fs/minix/dir.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/minix/dir.c
   4  *
   5  *  Copyright (C) 1991, 1992 Linus Torvalds
   6  *
   7  *  minix directory handling functions
   8  *
   9  *  Updated to filesystem version 3 by Daniel Aragones
  10  */
  11
  12 #include "minix.h"
  13 #include <linux/buffer_head.h>
  14 #include <linux/highmem.h>
  15 #include <linux/swap.h>
  16
  17 typedef struct minix_dir_entry minix_dirent;
  18 typedef struct minix3_dir_entry minix3_dirent;
  19
  20 static int minix_readdir(struct file *, struct dir_context *);
  21
  22 const struct file_operations minix_dir_operations = {
  23         .llseek         = generic_file_llseek,
  24         .read           = generic_read_dir,
  25         .iterate_shared = minix_readdir,
  26         .fsync          = generic_file_fsync,
  27 };
  28
  29 /*
  30  * Return the offset into page `page_nr' of the last valid
  31  * byte in that page, plus one.
  32  */
  33 static unsigned
  34 minix_last_byte(struct inode *inode, unsigned long page_nr)
  35 {
  36         unsigned last_byte = PAGE_SIZE;
  37
  38         if (page_nr == (inode->i_size >> PAGE_SHIFT))
  39                 last_byte = inode->i_size & (PAGE_SIZE - 1);
  40         return last_byte;
  41 }
  42
  43 static void dir_commit_chunk(struct folio *folio, loff_t pos, unsigned len)
  44 {
  45         struct address_space *mapping = folio->mapping;
  46         struct inode *dir = mapping->host;
  47
  48         block_write_end(NULL, mapping, pos, len, len, folio, NULL);
  49
  50         if (pos+len > dir->i_size) {
  51                 i_size_write(dir, pos+len);
  52                 mark_inode_dirty(dir);
  53         }
  54         folio_unlock(folio);
  55 }
  56
  57 static int minix_handle_dirsync(struct inode *dir)
  58 {
  59         int err;
  60
  61         err = filemap_write_and_wait(dir->i_mapping);
  62         if (!err)
  63                 err = sync_inode_metadata(dir, 1);
  64         return err;
  65 }
  66
  67 static void *dir_get_folio(struct inode *dir, unsigned long n,
  68                 struct folio **foliop)
  69 {
  70         struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);
  71
  72         if (IS_ERR(folio))
  73                 return ERR_CAST(folio);
  74         *foliop = folio;
  75         return kmap_local_folio(folio, 0);
  76 }
  77
  78 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
  79 {
  80         return (void*)((char*)de + sbi->s_dirsize);
  81 }
  82
  83 static int minix_readdir(struct file *file, struct dir_context *ctx)
  84 {
  85         struct inode *inode = file_inode(file);
  86         struct super_block *sb = inode->i_sb;
  87         struct minix_sb_info *sbi = minix_sb(sb);
  88         unsigned chunk_size = sbi->s_dirsize;
  89         unsigned long npages = dir_pages(inode);
  90         unsigned long pos = ctx->pos;
  91         unsigned offset;
  92         unsigned long n;
  93
  94         ctx->pos = pos = ALIGN(pos, chunk_size);
  95         if (pos >= inode->i_size)
  96                 return 0;
  97
  98         offset = pos & ~PAGE_MASK;
  99         n = pos >> PAGE_SHIFT;
 100
 101         for ( ; n < npages; n++, offset = 0) {
 102                 char *p, *kaddr, *limit;
 103                 struct folio *folio;
 104
 105                 kaddr = dir_get_folio(inode, n, &folio);
 106                 if (IS_ERR(kaddr))
 107                         continue;
 108                 p = kaddr+offset;
 109                 limit = kaddr + minix_last_byte(inode, n) - chunk_size;
 110                 for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
 111                         const char *name;
 112                         __u32 inumber;
 113                         if (sbi->s_version == MINIX_V3) {
 114                                 minix3_dirent *de3 = (minix3_dirent *)p;
 115                                 name = de3->name;
 116                                 inumber = de3->inode;
 117                         } else {
 118                                 minix_dirent *de = (minix_dirent *)p;
 119                                 name = de->name;
 120                                 inumber = de->inode;
 121                         }
 122                         if (inumber) {
 123                                 unsigned l = strnlen(name, sbi->s_namelen);
 124                                 if (!dir_emit(ctx, name, l,
 125                                               inumber, DT_UNKNOWN)) {
 126                                         folio_release_kmap(folio, p);
 127                                         return 0;
 128                                 }
 129                         }
 130                         ctx->pos += chunk_size;
 131                 }
 132                 folio_release_kmap(folio, kaddr);
 133         }
 134         return 0;
 135 }
 136
 137 static inline int namecompare(int len, int maxlen,
 138         const char * name, const char * buffer)
 139 {
 140         if (len < maxlen && buffer[len])
 141                 return 0;
 142         return !memcmp(name, buffer, len);
 143 }
 144
 145 /*
 146  *      minix_find_entry()
 147  *
 148  * finds an entry in the specified directory with the wanted name.
 149  * It does NOT read the inode of the
 150  * entry - you'll have to do that yourself if you want to.
 151  *
 152  * On Success folio_release_kmap() should be called on *foliop.
 153  */
 154 minix_dirent *minix_find_entry(struct dentry *dentry, struct folio **foliop)
 155 {
 156         const char * name = dentry->d_name.name;
 157         int namelen = dentry->d_name.len;
 158         struct inode * dir = d_inode(dentry->d_parent);
 159         struct super_block * sb = dir->i_sb;
 160         struct minix_sb_info * sbi = minix_sb(sb);
 161         unsigned long n;
 162         unsigned long npages = dir_pages(dir);
 163         char *p;
 164
 165         char *namx;
 166         __u32 inumber;
 167
 168         for (n = 0; n < npages; n++) {
 169                 char *kaddr, *limit;
 170
 171                 kaddr = dir_get_folio(dir, n, foliop);
 172                 if (IS_ERR(kaddr))
 173                         continue;
 174
 175                 limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
 176                 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 177                         if (sbi->s_version == MINIX_V3) {
 178                                 minix3_dirent *de3 = (minix3_dirent *)p;
 179                                 namx = de3->name;
 180                                 inumber = de3->inode;
 181                         } else {
 182                                 minix_dirent *de = (minix_dirent *)p;
 183                                 namx = de->name;
 184                                 inumber = de->inode;
 185                         }
 186                         if (!inumber)
 187                                 continue;
 188                         if (namecompare(namelen, sbi->s_namelen, name, namx))
 189                                 goto found;
 190                 }
 191                 folio_release_kmap(*foliop, kaddr);
 192         }
 193         return NULL;
 194
 195 found:
 196         return (minix_dirent *)p;
 197 }
 198
 199 int minix_add_link(struct dentry *dentry, struct inode *inode)
 200 {
 201         struct inode *dir = d_inode(dentry->d_parent);
 202         const char * name = dentry->d_name.name;
 203         int namelen = dentry->d_name.len;
 204         struct super_block * sb = dir->i_sb;
 205         struct minix_sb_info * sbi = minix_sb(sb);
 206         struct folio *folio = NULL;
 207         unsigned long npages = dir_pages(dir);
 208         unsigned long n;
 209         char *kaddr, *p;
 210         minix_dirent *de;
 211         minix3_dirent *de3;
 212         loff_t pos;
 213         int err;
 214         char *namx = NULL;
 215         __u32 inumber;
 216
 217         /*
 218          * We take care of directory expansion in the same loop
 219          * This code plays outside i_size, so it locks the page
 220          * to protect that region.
 221          */
 222         for (n = 0; n <= npages; n++) {
 223                 char *limit, *dir_end;
 224
 225                 kaddr = dir_get_folio(dir, n, &folio);
 226                 if (IS_ERR(kaddr))
 227                         return PTR_ERR(kaddr);
 228                 folio_lock(folio);
 229                 dir_end = kaddr + minix_last_byte(dir, n);
 230                 limit = kaddr + PAGE_SIZE - sbi->s_dirsize;
 231                 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 232                         de = (minix_dirent *)p;
 233                         de3 = (minix3_dirent *)p;
 234                         if (sbi->s_version == MINIX_V3) {
 235                                 namx = de3->name;
 236                                 inumber = de3->inode;
 237                         } else {
 238                                 namx = de->name;
 239                                 inumber = de->inode;
 240                         }
 241                         if (p == dir_end) {
 242                                 /* We hit i_size */
 243                                 if (sbi->s_version == MINIX_V3)
 244                                         de3->inode = 0;
 245                                 else
 246                                         de->inode = 0;
 247                                 goto got_it;
 248                         }
 249                         if (!inumber)
 250                                 goto got_it;
 251                         err = -EEXIST;
 252                         if (namecompare(namelen, sbi->s_namelen, name, namx))
 253                                 goto out_unlock;
 254                 }
 255                 folio_unlock(folio);
 256                 folio_release_kmap(folio, kaddr);
 257         }
 258         BUG();
 259         return -EINVAL;
 260
 261 got_it:
 262         pos = folio_pos(folio) + offset_in_folio(folio, p);
 263         err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
 264         if (err)
 265                 goto out_unlock;
 266         memcpy (namx, name, namelen);
 267         if (sbi->s_version == MINIX_V3) {
 268                 memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
 269                 de3->inode = inode->i_ino;
 270         } else {
 271                 memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
 272                 de->inode = inode->i_ino;
 273         }
 274         dir_commit_chunk(folio, pos, sbi->s_dirsize);
 275         inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 276         mark_inode_dirty(dir);
 277         err = minix_handle_dirsync(dir);
 278 out_put:
 279         folio_release_kmap(folio, kaddr);
 280         return err;
 281 out_unlock:
 282         folio_unlock(folio);
 283         goto out_put;
 284 }
 285
 286 int minix_delete_entry(struct minix_dir_entry *de, struct folio *folio)
 287 {
 288         struct inode *inode = folio->mapping->host;
 289         loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
 290         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 291         unsigned len = sbi->s_dirsize;
 292         int err;
 293
 294         folio_lock(folio);
 295         err = minix_prepare_chunk(folio, pos, len);
 296         if (err) {
 297                 folio_unlock(folio);
 298                 return err;
 299         }
 300         if (sbi->s_version == MINIX_V3)
 301                 ((minix3_dirent *)de)->inode = 0;
 302         else
 303                 de->inode = 0;
 304         dir_commit_chunk(folio, pos, len);
 305         inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
 306         mark_inode_dirty(inode);
 307         return minix_handle_dirsync(inode);
 308 }
 309
 310 int minix_make_empty(struct inode *inode, struct inode *dir)
 311 {
 312         struct folio *folio = filemap_grab_folio(inode->i_mapping, 0);
 313         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 314         char *kaddr;
 315         int err;
 316
 317         if (IS_ERR(folio))
 318                 return PTR_ERR(folio);
 319         err = minix_prepare_chunk(folio, 0, 2 * sbi->s_dirsize);
 320         if (err) {
 321                 folio_unlock(folio);
 322                 goto fail;
 323         }
 324
 325         kaddr = kmap_local_folio(folio, 0);
 326         memset(kaddr, 0, folio_size(folio));
 327
 328         if (sbi->s_version == MINIX_V3) {
 329                 minix3_dirent *de3 = (minix3_dirent *)kaddr;
 330
 331                 de3->inode = inode->i_ino;
 332                 strcpy(de3->name, ".");
 333                 de3 = minix_next_entry(de3, sbi);
 334                 de3->inode = dir->i_ino;
 335                 strcpy(de3->name, "..");
 336         } else {
 337                 minix_dirent *de = (minix_dirent *)kaddr;
 338
 339                 de->inode = inode->i_ino;
 340                 strcpy(de->name, ".");
 341                 de = minix_next_entry(de, sbi);
 342                 de->inode = dir->i_ino;
 343                 strcpy(de->name, "..");
 344         }
 345         kunmap_local(kaddr);
 346
 347         dir_commit_chunk(folio, 0, 2 * sbi->s_dirsize);
 348         err = minix_handle_dirsync(inode);
 349 fail:
 350         folio_put(folio);
 351         return err;
 352 }
 353
 354 /*
 355  * routine to check that the specified directory is empty (for rmdir)
 356  */
 357 int minix_empty_dir(struct inode * inode)
 358 {
 359         struct folio *folio = NULL;
 360         unsigned long i, npages = dir_pages(inode);
 361         struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 362         char *name, *kaddr;
 363         __u32 inumber;
 364
 365         for (i = 0; i < npages; i++) {
 366                 char *p, *limit;
 367
 368                 kaddr = dir_get_folio(inode, i, &folio);
 369                 if (IS_ERR(kaddr))
 370                         continue;
 371
 372                 limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
 373                 for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 374                         if (sbi->s_version == MINIX_V3) {
 375                                 minix3_dirent *de3 = (minix3_dirent *)p;
 376                                 name = de3->name;
 377                                 inumber = de3->inode;
 378                         } else {
 379                                 minix_dirent *de = (minix_dirent *)p;
 380                                 name = de->name;
 381                                 inumber = de->inode;
 382                         }
 383
 384                         if (inumber != 0) {
 385                                 /* check for . and .. */
 386                                 if (name[0] != '.')
 387                                         goto not_empty;
 388                                 if (!name[1]) {
 389                                         if (inumber != inode->i_ino)
 390                                                 goto not_empty;
 391                                 } else if (name[1] != '.')
 392                                         goto not_empty;
 393                                 else if (name[2])
 394                                         goto not_empty;
 395                         }
 396                 }
 397                 folio_release_kmap(folio, kaddr);
 398         }
 399         return 1;
 400
 401 not_empty:
 402         folio_release_kmap(folio, kaddr);
 403         return 0;
 404 }
 405
 406 /* Releases the page */
 407 int minix_set_link(struct minix_dir_entry *de, struct folio *folio,
 408                 struct inode *inode)
 409 {
 410         struct inode *dir = folio->mapping->host;
 411         struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 412         loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
 413         int err;
 414
 415         folio_lock(folio);
 416         err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
 417         if (err) {
 418                 folio_unlock(folio);
 419                 return err;
 420         }
 421         if (sbi->s_version == MINIX_V3)
 422                 ((minix3_dirent *)de)->inode = inode->i_ino;
 423         else
 424                 de->inode = inode->i_ino;
 425         dir_commit_chunk(folio, pos, sbi->s_dirsize);
 426         inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 427         mark_inode_dirty(dir);
 428         return minix_handle_dirsync(dir);
 429 }
 430
 431 struct minix_dir_entry *minix_dotdot(struct inode *dir, struct folio **foliop)
 432 {
 433         struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 434         struct minix_dir_entry *de = dir_get_folio(dir, 0, foliop);
 435
 436         if (!IS_ERR(de))
 437                 return minix_next_entry(de, sbi);
 438         return NULL;
 439 }
 440
 441 ino_t minix_inode_by_name(struct dentry *dentry)
 442 {
 443         struct folio *folio;
 444         struct minix_dir_entry *de = minix_find_entry(dentry, &folio);
 445         ino_t res = 0;
 446
 447         if (de) {
 448                 struct inode *inode = folio->mapping->host;
 449                 struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 450
 451                 if (sbi->s_version == MINIX_V3)
 452                         res = ((minix3_dirent *) de)->inode;
 453                 else
 454                         res = de->inode;
 455                 folio_release_kmap(folio, de);
 456         }
 457         return res;
 458 }