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

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  1 /*
  2  *  linux/fs/vfat/namei.c
  3  *
  4  *  Written 1992,1993 by Werner Almesberger
  5  *
  6  *  Windows95/Windows NT compatible extended MSDOS filesystem
  7  *    by Gordon Chaffee Copyright (C) 1995.  Send bug reports for the
  8  *    VFAT filesystem to <chaffee@cs.berkeley.edu>.  Specify
  9  *    what file operation caused you trouble and if you can duplicate
 10  *    the problem, send a script that demonstrates it.
 11  *
 12  *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
 13  *
 14  *  Support Multibyte characters and cleanup by
 15  *                              OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
 16  */
 17 
 18 #include <linux/module.h>
 19 #include <linux/ctype.h>
 20 #include <linux/slab.h>
 21 #include <linux/namei.h>
 22 #include <linux/kernel.h>
 23 #include <linux/iversion.h>
 24 #include "fat.h"
 25 
 26 static inline unsigned long vfat_d_version(struct dentry *dentry)
 27 {
 28         return (unsigned long) dentry->d_fsdata;
 29 }
 30 
 31 static inline void vfat_d_version_set(struct dentry *dentry,
 32                                       unsigned long version)
 33 {
 34         dentry->d_fsdata = (void *) version;
 35 }
 36 
 37 /*
 38  * If new entry was created in the parent, it could create the 8.3
 39  * alias (the shortname of logname).  So, the parent may have the
 40  * negative-dentry which matches the created 8.3 alias.
 41  *
 42  * If it happened, the negative dentry isn't actually negative
 43  * anymore.  So, drop it.
 44  */
 45 static int vfat_revalidate_shortname(struct dentry *dentry)
 46 {
 47         int ret = 1;
 48         spin_lock(&dentry->d_lock);
 49         if (!inode_eq_iversion(d_inode(dentry->d_parent), vfat_d_version(dentry)))
 50                 ret = 0;
 51         spin_unlock(&dentry->d_lock);
 52         return ret;
 53 }
 54 
 55 static int vfat_revalidate(struct dentry *dentry, unsigned int flags)
 56 {
 57         if (flags & LOOKUP_RCU)
 58                 return -ECHILD;
 59 
 60         /* This is not negative dentry. Always valid. */
 61         if (d_really_is_positive(dentry))
 62                 return 1;
 63         return vfat_revalidate_shortname(dentry);
 64 }
 65 
 66 static int vfat_revalidate_ci(struct dentry *dentry, unsigned int flags)
 67 {
 68         if (flags & LOOKUP_RCU)
 69                 return -ECHILD;
 70 
 71         /*
 72          * This is not negative dentry. Always valid.
 73          *
 74          * Note, rename() to existing directory entry will have ->d_inode,
 75          * and will use existing name which isn't specified name by user.
 76          *
 77          * We may be able to drop this positive dentry here. But dropping
 78          * positive dentry isn't good idea. So it's unsupported like
 79          * rename("filename", "FILENAME") for now.
 80          */
 81         if (d_really_is_positive(dentry))
 82                 return 1;
 83 
 84         /*
 85          * This may be nfsd (or something), anyway, we can't see the
 86          * intent of this. So, since this can be for creation, drop it.
 87          */
 88         if (!flags)
 89                 return 0;
 90 
 91         /*
 92          * Drop the negative dentry, in order to make sure to use the
 93          * case sensitive name which is specified by user if this is
 94          * for creation.
 95          */
 96         if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
 97                 return 0;
 98 
 99         return vfat_revalidate_shortname(dentry);
100 }
101 
102 /* returns the length of a struct qstr, ignoring trailing dots */
103 static unsigned int __vfat_striptail_len(unsigned int len, const char *name)
104 {
105         while (len && name[len - 1] == '.')
106                 len--;
107         return len;
108 }
109 
110 static unsigned int vfat_striptail_len(const struct qstr *qstr)
111 {
112         return __vfat_striptail_len(qstr->len, qstr->name);
113 }
114 
115 /*
116  * Compute the hash for the vfat name corresponding to the dentry.
117  * Note: if the name is invalid, we leave the hash code unchanged so
118  * that the existing dentry can be used. The vfat fs routines will
119  * return ENOENT or EINVAL as appropriate.
120  */
121 static int vfat_hash(const struct dentry *dentry, struct qstr *qstr)
122 {
123         qstr->hash = full_name_hash(dentry, qstr->name, vfat_striptail_len(qstr));
124         return 0;
125 }
126 
127 /*
128  * Compute the hash for the vfat name corresponding to the dentry.
129  * Note: if the name is invalid, we leave the hash code unchanged so
130  * that the existing dentry can be used. The vfat fs routines will
131  * return ENOENT or EINVAL as appropriate.
132  */
133 static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
134 {
135         struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
136         const unsigned char *name;
137         unsigned int len;
138         unsigned long hash;
139 
140         name = qstr->name;
141         len = vfat_striptail_len(qstr);
142 
143         hash = init_name_hash(dentry);
144         while (len--)
145                 hash = partial_name_hash(nls_tolower(t, *name++), hash);
146         qstr->hash = end_name_hash(hash);
147 
148         return 0;
149 }
150 
151 /*
152  * Case insensitive compare of two vfat names.
153  */
154 static int vfat_cmpi(const struct dentry *dentry,
155                 unsigned int len, const char *str, const struct qstr *name)
156 {
157         struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
158         unsigned int alen, blen;
159 
160         /* A filename cannot end in '.' or we treat it like it has none */
161         alen = vfat_striptail_len(name);
162         blen = __vfat_striptail_len(len, str);
163         if (alen == blen) {
164                 if (nls_strnicmp(t, name->name, str, alen) == 0)
165                         return 0;
166         }
167         return 1;
168 }
169 
170 /*
171  * Case sensitive compare of two vfat names.
172  */
173 static int vfat_cmp(const struct dentry *dentry,
174                 unsigned int len, const char *str, const struct qstr *name)
175 {
176         unsigned int alen, blen;
177 
178         /* A filename cannot end in '.' or we treat it like it has none */
179         alen = vfat_striptail_len(name);
180         blen = __vfat_striptail_len(len, str);
181         if (alen == blen) {
182                 if (strncmp(name->name, str, alen) == 0)
183                         return 0;
184         }
185         return 1;
186 }
187 
188 static const struct dentry_operations vfat_ci_dentry_ops = {
189         .d_revalidate   = vfat_revalidate_ci,
190         .d_hash         = vfat_hashi,
191         .d_compare      = vfat_cmpi,
192 };
193 
194 static const struct dentry_operations vfat_dentry_ops = {
195         .d_revalidate   = vfat_revalidate,
196         .d_hash         = vfat_hash,
197         .d_compare      = vfat_cmp,
198 };
199 
200 /* Characters that are undesirable in an MS-DOS file name */
201 
202 static inline wchar_t vfat_bad_char(wchar_t w)
203 {
204         return (w < 0x0020)
205             || (w == '*') || (w == '?') || (w == '<') || (w == '>')
206             || (w == '|') || (w == '"') || (w == ':') || (w == '/')
207             || (w == '\\');
208 }
209 
210 static inline wchar_t vfat_replace_char(wchar_t w)
211 {
212         return (w == '[') || (w == ']') || (w == ';') || (w == ',')
213             || (w == '+') || (w == '=');
214 }
215 
216 static wchar_t vfat_skip_char(wchar_t w)
217 {
218         return (w == '.') || (w == ' ');
219 }
220 
221 static inline int vfat_is_used_badchars(const wchar_t *s, int len)
222 {
223         int i;
224 
225         for (i = 0; i < len; i++)
226                 if (vfat_bad_char(s[i]))
227                         return -EINVAL;
228 
229         if (s[i - 1] == ' ') /* last character cannot be space */
230                 return -EINVAL;
231 
232         return 0;
233 }
234 
235 static int vfat_find_form(struct inode *dir, unsigned char *name)
236 {
237         struct fat_slot_info sinfo;
238         int err = fat_scan(dir, name, &sinfo);
239         if (err)
240                 return -ENOENT;
241         brelse(sinfo.bh);
242         return 0;
243 }
244 
245 /*
246  * 1) Valid characters for the 8.3 format alias are any combination of
247  * letters, uppercase alphabets, digits, any of the
248  * following special characters:
249  *     $ % ' ` - @ { } ~ ! # ( ) & _ ^
250  * In this case Longfilename is not stored in disk.
251  *
252  * WinNT's Extension:
253  * File name and extension name is contain uppercase/lowercase
254  * only. And it is expressed by CASE_LOWER_BASE and CASE_LOWER_EXT.
255  *
256  * 2) File name is 8.3 format, but it contain the uppercase and
257  * lowercase char, muliti bytes char, etc. In this case numtail is not
258  * added, but Longfilename is stored.
259  *
260  * 3) When the one except for the above, or the following special
261  * character are contained:
262  *        .   [ ] ; , + =
263  * numtail is added, and Longfilename must be stored in disk .
264  */
265 struct shortname_info {
266         unsigned char lower:1,
267                       upper:1,
268                       valid:1;
269 };
270 #define INIT_SHORTNAME_INFO(x)  do {            \
271         (x)->lower = 1;                         \
272         (x)->upper = 1;                         \
273         (x)->valid = 1;                         \
274 } while (0)
275 
276 static inline int to_shortname_char(struct nls_table *nls,
277                                     unsigned char *buf, int buf_size,
278                                     wchar_t *src, struct shortname_info *info)
279 {
280         int len;
281 
282         if (vfat_skip_char(*src)) {
283                 info->valid = 0;
284                 return 0;
285         }
286         if (vfat_replace_char(*src)) {
287                 info->valid = 0;
288                 buf[0] = '_';
289                 return 1;
290         }
291 
292         len = nls->uni2char(*src, buf, buf_size);
293         if (len <= 0) {
294                 info->valid = 0;
295                 buf[0] = '_';
296                 len = 1;
297         } else if (len == 1) {
298                 unsigned char prev = buf[0];
299 
300                 if (buf[0] >= 0x7F) {
301                         info->lower = 0;
302                         info->upper = 0;
303                 }
304 
305                 buf[0] = nls_toupper(nls, buf[0]);
306                 if (isalpha(buf[0])) {
307                         if (buf[0] == prev)
308                                 info->lower = 0;
309                         else
310                                 info->upper = 0;
311                 }
312         } else {
313                 info->lower = 0;
314                 info->upper = 0;
315         }
316 
317         return len;
318 }
319 
320 /*
321  * Given a valid longname, create a unique shortname.  Make sure the
322  * shortname does not exist
323  * Returns negative number on error, 0 for a normal
324  * return, and 1 for valid shortname
325  */
326 static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
327                                  wchar_t *uname, int ulen,
328                                  unsigned char *name_res, unsigned char *lcase)
329 {
330         struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
331         wchar_t *ip, *ext_start, *end, *name_start;
332         unsigned char base[9], ext[4], buf[5], *p;
333         unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
334         int chl, chi;
335         int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
336         int is_shortname;
337         struct shortname_info base_info, ext_info;
338 
339         is_shortname = 1;
340         INIT_SHORTNAME_INFO(&base_info);
341         INIT_SHORTNAME_INFO(&ext_info);
342 
343         /* Now, we need to create a shortname from the long name */
344         ext_start = end = &uname[ulen];
345         while (--ext_start >= uname) {
346                 if (*ext_start == 0x002E) {     /* is `.' */
347                         if (ext_start == end - 1) {
348                                 sz = ulen;
349                                 ext_start = NULL;
350                         }
351                         break;
352                 }
353         }
354 
355         if (ext_start == uname - 1) {
356                 sz = ulen;
357                 ext_start = NULL;
358         } else if (ext_start) {
359                 /*
360                  * Names which start with a dot could be just
361                  * an extension eg. "...test".  In this case Win95
362                  * uses the extension as the name and sets no extension.
363                  */
364                 name_start = &uname[0];
365                 while (name_start < ext_start) {
366                         if (!vfat_skip_char(*name_start))
367                                 break;
368                         name_start++;
369                 }
370                 if (name_start != ext_start) {
371                         sz = ext_start - uname;
372                         ext_start++;
373                 } else {
374                         sz = ulen;
375                         ext_start = NULL;
376                 }
377         }
378 
379         numtail_baselen = 6;
380         numtail2_baselen = 2;
381         for (baselen = i = 0, p = base, ip = uname; i < sz; i++, ip++) {
382                 chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
383                                         ip, &base_info);
384                 if (chl == 0)
385                         continue;
386 
387                 if (baselen < 2 && (baselen + chl) > 2)
388                         numtail2_baselen = baselen;
389                 if (baselen < 6 && (baselen + chl) > 6)
390                         numtail_baselen = baselen;
391                 for (chi = 0; chi < chl; chi++) {
392                         *p++ = charbuf[chi];
393                         baselen++;
394                         if (baselen >= 8)
395                                 break;
396                 }
397                 if (baselen >= 8) {
398                         if ((chi < chl - 1) || (ip + 1) - uname < sz)
399                                 is_shortname = 0;
400                         break;
401                 }
402         }
403         if (baselen == 0) {
404                 return -EINVAL;
405         }
406 
407         extlen = 0;
408         if (ext_start) {
409                 for (p = ext, ip = ext_start; extlen < 3 && ip < end; ip++) {
410                         chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
411                                                 ip, &ext_info);
412                         if (chl == 0)
413                                 continue;
414 
415                         if ((extlen + chl) > 3) {
416                                 is_shortname = 0;
417                                 break;
418                         }
419                         for (chi = 0; chi < chl; chi++) {
420                                 *p++ = charbuf[chi];
421                                 extlen++;
422                         }
423                         if (extlen >= 3) {
424                                 if (ip + 1 != end)
425                                         is_shortname = 0;
426                                 break;
427                         }
428                 }
429         }
430         ext[extlen] = '\0';
431         base[baselen] = '\0';
432 
433         /* Yes, it can happen. ".\xe5" would do it. */
434         if (base[0] == DELETED_FLAG)
435                 base[0] = 0x05;
436 
437         /* OK, at this point we know that base is not longer than 8 symbols,
438          * ext is not longer than 3, base is nonempty, both don't contain
439          * any bad symbols (lowercase transformed to uppercase).
440          */
441 
442         memset(name_res, ' ', MSDOS_NAME);
443         memcpy(name_res, base, baselen);
444         memcpy(name_res + 8, ext, extlen);
445         *lcase = 0;
446         if (is_shortname && base_info.valid && ext_info.valid) {
447                 if (vfat_find_form(dir, name_res) == 0)
448                         return -EEXIST;
449 
450                 if (opts->shortname & VFAT_SFN_CREATE_WIN95) {
451                         return (base_info.upper && ext_info.upper);
452                 } else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
453                         if ((base_info.upper || base_info.lower) &&
454                             (ext_info.upper || ext_info.lower)) {
455                                 if (!base_info.upper && base_info.lower)
456                                         *lcase |= CASE_LOWER_BASE;
457                                 if (!ext_info.upper && ext_info.lower)
458                                         *lcase |= CASE_LOWER_EXT;
459                                 return 1;
460                         }
461                         return 0;
462                 } else {
463                         BUG();
464                 }
465         }
466 
467         if (opts->numtail == 0)
468                 if (vfat_find_form(dir, name_res) < 0)
469                         return 0;
470 
471         /*
472          * Try to find a unique extension.  This used to
473          * iterate through all possibilities sequentially,
474          * but that gave extremely bad performance.  Windows
475          * only tries a few cases before using random
476          * values for part of the base.
477          */
478 
479         if (baselen > 6) {
480                 baselen = numtail_baselen;
481                 name_res[7] = ' ';
482         }
483         name_res[baselen] = '~';
484         for (i = 1; i < 10; i++) {
485                 name_res[baselen + 1] = i + '';
486                 if (vfat_find_form(dir, name_res) < 0)
487                         return 0;
488         }
489 
490         i = jiffies;
491         sz = (jiffies >> 16) & 0x7;
492         if (baselen > 2) {
493                 baselen = numtail2_baselen;
494                 name_res[7] = ' ';
495         }
496         name_res[baselen + 4] = '~';
497         name_res[baselen + 5] = '1' + sz;
498         while (1) {
499                 snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
500                 memcpy(&name_res[baselen], buf, 4);
501                 if (vfat_find_form(dir, name_res) < 0)
502                         break;
503                 i -= 11;
504         }
505         return 0;
506 }
507 
508 /* Translate a string, including coded sequences into Unicode */
509 static int
510 xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
511              int *longlen, int *outlen, int escape, int utf8,
512              struct nls_table *nls)
513 {
514         const unsigned char *ip;
515         unsigned char *op;
516         int i, fill;
517         int charlen;
518 
519         if (utf8) {
520                 *outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
521                                 (wchar_t *) outname, FAT_LFN_LEN + 2);
522                 if (*outlen < 0)
523                         return *outlen;
524                 else if (*outlen > FAT_LFN_LEN)
525                         return -ENAMETOOLONG;
526 
527                 op = &outname[*outlen * sizeof(wchar_t)];
528         } else {
529                 for (i = 0, ip = name, op = outname, *outlen = 0;
530                          i < len && *outlen < FAT_LFN_LEN;
531                          *outlen += 1) {
532                         if (escape && (*ip == ':')) {
533                                 u8 uc[2];
534 
535                                 if (i > len - 5)
536                                         return -EINVAL;
537 
538                                 if (hex2bin(uc, ip + 1, 2) < 0)
539                                         return -EINVAL;
540 
541                                 *(wchar_t *)op = uc[0] << 8 | uc[1];
542 
543                                 op += 2;
544                                 ip += 5;
545                                 i += 5;
546                         } else {
547                                 charlen = nls->char2uni(ip, len - i,
548                                                         (wchar_t *)op);
549                                 if (charlen < 0)
550                                         return -EINVAL;
551                                 ip += charlen;
552                                 i += charlen;
553                                 op += 2;
554                         }
555                 }
556                 if (i < len)
557                         return -ENAMETOOLONG;
558         }
559 
560         *longlen = *outlen;
561         if (*outlen % 13) {
562                 *op++ = 0;
563                 *op++ = 0;
564                 *outlen += 1;
565                 if (*outlen % 13) {
566                         fill = 13 - (*outlen % 13);
567                         for (i = 0; i < fill; i++) {
568                                 *op++ = 0xff;
569                                 *op++ = 0xff;
570                         }
571                         *outlen += fill;
572                 }
573         }
574 
575         return 0;
576 }
577 
578 static int vfat_build_slots(struct inode *dir, const unsigned char *name,
579                             int len, int is_dir, int cluster,
580                             struct timespec64 *ts,
581                             struct msdos_dir_slot *slots, int *nr_slots)
582 {
583         struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
584         struct fat_mount_options *opts = &sbi->options;
585         struct msdos_dir_slot *ps;
586         struct msdos_dir_entry *de;
587         unsigned char cksum, lcase;
588         unsigned char msdos_name[MSDOS_NAME];
589         wchar_t *uname;
590         __le16 time, date;
591         u8 time_cs;
592         int err, ulen, usize, i;
593         loff_t offset;
594 
595         *nr_slots = 0;
596 
597         uname = __getname();
598         if (!uname)
599                 return -ENOMEM;
600 
601         err = xlate_to_uni(name, len, (unsigned char *)uname, &ulen, &usize,
602                            opts->unicode_xlate, opts->utf8, sbi->nls_io);
603         if (err)
604                 goto out_free;
605 
606         err = vfat_is_used_badchars(uname, ulen);
607         if (err)
608                 goto out_free;
609 
610         err = vfat_create_shortname(dir, sbi->nls_disk, uname, ulen,
611                                     msdos_name, &lcase);
612         if (err < 0)
613                 goto out_free;
614         else if (err == 1) {
615                 de = (struct msdos_dir_entry *)slots;
616                 err = 0;
617                 goto shortname;
618         }
619 
620         /* build the entry of long file name */
621         cksum = fat_checksum(msdos_name);
622 
623         *nr_slots = usize / 13;
624         for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
625                 ps->id = i;
626                 ps->attr = ATTR_EXT;
627                 ps->reserved = 0;
628                 ps->alias_checksum = cksum;
629                 ps->start = 0;
630                 offset = (i - 1) * 13;
631                 fatwchar_to16(ps->name0_4, uname + offset, 5);
632                 fatwchar_to16(ps->name5_10, uname + offset + 5, 6);
633                 fatwchar_to16(ps->name11_12, uname + offset + 11, 2);
634         }
635         slots[0].id |= 0x40;
636         de = (struct msdos_dir_entry *)ps;
637 
638 shortname:
639         /* build the entry of 8.3 alias name */
640         (*nr_slots)++;
641         memcpy(de->name, msdos_name, MSDOS_NAME);
642         de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
643         de->lcase = lcase;
644         fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
645         de->time = de->ctime = time;
646         de->date = de->cdate = de->adate = date;
647         de->ctime_cs = time_cs;
648         fat_set_start(de, cluster);
649         de->size = 0;
650 out_free:
651         __putname(uname);
652         return err;
653 }
654 
655 static int vfat_add_entry(struct inode *dir, const struct qstr *qname,
656                           int is_dir, int cluster, struct timespec64 *ts,
657                           struct fat_slot_info *sinfo)
658 {
659         struct msdos_dir_slot *slots;
660         unsigned int len;
661         int err, nr_slots;
662 
663         len = vfat_striptail_len(qname);
664         if (len == 0)
665                 return -ENOENT;
666 
667         slots = kmalloc_array(MSDOS_SLOTS, sizeof(*slots), GFP_NOFS);
668         if (slots == NULL)
669                 return -ENOMEM;
670 
671         err = vfat_build_slots(dir, qname->name, len, is_dir, cluster, ts,
672                                slots, &nr_slots);
673         if (err)
674                 goto cleanup;
675 
676         err = fat_add_entries(dir, slots, nr_slots, sinfo);
677         if (err)
678                 goto cleanup;
679 
680         /* update timestamp */
681         fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
682         if (IS_DIRSYNC(dir))
683                 (void)fat_sync_inode(dir);
684         else
685                 mark_inode_dirty(dir);
686 cleanup:
687         kfree(slots);
688         return err;
689 }
690 
691 static int vfat_find(struct inode *dir, const struct qstr *qname,
692                      struct fat_slot_info *sinfo)
693 {
694         unsigned int len = vfat_striptail_len(qname);
695         if (len == 0)
696                 return -ENOENT;
697         return fat_search_long(dir, qname->name, len, sinfo);
698 }
699 
700 static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
701                                   unsigned int flags)
702 {
703         struct super_block *sb = dir->i_sb;
704         struct fat_slot_info sinfo;
705         struct inode *inode;
706         struct dentry *alias;
707         int err;
708 
709         mutex_lock(&MSDOS_SB(sb)->s_lock);
710 
711         err = vfat_find(dir, &dentry->d_name, &sinfo);
712         if (err) {
713                 if (err == -ENOENT) {
714                         inode = NULL;
715                         goto out;
716                 }
717                 goto error;
718         }
719 
720         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
721         brelse(sinfo.bh);
722         if (IS_ERR(inode)) {
723                 err = PTR_ERR(inode);
724                 goto error;
725         }
726 
727         alias = d_find_alias(inode);
728         /*
729          * Checking "alias->d_parent == dentry->d_parent" to make sure
730          * FS is not corrupted (especially double linked dir).
731          */
732         if (alias && alias->d_parent == dentry->d_parent) {
733                 /*
734                  * This inode has non anonymous-DCACHE_DISCONNECTED
735                  * dentry. This means, the user did ->lookup() by an
736                  * another name (longname vs 8.3 alias of it) in past.
737                  *
738                  * Switch to new one for reason of locality if possible.
739                  */
740                 if (!S_ISDIR(inode->i_mode))
741                         d_move(alias, dentry);
742                 iput(inode);
743                 mutex_unlock(&MSDOS_SB(sb)->s_lock);
744                 return alias;
745         } else
746                 dput(alias);
747 
748 out:
749         mutex_unlock(&MSDOS_SB(sb)->s_lock);
750         if (!inode)
751                 vfat_d_version_set(dentry, inode_query_iversion(dir));
752         return d_splice_alias(inode, dentry);
753 error:
754         mutex_unlock(&MSDOS_SB(sb)->s_lock);
755         return ERR_PTR(err);
756 }
757 
758 static int vfat_create(struct inode *dir, struct dentry *dentry, umode_t mode,
759                        bool excl)
760 {
761         struct super_block *sb = dir->i_sb;
762         struct inode *inode;
763         struct fat_slot_info sinfo;
764         struct timespec64 ts;
765         int err;
766 
767         mutex_lock(&MSDOS_SB(sb)->s_lock);
768 
769         ts = current_time(dir);
770         err = vfat_add_entry(dir, &dentry->d_name, 0, 0, &ts, &sinfo);
771         if (err)
772                 goto out;
773         inode_inc_iversion(dir);
774 
775         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
776         brelse(sinfo.bh);
777         if (IS_ERR(inode)) {
778                 err = PTR_ERR(inode);
779                 goto out;
780         }
781         inode_inc_iversion(inode);
782         fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
783         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
784 
785         d_instantiate(dentry, inode);
786 out:
787         mutex_unlock(&MSDOS_SB(sb)->s_lock);
788         return err;
789 }
790 
791 static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
792 {
793         struct inode *inode = d_inode(dentry);
794         struct super_block *sb = dir->i_sb;
795         struct fat_slot_info sinfo;
796         int err;
797 
798         mutex_lock(&MSDOS_SB(sb)->s_lock);
799 
800         err = fat_dir_empty(inode);
801         if (err)
802                 goto out;
803         err = vfat_find(dir, &dentry->d_name, &sinfo);
804         if (err)
805                 goto out;
806 
807         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
808         if (err)
809                 goto out;
810         drop_nlink(dir);
811 
812         clear_nlink(inode);
813         fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
814         fat_detach(inode);
815         vfat_d_version_set(dentry, inode_query_iversion(dir));
816 out:
817         mutex_unlock(&MSDOS_SB(sb)->s_lock);
818 
819         return err;
820 }
821 
822 static int vfat_unlink(struct inode *dir, struct dentry *dentry)
823 {
824         struct inode *inode = d_inode(dentry);
825         struct super_block *sb = dir->i_sb;
826         struct fat_slot_info sinfo;
827         int err;
828 
829         mutex_lock(&MSDOS_SB(sb)->s_lock);
830 
831         err = vfat_find(dir, &dentry->d_name, &sinfo);
832         if (err)
833                 goto out;
834 
835         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
836         if (err)
837                 goto out;
838         clear_nlink(inode);
839         fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
840         fat_detach(inode);
841         vfat_d_version_set(dentry, inode_query_iversion(dir));
842 out:
843         mutex_unlock(&MSDOS_SB(sb)->s_lock);
844 
845         return err;
846 }
847 
848 static int vfat_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
849 {
850         struct super_block *sb = dir->i_sb;
851         struct inode *inode;
852         struct fat_slot_info sinfo;
853         struct timespec64 ts;
854         int err, cluster;
855 
856         mutex_lock(&MSDOS_SB(sb)->s_lock);
857 
858         ts = current_time(dir);
859         cluster = fat_alloc_new_dir(dir, &ts);
860         if (cluster < 0) {
861                 err = cluster;
862                 goto out;
863         }
864         err = vfat_add_entry(dir, &dentry->d_name, 1, cluster, &ts, &sinfo);
865         if (err)
866                 goto out_free;
867         inode_inc_iversion(dir);
868         inc_nlink(dir);
869 
870         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
871         brelse(sinfo.bh);
872         if (IS_ERR(inode)) {
873                 err = PTR_ERR(inode);
874                 /* the directory was completed, just return a error */
875                 goto out;
876         }
877         inode_inc_iversion(inode);
878         set_nlink(inode, 2);
879         fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
880         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
881 
882         d_instantiate(dentry, inode);
883 
884         mutex_unlock(&MSDOS_SB(sb)->s_lock);
885         return 0;
886 
887 out_free:
888         fat_free_clusters(dir, cluster);
889 out:
890         mutex_unlock(&MSDOS_SB(sb)->s_lock);
891         return err;
892 }
893 
894 static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
895                        struct inode *new_dir, struct dentry *new_dentry,
896                        unsigned int flags)
897 {
898         struct buffer_head *dotdot_bh;
899         struct msdos_dir_entry *dotdot_de;
900         struct inode *old_inode, *new_inode;
901         struct fat_slot_info old_sinfo, sinfo;
902         struct timespec64 ts;
903         loff_t new_i_pos;
904         int err, is_dir, update_dotdot, corrupt = 0;
905         struct super_block *sb = old_dir->i_sb;
906 
907         if (flags & ~RENAME_NOREPLACE)
908                 return -EINVAL;
909 
910         old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
911         old_inode = d_inode(old_dentry);
912         new_inode = d_inode(new_dentry);
913         mutex_lock(&MSDOS_SB(sb)->s_lock);
914         err = vfat_find(old_dir, &old_dentry->d_name, &old_sinfo);
915         if (err)
916                 goto out;
917 
918         is_dir = S_ISDIR(old_inode->i_mode);
919         update_dotdot = (is_dir && old_dir != new_dir);
920         if (update_dotdot) {
921                 if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
922                         err = -EIO;
923                         goto out;
924                 }
925         }
926 
927         ts = current_time(old_dir);
928         if (new_inode) {
929                 if (is_dir) {
930                         err = fat_dir_empty(new_inode);
931                         if (err)
932                                 goto out;
933                 }
934                 new_i_pos = MSDOS_I(new_inode)->i_pos;
935                 fat_detach(new_inode);
936         } else {
937                 err = vfat_add_entry(new_dir, &new_dentry->d_name, is_dir, 0,
938                                      &ts, &sinfo);
939                 if (err)
940                         goto out;
941                 new_i_pos = sinfo.i_pos;
942         }
943         inode_inc_iversion(new_dir);
944 
945         fat_detach(old_inode);
946         fat_attach(old_inode, new_i_pos);
947         if (IS_DIRSYNC(new_dir)) {
948                 err = fat_sync_inode(old_inode);
949                 if (err)
950                         goto error_inode;
951         } else
952                 mark_inode_dirty(old_inode);
953 
954         if (update_dotdot) {
955                 fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
956                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
957                 if (IS_DIRSYNC(new_dir)) {
958                         err = sync_dirty_buffer(dotdot_bh);
959                         if (err)
960                                 goto error_dotdot;
961                 }
962                 drop_nlink(old_dir);
963                 if (!new_inode)
964                         inc_nlink(new_dir);
965         }
966 
967         err = fat_remove_entries(old_dir, &old_sinfo);  /* and releases bh */
968         old_sinfo.bh = NULL;
969         if (err)
970                 goto error_dotdot;
971         inode_inc_iversion(old_dir);
972         fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
973         if (IS_DIRSYNC(old_dir))
974                 (void)fat_sync_inode(old_dir);
975         else
976                 mark_inode_dirty(old_dir);
977 
978         if (new_inode) {
979                 drop_nlink(new_inode);
980                 if (is_dir)
981                         drop_nlink(new_inode);
982                 fat_truncate_time(new_inode, &ts, S_CTIME);
983         }
984 out:
985         brelse(sinfo.bh);
986         brelse(dotdot_bh);
987         brelse(old_sinfo.bh);
988         mutex_unlock(&MSDOS_SB(sb)->s_lock);
989 
990         return err;
991 
992 error_dotdot:
993         /* data cluster is shared, serious corruption */
994         corrupt = 1;
995 
996         if (update_dotdot) {
997                 fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
998                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
999                 corrupt |= sync_dirty_buffer(dotdot_bh);
1000         }
1001 error_inode:
1002         fat_detach(old_inode);
1003         fat_attach(old_inode, old_sinfo.i_pos);
1004         if (new_inode) {
1005                 fat_attach(new_inode, new_i_pos);
1006                 if (corrupt)
1007                         corrupt |= fat_sync_inode(new_inode);
1008         } else {
1009                 /*
1010                  * If new entry was not sharing the data cluster, it
1011                  * shouldn't be serious corruption.
1012                  */
1013                 int err2 = fat_remove_entries(new_dir, &sinfo);
1014                 if (corrupt)
1015                         corrupt |= err2;
1016                 sinfo.bh = NULL;
1017         }
1018         if (corrupt < 0) {
1019                 fat_fs_error(new_dir->i_sb,
1020                              "%s: Filesystem corrupted (i_pos %lld)",
1021                              __func__, sinfo.i_pos);
1022         }
1023         goto out;
1024 }
1025 
1026 static const struct inode_operations vfat_dir_inode_operations = {
1027         .create         = vfat_create,
1028         .lookup         = vfat_lookup,
1029         .unlink         = vfat_unlink,
1030         .mkdir          = vfat_mkdir,
1031         .rmdir          = vfat_rmdir,
1032         .rename         = vfat_rename,
1033         .setattr        = fat_setattr,
1034         .getattr        = fat_getattr,
1035         .update_time    = fat_update_time,
1036 };
1037 
1038 static void setup(struct super_block *sb)
1039 {
1040         MSDOS_SB(sb)->dir_ops = &vfat_dir_inode_operations;
1041         if (MSDOS_SB(sb)->options.name_check != 's')
1042                 sb->s_d_op = &vfat_ci_dentry_ops;
1043         else
1044                 sb->s_d_op = &vfat_dentry_ops;
1045 }
1046 
1047 static int vfat_fill_super(struct super_block *sb, void *data, int silent)
1048 {
1049         return fat_fill_super(sb, data, silent, 1, setup);
1050 }
1051 
1052 static struct dentry *vfat_mount(struct file_system_type *fs_type,
1053                        int flags, const char *dev_name,
1054                        void *data)
1055 {
1056         return mount_bdev(fs_type, flags, dev_name, data, vfat_fill_super);
1057 }
1058 
1059 static struct file_system_type vfat_fs_type = {
1060         .owner          = THIS_MODULE,
1061         .name           = "vfat",
1062         .mount          = vfat_mount,
1063         .kill_sb        = kill_block_super,
1064         .fs_flags       = FS_REQUIRES_DEV,
1065 };
1066 MODULE_ALIAS_FS("vfat");
1067 
1068 static int __init init_vfat_fs(void)
1069 {
1070         return register_filesystem(&vfat_fs_type);
1071 }
1072 
1073 static void __exit exit_vfat_fs(void)
1074 {
1075         unregister_filesystem(&vfat_fs_type);
1076 }
1077 
1078 MODULE_LICENSE("GPL");
1079 MODULE_DESCRIPTION("VFAT filesystem support");
1080 MODULE_AUTHOR("Gordon Chaffee");
1081 
1082 module_init(init_vfat_fs)
1083 module_exit(exit_vfat_fs)
1084 

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