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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/jiffies.h>
 20 #include <linux/ctype.h>
 21 #include <linux/slab.h>
 22 #include <linux/buffer_head.h>
 23 #include <linux/namei.h>
 24 #include "fat.h"
 25 
 26 /*
 27  * If new entry was created in the parent, it could create the 8.3
 28  * alias (the shortname of logname).  So, the parent may have the
 29  * negative-dentry which matches the created 8.3 alias.
 30  *
 31  * If it happened, the negative dentry isn't actually negative
 32  * anymore.  So, drop it.
 33  */
 34 static int vfat_revalidate_shortname(struct dentry *dentry)
 35 {
 36         int ret = 1;
 37         spin_lock(&dentry->d_lock);
 38         if (dentry->d_time != dentry->d_parent->d_inode->i_version)
 39                 ret = 0;
 40         spin_unlock(&dentry->d_lock);
 41         return ret;
 42 }
 43 
 44 static int vfat_revalidate(struct dentry *dentry, struct nameidata *nd)
 45 {
 46         if (nd && nd->flags & LOOKUP_RCU)
 47                 return -ECHILD;
 48 
 49         /* This is not negative dentry. Always valid. */
 50         if (dentry->d_inode)
 51                 return 1;
 52         return vfat_revalidate_shortname(dentry);
 53 }
 54 
 55 static int vfat_revalidate_ci(struct dentry *dentry, struct nameidata *nd)
 56 {
 57         if (nd && nd->flags & LOOKUP_RCU)
 58                 return -ECHILD;
 59 
 60         /*
 61          * This is not negative dentry. Always valid.
 62          *
 63          * Note, rename() to existing directory entry will have ->d_inode,
 64          * and will use existing name which isn't specified name by user.
 65          *
 66          * We may be able to drop this positive dentry here. But dropping
 67          * positive dentry isn't good idea. So it's unsupported like
 68          * rename("filename", "FILENAME") for now.
 69          */
 70         if (dentry->d_inode)
 71                 return 1;
 72 
 73         /*
 74          * This may be nfsd (or something), anyway, we can't see the
 75          * intent of this. So, since this can be for creation, drop it.
 76          */
 77         if (!nd)
 78                 return 0;
 79 
 80         /*
 81          * Drop the negative dentry, in order to make sure to use the
 82          * case sensitive name which is specified by user if this is
 83          * for creation.
 84          */
 85         if (!(nd->flags & (LOOKUP_CONTINUE | LOOKUP_PARENT))) {
 86                 if (nd->flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
 87                         return 0;
 88         }
 89 
 90         return vfat_revalidate_shortname(dentry);
 91 }
 92 
 93 /* returns the length of a struct qstr, ignoring trailing dots */
 94 static unsigned int __vfat_striptail_len(unsigned int len, const char *name)
 95 {
 96         while (len && name[len - 1] == '.')
 97                 len--;
 98         return len;
 99 }
100 
101 static unsigned int vfat_striptail_len(const struct qstr *qstr)
102 {
103         return __vfat_striptail_len(qstr->len, qstr->name);
104 }
105 
106 /*
107  * Compute the hash for the vfat name corresponding to the dentry.
108  * Note: if the name is invalid, we leave the hash code unchanged so
109  * that the existing dentry can be used. The vfat fs routines will
110  * return ENOENT or EINVAL as appropriate.
111  */
112 static int vfat_hash(const struct dentry *dentry, const struct inode *inode,
113                 struct qstr *qstr)
114 {
115         qstr->hash = full_name_hash(qstr->name, vfat_striptail_len(qstr));
116         return 0;
117 }
118 
119 /*
120  * Compute the hash for the vfat name corresponding to the dentry.
121  * Note: if the name is invalid, we leave the hash code unchanged so
122  * that the existing dentry can be used. The vfat fs routines will
123  * return ENOENT or EINVAL as appropriate.
124  */
125 static int vfat_hashi(const struct dentry *dentry, const struct inode *inode,
126                 struct qstr *qstr)
127 {
128         struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
129         const unsigned char *name;
130         unsigned int len;
131         unsigned long hash;
132 
133         name = qstr->name;
134         len = vfat_striptail_len(qstr);
135 
136         hash = init_name_hash();
137         while (len--)
138                 hash = partial_name_hash(nls_tolower(t, *name++), hash);
139         qstr->hash = end_name_hash(hash);
140 
141         return 0;
142 }
143 
144 /*
145  * Case insensitive compare of two vfat names.
146  */
147 static int vfat_cmpi(const struct dentry *parent, const struct inode *pinode,
148                 const struct dentry *dentry, const struct inode *inode,
149                 unsigned int len, const char *str, const struct qstr *name)
150 {
151         struct nls_table *t = MSDOS_SB(parent->d_sb)->nls_io;
152         unsigned int alen, blen;
153 
154         /* A filename cannot end in '.' or we treat it like it has none */
155         alen = vfat_striptail_len(name);
156         blen = __vfat_striptail_len(len, str);
157         if (alen == blen) {
158                 if (nls_strnicmp(t, name->name, str, alen) == 0)
159                         return 0;
160         }
161         return 1;
162 }
163 
164 /*
165  * Case sensitive compare of two vfat names.
166  */
167 static int vfat_cmp(const struct dentry *parent, const struct inode *pinode,
168                 const struct dentry *dentry, const struct inode *inode,
169                 unsigned int len, const char *str, const struct qstr *name)
170 {
171         unsigned int alen, blen;
172 
173         /* A filename cannot end in '.' or we treat it like it has none */
174         alen = vfat_striptail_len(name);
175         blen = __vfat_striptail_len(len, str);
176         if (alen == blen) {
177                 if (strncmp(name->name, str, alen) == 0)
178                         return 0;
179         }
180         return 1;
181 }
182 
183 static const struct dentry_operations vfat_ci_dentry_ops = {
184         .d_revalidate   = vfat_revalidate_ci,
185         .d_hash         = vfat_hashi,
186         .d_compare      = vfat_cmpi,
187 };
188 
189 static const struct dentry_operations vfat_dentry_ops = {
190         .d_revalidate   = vfat_revalidate,
191         .d_hash         = vfat_hash,
192         .d_compare      = vfat_cmp,
193 };
194 
195 /* Characters that are undesirable in an MS-DOS file name */
196 
197 static inline wchar_t vfat_bad_char(wchar_t w)
198 {
199         return (w < 0x0020)
200             || (w == '*') || (w == '?') || (w == '<') || (w == '>')
201             || (w == '|') || (w == '"') || (w == ':') || (w == '/')
202             || (w == '\\');
203 }
204 
205 static inline wchar_t vfat_replace_char(wchar_t w)
206 {
207         return (w == '[') || (w == ']') || (w == ';') || (w == ',')
208             || (w == '+') || (w == '=');
209 }
210 
211 static wchar_t vfat_skip_char(wchar_t w)
212 {
213         return (w == '.') || (w == ' ');
214 }
215 
216 static inline int vfat_is_used_badchars(const wchar_t *s, int len)
217 {
218         int i;
219 
220         for (i = 0; i < len; i++)
221                 if (vfat_bad_char(s[i]))
222                         return -EINVAL;
223 
224         if (s[i - 1] == ' ') /* last character cannot be space */
225                 return -EINVAL;
226 
227         return 0;
228 }
229 
230 static int vfat_find_form(struct inode *dir, unsigned char *name)
231 {
232         struct fat_slot_info sinfo;
233         int err = fat_scan(dir, name, &sinfo);
234         if (err)
235                 return -ENOENT;
236         brelse(sinfo.bh);
237         return 0;
238 }
239 
240 /*
241  * 1) Valid characters for the 8.3 format alias are any combination of
242  * letters, uppercase alphabets, digits, any of the
243  * following special characters:
244  *     $ % ' ` - @ { } ~ ! # ( ) & _ ^
245  * In this case Longfilename is not stored in disk.
246  *
247  * WinNT's Extension:
248  * File name and extension name is contain uppercase/lowercase
249  * only. And it is expressed by CASE_LOWER_BASE and CASE_LOWER_EXT.
250  *
251  * 2) File name is 8.3 format, but it contain the uppercase and
252  * lowercase char, muliti bytes char, etc. In this case numtail is not
253  * added, but Longfilename is stored.
254  *
255  * 3) When the one except for the above, or the following special
256  * character are contained:
257  *        .   [ ] ; , + =
258  * numtail is added, and Longfilename must be stored in disk .
259  */
260 struct shortname_info {
261         unsigned char lower:1,
262                       upper:1,
263                       valid:1;
264 };
265 #define INIT_SHORTNAME_INFO(x)  do {            \
266         (x)->lower = 1;                         \
267         (x)->upper = 1;                         \
268         (x)->valid = 1;                         \
269 } while (0)
270 
271 static inline int to_shortname_char(struct nls_table *nls,
272                                     unsigned char *buf, int buf_size,
273                                     wchar_t *src, struct shortname_info *info)
274 {
275         int len;
276 
277         if (vfat_skip_char(*src)) {
278                 info->valid = 0;
279                 return 0;
280         }
281         if (vfat_replace_char(*src)) {
282                 info->valid = 0;
283                 buf[0] = '_';
284                 return 1;
285         }
286 
287         len = nls->uni2char(*src, buf, buf_size);
288         if (len <= 0) {
289                 info->valid = 0;
290                 buf[0] = '_';
291                 len = 1;
292         } else if (len == 1) {
293                 unsigned char prev = buf[0];
294 
295                 if (buf[0] >= 0x7F) {
296                         info->lower = 0;
297                         info->upper = 0;
298                 }
299 
300                 buf[0] = nls_toupper(nls, buf[0]);
301                 if (isalpha(buf[0])) {
302                         if (buf[0] == prev)
303                                 info->lower = 0;
304                         else
305                                 info->upper = 0;
306                 }
307         } else {
308                 info->lower = 0;
309                 info->upper = 0;
310         }
311 
312         return len;
313 }
314 
315 /*
316  * Given a valid longname, create a unique shortname.  Make sure the
317  * shortname does not exist
318  * Returns negative number on error, 0 for a normal
319  * return, and 1 for valid shortname
320  */
321 static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
322                                  wchar_t *uname, int ulen,
323                                  unsigned char *name_res, unsigned char *lcase)
324 {
325         struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
326         wchar_t *ip, *ext_start, *end, *name_start;
327         unsigned char base[9], ext[4], buf[5], *p;
328         unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
329         int chl, chi;
330         int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
331         int is_shortname;
332         struct shortname_info base_info, ext_info;
333 
334         is_shortname = 1;
335         INIT_SHORTNAME_INFO(&base_info);
336         INIT_SHORTNAME_INFO(&ext_info);
337 
338         /* Now, we need to create a shortname from the long name */
339         ext_start = end = &uname[ulen];
340         while (--ext_start >= uname) {
341                 if (*ext_start == 0x002E) {     /* is `.' */
342                         if (ext_start == end - 1) {
343                                 sz = ulen;
344                                 ext_start = NULL;
345                         }
346                         break;
347                 }
348         }
349 
350         if (ext_start == uname - 1) {
351                 sz = ulen;
352                 ext_start = NULL;
353         } else if (ext_start) {
354                 /*
355                  * Names which start with a dot could be just
356                  * an extension eg. "...test".  In this case Win95
357                  * uses the extension as the name and sets no extension.
358                  */
359                 name_start = &uname[0];
360                 while (name_start < ext_start) {
361                         if (!vfat_skip_char(*name_start))
362                                 break;
363                         name_start++;
364                 }
365                 if (name_start != ext_start) {
366                         sz = ext_start - uname;
367                         ext_start++;
368                 } else {
369                         sz = ulen;
370                         ext_start = NULL;
371                 }
372         }
373 
374         numtail_baselen = 6;
375         numtail2_baselen = 2;
376         for (baselen = i = 0, p = base, ip = uname; i < sz; i++, ip++) {
377                 chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
378                                         ip, &base_info);
379                 if (chl == 0)
380                         continue;
381 
382                 if (baselen < 2 && (baselen + chl) > 2)
383                         numtail2_baselen = baselen;
384                 if (baselen < 6 && (baselen + chl) > 6)
385                         numtail_baselen = baselen;
386                 for (chi = 0; chi < chl; chi++) {
387                         *p++ = charbuf[chi];
388                         baselen++;
389                         if (baselen >= 8)
390                                 break;
391                 }
392                 if (baselen >= 8) {
393                         if ((chi < chl - 1) || (ip + 1) - uname < sz)
394                                 is_shortname = 0;
395                         break;
396                 }
397         }
398         if (baselen == 0) {
399                 return -EINVAL;
400         }
401 
402         extlen = 0;
403         if (ext_start) {
404                 for (p = ext, ip = ext_start; extlen < 3 && ip < end; ip++) {
405                         chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
406                                                 ip, &ext_info);
407                         if (chl == 0)
408                                 continue;
409 
410                         if ((extlen + chl) > 3) {
411                                 is_shortname = 0;
412                                 break;
413                         }
414                         for (chi = 0; chi < chl; chi++) {
415                                 *p++ = charbuf[chi];
416                                 extlen++;
417                         }
418                         if (extlen >= 3) {
419                                 if (ip + 1 != end)
420                                         is_shortname = 0;
421                                 break;
422                         }
423                 }
424         }
425         ext[extlen] = '\0';
426         base[baselen] = '\0';
427 
428         /* Yes, it can happen. ".\xe5" would do it. */
429         if (base[0] == DELETED_FLAG)
430                 base[0] = 0x05;
431 
432         /* OK, at this point we know that base is not longer than 8 symbols,
433          * ext is not longer than 3, base is nonempty, both don't contain
434          * any bad symbols (lowercase transformed to uppercase).
435          */
436 
437         memset(name_res, ' ', MSDOS_NAME);
438         memcpy(name_res, base, baselen);
439         memcpy(name_res + 8, ext, extlen);
440         *lcase = 0;
441         if (is_shortname && base_info.valid && ext_info.valid) {
442                 if (vfat_find_form(dir, name_res) == 0)
443                         return -EEXIST;
444 
445                 if (opts->shortname & VFAT_SFN_CREATE_WIN95) {
446                         return (base_info.upper && ext_info.upper);
447                 } else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
448                         if ((base_info.upper || base_info.lower) &&
449                             (ext_info.upper || ext_info.lower)) {
450                                 if (!base_info.upper && base_info.lower)
451                                         *lcase |= CASE_LOWER_BASE;
452                                 if (!ext_info.upper && ext_info.lower)
453                                         *lcase |= CASE_LOWER_EXT;
454                                 return 1;
455                         }
456                         return 0;
457                 } else {
458                         BUG();
459                 }
460         }
461 
462         if (opts->numtail == 0)
463                 if (vfat_find_form(dir, name_res) < 0)
464                         return 0;
465 
466         /*
467          * Try to find a unique extension.  This used to
468          * iterate through all possibilities sequentially,
469          * but that gave extremely bad performance.  Windows
470          * only tries a few cases before using random
471          * values for part of the base.
472          */
473 
474         if (baselen > 6) {
475                 baselen = numtail_baselen;
476                 name_res[7] = ' ';
477         }
478         name_res[baselen] = '~';
479         for (i = 1; i < 10; i++) {
480                 name_res[baselen + 1] = i + '';
481                 if (vfat_find_form(dir, name_res) < 0)
482                         return 0;
483         }
484 
485         i = jiffies;
486         sz = (jiffies >> 16) & 0x7;
487         if (baselen > 2) {
488                 baselen = numtail2_baselen;
489                 name_res[7] = ' ';
490         }
491         name_res[baselen + 4] = '~';
492         name_res[baselen + 5] = '1' + sz;
493         while (1) {
494                 snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
495                 memcpy(&name_res[baselen], buf, 4);
496                 if (vfat_find_form(dir, name_res) < 0)
497                         break;
498                 i -= 11;
499         }
500         return 0;
501 }
502 
503 /* Translate a string, including coded sequences into Unicode */
504 static int
505 xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
506              int *longlen, int *outlen, int escape, int utf8,
507              struct nls_table *nls)
508 {
509         const unsigned char *ip;
510         unsigned char nc;
511         unsigned char *op;
512         unsigned int ec;
513         int i, k, fill;
514         int charlen;
515 
516         if (utf8) {
517                 *outlen = utf8s_to_utf16s(name, len, (wchar_t *)outname);
518                 if (*outlen < 0)
519                         return *outlen;
520                 else if (*outlen > FAT_LFN_LEN)
521                         return -ENAMETOOLONG;
522 
523                 op = &outname[*outlen * sizeof(wchar_t)];
524         } else {
525                 if (nls) {
526                         for (i = 0, ip = name, op = outname, *outlen = 0;
527                              i < len && *outlen <= FAT_LFN_LEN;
528                              *outlen += 1)
529                         {
530                                 if (escape && (*ip == ':')) {
531                                         if (i > len - 5)
532                                                 return -EINVAL;
533                                         ec = 0;
534                                         for (k = 1; k < 5; k++) {
535                                                 nc = ip[k];
536                                                 ec <<= 4;
537                                                 if (nc >= '' && nc <= '9') {
538                                                         ec |= nc - '';
539                                                         continue;
540                                                 }
541                                                 if (nc >= 'a' && nc <= 'f') {
542                                                         ec |= nc - ('a' - 10);
543                                                         continue;
544                                                 }
545                                                 if (nc >= 'A' && nc <= 'F') {
546                                                         ec |= nc - ('A' - 10);
547                                                         continue;
548                                                 }
549                                                 return -EINVAL;
550                                         }
551                                         *op++ = ec & 0xFF;
552                                         *op++ = ec >> 8;
553                                         ip += 5;
554                                         i += 5;
555                                 } else {
556                                         if ((charlen = nls->char2uni(ip, len - i, (wchar_t *)op)) < 0)
557                                                 return -EINVAL;
558                                         ip += charlen;
559                                         i += charlen;
560                                         op += 2;
561                                 }
562                         }
563                         if (i < len)
564                                 return -ENAMETOOLONG;
565                 } else {
566                         for (i = 0, ip = name, op = outname, *outlen = 0;
567                              i < len && *outlen <= FAT_LFN_LEN;
568                              i++, *outlen += 1)
569                         {
570                                 *op++ = *ip++;
571                                 *op++ = 0;
572                         }
573                         if (i < len)
574                                 return -ENAMETOOLONG;
575                 }
576         }
577 
578         *longlen = *outlen;
579         if (*outlen % 13) {
580                 *op++ = 0;
581                 *op++ = 0;
582                 *outlen += 1;
583                 if (*outlen % 13) {
584                         fill = 13 - (*outlen % 13);
585                         for (i = 0; i < fill; i++) {
586                                 *op++ = 0xff;
587                                 *op++ = 0xff;
588                         }
589                         *outlen += fill;
590                 }
591         }
592 
593         return 0;
594 }
595 
596 static int vfat_build_slots(struct inode *dir, const unsigned char *name,
597                             int len, int is_dir, int cluster,
598                             struct timespec *ts,
599                             struct msdos_dir_slot *slots, int *nr_slots)
600 {
601         struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
602         struct fat_mount_options *opts = &sbi->options;
603         struct msdos_dir_slot *ps;
604         struct msdos_dir_entry *de;
605         unsigned char cksum, lcase;
606         unsigned char msdos_name[MSDOS_NAME];
607         wchar_t *uname;
608         __le16 time, date;
609         u8 time_cs;
610         int err, ulen, usize, i;
611         loff_t offset;
612 
613         *nr_slots = 0;
614 
615         uname = __getname();
616         if (!uname)
617                 return -ENOMEM;
618 
619         err = xlate_to_uni(name, len, (unsigned char *)uname, &ulen, &usize,
620                            opts->unicode_xlate, opts->utf8, sbi->nls_io);
621         if (err)
622                 goto out_free;
623 
624         err = vfat_is_used_badchars(uname, ulen);
625         if (err)
626                 goto out_free;
627 
628         err = vfat_create_shortname(dir, sbi->nls_disk, uname, ulen,
629                                     msdos_name, &lcase);
630         if (err < 0)
631                 goto out_free;
632         else if (err == 1) {
633                 de = (struct msdos_dir_entry *)slots;
634                 err = 0;
635                 goto shortname;
636         }
637 
638         /* build the entry of long file name */
639         cksum = fat_checksum(msdos_name);
640 
641         *nr_slots = usize / 13;
642         for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
643                 ps->id = i;
644                 ps->attr = ATTR_EXT;
645                 ps->reserved = 0;
646                 ps->alias_checksum = cksum;
647                 ps->start = 0;
648                 offset = (i - 1) * 13;
649                 fatwchar_to16(ps->name0_4, uname + offset, 5);
650                 fatwchar_to16(ps->name5_10, uname + offset + 5, 6);
651                 fatwchar_to16(ps->name11_12, uname + offset + 11, 2);
652         }
653         slots[0].id |= 0x40;
654         de = (struct msdos_dir_entry *)ps;
655 
656 shortname:
657         /* build the entry of 8.3 alias name */
658         (*nr_slots)++;
659         memcpy(de->name, msdos_name, MSDOS_NAME);
660         de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
661         de->lcase = lcase;
662         fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
663         de->time = de->ctime = time;
664         de->date = de->cdate = de->adate = date;
665         de->ctime_cs = time_cs;
666         de->start = cpu_to_le16(cluster);
667         de->starthi = cpu_to_le16(cluster >> 16);
668         de->size = 0;
669 out_free:
670         __putname(uname);
671         return err;
672 }
673 
674 static int vfat_add_entry(struct inode *dir, struct qstr *qname, int is_dir,
675                           int cluster, struct timespec *ts,
676                           struct fat_slot_info *sinfo)
677 {
678         struct msdos_dir_slot *slots;
679         unsigned int len;
680         int err, nr_slots;
681 
682         len = vfat_striptail_len(qname);
683         if (len == 0)
684                 return -ENOENT;
685 
686         slots = kmalloc(sizeof(*slots) * MSDOS_SLOTS, GFP_NOFS);
687         if (slots == NULL)
688                 return -ENOMEM;
689 
690         err = vfat_build_slots(dir, qname->name, len, is_dir, cluster, ts,
691                                slots, &nr_slots);
692         if (err)
693                 goto cleanup;
694 
695         err = fat_add_entries(dir, slots, nr_slots, sinfo);
696         if (err)
697                 goto cleanup;
698 
699         /* update timestamp */
700         dir->i_ctime = dir->i_mtime = dir->i_atime = *ts;
701         if (IS_DIRSYNC(dir))
702                 (void)fat_sync_inode(dir);
703         else
704                 mark_inode_dirty(dir);
705 cleanup:
706         kfree(slots);
707         return err;
708 }
709 
710 static int vfat_find(struct inode *dir, struct qstr *qname,
711                      struct fat_slot_info *sinfo)
712 {
713         unsigned int len = vfat_striptail_len(qname);
714         if (len == 0)
715                 return -ENOENT;
716         return fat_search_long(dir, qname->name, len, sinfo);
717 }
718 
719 /*
720  * (nfsd's) anonymous disconnected dentry?
721  * NOTE: !IS_ROOT() is not anonymous (I.e. d_splice_alias() did the job).
722  */
723 static int vfat_d_anon_disconn(struct dentry *dentry)
724 {
725         return IS_ROOT(dentry) && (dentry->d_flags & DCACHE_DISCONNECTED);
726 }
727 
728 static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
729                                   struct nameidata *nd)
730 {
731         struct super_block *sb = dir->i_sb;
732         struct fat_slot_info sinfo;
733         struct inode *inode;
734         struct dentry *alias;
735         int err;
736 
737         lock_super(sb);
738 
739         err = vfat_find(dir, &dentry->d_name, &sinfo);
740         if (err) {
741                 if (err == -ENOENT) {
742                         inode = NULL;
743                         goto out;
744                 }
745                 goto error;
746         }
747 
748         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
749         brelse(sinfo.bh);
750         if (IS_ERR(inode)) {
751                 err = PTR_ERR(inode);
752                 goto error;
753         }
754 
755         alias = d_find_alias(inode);
756         if (alias && !vfat_d_anon_disconn(alias)) {
757                 /*
758                  * This inode has non anonymous-DCACHE_DISCONNECTED
759                  * dentry. This means, the user did ->lookup() by an
760                  * another name (longname vs 8.3 alias of it) in past.
761                  *
762                  * Switch to new one for reason of locality if possible.
763                  */
764                 BUG_ON(d_unhashed(alias));
765                 if (!S_ISDIR(inode->i_mode))
766                         d_move(alias, dentry);
767                 iput(inode);
768                 unlock_super(sb);
769                 return alias;
770         } else
771                 dput(alias);
772 
773 out:
774         unlock_super(sb);
775         dentry->d_time = dentry->d_parent->d_inode->i_version;
776         dentry = d_splice_alias(inode, dentry);
777         if (dentry)
778                 dentry->d_time = dentry->d_parent->d_inode->i_version;
779         return dentry;
780 
781 error:
782         unlock_super(sb);
783         return ERR_PTR(err);
784 }
785 
786 static int vfat_create(struct inode *dir, struct dentry *dentry, int mode,
787                        struct nameidata *nd)
788 {
789         struct super_block *sb = dir->i_sb;
790         struct inode *inode;
791         struct fat_slot_info sinfo;
792         struct timespec ts;
793         int err;
794 
795         lock_super(sb);
796 
797         ts = CURRENT_TIME_SEC;
798         err = vfat_add_entry(dir, &dentry->d_name, 0, 0, &ts, &sinfo);
799         if (err)
800                 goto out;
801         dir->i_version++;
802 
803         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
804         brelse(sinfo.bh);
805         if (IS_ERR(inode)) {
806                 err = PTR_ERR(inode);
807                 goto out;
808         }
809         inode->i_version++;
810         inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
811         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
812 
813         dentry->d_time = dentry->d_parent->d_inode->i_version;
814         d_instantiate(dentry, inode);
815 out:
816         unlock_super(sb);
817         return err;
818 }
819 
820 static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
821 {
822         struct inode *inode = dentry->d_inode;
823         struct super_block *sb = dir->i_sb;
824         struct fat_slot_info sinfo;
825         int err;
826 
827         lock_super(sb);
828 
829         err = fat_dir_empty(inode);
830         if (err)
831                 goto out;
832         err = vfat_find(dir, &dentry->d_name, &sinfo);
833         if (err)
834                 goto out;
835 
836         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
837         if (err)
838                 goto out;
839         drop_nlink(dir);
840 
841         clear_nlink(inode);
842         inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
843         fat_detach(inode);
844 out:
845         unlock_super(sb);
846 
847         return err;
848 }
849 
850 static int vfat_unlink(struct inode *dir, struct dentry *dentry)
851 {
852         struct inode *inode = dentry->d_inode;
853         struct super_block *sb = dir->i_sb;
854         struct fat_slot_info sinfo;
855         int err;
856 
857         lock_super(sb);
858 
859         err = vfat_find(dir, &dentry->d_name, &sinfo);
860         if (err)
861                 goto out;
862 
863         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
864         if (err)
865                 goto out;
866         clear_nlink(inode);
867         inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
868         fat_detach(inode);
869 out:
870         unlock_super(sb);
871 
872         return err;
873 }
874 
875 static int vfat_mkdir(struct inode *dir, struct dentry *dentry, int mode)
876 {
877         struct super_block *sb = dir->i_sb;
878         struct inode *inode;
879         struct fat_slot_info sinfo;
880         struct timespec ts;
881         int err, cluster;
882 
883         lock_super(sb);
884 
885         ts = CURRENT_TIME_SEC;
886         cluster = fat_alloc_new_dir(dir, &ts);
887         if (cluster < 0) {
888                 err = cluster;
889                 goto out;
890         }
891         err = vfat_add_entry(dir, &dentry->d_name, 1, cluster, &ts, &sinfo);
892         if (err)
893                 goto out_free;
894         dir->i_version++;
895         inc_nlink(dir);
896 
897         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
898         brelse(sinfo.bh);
899         if (IS_ERR(inode)) {
900                 err = PTR_ERR(inode);
901                 /* the directory was completed, just return a error */
902                 goto out;
903         }
904         inode->i_version++;
905         inode->i_nlink = 2;
906         inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
907         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
908 
909         dentry->d_time = dentry->d_parent->d_inode->i_version;
910         d_instantiate(dentry, inode);
911 
912         unlock_super(sb);
913         return 0;
914 
915 out_free:
916         fat_free_clusters(dir, cluster);
917 out:
918         unlock_super(sb);
919         return err;
920 }
921 
922 static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
923                        struct inode *new_dir, struct dentry *new_dentry)
924 {
925         struct buffer_head *dotdot_bh;
926         struct msdos_dir_entry *dotdot_de;
927         struct inode *old_inode, *new_inode;
928         struct fat_slot_info old_sinfo, sinfo;
929         struct timespec ts;
930         loff_t dotdot_i_pos, new_i_pos;
931         int err, is_dir, update_dotdot, corrupt = 0;
932         struct super_block *sb = old_dir->i_sb;
933 
934         old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
935         old_inode = old_dentry->d_inode;
936         new_inode = new_dentry->d_inode;
937         lock_super(sb);
938         err = vfat_find(old_dir, &old_dentry->d_name, &old_sinfo);
939         if (err)
940                 goto out;
941 
942         is_dir = S_ISDIR(old_inode->i_mode);
943         update_dotdot = (is_dir && old_dir != new_dir);
944         if (update_dotdot) {
945                 if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de,
946                                          &dotdot_i_pos) < 0) {
947                         err = -EIO;
948                         goto out;
949                 }
950         }
951 
952         ts = CURRENT_TIME_SEC;
953         if (new_inode) {
954                 if (is_dir) {
955                         err = fat_dir_empty(new_inode);
956                         if (err)
957                                 goto out;
958                 }
959                 new_i_pos = MSDOS_I(new_inode)->i_pos;
960                 fat_detach(new_inode);
961         } else {
962                 err = vfat_add_entry(new_dir, &new_dentry->d_name, is_dir, 0,
963                                      &ts, &sinfo);
964                 if (err)
965                         goto out;
966                 new_i_pos = sinfo.i_pos;
967         }
968         new_dir->i_version++;
969 
970         fat_detach(old_inode);
971         fat_attach(old_inode, new_i_pos);
972         if (IS_DIRSYNC(new_dir)) {
973                 err = fat_sync_inode(old_inode);
974                 if (err)
975                         goto error_inode;
976         } else
977                 mark_inode_dirty(old_inode);
978 
979         if (update_dotdot) {
980                 int start = MSDOS_I(new_dir)->i_logstart;
981                 dotdot_de->start = cpu_to_le16(start);
982                 dotdot_de->starthi = cpu_to_le16(start >> 16);
983                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
984                 if (IS_DIRSYNC(new_dir)) {
985                         err = sync_dirty_buffer(dotdot_bh);
986                         if (err)
987                                 goto error_dotdot;
988                 }
989                 drop_nlink(old_dir);
990                 if (!new_inode)
991                         inc_nlink(new_dir);
992         }
993 
994         err = fat_remove_entries(old_dir, &old_sinfo);  /* and releases bh */
995         old_sinfo.bh = NULL;
996         if (err)
997                 goto error_dotdot;
998         old_dir->i_version++;
999         old_dir->i_ctime = old_dir->i_mtime = ts;
1000         if (IS_DIRSYNC(old_dir))
1001                 (void)fat_sync_inode(old_dir);
1002         else
1003                 mark_inode_dirty(old_dir);
1004 
1005         if (new_inode) {
1006                 drop_nlink(new_inode);
1007                 if (is_dir)
1008                         drop_nlink(new_inode);
1009                 new_inode->i_ctime = ts;
1010         }
1011 out:
1012         brelse(sinfo.bh);
1013         brelse(dotdot_bh);
1014         brelse(old_sinfo.bh);
1015         unlock_super(sb);
1016 
1017         return err;
1018 
1019 error_dotdot:
1020         /* data cluster is shared, serious corruption */
1021         corrupt = 1;
1022 
1023         if (update_dotdot) {
1024                 int start = MSDOS_I(old_dir)->i_logstart;
1025                 dotdot_de->start = cpu_to_le16(start);
1026                 dotdot_de->starthi = cpu_to_le16(start >> 16);
1027                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
1028                 corrupt |= sync_dirty_buffer(dotdot_bh);
1029         }
1030 error_inode:
1031         fat_detach(old_inode);
1032         fat_attach(old_inode, old_sinfo.i_pos);
1033         if (new_inode) {
1034                 fat_attach(new_inode, new_i_pos);
1035                 if (corrupt)
1036                         corrupt |= fat_sync_inode(new_inode);
1037         } else {
1038                 /*
1039                  * If new entry was not sharing the data cluster, it
1040                  * shouldn't be serious corruption.
1041                  */
1042                 int err2 = fat_remove_entries(new_dir, &sinfo);
1043                 if (corrupt)
1044                         corrupt |= err2;
1045                 sinfo.bh = NULL;
1046         }
1047         if (corrupt < 0) {
1048                 fat_fs_error(new_dir->i_sb,
1049                              "%s: Filesystem corrupted (i_pos %lld)",
1050                              __func__, sinfo.i_pos);
1051         }
1052         goto out;
1053 }
1054 
1055 static const struct inode_operations vfat_dir_inode_operations = {
1056         .create         = vfat_create,
1057         .lookup         = vfat_lookup,
1058         .unlink         = vfat_unlink,
1059         .mkdir          = vfat_mkdir,
1060         .rmdir          = vfat_rmdir,
1061         .rename         = vfat_rename,
1062         .setattr        = fat_setattr,
1063         .getattr        = fat_getattr,
1064 };
1065 
1066 static void setup(struct super_block *sb)
1067 {
1068         if (MSDOS_SB(sb)->options.name_check != 's')
1069                 sb->s_d_op = &vfat_ci_dentry_ops;
1070         else
1071                 sb->s_d_op = &vfat_dentry_ops;
1072 }
1073 
1074 static int vfat_fill_super(struct super_block *sb, void *data, int silent)
1075 {
1076         return fat_fill_super(sb, data, silent, &vfat_dir_inode_operations,
1077                              1, setup);
1078 }
1079 
1080 static struct dentry *vfat_mount(struct file_system_type *fs_type,
1081                        int flags, const char *dev_name,
1082                        void *data)
1083 {
1084         return mount_bdev(fs_type, flags, dev_name, data, vfat_fill_super);
1085 }
1086 
1087 static struct file_system_type vfat_fs_type = {
1088         .owner          = THIS_MODULE,
1089         .name           = "vfat",
1090         .mount          = vfat_mount,
1091         .kill_sb        = kill_block_super,
1092         .fs_flags       = FS_REQUIRES_DEV,
1093 };
1094 
1095 static int __init init_vfat_fs(void)
1096 {
1097         return register_filesystem(&vfat_fs_type);
1098 }
1099 
1100 static void __exit exit_vfat_fs(void)
1101 {
1102         unregister_filesystem(&vfat_fs_type);
1103 }
1104 
1105 MODULE_LICENSE("GPL");
1106 MODULE_DESCRIPTION("VFAT filesystem support");
1107 MODULE_AUTHOR("Gordon Chaffee");
1108 
1109 module_init(init_vfat_fs)
1110 module_exit(exit_vfat_fs)
1111 

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