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1 /*
2  * set_fields.c --- set a superblock value
3  *
4  * Copyright (C) 2000, 2001, 2002, 2003, 2004 by 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 #define _XOPEN_SOURCE 600 /* for inclusion of strptime() and strtoull */
13 
14 #ifdef HAVE_STRTOULL
15 #define STRTOULL strtoull
16 #else
17 #define STRTOULL strtoul
18 #endif
19 
20 #include <stdio.h>
21 #include <unistd.h>
22 #include <stdlib.h>
23 #include <ctype.h>
24 #include <string.h>
25 #include <strings.h>
26 #include <time.h>
27 #include <sys/types.h>
28 #include <sys/stat.h>
29 #ifdef HAVE_ERRNO_H
30 #include <errno.h>
31 #endif
32 #if HAVE_STRINGS_H
33 #include <strings.h>
34 #endif
35 #include <fcntl.h>
36 #include <utime.h>
37 
38 #include "debugfs.h"
39 #include "uuid/uuid.h"
40 #include "e2p/e2p.h"
41 
42 static struct ext2_super_block set_sb;
43 static struct ext2_inode set_inode;
44 static struct ext2_group_desc set_gd;
45 static dgrp_t set_bg;
46 static ext2_ino_t set_ino;
47 static int array_idx;
48 
49 #define FLAG_ARRAY	0x0001
50 
51 struct field_set_info {
52 	const char	*name;
53 	void	*ptr;
54 	unsigned int	size;
55 	errcode_t (*func)(struct field_set_info *info, char *arg);
56 	int flags;
57 	int max_idx;
58 };
59 
60 static errcode_t parse_uint(struct field_set_info *info, char *arg);
61 static errcode_t parse_int(struct field_set_info *info, char *arg);
62 static errcode_t parse_string(struct field_set_info *info, char *arg);
63 static errcode_t parse_uuid(struct field_set_info *info, char *arg);
64 static errcode_t parse_hashalg(struct field_set_info *info, char *arg);
65 static errcode_t parse_time(struct field_set_info *info, char *arg);
66 static errcode_t parse_bmap(struct field_set_info *info, char *arg);
67 static errcode_t parse_gd_csum(struct field_set_info *info, char *arg);
68 
69 static struct field_set_info super_fields[] = {
70 	{ "inodes_count", &set_sb.s_inodes_count, 4, parse_uint },
71 	{ "blocks_count", &set_sb.s_blocks_count, 4, parse_uint },
72 	{ "r_blocks_count", &set_sb.s_r_blocks_count, 4, parse_uint },
73 	{ "free_blocks_count", &set_sb.s_free_blocks_count, 4, parse_uint },
74 	{ "free_inodes_count", &set_sb.s_free_inodes_count, 4, parse_uint },
75 	{ "first_data_block", &set_sb.s_first_data_block, 4, parse_uint },
76 	{ "log_block_size", &set_sb.s_log_block_size, 4, parse_uint },
77 	{ "log_frag_size", &set_sb.s_log_frag_size, 4, parse_int },
78 	{ "blocks_per_group", &set_sb.s_blocks_per_group, 4, parse_uint },
79 	{ "frags_per_group", &set_sb.s_frags_per_group, 4, parse_uint },
80 	{ "inodes_per_group", &set_sb.s_inodes_per_group, 4, parse_uint },
81 	{ "mtime", &set_sb.s_mtime, 4, parse_time },
82 	{ "wtime", &set_sb.s_wtime, 4, parse_time },
83 	{ "mnt_count", &set_sb.s_mnt_count, 2, parse_uint },
84 	{ "max_mnt_count", &set_sb.s_max_mnt_count, 2, parse_int },
85 	/* s_magic */
86 	{ "state", &set_sb.s_state, 2, parse_uint },
87 	{ "errors", &set_sb.s_errors, 2, parse_uint },
88 	{ "minor_rev_level", &set_sb.s_minor_rev_level, 2, parse_uint },
89 	{ "lastcheck", &set_sb.s_lastcheck, 4, parse_time },
90 	{ "checkinterval", &set_sb.s_checkinterval, 4, parse_uint },
91 	{ "creator_os", &set_sb.s_creator_os, 4, parse_uint },
92 	{ "rev_level", &set_sb.s_rev_level, 4, parse_uint },
93 	{ "def_resuid", &set_sb.s_def_resuid, 2, parse_uint },
94 	{ "def_resgid", &set_sb.s_def_resgid, 2, parse_uint },
95 	{ "first_ino", &set_sb.s_first_ino, 4, parse_uint },
96 	{ "inode_size", &set_sb.s_inode_size, 2, parse_uint },
97 	{ "block_group_nr", &set_sb.s_block_group_nr, 2, parse_uint },
98 	{ "feature_compat", &set_sb.s_feature_compat, 4, parse_uint },
99 	{ "feature_incompat", &set_sb.s_feature_incompat, 4, parse_uint },
100 	{ "feature_ro_compat", &set_sb.s_feature_ro_compat, 4, parse_uint },
101 	{ "uuid", &set_sb.s_uuid, 16, parse_uuid },
102 	{ "volume_name",  &set_sb.s_volume_name, 16, parse_string },
103 	{ "last_mounted",  &set_sb.s_last_mounted, 64, parse_string },
104 	{ "lastcheck",  &set_sb.s_lastcheck, 4, parse_uint },
105 	{ "algorithm_usage_bitmap", &set_sb.s_algorithm_usage_bitmap,
106 		  4, parse_uint },
107 	{ "prealloc_blocks", &set_sb.s_prealloc_blocks, 1, parse_uint },
108 	{ "prealloc_dir_blocks", &set_sb.s_prealloc_dir_blocks, 1,
109 		  parse_uint },
110 	{ "reserved_gdt_blocks", &set_sb.s_reserved_gdt_blocks, 2,
111 		  parse_uint },
112 	{ "journal_uuid", &set_sb.s_journal_uuid, 16, parse_uuid },
113 	{ "journal_inum", &set_sb.s_journal_inum, 4, parse_uint },
114 	{ "journal_dev", &set_sb.s_journal_dev, 4, parse_uint },
115 	{ "last_orphan", &set_sb.s_last_orphan, 4, parse_uint },
116 	{ "hash_seed", &set_sb.s_hash_seed, 16, parse_uuid },
117 	{ "def_hash_version", &set_sb.s_def_hash_version, 1, parse_hashalg },
118 	{ "jnl_backup_type", &set_sb.s_jnl_backup_type, 1, parse_uint },
119 	{ "desc_size", &set_sb.s_desc_size, 2, parse_uint },
120 	{ "default_mount_opts", &set_sb.s_default_mount_opts, 4, parse_uint },
121 	{ "first_meta_bg", &set_sb.s_first_meta_bg, 4, parse_uint },
122 	{ "mkfs_time", &set_sb.s_mkfs_time, 4, parse_time },
123 	{ "jnl_blocks", &set_sb.s_jnl_blocks[0], 4, parse_uint, FLAG_ARRAY,
124 	  17 },
125 	{ "blocks_count_hi", &set_sb.s_blocks_count_hi, 4, parse_uint },
126 	{ "r_blocks_count_hi", &set_sb.s_r_blocks_count_hi, 4, parse_uint },
127 	{ "min_extra_isize", &set_sb.s_min_extra_isize, 2, parse_uint },
128 	{ "want_extra_isize", &set_sb.s_want_extra_isize, 2, parse_uint },
129 	{ "flags", &set_sb.s_flags, 4, parse_uint },
130 	{ "raid_stride", &set_sb.s_raid_stride, 2, parse_uint },
131 	{ "min_extra_isize", &set_sb.s_min_extra_isize, 4, parse_uint },
132 	{ "mmp_interval", &set_sb.s_mmp_interval, 2, parse_uint },
133 	{ "mmp_block", &set_sb.s_mmp_block, 8, parse_uint },
134 	{ "raid_stripe_width", &set_sb.s_raid_stripe_width, 4, parse_uint },
135 	{ "log_groups_per_flex", &set_sb.s_log_groups_per_flex, 1, parse_uint },
136 	{ "kbytes_written", &set_sb.s_kbytes_written, 8, parse_uint },
137 	{ "snapshot_inum", &set_sb.s_snapshot_inum, 4, parse_uint },
138 	{ "snapshot_id", &set_sb.s_snapshot_id, 4, parse_uint },
139 	{ "snapshot_r_blocks_count", &set_sb.s_snapshot_r_blocks_count, 8,
140 	  parse_uint },
141 	{ "snapshot_list", &set_sb.s_snapshot_list, 4, parse_uint },
142 	{ "mount_opts",  &set_sb.s_mount_opts, 64, parse_string },
143 	{ 0, 0, 0, 0 }
144 };
145 
146 static struct field_set_info inode_fields[] = {
147 	{ "inodes_count", &set_sb.s_inodes_count, 4, parse_uint },
148 	{ "mode", &set_inode.i_mode, 2, parse_uint },
149 	{ "uid", &set_inode.i_uid, 2, parse_uint },
150 	{ "size", &set_inode.i_size, 4, parse_uint },
151 	{ "atime", &set_inode.i_atime, 4, parse_time },
152 	{ "ctime", &set_inode.i_ctime, 4, parse_time },
153 	{ "mtime", &set_inode.i_mtime, 4, parse_time },
154 	{ "dtime", &set_inode.i_dtime, 4, parse_time },
155 	{ "gid", &set_inode.i_gid, 2, parse_uint },
156 	{ "links_count", &set_inode.i_links_count, 2, parse_uint },
157 	{ "blocks", &set_inode.i_blocks, 4, parse_uint },
158 	{ "flags", &set_inode.i_flags, 4, parse_uint },
159 	{ "version", &set_inode.osd1.linux1.l_i_version, 4, parse_uint },
160 	{ "translator", &set_inode.osd1.hurd1.h_i_translator, 4, parse_uint },
161 	{ "block", &set_inode.i_block[0], 4, parse_uint, FLAG_ARRAY,
162 	  EXT2_NDIR_BLOCKS },
163 	{ "block[IND]", &set_inode.i_block[EXT2_IND_BLOCK], 4, parse_uint },
164 	{ "block[DIND]", &set_inode.i_block[EXT2_DIND_BLOCK], 4, parse_uint },
165 	{ "block[TIND]", &set_inode.i_block[EXT2_TIND_BLOCK], 4, parse_uint },
166 	{ "generation", &set_inode.i_generation, 4, parse_uint },
167 	{ "file_acl", &set_inode.i_file_acl, 4, parse_uint },
168 	{ "file_acl_high", &set_inode.osd2.linux2.l_i_file_acl_high, 2,
169 	  parse_uint },
170 	{ "dir_acl", &set_inode.i_dir_acl, 4, parse_uint },
171 	{ "size_high", &set_inode.i_size_high, 4, parse_uint },
172 	{ "faddr", &set_inode.i_faddr, 4, parse_uint },
173 	{ "blocks_hi", &set_inode.osd2.linux2.l_i_blocks_hi, 2, parse_uint },
174 	{ "frag", &set_inode.osd2.hurd2.h_i_frag, 1, parse_uint },
175 	{ "fsize", &set_inode.osd2.hurd2.h_i_fsize, 1, parse_uint },
176 	{ "uid_high", &set_inode.osd2.linux2.l_i_uid_high, 2, parse_uint },
177 	{ "gid_high", &set_inode.osd2.linux2.l_i_gid_high, 2, parse_uint },
178 	{ "author", &set_inode.osd2.hurd2.h_i_author, 4, parse_uint },
179 	{ "bmap", NULL, 4, parse_bmap, FLAG_ARRAY },
180 	{ 0, 0, 0, 0 }
181 };
182 
183 static struct field_set_info ext2_bg_fields[] = {
184 	{ "block_bitmap", &set_gd.bg_block_bitmap, 4, parse_uint },
185 	{ "inode_bitmap", &set_gd.bg_inode_bitmap, 4, parse_uint },
186 	{ "inode_table", &set_gd.bg_inode_table, 4, parse_uint },
187 	{ "free_blocks_count", &set_gd.bg_free_blocks_count, 2, parse_uint },
188 	{ "free_inodes_count", &set_gd.bg_free_inodes_count, 2, parse_uint },
189 	{ "used_dirs_count", &set_gd.bg_used_dirs_count, 2, parse_uint },
190 	{ "flags", &set_gd.bg_flags, 2, parse_uint },
191 	{ "reserved", &set_gd.bg_reserved, 2, parse_uint, FLAG_ARRAY, 2 },
192 	{ "itable_unused", &set_gd.bg_itable_unused, 2, parse_uint },
193 	{ "checksum", &set_gd.bg_checksum, 2, parse_gd_csum },
194 	{ 0, 0, 0, 0 }
195 };
196 
197 
find_field(struct field_set_info * fields,char * field)198 static struct field_set_info *find_field(struct field_set_info *fields,
199 					 char *field)
200 {
201 	struct field_set_info *ss;
202 	const char	*prefix;
203 	char		*arg, *delim, *idx, *tmp;
204 	int		prefix_len;
205 
206 	if (fields == super_fields)
207 		prefix = "s_";
208 	else if (fields == inode_fields)
209 		prefix = "i_";
210 	else
211 		prefix = "bg_";
212 	prefix_len = strlen(prefix);
213 	if (strncmp(field, prefix, prefix_len) == 0)
214 		field += prefix_len;
215 
216 	arg = malloc(strlen(field)+1);
217 	if (!arg)
218 		return NULL;
219 	strcpy(arg, field);
220 
221 	idx = strchr(arg, '[');
222 	if (idx) {
223 		*idx++ = 0;
224 		delim = idx + strlen(idx) - 1;
225 		if (!*idx || *delim != ']')
226 			idx = 0;
227 		else
228 			*delim = 0;
229 	}
230 	/*
231 	 * Can we parse the number?
232 	 */
233 	if (idx) {
234 		array_idx = strtol(idx, &tmp, 0);
235 		if (*tmp)
236 			idx = 0;
237 	}
238 
239 	for (ss = fields ; ss->name ; ss++) {
240 		if (ss->flags & FLAG_ARRAY) {
241 			if (!idx || (strcmp(ss->name, arg) != 0))
242 				continue;
243 			if (ss->max_idx > 0 && array_idx >= ss->max_idx)
244 				continue;
245 		} else {
246 			if (strcmp(ss->name, field) != 0)
247 				continue;
248 		}
249 		free(arg);
250 		return ss;
251 	}
252 	free(arg);
253 	return NULL;
254 }
255 
parse_uint(struct field_set_info * info,char * arg)256 static errcode_t parse_uint(struct field_set_info *info, char *arg)
257 {
258 	unsigned long long num, limit;
259 	char *tmp;
260 	union {
261 		__u64	*ptr64;
262 		__u32	*ptr32;
263 		__u16	*ptr16;
264 		__u8	*ptr8;
265 	} u;
266 
267 	u.ptr8 = (__u8 *) info->ptr;
268 	if (info->flags & FLAG_ARRAY)
269 		u.ptr8 += array_idx * info->size;
270 
271 	errno = 0;
272 	num = STRTOULL(arg, &tmp, 0);
273 	if (*tmp || errno) {
274 		fprintf(stderr, "Couldn't parse '%s' for field %s.\n",
275 			arg, info->name);
276 		return EINVAL;
277 	}
278 	limit = ~0ULL >> ((8 - info->size) * 8);
279 	if (num > limit) {
280 		fprintf(stderr, "Value '%s' exceeds field %s maximum %llu.\n",
281 			arg, info->name, limit);
282 		return EINVAL;
283 	}
284 	switch (info->size) {
285 	case 8:
286 		*u.ptr64 = num;
287 		break;
288 	case 4:
289 		*u.ptr32 = num;
290 		break;
291 	case 2:
292 		*u.ptr16 = num;
293 		break;
294 	case 1:
295 		*u.ptr8 = num;
296 		break;
297 	}
298 	return 0;
299 }
300 
parse_int(struct field_set_info * info,char * arg)301 static errcode_t parse_int(struct field_set_info *info, char *arg)
302 {
303 	long	num;
304 	char *tmp;
305 	__s32	*ptr32;
306 	__s16	*ptr16;
307 	__s8	*ptr8;
308 
309 	num = strtol(arg, &tmp, 0);
310 	if (*tmp) {
311 		fprintf(stderr, "Couldn't parse '%s' for field %s.\n",
312 			arg, info->name);
313 		return EINVAL;
314 	}
315 	switch (info->size) {
316 	case 4:
317 		ptr32 = (__s32 *) info->ptr;
318 		*ptr32 = num;
319 		break;
320 	case 2:
321 		ptr16 = (__s16 *) info->ptr;
322 		*ptr16 = num;
323 		break;
324 	case 1:
325 		ptr8 = (__s8 *) info->ptr;
326 		*ptr8 = num;
327 		break;
328 	}
329 	return 0;
330 }
331 
parse_string(struct field_set_info * info,char * arg)332 static errcode_t parse_string(struct field_set_info *info, char *arg)
333 {
334 	char	*cp = (char *) info->ptr;
335 
336 	if (strlen(arg) >= info->size) {
337 		fprintf(stderr, "Error maximum size for %s is %d.\n",
338 			info->name, info->size);
339 		return EINVAL;
340 	}
341 	strcpy(cp, arg);
342 	return 0;
343 }
344 
parse_time(struct field_set_info * info,char * arg)345 static errcode_t parse_time(struct field_set_info *info, char *arg)
346 {
347 	time_t		t;
348 	__u32		*ptr32;
349 
350 	ptr32 = (__u32 *) info->ptr;
351 
352 	t = string_to_time(arg);
353 
354 	if (t == ((time_t) -1)) {
355 		fprintf(stderr, "Couldn't parse '%s' for field %s.\n",
356 			arg, info->name);
357 		return EINVAL;
358 	}
359 	*ptr32 = t;
360 	return 0;
361 }
362 
parse_uuid(struct field_set_info * info,char * arg)363 static errcode_t parse_uuid(struct field_set_info *info, char *arg)
364 {
365 	unsigned char *	p = (unsigned char *) info->ptr;
366 
367 	if ((strcasecmp(arg, "null") == 0) ||
368 	    (strcasecmp(arg, "clear") == 0)) {
369 		uuid_clear(p);
370 	} else if (strcasecmp(arg, "time") == 0) {
371 		uuid_generate_time(p);
372 	} else if (strcasecmp(arg, "random") == 0) {
373 		uuid_generate(p);
374 	} else if (uuid_parse(arg, p)) {
375 		fprintf(stderr, "Invalid UUID format: %s\n", arg);
376 		return EINVAL;
377 	}
378 	return 0;
379 }
380 
parse_hashalg(struct field_set_info * info,char * arg)381 static errcode_t parse_hashalg(struct field_set_info *info, char *arg)
382 {
383 	int	hashv;
384 	unsigned char	*p = (unsigned char *) info->ptr;
385 
386 	hashv = e2p_string2hash(arg);
387 	if (hashv < 0) {
388 		fprintf(stderr, "Invalid hash algorithm: %s\n", arg);
389 		return EINVAL;
390 	}
391 	*p = hashv;
392 	return 0;
393 }
394 
parse_bmap(struct field_set_info * info,char * arg)395 static errcode_t parse_bmap(struct field_set_info *info, char *arg)
396 {
397 	unsigned long	num;
398 	blk_t		blk;
399 	errcode_t	retval;
400 	char		*tmp;
401 
402 	num = strtoul(arg, &tmp, 0);
403 	if (*tmp) {
404 		fprintf(stderr, "Couldn't parse '%s' for field %s.\n",
405 			arg, info->name);
406 		return EINVAL;
407 	}
408 	blk = num;
409 
410 	retval = ext2fs_bmap(current_fs, set_ino, &set_inode, 0, BMAP_SET,
411 			     array_idx, &blk);
412 	if (retval) {
413 		com_err("set_inode", retval, "while setting block map");
414 	}
415 	return retval;
416 }
417 
parse_gd_csum(struct field_set_info * info,char * arg)418 static errcode_t parse_gd_csum(struct field_set_info *info, char *arg)
419 {
420 
421 	if (strcmp(arg, "calc") == 0) {
422 		ext2fs_group_desc_csum_set(current_fs, set_bg);
423 		set_gd = current_fs->group_desc[set_bg];
424 		printf("Checksum set to 0x%04x\n",
425 		       current_fs->group_desc[set_bg].bg_checksum);
426 		return 0;
427 	}
428 
429 	return parse_uint(info, arg);
430 }
431 
print_possible_fields(struct field_set_info * fields)432 static void print_possible_fields(struct field_set_info *fields)
433 {
434 	struct field_set_info *ss;
435 	const char	*type, *cmd;
436 	FILE *f;
437 	char name[40], idx[40];
438 
439 	if (fields == super_fields) {
440 		type = "Superblock";
441 		cmd = "set_super_value";
442 	} else if (fields == inode_fields) {
443 		type = "Inode";
444 		cmd = "set_inode";
445 	} else {
446 		type = "Block group descriptor";
447 		cmd = "set_block_group";
448 	}
449 	f = open_pager();
450 
451 	fprintf(f, "%s fields supported by the %s command:\n", type, cmd);
452 
453 	for (ss = fields ; ss->name ; ss++) {
454 		type = "unknown";
455 		if (ss->func == parse_string)
456 			type = "string";
457 		else if (ss->func == parse_int)
458 			type = "integer";
459 		else if (ss->func == parse_uint)
460 			type = "unsigned integer";
461 		else if (ss->func == parse_uuid)
462 			type = "UUID";
463 		else if (ss->func == parse_hashalg)
464 			type = "hash algorithm";
465 		else if (ss->func == parse_time)
466 			type = "date/time";
467 		else if (ss->func == parse_bmap)
468 			type = "set physical->logical block map";
469 		strcpy(name, ss->name);
470 		if (ss->flags & FLAG_ARRAY) {
471 			if (ss->max_idx > 0)
472 				sprintf(idx, "[%d]", ss->max_idx);
473 			else
474 				strcpy(idx, "[]");
475 			strcat(name, idx);
476 		}
477 		fprintf(f, "\t%-20s\t%s\n", name, type);
478 	}
479 	close_pager(f);
480 }
481 
482 
do_set_super(int argc,char * argv[])483 void do_set_super(int argc, char *argv[])
484 {
485 	const char *usage = "<field> <value>\n"
486 		"\t\"set_super_value -l\" will list the names of "
487 		"superblock fields\n\twhich can be set.";
488 	static struct field_set_info *ss;
489 
490 	if ((argc == 2) && !strcmp(argv[1], "-l")) {
491 		print_possible_fields(super_fields);
492 		return;
493 	}
494 
495 	if (common_args_process(argc, argv, 3, 3, "set_super_value",
496 				usage, CHECK_FS_RW))
497 		return;
498 
499 	if ((ss = find_field(super_fields, argv[1])) == 0) {
500 		com_err(argv[0], 0, "invalid field specifier: %s", argv[1]);
501 		return;
502 	}
503 	set_sb = *current_fs->super;
504 	if (ss->func(ss, argv[2]) == 0) {
505 		*current_fs->super = set_sb;
506 		ext2fs_mark_super_dirty(current_fs);
507 	}
508 }
509 
do_set_inode(int argc,char * argv[])510 void do_set_inode(int argc, char *argv[])
511 {
512 	const char *usage = "<inode> <field> <value>\n"
513 		"\t\"set_inode_field -l\" will list the names of "
514 		"the fields in an ext2 inode\n\twhich can be set.";
515 	static struct field_set_info *ss;
516 
517 	if ((argc == 2) && !strcmp(argv[1], "-l")) {
518 		print_possible_fields(inode_fields);
519 		return;
520 	}
521 
522 	if (common_args_process(argc, argv, 4, 4, "set_inode",
523 				usage, CHECK_FS_RW))
524 		return;
525 
526 	if ((ss = find_field(inode_fields, argv[2])) == 0) {
527 		com_err(argv[0], 0, "invalid field specifier: %s", argv[2]);
528 		return;
529 	}
530 
531 	set_ino = string_to_inode(argv[1]);
532 	if (!set_ino)
533 		return;
534 
535 	if (debugfs_read_inode(set_ino, &set_inode, argv[1]))
536 		return;
537 
538 	if (ss->func(ss, argv[3]) == 0) {
539 		if (debugfs_write_inode(set_ino, &set_inode, argv[1]))
540 			return;
541 	}
542 }
543 
do_set_block_group_descriptor(int argc,char * argv[])544 void do_set_block_group_descriptor(int argc, char *argv[])
545 {
546 	const char *usage = "<bg number> <field> <value>\n"
547 		"\t\"set_block_group_descriptor -l\" will list the names of "
548 		"the fields in a block group descriptor\n\twhich can be set.";
549 	struct field_set_info	*ss;
550 	char			*end;
551 
552 	if ((argc == 2) && !strcmp(argv[1], "-l")) {
553 		print_possible_fields(ext2_bg_fields);
554 		return;
555 	}
556 
557 	if (common_args_process(argc, argv, 4, 4, "set_block_group_descriptor",
558 				usage, CHECK_FS_RW))
559 		return;
560 
561 	set_bg = strtoul(argv[1], &end, 0);
562 	if (*end) {
563 		com_err(argv[0], 0, "invalid block group number: %s", argv[1]);
564 		return;
565 	}
566 
567 	if (set_bg >= current_fs->group_desc_count) {
568 		com_err(argv[0], 0, "block group number too big: %d", set_bg);
569 		return;
570 	}
571 
572 
573 	if ((ss = find_field(ext2_bg_fields, argv[2])) == 0) {
574 		com_err(argv[0], 0, "invalid field specifier: %s", argv[2]);
575 		return;
576 	}
577 
578 	set_gd = current_fs->group_desc[set_bg];
579 
580 	if (ss->func(ss, argv[3]) == 0) {
581 		current_fs->group_desc[set_bg] = set_gd;
582 		ext2fs_mark_super_dirty(current_fs);
583 	}
584 }
585