linux/fs/sysv/dir.c
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   1/*
   2 *  linux/fs/sysv/dir.c
   3 *
   4 *  minix/dir.c
   5 *  Copyright (C) 1991, 1992  Linus Torvalds
   6 *
   7 *  coh/dir.c
   8 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
   9 *
  10 *  sysv/dir.c
  11 *  Copyright (C) 1993  Bruno Haible
  12 *
  13 *  SystemV/Coherent directory handling functions
  14 */
  15
  16#include <linux/pagemap.h>
  17#include <linux/highmem.h>
  18#include <linux/swap.h>
  19#include "sysv.h"
  20
  21static int sysv_readdir(struct file *, void *, filldir_t);
  22
  23const struct file_operations sysv_dir_operations = {
  24        .llseek         = generic_file_llseek,
  25        .read           = generic_read_dir,
  26        .readdir        = sysv_readdir,
  27        .fsync          = generic_file_fsync,
  28};
  29
  30static inline void dir_put_page(struct page *page)
  31{
  32        kunmap(page);
  33        page_cache_release(page);
  34}
  35
  36static inline unsigned long dir_pages(struct inode *inode)
  37{
  38        return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  39}
  40
  41static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
  42{
  43        struct address_space *mapping = page->mapping;
  44        struct inode *dir = mapping->host;
  45        int err = 0;
  46
  47        block_write_end(NULL, mapping, pos, len, len, page, NULL);
  48        if (pos+len > dir->i_size) {
  49                i_size_write(dir, pos+len);
  50                mark_inode_dirty(dir);
  51        }
  52        if (IS_DIRSYNC(dir))
  53                err = write_one_page(page, 1);
  54        else
  55                unlock_page(page);
  56        return err;
  57}
  58
  59static struct page * dir_get_page(struct inode *dir, unsigned long n)
  60{
  61        struct address_space *mapping = dir->i_mapping;
  62        struct page *page = read_mapping_page(mapping, n, NULL);
  63        if (!IS_ERR(page))
  64                kmap(page);
  65        return page;
  66}
  67
  68static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
  69{
  70        unsigned long pos = filp->f_pos;
  71        struct inode *inode = filp->f_path.dentry->d_inode;
  72        struct super_block *sb = inode->i_sb;
  73        unsigned offset = pos & ~PAGE_CACHE_MASK;
  74        unsigned long n = pos >> PAGE_CACHE_SHIFT;
  75        unsigned long npages = dir_pages(inode);
  76
  77        pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
  78        if (pos >= inode->i_size)
  79                goto done;
  80
  81        for ( ; n < npages; n++, offset = 0) {
  82                char *kaddr, *limit;
  83                struct sysv_dir_entry *de;
  84                struct page *page = dir_get_page(inode, n);
  85
  86                if (IS_ERR(page))
  87                        continue;
  88                kaddr = (char *)page_address(page);
  89                de = (struct sysv_dir_entry *)(kaddr+offset);
  90                limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
  91                for ( ;(char*)de <= limit; de++) {
  92                        char *name = de->name;
  93                        int over;
  94
  95                        if (!de->inode)
  96                                continue;
  97
  98                        offset = (char *)de - kaddr;
  99
 100                        over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
 101                                        ((loff_t)n<<PAGE_CACHE_SHIFT) | offset,
 102                                        fs16_to_cpu(SYSV_SB(sb), de->inode),
 103                                        DT_UNKNOWN);
 104                        if (over) {
 105                                dir_put_page(page);
 106                                goto done;
 107                        }
 108                }
 109                dir_put_page(page);
 110        }
 111
 112done:
 113        filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) | offset;
 114        return 0;
 115}
 116
 117/* compare strings: name[0..len-1] (not zero-terminated) and
 118 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
 119 */
 120static inline int namecompare(int len, int maxlen,
 121        const char * name, const char * buffer)
 122{
 123        if (len < maxlen && buffer[len])
 124                return 0;
 125        return !memcmp(name, buffer, len);
 126}
 127
 128/*
 129 *      sysv_find_entry()
 130 *
 131 * finds an entry in the specified directory with the wanted name. It
 132 * returns the cache buffer in which the entry was found, and the entry
 133 * itself (as a parameter - res_dir). It does NOT read the inode of the
 134 * entry - you'll have to do that yourself if you want to.
 135 */
 136struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
 137{
 138        const char * name = dentry->d_name.name;
 139        int namelen = dentry->d_name.len;
 140        struct inode * dir = dentry->d_parent->d_inode;
 141        unsigned long start, n;
 142        unsigned long npages = dir_pages(dir);
 143        struct page *page = NULL;
 144        struct sysv_dir_entry *de;
 145
 146        *res_page = NULL;
 147
 148        start = SYSV_I(dir)->i_dir_start_lookup;
 149        if (start >= npages)
 150                start = 0;
 151        n = start;
 152
 153        do {
 154                char *kaddr;
 155                page = dir_get_page(dir, n);
 156                if (!IS_ERR(page)) {
 157                        kaddr = (char*)page_address(page);
 158                        de = (struct sysv_dir_entry *) kaddr;
 159                        kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
 160                        for ( ; (char *) de <= kaddr ; de++) {
 161                                if (!de->inode)
 162                                        continue;
 163                                if (namecompare(namelen, SYSV_NAMELEN,
 164                                                        name, de->name))
 165                                        goto found;
 166                        }
 167                        dir_put_page(page);
 168                }
 169
 170                if (++n >= npages)
 171                        n = 0;
 172        } while (n != start);
 173
 174        return NULL;
 175
 176found:
 177        SYSV_I(dir)->i_dir_start_lookup = n;
 178        *res_page = page;
 179        return de;
 180}
 181
 182int sysv_add_link(struct dentry *dentry, struct inode *inode)
 183{
 184        struct inode *dir = dentry->d_parent->d_inode;
 185        const char * name = dentry->d_name.name;
 186        int namelen = dentry->d_name.len;
 187        struct page *page = NULL;
 188        struct sysv_dir_entry * de;
 189        unsigned long npages = dir_pages(dir);
 190        unsigned long n;
 191        char *kaddr;
 192        loff_t pos;
 193        int err;
 194
 195        /* We take care of directory expansion in the same loop */
 196        for (n = 0; n <= npages; n++) {
 197                page = dir_get_page(dir, n);
 198                err = PTR_ERR(page);
 199                if (IS_ERR(page))
 200                        goto out;
 201                kaddr = (char*)page_address(page);
 202                de = (struct sysv_dir_entry *)kaddr;
 203                kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
 204                while ((char *)de <= kaddr) {
 205                        if (!de->inode)
 206                                goto got_it;
 207                        err = -EEXIST;
 208                        if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) 
 209                                goto out_page;
 210                        de++;
 211                }
 212                dir_put_page(page);
 213        }
 214        BUG();
 215        return -EINVAL;
 216
 217got_it:
 218        pos = page_offset(page) +
 219                        (char*)de - (char*)page_address(page);
 220        lock_page(page);
 221        err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 222        if (err)
 223                goto out_unlock;
 224        memcpy (de->name, name, namelen);
 225        memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
 226        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 227        err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 228        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 229        mark_inode_dirty(dir);
 230out_page:
 231        dir_put_page(page);
 232out:
 233        return err;
 234out_unlock:
 235        unlock_page(page);
 236        goto out_page;
 237}
 238
 239int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
 240{
 241        struct inode *inode = page->mapping->host;
 242        char *kaddr = (char*)page_address(page);
 243        loff_t pos = page_offset(page) + (char *)de - kaddr;
 244        int err;
 245
 246        lock_page(page);
 247        err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 248        BUG_ON(err);
 249        de->inode = 0;
 250        err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 251        dir_put_page(page);
 252        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 253        mark_inode_dirty(inode);
 254        return err;
 255}
 256
 257int sysv_make_empty(struct inode *inode, struct inode *dir)
 258{
 259        struct page *page = grab_cache_page(inode->i_mapping, 0);
 260        struct sysv_dir_entry * de;
 261        char *base;
 262        int err;
 263
 264        if (!page)
 265                return -ENOMEM;
 266        err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
 267        if (err) {
 268                unlock_page(page);
 269                goto fail;
 270        }
 271        kmap(page);
 272
 273        base = (char*)page_address(page);
 274        memset(base, 0, PAGE_CACHE_SIZE);
 275
 276        de = (struct sysv_dir_entry *) base;
 277        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 278        strcpy(de->name,".");
 279        de++;
 280        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
 281        strcpy(de->name,"..");
 282
 283        kunmap(page);
 284        err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
 285fail:
 286        page_cache_release(page);
 287        return err;
 288}
 289
 290/*
 291 * routine to check that the specified directory is empty (for rmdir)
 292 */
 293int sysv_empty_dir(struct inode * inode)
 294{
 295        struct super_block *sb = inode->i_sb;
 296        struct page *page = NULL;
 297        unsigned long i, npages = dir_pages(inode);
 298
 299        for (i = 0; i < npages; i++) {
 300                char *kaddr;
 301                struct sysv_dir_entry * de;
 302                page = dir_get_page(inode, i);
 303
 304                if (IS_ERR(page))
 305                        continue;
 306
 307                kaddr = (char *)page_address(page);
 308                de = (struct sysv_dir_entry *)kaddr;
 309                kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;
 310
 311                for ( ;(char *)de <= kaddr; de++) {
 312                        if (!de->inode)
 313                                continue;
 314                        /* check for . and .. */
 315                        if (de->name[0] != '.')
 316                                goto not_empty;
 317                        if (!de->name[1]) {
 318                                if (de->inode == cpu_to_fs16(SYSV_SB(sb),
 319                                                        inode->i_ino))
 320                                        continue;
 321                                goto not_empty;
 322                        }
 323                        if (de->name[1] != '.' || de->name[2])
 324                                goto not_empty;
 325                }
 326                dir_put_page(page);
 327        }
 328        return 1;
 329
 330not_empty:
 331        dir_put_page(page);
 332        return 0;
 333}
 334
 335/* Releases the page */
 336void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
 337        struct inode *inode)
 338{
 339        struct inode *dir = page->mapping->host;
 340        loff_t pos = page_offset(page) +
 341                        (char *)de-(char*)page_address(page);
 342        int err;
 343
 344        lock_page(page);
 345        err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 346        BUG_ON(err);
 347        de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 348        err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 349        dir_put_page(page);
 350        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
 351        mark_inode_dirty(dir);
 352}
 353
 354struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
 355{
 356        struct page *page = dir_get_page(dir, 0);
 357        struct sysv_dir_entry *de = NULL;
 358
 359        if (!IS_ERR(page)) {
 360                de = (struct sysv_dir_entry*) page_address(page) + 1;
 361                *p = page;
 362        }
 363        return de;
 364}
 365
 366ino_t sysv_inode_by_name(struct dentry *dentry)
 367{
 368        struct page *page;
 369        struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
 370        ino_t res = 0;
 371        
 372        if (de) {
 373                res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
 374                dir_put_page(page);
 375        }
 376        return res;
 377}
 378
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