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TOMOYO Linux Cross Reference
Linux/fs/fat/namei_msdos.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/fs/msdos/namei.c
  4  *
  5  *  Written 1992,1993 by Werner Almesberger
  6  *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
  7  *  Rewritten for constant inumbers 1999 by Al Viro
  8  */
  9 
 10 #include <linux/module.h>
 11 #include <linux/iversion.h>
 12 #include "fat.h"
 13 
 14 /* Characters that are undesirable in an MS-DOS file name */
 15 static unsigned char bad_chars[] = "*?<>|\"";
 16 static unsigned char bad_if_strict[] = "+=,; ";
 17 
 18 /***** Formats an MS-DOS file name. Rejects invalid names. */
 19 static int msdos_format_name(const unsigned char *name, int len,
 20                              unsigned char *res, struct fat_mount_options *opts)
 21         /*
 22          * name is the proposed name, len is its length, res is
 23          * the resulting name, opts->name_check is either (r)elaxed,
 24          * (n)ormal or (s)trict, opts->dotsOK allows dots at the
 25          * beginning of name (for hidden files)
 26          */
 27 {
 28         unsigned char *walk;
 29         unsigned char c;
 30         int space;
 31 
 32         if (name[0] == '.') {   /* dotfile because . and .. already done */
 33                 if (opts->dotsOK) {
 34                         /* Get rid of dot - test for it elsewhere */
 35                         name++;
 36                         len--;
 37                 } else
 38                         return -EINVAL;
 39         }
 40         /*
 41          * disallow names that _really_ start with a dot
 42          */
 43         space = 1;
 44         c = 0;
 45         for (walk = res; len && walk - res < 8; walk++) {
 46                 c = *name++;
 47                 len--;
 48                 if (opts->name_check != 'r' && strchr(bad_chars, c))
 49                         return -EINVAL;
 50                 if (opts->name_check == 's' && strchr(bad_if_strict, c))
 51                         return -EINVAL;
 52                 if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
 53                         return -EINVAL;
 54                 if (c < ' ' || c == ':' || c == '\\')
 55                         return -EINVAL;
 56         /*
 57          * 0xE5 is legal as a first character, but we must substitute
 58          * 0x05 because 0xE5 marks deleted files.  Yes, DOS really
 59          * does this.
 60          * It seems that Microsoft hacked DOS to support non-US
 61          * characters after the 0xE5 character was already in use to
 62          * mark deleted files.
 63          */
 64                 if ((res == walk) && (c == 0xE5))
 65                         c = 0x05;
 66                 if (c == '.')
 67                         break;
 68                 space = (c == ' ');
 69                 *walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
 70         }
 71         if (space)
 72                 return -EINVAL;
 73         if (opts->name_check == 's' && len && c != '.') {
 74                 c = *name++;
 75                 len--;
 76                 if (c != '.')
 77                         return -EINVAL;
 78         }
 79         while (c != '.' && len--)
 80                 c = *name++;
 81         if (c == '.') {
 82                 while (walk - res < 8)
 83                         *walk++ = ' ';
 84                 while (len > 0 && walk - res < MSDOS_NAME) {
 85                         c = *name++;
 86                         len--;
 87                         if (opts->name_check != 'r' && strchr(bad_chars, c))
 88                                 return -EINVAL;
 89                         if (opts->name_check == 's' &&
 90                             strchr(bad_if_strict, c))
 91                                 return -EINVAL;
 92                         if (c < ' ' || c == ':' || c == '\\')
 93                                 return -EINVAL;
 94                         if (c == '.') {
 95                                 if (opts->name_check == 's')
 96                                         return -EINVAL;
 97                                 break;
 98                         }
 99                         if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
100                                 return -EINVAL;
101                         space = c == ' ';
102                         if (!opts->nocase && c >= 'a' && c <= 'z')
103                                 *walk++ = c - 32;
104                         else
105                                 *walk++ = c;
106                 }
107                 if (space)
108                         return -EINVAL;
109                 if (opts->name_check == 's' && len)
110                         return -EINVAL;
111         }
112         while (walk - res < MSDOS_NAME)
113                 *walk++ = ' ';
114 
115         return 0;
116 }
117 
118 /***** Locates a directory entry.  Uses unformatted name. */
119 static int msdos_find(struct inode *dir, const unsigned char *name, int len,
120                       struct fat_slot_info *sinfo)
121 {
122         struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
123         unsigned char msdos_name[MSDOS_NAME];
124         int err;
125 
126         err = msdos_format_name(name, len, msdos_name, &sbi->options);
127         if (err)
128                 return -ENOENT;
129 
130         err = fat_scan(dir, msdos_name, sinfo);
131         if (!err && sbi->options.dotsOK) {
132                 if (name[0] == '.') {
133                         if (!(sinfo->de->attr & ATTR_HIDDEN))
134                                 err = -ENOENT;
135                 } else {
136                         if (sinfo->de->attr & ATTR_HIDDEN)
137                                 err = -ENOENT;
138                 }
139                 if (err)
140                         brelse(sinfo->bh);
141         }
142         return err;
143 }
144 
145 /*
146  * Compute the hash for the msdos name corresponding to the dentry.
147  * Note: if the name is invalid, we leave the hash code unchanged so
148  * that the existing dentry can be used. The msdos fs routines will
149  * return ENOENT or EINVAL as appropriate.
150  */
151 static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
152 {
153         struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
154         unsigned char msdos_name[MSDOS_NAME];
155         int error;
156 
157         error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
158         if (!error)
159                 qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
160         return 0;
161 }
162 
163 /*
164  * Compare two msdos names. If either of the names are invalid,
165  * we fall back to doing the standard name comparison.
166  */
167 static int msdos_cmp(const struct dentry *dentry,
168                 unsigned int len, const char *str, const struct qstr *name)
169 {
170         struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
171         unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
172         int error;
173 
174         error = msdos_format_name(name->name, name->len, a_msdos_name, options);
175         if (error)
176                 goto old_compare;
177         error = msdos_format_name(str, len, b_msdos_name, options);
178         if (error)
179                 goto old_compare;
180         error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
181 out:
182         return error;
183 
184 old_compare:
185         error = 1;
186         if (name->len == len)
187                 error = memcmp(name->name, str, len);
188         goto out;
189 }
190 
191 static const struct dentry_operations msdos_dentry_operations = {
192         .d_hash         = msdos_hash,
193         .d_compare      = msdos_cmp,
194 };
195 
196 /*
197  * AV. Wrappers for FAT sb operations. Is it wise?
198  */
199 
200 /***** Get inode using directory and name */
201 static struct dentry *msdos_lookup(struct inode *dir, struct dentry *dentry,
202                                    unsigned int flags)
203 {
204         struct super_block *sb = dir->i_sb;
205         struct fat_slot_info sinfo;
206         struct inode *inode;
207         int err;
208 
209         mutex_lock(&MSDOS_SB(sb)->s_lock);
210         err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
211         switch (err) {
212         case -ENOENT:
213                 inode = NULL;
214                 break;
215         case 0:
216                 inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
217                 brelse(sinfo.bh);
218                 break;
219         default:
220                 inode = ERR_PTR(err);
221         }
222         mutex_unlock(&MSDOS_SB(sb)->s_lock);
223         return d_splice_alias(inode, dentry);
224 }
225 
226 /***** Creates a directory entry (name is already formatted). */
227 static int msdos_add_entry(struct inode *dir, const unsigned char *name,
228                            int is_dir, int is_hid, int cluster,
229                            struct timespec64 *ts, struct fat_slot_info *sinfo)
230 {
231         struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
232         struct msdos_dir_entry de;
233         __le16 time, date;
234         int err;
235 
236         memcpy(de.name, name, MSDOS_NAME);
237         de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
238         if (is_hid)
239                 de.attr |= ATTR_HIDDEN;
240         de.lcase = 0;
241         fat_time_unix2fat(sbi, ts, &time, &date, NULL);
242         de.cdate = de.adate = 0;
243         de.ctime = 0;
244         de.ctime_cs = 0;
245         de.time = time;
246         de.date = date;
247         fat_set_start(&de, cluster);
248         de.size = 0;
249 
250         err = fat_add_entries(dir, &de, 1, sinfo);
251         if (err)
252                 return err;
253 
254         fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
255         if (IS_DIRSYNC(dir))
256                 (void)fat_sync_inode(dir);
257         else
258                 mark_inode_dirty(dir);
259 
260         return 0;
261 }
262 
263 /***** Create a file */
264 static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
265                         struct dentry *dentry, umode_t mode, bool excl)
266 {
267         struct super_block *sb = dir->i_sb;
268         struct inode *inode = NULL;
269         struct fat_slot_info sinfo;
270         struct timespec64 ts;
271         unsigned char msdos_name[MSDOS_NAME];
272         int err, is_hid;
273 
274         mutex_lock(&MSDOS_SB(sb)->s_lock);
275 
276         err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
277                                 msdos_name, &MSDOS_SB(sb)->options);
278         if (err)
279                 goto out;
280         is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
281         /* Have to do it due to foo vs. .foo conflicts */
282         if (!fat_scan(dir, msdos_name, &sinfo)) {
283                 brelse(sinfo.bh);
284                 err = -EINVAL;
285                 goto out;
286         }
287 
288         ts = current_time(dir);
289         err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &ts, &sinfo);
290         if (err)
291                 goto out;
292         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
293         brelse(sinfo.bh);
294         if (IS_ERR(inode)) {
295                 err = PTR_ERR(inode);
296                 goto out;
297         }
298         fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
299         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
300 
301         d_instantiate(dentry, inode);
302 out:
303         mutex_unlock(&MSDOS_SB(sb)->s_lock);
304         if (!err)
305                 err = fat_flush_inodes(sb, dir, inode);
306         return err;
307 }
308 
309 /***** Remove a directory */
310 static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
311 {
312         struct super_block *sb = dir->i_sb;
313         struct inode *inode = d_inode(dentry);
314         struct fat_slot_info sinfo;
315         int err;
316 
317         mutex_lock(&MSDOS_SB(sb)->s_lock);
318         err = fat_dir_empty(inode);
319         if (err)
320                 goto out;
321         err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
322         if (err)
323                 goto out;
324 
325         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
326         if (err)
327                 goto out;
328         drop_nlink(dir);
329 
330         clear_nlink(inode);
331         fat_truncate_time(inode, NULL, S_CTIME);
332         fat_detach(inode);
333 out:
334         mutex_unlock(&MSDOS_SB(sb)->s_lock);
335         if (!err)
336                 err = fat_flush_inodes(sb, dir, inode);
337 
338         return err;
339 }
340 
341 /***** Make a directory */
342 static int msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
343                        struct dentry *dentry, umode_t mode)
344 {
345         struct super_block *sb = dir->i_sb;
346         struct fat_slot_info sinfo;
347         struct inode *inode;
348         unsigned char msdos_name[MSDOS_NAME];
349         struct timespec64 ts;
350         int err, is_hid, cluster;
351 
352         mutex_lock(&MSDOS_SB(sb)->s_lock);
353 
354         err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
355                                 msdos_name, &MSDOS_SB(sb)->options);
356         if (err)
357                 goto out;
358         is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
359         /* foo vs .foo situation */
360         if (!fat_scan(dir, msdos_name, &sinfo)) {
361                 brelse(sinfo.bh);
362                 err = -EINVAL;
363                 goto out;
364         }
365 
366         ts = current_time(dir);
367         cluster = fat_alloc_new_dir(dir, &ts);
368         if (cluster < 0) {
369                 err = cluster;
370                 goto out;
371         }
372         err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &ts, &sinfo);
373         if (err)
374                 goto out_free;
375         inc_nlink(dir);
376 
377         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
378         brelse(sinfo.bh);
379         if (IS_ERR(inode)) {
380                 err = PTR_ERR(inode);
381                 /* the directory was completed, just return a error */
382                 goto out;
383         }
384         set_nlink(inode, 2);
385         fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
386         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
387 
388         d_instantiate(dentry, inode);
389 
390         mutex_unlock(&MSDOS_SB(sb)->s_lock);
391         fat_flush_inodes(sb, dir, inode);
392         return 0;
393 
394 out_free:
395         fat_free_clusters(dir, cluster);
396 out:
397         mutex_unlock(&MSDOS_SB(sb)->s_lock);
398         return err;
399 }
400 
401 /***** Unlink a file */
402 static int msdos_unlink(struct inode *dir, struct dentry *dentry)
403 {
404         struct inode *inode = d_inode(dentry);
405         struct super_block *sb = inode->i_sb;
406         struct fat_slot_info sinfo;
407         int err;
408 
409         mutex_lock(&MSDOS_SB(sb)->s_lock);
410         err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
411         if (err)
412                 goto out;
413 
414         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
415         if (err)
416                 goto out;
417         clear_nlink(inode);
418         fat_truncate_time(inode, NULL, S_CTIME);
419         fat_detach(inode);
420 out:
421         mutex_unlock(&MSDOS_SB(sb)->s_lock);
422         if (!err)
423                 err = fat_flush_inodes(sb, dir, inode);
424 
425         return err;
426 }
427 
428 static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
429                            struct dentry *old_dentry,
430                            struct inode *new_dir, unsigned char *new_name,
431                            struct dentry *new_dentry, int is_hid)
432 {
433         struct buffer_head *dotdot_bh;
434         struct msdos_dir_entry *dotdot_de;
435         struct inode *old_inode, *new_inode;
436         struct fat_slot_info old_sinfo, sinfo;
437         struct timespec64 ts;
438         loff_t new_i_pos;
439         int err, old_attrs, is_dir, update_dotdot, corrupt = 0;
440 
441         old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
442         old_inode = d_inode(old_dentry);
443         new_inode = d_inode(new_dentry);
444 
445         err = fat_scan(old_dir, old_name, &old_sinfo);
446         if (err) {
447                 err = -EIO;
448                 goto out;
449         }
450 
451         is_dir = S_ISDIR(old_inode->i_mode);
452         update_dotdot = (is_dir && old_dir != new_dir);
453         if (update_dotdot) {
454                 if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
455                         err = -EIO;
456                         goto out;
457                 }
458         }
459 
460         old_attrs = MSDOS_I(old_inode)->i_attrs;
461         err = fat_scan(new_dir, new_name, &sinfo);
462         if (!err) {
463                 if (!new_inode) {
464                         /* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
465                         if (sinfo.de != old_sinfo.de) {
466                                 err = -EINVAL;
467                                 goto out;
468                         }
469                         if (is_hid)
470                                 MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
471                         else
472                                 MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
473                         if (IS_DIRSYNC(old_dir)) {
474                                 err = fat_sync_inode(old_inode);
475                                 if (err) {
476                                         MSDOS_I(old_inode)->i_attrs = old_attrs;
477                                         goto out;
478                                 }
479                         } else
480                                 mark_inode_dirty(old_inode);
481 
482                         inode_inc_iversion(old_dir);
483                         fat_truncate_time(old_dir, NULL, S_CTIME|S_MTIME);
484                         if (IS_DIRSYNC(old_dir))
485                                 (void)fat_sync_inode(old_dir);
486                         else
487                                 mark_inode_dirty(old_dir);
488                         goto out;
489                 }
490         }
491 
492         ts = current_time(old_inode);
493         if (new_inode) {
494                 if (err)
495                         goto out;
496                 if (is_dir) {
497                         err = fat_dir_empty(new_inode);
498                         if (err)
499                                 goto out;
500                 }
501                 new_i_pos = MSDOS_I(new_inode)->i_pos;
502                 fat_detach(new_inode);
503         } else {
504                 err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
505                                       &ts, &sinfo);
506                 if (err)
507                         goto out;
508                 new_i_pos = sinfo.i_pos;
509         }
510         inode_inc_iversion(new_dir);
511 
512         fat_detach(old_inode);
513         fat_attach(old_inode, new_i_pos);
514         if (is_hid)
515                 MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
516         else
517                 MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
518         if (IS_DIRSYNC(new_dir)) {
519                 err = fat_sync_inode(old_inode);
520                 if (err)
521                         goto error_inode;
522         } else
523                 mark_inode_dirty(old_inode);
524 
525         if (update_dotdot) {
526                 fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
527                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
528                 if (IS_DIRSYNC(new_dir)) {
529                         err = sync_dirty_buffer(dotdot_bh);
530                         if (err)
531                                 goto error_dotdot;
532                 }
533                 drop_nlink(old_dir);
534                 if (!new_inode)
535                         inc_nlink(new_dir);
536         }
537 
538         err = fat_remove_entries(old_dir, &old_sinfo);  /* and releases bh */
539         old_sinfo.bh = NULL;
540         if (err)
541                 goto error_dotdot;
542         inode_inc_iversion(old_dir);
543         fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
544         if (IS_DIRSYNC(old_dir))
545                 (void)fat_sync_inode(old_dir);
546         else
547                 mark_inode_dirty(old_dir);
548 
549         if (new_inode) {
550                 drop_nlink(new_inode);
551                 if (is_dir)
552                         drop_nlink(new_inode);
553                 fat_truncate_time(new_inode, &ts, S_CTIME);
554         }
555 out:
556         brelse(sinfo.bh);
557         brelse(dotdot_bh);
558         brelse(old_sinfo.bh);
559         return err;
560 
561 error_dotdot:
562         /* data cluster is shared, serious corruption */
563         corrupt = 1;
564 
565         if (update_dotdot) {
566                 fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
567                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
568                 corrupt |= sync_dirty_buffer(dotdot_bh);
569         }
570 error_inode:
571         fat_detach(old_inode);
572         fat_attach(old_inode, old_sinfo.i_pos);
573         MSDOS_I(old_inode)->i_attrs = old_attrs;
574         if (new_inode) {
575                 fat_attach(new_inode, new_i_pos);
576                 if (corrupt)
577                         corrupt |= fat_sync_inode(new_inode);
578         } else {
579                 /*
580                  * If new entry was not sharing the data cluster, it
581                  * shouldn't be serious corruption.
582                  */
583                 int err2 = fat_remove_entries(new_dir, &sinfo);
584                 if (corrupt)
585                         corrupt |= err2;
586                 sinfo.bh = NULL;
587         }
588         if (corrupt < 0) {
589                 fat_fs_error(new_dir->i_sb,
590                              "%s: Filesystem corrupted (i_pos %lld)",
591                              __func__, sinfo.i_pos);
592         }
593         goto out;
594 }
595 
596 /***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
597 static int msdos_rename(struct mnt_idmap *idmap,
598                         struct inode *old_dir, struct dentry *old_dentry,
599                         struct inode *new_dir, struct dentry *new_dentry,
600                         unsigned int flags)
601 {
602         struct super_block *sb = old_dir->i_sb;
603         unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
604         int err, is_hid;
605 
606         if (flags & ~RENAME_NOREPLACE)
607                 return -EINVAL;
608 
609         mutex_lock(&MSDOS_SB(sb)->s_lock);
610 
611         err = msdos_format_name(old_dentry->d_name.name,
612                                 old_dentry->d_name.len, old_msdos_name,
613                                 &MSDOS_SB(old_dir->i_sb)->options);
614         if (err)
615                 goto out;
616         err = msdos_format_name(new_dentry->d_name.name,
617                                 new_dentry->d_name.len, new_msdos_name,
618                                 &MSDOS_SB(new_dir->i_sb)->options);
619         if (err)
620                 goto out;
621 
622         is_hid =
623              (new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');
624 
625         err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
626                               new_dir, new_msdos_name, new_dentry, is_hid);
627 out:
628         mutex_unlock(&MSDOS_SB(sb)->s_lock);
629         if (!err)
630                 err = fat_flush_inodes(sb, old_dir, new_dir);
631         return err;
632 }
633 
634 static const struct inode_operations msdos_dir_inode_operations = {
635         .create         = msdos_create,
636         .lookup         = msdos_lookup,
637         .unlink         = msdos_unlink,
638         .mkdir          = msdos_mkdir,
639         .rmdir          = msdos_rmdir,
640         .rename         = msdos_rename,
641         .setattr        = fat_setattr,
642         .getattr        = fat_getattr,
643         .update_time    = fat_update_time,
644 };
645 
646 static void setup(struct super_block *sb)
647 {
648         MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
649         sb->s_d_op = &msdos_dentry_operations;
650         sb->s_flags |= SB_NOATIME;
651 }
652 
653 static int msdos_fill_super(struct super_block *sb, struct fs_context *fc)
654 {
655         return fat_fill_super(sb, fc, setup);
656 }
657 
658 static int msdos_get_tree(struct fs_context *fc)
659 {
660         return get_tree_bdev(fc, msdos_fill_super);
661 }
662 
663 static int msdos_parse_param(struct fs_context *fc, struct fs_parameter *param)
664 {
665         return fat_parse_param(fc, param, false);
666 }
667 
668 static const struct fs_context_operations msdos_context_ops = {
669         .parse_param    = msdos_parse_param,
670         .get_tree       = msdos_get_tree,
671         .reconfigure    = fat_reconfigure,
672         .free           = fat_free_fc,
673 };
674 
675 static int msdos_init_fs_context(struct fs_context *fc)
676 {
677         int err;
678 
679         /* Initialize with is_vfat == false */
680         err = fat_init_fs_context(fc, false);
681         if (err)
682                 return err;
683 
684         fc->ops = &msdos_context_ops;
685         return 0;
686 }
687 
688 static struct file_system_type msdos_fs_type = {
689         .owner          = THIS_MODULE,
690         .name           = "msdos",
691         .kill_sb        = kill_block_super,
692         .fs_flags       = FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
693         .init_fs_context = msdos_init_fs_context,
694         .parameters     = fat_param_spec,
695 };
696 MODULE_ALIAS_FS("msdos");
697 
698 static int __init init_msdos_fs(void)
699 {
700         return register_filesystem(&msdos_fs_type);
701 }
702 
703 static void __exit exit_msdos_fs(void)
704 {
705         unregister_filesystem(&msdos_fs_type);
706 }
707 
708 MODULE_LICENSE("GPL");
709 MODULE_AUTHOR("Werner Almesberger");
710 MODULE_DESCRIPTION("MS-DOS filesystem support");
711 
712 module_init(init_msdos_fs)
713 module_exit(exit_msdos_fs)
714 

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