s_feature_incompat;
202#ifdef EXT2_LIB_SOFTSUPP_INCOMPAT
203		if (flags & EXT2_FLAG_SOFTSUPP_FEATURES)
204			features &= !EXT2_LIB_SOFTSUPP_INCOMPAT;
205#endif
206		if (features & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
207			retval = EXT2_ET_UNSUPP_FEATURE;
208			goto cleanup;
209		}
210
211		features = fs->super->s_feature_ro_compat;
212#ifdef EXT2_LIB_SOFTSUPP_RO_COMPAT
213		if (flags & EXT2_FLAG_SOFTSUPP_FEATURES)
214			features &= !EXT2_LIB_SOFTSUPP_RO_COMPAT;
215#endif
216		if ((flags & EXT2_FLAG_RW) &&
217		    (features & ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
218			retval = EXT2_ET_RO_UNSUPP_FEATURE;
219			goto cleanup;
220		}
221
222		if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
223		    (fs->super->s_feature_incompat &
224		     EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
225			retval = EXT2_ET_UNSUPP_FEATURE;
226			goto cleanup;
227		}
228	}
229
230	fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
231	if (fs->blocksize == 0) {
232		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
233		goto cleanup;
234	}
235	fs->fragsize = EXT2_FRAG_SIZE(fs->super);
236	fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
237				       EXT2_INODE_SIZE(fs->super) +
238				       EXT2_BLOCK_SIZE(fs->super) - 1) /
239				      EXT2_BLOCK_SIZE(fs->super));
240	if (block_size) {
241		if (block_size != fs->blocksize) {
242			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
243			goto cleanup;
244		}
245	}
246	/*
247	 * Set the blocksize to the filesystem's blocksize.
248	 */
249	io_channel_set_blksize(fs->io, fs->blocksize);
250
251	/*
252	 * If this is an external journal device, don't try to read
253	 * the group descriptors, because they're not there.
254	 */
255	if (fs->super->s_feature_incompat &
256	    EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
257		fs->group_desc_count = 0;
258		*ret_fs = fs;
259		return 0;
260	}
261
262	/*
263	 * Read group descriptors
264	 */
265	blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);
266	if (blocks_per_group == 0 ||
267	    blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||
268	    fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super)) {
269		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
270		goto cleanup;
271	}
272	fs->group_desc_count = ext2fs_div_ceil(fs->super->s_blocks_count -
273					       fs->super->s_first_data_block,
274					       blocks_per_group);
275	fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count,
276					  EXT2_DESC_PER_BLOCK(fs->super));
277	retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
278				&fs->group_desc);
279	if (retval)
280		goto cleanup;
281	if (!group_block)
282		group_block = fs->super->s_first_data_block;
283	dest = (char *) fs->group_desc;
284	groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc);
285	for (i=0 ; i < fs->desc_blocks; i++) {
286		blk = ext2fs_descriptor_block_loc(fs, group_block, i);
287		retval = io_channel_read_blk(fs->io, blk, 1, dest);
288		if (retval)
289			goto cleanup;
290#ifdef EXT2FS_ENABLE_SWAPFS
291		if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
292			gdp = (struct ext2_group_desc *) dest;
293			for (j=0; j < groups_per_block; j++)
294				ext2fs_swap_group_desc(gdp++);
295		}
296#endif
297		dest += fs->blocksize;
298	}
299
300	*ret_fs = fs;
301	return 0;
302cleanup:
303	ext2fs_free(fs);
304	return retval;
305}
306
307/*
308 * Set/get the filesystem data I/O channel.
309 *
310 * These functions are only valid if EXT2_FLAG_IMAGE_FILE is true.
311 */
312errcode_t ext2fs_get_data_io(ext2_filsys fs, io_channel *old_io)
313{
314	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
315		return EXT2_ET_NOT_IMAGE_FILE;
316	if (old_io) {
317		*old_io = (fs->image_io == fs->io) ? 0 : fs->io;
318	}
319	return 0;
320}
321
322errcode_t ext2fs_set_data_io(ext2_filsys fs, io_channel new_io)
323{
324	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
325		return EXT2_ET_NOT_IMAGE_FILE;
326	fs->io = new_io ? new_io : fs->image_io;
327	return 0;
328}
329
330errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io)
331{
332	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
333		return EXT2_ET_NOT_IMAGE_FILE;
334	fs->io = fs->image_io = new_io;
335	fs->flags |= EXT2_FLAG_DIRTY | EXT2_FLAG_RW |
336		EXT2_FLAG_BB_DIRTY | EXT2_FLAG_IB_DIRTY;
337	fs->flags &= ~EXT2_FLAG_IMAGE_FILE;
338	return 0;
339}
340