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