linux/fs/minix/dir.c
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   1/*
   2 *  linux/fs/minix/dir.c
   3 *
   4 *  Copyright (C) 1991, 1992 Linus Torvalds
   5 *
   6 *  minix directory handling functions
   7 *
   8 *  Updated to filesystem version 3 by Daniel Aragones
   9 */
  10
  11#include "minix.h"
  12#include <linux/buffer_head.h>
  13#include <linux/highmem.h>
  14#include <linux/smp_lock.h>
  15#include <linux/swap.h>
  16
  17typedef struct minix_dir_entry minix_dirent;
  18typedef struct minix3_dir_entry minix3_dirent;
  19
  20static int minix_readdir(struct file *, void *, filldir_t);
  21
  22const struct file_operations minix_dir_operations = {
  23        .read           = generic_read_dir,
  24        .readdir        = minix_readdir,
  25        .fsync          = minix_sync_file,
  26};
  27
  28static inline void dir_put_page(struct page *page)
  29{
  30        kunmap(page);
  31        page_cache_release(page);
  32}
  33
  34/*
  35 * Return the offset into page `page_nr' of the last valid
  36 * byte in that page, plus one.
  37 */
  38static unsigned
  39minix_last_byte(struct inode *inode, unsigned long page_nr)
  40{
  41        unsigned last_byte = PAGE_CACHE_SIZE;
  42
  43        if (page_nr == (inode->i_size >> PAGE_CACHE_SHIFT))
  44                last_byte = inode->i_size & (PAGE_CACHE_SIZE - 1);
  45        return last_byte;
  46}
  47
  48static inline unsigned long dir_pages(struct inode *inode)
  49{
  50        return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  51}
  52
  53static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
  54{
  55        struct address_space *mapping = page->mapping;
  56        struct inode *dir = mapping->host;
  57        int err = 0;
  58        block_write_end(NULL, mapping, pos, len, len, page, NULL);
  59
  60        if (pos+len > dir->i_size) {
  61                i_size_write(dir, pos+len);
  62                mark_inode_dirty(dir);
  63        }
  64        if (IS_DIRSYNC(dir))
  65                err = write_one_page(page, 1);
  66        else
  67                unlock_page(page);
  68        return err;
  69}
  70
  71static struct page * dir_get_page(struct inode *dir, unsigned long n)
  72{
  73        struct address_space *mapping = dir->i_mapping;
  74        struct page *page = read_mapping_page(mapping, n, NULL);
  75        if (!IS_ERR(page)) {
  76                kmap(page);
  77                if (!PageUptodate(page))
  78                        goto fail;
  79        }
  80        return page;
  81
  82fail:
  83        dir_put_page(page);
  84        return ERR_PTR(-EIO);
  85}
  86
  87static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
  88{
  89        return (void*)((char*)de + sbi->s_dirsize);
  90}
  91
  92static int minix_readdir(struct file * filp, void * dirent, filldir_t filldir)
  93{
  94        unsigned long pos = filp->f_pos;
  95        struct inode *inode = filp->f_path.dentry->d_inode;
  96        struct super_block *sb = inode->i_sb;
  97        unsigned offset = pos & ~PAGE_CACHE_MASK;
  98        unsigned long n = pos >> PAGE_CACHE_SHIFT;
  99        unsigned long npages = dir_pages(inode);
 100        struct minix_sb_info *sbi = minix_sb(sb);
 101        unsigned chunk_size = sbi->s_dirsize;
 102        char *name;
 103        __u32 inumber;
 104
 105        lock_kernel();
 106
 107        pos = (pos + chunk_size-1) & ~(chunk_size-1);
 108        if (pos >= inode->i_size)
 109                goto done;
 110
 111        for ( ; n < npages; n++, offset = 0) {
 112                char *p, *kaddr, *limit;
 113                struct page *page = dir_get_page(inode, n);
 114
 115                if (IS_ERR(page))
 116                        continue;
 117                kaddr = (char *)page_address(page);
 118                p = kaddr+offset;
 119                limit = kaddr + minix_last_byte(inode, n) - chunk_size;
 120                for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
 121                        if (sbi->s_version == MINIX_V3) {
 122                                minix3_dirent *de3 = (minix3_dirent *)p;
 123                                name = de3->name;
 124                                inumber = de3->inode;
 125                        } else {
 126                                minix_dirent *de = (minix_dirent *)p;
 127                                name = de->name;
 128                                inumber = de->inode;
 129                        }
 130                        if (inumber) {
 131                                int over;
 132
 133                                unsigned l = strnlen(name, sbi->s_namelen);
 134                                offset = p - kaddr;
 135                                over = filldir(dirent, name, l,
 136                                        (n << PAGE_CACHE_SHIFT) | offset,
 137                                        inumber, DT_UNKNOWN);
 138                                if (over) {
 139                                        dir_put_page(page);
 140                                        goto done;
 141                                }
 142                        }
 143                }
 144                dir_put_page(page);
 145        }
 146
 147done:
 148        filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
 149        unlock_kernel();
 150        return 0;
 151}
 152
 153static inline int namecompare(int len, int maxlen,
 154        const char * name, const char * buffer)
 155{
 156        if (len < maxlen && buffer[len])
 157                return 0;
 158        return !memcmp(name, buffer, len);
 159}
 160
 161/*
 162 *      minix_find_entry()
 163 *
 164 * finds an entry in the specified directory with the wanted name. It
 165 * returns the cache buffer in which the entry was found, and the entry
 166 * itself (as a parameter - res_dir). It does NOT read the inode of the
 167 * entry - you'll have to do that yourself if you want to.
 168 */
 169minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)
 170{
 171        const char * name = dentry->d_name.name;
 172        int namelen = dentry->d_name.len;
 173        struct inode * dir = dentry->d_parent->d_inode;
 174        struct super_block * sb = dir->i_sb;
 175        struct minix_sb_info * sbi = minix_sb(sb);
 176        unsigned long n;
 177        unsigned long npages = dir_pages(dir);
 178        struct page *page = NULL;
 179        char *p;
 180
 181        char *namx;
 182        __u32 inumber;
 183        *res_page = NULL;
 184
 185        for (n = 0; n < npages; n++) {
 186                char *kaddr, *limit;
 187
 188                page = dir_get_page(dir, n);
 189                if (IS_ERR(page))
 190                        continue;
 191
 192                kaddr = (char*)page_address(page);
 193                limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
 194                for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 195                        if (sbi->s_version == MINIX_V3) {
 196                                minix3_dirent *de3 = (minix3_dirent *)p;
 197                                namx = de3->name;
 198                                inumber = de3->inode;
 199                        } else {
 200                                minix_dirent *de = (minix_dirent *)p;
 201                                namx = de->name;
 202                                inumber = de->inode;
 203                        }
 204                        if (!inumber)
 205                                continue;
 206                        if (namecompare(namelen, sbi->s_namelen, name, namx))
 207                                goto found;
 208                }
 209                dir_put_page(page);
 210        }
 211        return NULL;
 212
 213found:
 214        *res_page = page;
 215        return (minix_dirent *)p;
 216}
 217
 218int minix_add_link(struct dentry *dentry, struct inode *inode)
 219{
 220        struct inode *dir = dentry->d_parent->d_inode;
 221        const char * name = dentry->d_name.name;
 222        int namelen = dentry->d_name.len;
 223        struct super_block * sb = dir->i_sb;
 224        struct minix_sb_info * sbi = minix_sb(sb);
 225        struct page *page = NULL;
 226        unsigned long npages = dir_pages(dir);
 227        unsigned long n;
 228        char *kaddr, *p;
 229        minix_dirent *de;
 230        minix3_dirent *de3;
 231        loff_t pos;
 232        int err;
 233        char *namx = NULL;
 234        __u32 inumber;
 235
 236        /*
 237         * We take care of directory expansion in the same loop
 238         * This code plays outside i_size, so it locks the page
 239         * to protect that region.
 240         */
 241        for (n = 0; n <= npages; n++) {
 242                char *limit, *dir_end;
 243
 244                page = dir_get_page(dir, n);
 245                err = PTR_ERR(page);
 246                if (IS_ERR(page))
 247                        goto out;
 248                lock_page(page);
 249                kaddr = (char*)page_address(page);
 250                dir_end = kaddr + minix_last_byte(dir, n);
 251                limit = kaddr + PAGE_CACHE_SIZE - sbi->s_dirsize;
 252                for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 253                        de = (minix_dirent *)p;
 254                        de3 = (minix3_dirent *)p;
 255                        if (sbi->s_version == MINIX_V3) {
 256                                namx = de3->name;
 257                                inumber = de3->inode;
 258                        } else {
 259                                namx = de->name;
 260                                inumber = de->inode;
 261                        }
 262                        if (p == dir_end) {
 263                                /* We hit i_size */
 264                                if (sbi->s_version == MINIX_V3)
 265                                        de3->inode = 0;
 266                                else
 267                                        de->inode = 0;
 268                                goto got_it;
 269                        }
 270                        if (!inumber)
 271                                goto got_it;
 272                        err = -EEXIST;
 273                        if (namecompare(namelen, sbi->s_namelen, name, namx))
 274                                goto out_unlock;
 275                }
 276                unlock_page(page);
 277                dir_put_page(page);
 278        }
 279        BUG();
 280        return -EINVAL;
 281
 282got_it:
 283        pos = (page->index >> PAGE_CACHE_SHIFT) + p - (char*)page_address(page);
 284        err = __minix_write_begin(NULL, page->mapping, pos, sbi->s_dirsize,
 285                                        AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 286        if (err)
 287                goto out_unlock;
 288        memcpy (namx, name, namelen);
 289        if (sbi->s_version == MINIX_V3) {
 290                memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
 291                de3->inode = inode->i_ino;
 292        } else {
 293                memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
 294                de->inode = inode->i_ino;
 295        }
 296        err = dir_commit_chunk(page, pos, sbi->s_dirsize);
 297        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 298        mark_inode_dirty(dir);
 299out_put:
 300        dir_put_page(page);
 301out:
 302        return err;
 303out_unlock:
 304        unlock_page(page);
 305        goto out_put;
 306}
 307
 308int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
 309{
 310        struct address_space *mapping = page->mapping;
 311        struct inode *inode = (struct inode*)mapping->host;
 312        char *kaddr = page_address(page);
 313        loff_t pos = page_offset(page) + (char*)de - kaddr;
 314        unsigned len = minix_sb(inode->i_sb)->s_dirsize;
 315        int err;
 316
 317        lock_page(page);
 318        err = __minix_write_begin(NULL, mapping, pos, len,
 319                                        AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 320        if (err == 0) {
 321                de->inode = 0;
 322                err = dir_commit_chunk(page, pos, len);
 323        } else {
 324                unlock_page(page);
 325        }
 326        dir_put_page(page);
 327        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 328        mark_inode_dirty(inode);
 329        return err;
 330}
 331
 332int minix_make_empty(struct inode *inode, struct inode *dir)
 333{
 334        struct address_space *mapping = inode->i_mapping;
 335        struct page *page = grab_cache_page(mapping, 0);
 336        struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 337        char *kaddr;
 338        int err;
 339
 340        if (!page)
 341                return -ENOMEM;
 342        err = __minix_write_begin(NULL, mapping, 0, 2 * sbi->s_dirsize,
 343                                        AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 344        if (err) {
 345                unlock_page(page);
 346                goto fail;
 347        }
 348
 349        kaddr = kmap_atomic(page, KM_USER0);
 350        memset(kaddr, 0, PAGE_CACHE_SIZE);
 351
 352        if (sbi->s_version == MINIX_V3) {
 353                minix3_dirent *de3 = (minix3_dirent *)kaddr;
 354
 355                de3->inode = inode->i_ino;
 356                strcpy(de3->name, ".");
 357                de3 = minix_next_entry(de3, sbi);
 358                de3->inode = dir->i_ino;
 359                strcpy(de3->name, "..");
 360        } else {
 361                minix_dirent *de = (minix_dirent *)kaddr;
 362
 363                de->inode = inode->i_ino;
 364                strcpy(de->name, ".");
 365                de = minix_next_entry(de, sbi);
 366                de->inode = dir->i_ino;
 367                strcpy(de->name, "..");
 368        }
 369        kunmap_atomic(kaddr, KM_USER0);
 370
 371        err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
 372fail:
 373        page_cache_release(page);
 374        return err;
 375}
 376
 377/*
 378 * routine to check that the specified directory is empty (for rmdir)
 379 */
 380int minix_empty_dir(struct inode * inode)
 381{
 382        struct page *page = NULL;
 383        unsigned long i, npages = dir_pages(inode);
 384        struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 385        char *name;
 386        __u32 inumber;
 387
 388        for (i = 0; i < npages; i++) {
 389                char *p, *kaddr, *limit;
 390
 391                page = dir_get_page(inode, i);
 392                if (IS_ERR(page))
 393                        continue;
 394
 395                kaddr = (char *)page_address(page);
 396                limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
 397                for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 398                        if (sbi->s_version == MINIX_V3) {
 399                                minix3_dirent *de3 = (minix3_dirent *)p;
 400                                name = de3->name;
 401                                inumber = de3->inode;
 402                        } else {
 403                                minix_dirent *de = (minix_dirent *)p;
 404                                name = de->name;
 405                                inumber = de->inode;
 406                        }
 407
 408                        if (inumber != 0) {
 409                                /* check for . and .. */
 410                                if (name[0] != '.')
 411                                        goto not_empty;
 412                                if (!name[1]) {
 413                                        if (inumber != inode->i_ino)
 414                                                goto not_empty;
 415                                } else if (name[1] != '.')
 416                                        goto not_empty;
 417                                else if (name[2])
 418                                        goto not_empty;
 419                        }
 420                }
 421                dir_put_page(page);
 422        }
 423        return 1;
 424
 425not_empty:
 426        dir_put_page(page);
 427        return 0;
 428}
 429
 430/* Releases the page */
 431void minix_set_link(struct minix_dir_entry *de, struct page *page,
 432        struct inode *inode)
 433{
 434        struct address_space *mapping = page->mapping;
 435        struct inode *dir = mapping->host;
 436        struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 437        loff_t pos = page_offset(page) +
 438                        (char *)de-(char*)page_address(page);
 439        int err;
 440
 441        lock_page(page);
 442
 443        err = __minix_write_begin(NULL, mapping, pos, sbi->s_dirsize,
 444                                        AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
 445        if (err == 0) {
 446                de->inode = inode->i_ino;
 447                err = dir_commit_chunk(page, pos, sbi->s_dirsize);
 448        } else {
 449                unlock_page(page);
 450        }
 451        dir_put_page(page);
 452        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 453        mark_inode_dirty(dir);
 454}
 455
 456struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
 457{
 458        struct page *page = dir_get_page(dir, 0);
 459        struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 460        struct minix_dir_entry *de = NULL;
 461
 462        if (!IS_ERR(page)) {
 463                de = minix_next_entry(page_address(page), sbi);
 464                *p = page;
 465        }
 466        return de;
 467}
 468
 469ino_t minix_inode_by_name(struct dentry *dentry)
 470{
 471        struct page *page;
 472        struct minix_dir_entry *de = minix_find_entry(dentry, &page);
 473        ino_t res = 0;
 474
 475        if (de) {
 476                res = de->inode;
 477                dir_put_page(page);
 478        }
 479        return res;
 480}
 481