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TOMOYO Linux Cross Reference
Linux/fs/ext3/dir.c

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  1 /*
  2  *  linux/fs/ext3/dir.c
  3  *
  4  * Copyright (C) 1992, 1993, 1994, 1995
  5  * Remy Card (card@masi.ibp.fr)
  6  * Laboratoire MASI - Institut Blaise Pascal
  7  * Universite Pierre et Marie Curie (Paris VI)
  8  *
  9  *  from
 10  *
 11  *  linux/fs/minix/dir.c
 12  *
 13  *  Copyright (C) 1991, 1992  Linus Torvalds
 14  *
 15  *  ext3 directory handling functions
 16  *
 17  *  Big-endian to little-endian byte-swapping/bitmaps by
 18  *        David S. Miller (davem@caip.rutgers.edu), 1995
 19  *
 20  * Hash Tree Directory indexing (c) 2001  Daniel Phillips
 21  *
 22  */
 23 
 24 #include <linux/compat.h>
 25 #include "ext3.h"
 26 
 27 static unsigned char ext3_filetype_table[] = {
 28         DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
 29 };
 30 
 31 static int ext3_dx_readdir(struct file *, struct dir_context *);
 32 
 33 static unsigned char get_dtype(struct super_block *sb, int filetype)
 34 {
 35         if (!EXT3_HAS_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_FILETYPE) ||
 36             (filetype >= EXT3_FT_MAX))
 37                 return DT_UNKNOWN;
 38 
 39         return (ext3_filetype_table[filetype]);
 40 }
 41 
 42 /**
 43  * Check if the given dir-inode refers to an htree-indexed directory
 44  * (or a directory which could potentially get converted to use htree
 45  * indexing).
 46  *
 47  * Return 1 if it is a dx dir, 0 if not
 48  */
 49 static int is_dx_dir(struct inode *inode)
 50 {
 51         struct super_block *sb = inode->i_sb;
 52 
 53         if (EXT3_HAS_COMPAT_FEATURE(inode->i_sb,
 54                      EXT3_FEATURE_COMPAT_DIR_INDEX) &&
 55             ((EXT3_I(inode)->i_flags & EXT3_INDEX_FL) ||
 56              ((inode->i_size >> sb->s_blocksize_bits) == 1)))
 57                 return 1;
 58 
 59         return 0;
 60 }
 61 
 62 int ext3_check_dir_entry (const char * function, struct inode * dir,
 63                           struct ext3_dir_entry_2 * de,
 64                           struct buffer_head * bh,
 65                           unsigned long offset)
 66 {
 67         const char * error_msg = NULL;
 68         const int rlen = ext3_rec_len_from_disk(de->rec_len);
 69 
 70         if (unlikely(rlen < EXT3_DIR_REC_LEN(1)))
 71                 error_msg = "rec_len is smaller than minimal";
 72         else if (unlikely(rlen % 4 != 0))
 73                 error_msg = "rec_len % 4 != 0";
 74         else if (unlikely(rlen < EXT3_DIR_REC_LEN(de->name_len)))
 75                 error_msg = "rec_len is too small for name_len";
 76         else if (unlikely((((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)))
 77                 error_msg = "directory entry across blocks";
 78         else if (unlikely(le32_to_cpu(de->inode) >
 79                         le32_to_cpu(EXT3_SB(dir->i_sb)->s_es->s_inodes_count)))
 80                 error_msg = "inode out of bounds";
 81 
 82         if (unlikely(error_msg != NULL))
 83                 ext3_error (dir->i_sb, function,
 84                         "bad entry in directory #%lu: %s - "
 85                         "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
 86                         dir->i_ino, error_msg, offset,
 87                         (unsigned long) le32_to_cpu(de->inode),
 88                         rlen, de->name_len);
 89 
 90         return error_msg == NULL ? 1 : 0;
 91 }
 92 
 93 static int ext3_readdir(struct file *file, struct dir_context *ctx)
 94 {
 95         unsigned long offset;
 96         int i;
 97         struct ext3_dir_entry_2 *de;
 98         int err;
 99         struct inode *inode = file_inode(file);
100         struct super_block *sb = inode->i_sb;
101         int dir_has_error = 0;
102 
103         if (is_dx_dir(inode)) {
104                 err = ext3_dx_readdir(file, ctx);
105                 if (err != ERR_BAD_DX_DIR)
106                         return err;
107                 /*
108                  * We don't set the inode dirty flag since it's not
109                  * critical that it get flushed back to the disk.
110                  */
111                 EXT3_I(inode)->i_flags &= ~EXT3_INDEX_FL;
112         }
113         offset = ctx->pos & (sb->s_blocksize - 1);
114 
115         while (ctx->pos < inode->i_size) {
116                 unsigned long blk = ctx->pos >> EXT3_BLOCK_SIZE_BITS(sb);
117                 struct buffer_head map_bh;
118                 struct buffer_head *bh = NULL;
119 
120                 map_bh.b_state = 0;
121                 err = ext3_get_blocks_handle(NULL, inode, blk, 1, &map_bh, 0);
122                 if (err > 0) {
123                         pgoff_t index = map_bh.b_blocknr >>
124                                         (PAGE_CACHE_SHIFT - inode->i_blkbits);
125                         if (!ra_has_index(&file->f_ra, index))
126                                 page_cache_sync_readahead(
127                                         sb->s_bdev->bd_inode->i_mapping,
128                                         &file->f_ra, file,
129                                         index, 1);
130                         file->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
131                         bh = ext3_bread(NULL, inode, blk, 0, &err);
132                 }
133 
134                 /*
135                  * We ignore I/O errors on directories so users have a chance
136                  * of recovering data when there's a bad sector
137                  */
138                 if (!bh) {
139                         if (!dir_has_error) {
140                                 ext3_error(sb, __func__, "directory #%lu "
141                                         "contains a hole at offset %lld",
142                                         inode->i_ino, ctx->pos);
143                                 dir_has_error = 1;
144                         }
145                         /* corrupt size?  Maybe no more blocks to read */
146                         if (ctx->pos > inode->i_blocks << 9)
147                                 break;
148                         ctx->pos += sb->s_blocksize - offset;
149                         continue;
150                 }
151 
152                 /* If the dir block has changed since the last call to
153                  * readdir(2), then we might be pointing to an invalid
154                  * dirent right now.  Scan from the start of the block
155                  * to make sure. */
156                 if (offset && file->f_version != inode->i_version) {
157                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
158                                 de = (struct ext3_dir_entry_2 *)
159                                         (bh->b_data + i);
160                                 /* It's too expensive to do a full
161                                  * dirent test each time round this
162                                  * loop, but we do have to test at
163                                  * least that it is non-zero.  A
164                                  * failure will be detected in the
165                                  * dirent test below. */
166                                 if (ext3_rec_len_from_disk(de->rec_len) <
167                                                 EXT3_DIR_REC_LEN(1))
168                                         break;
169                                 i += ext3_rec_len_from_disk(de->rec_len);
170                         }
171                         offset = i;
172                         ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
173                                 | offset;
174                         file->f_version = inode->i_version;
175                 }
176 
177                 while (ctx->pos < inode->i_size
178                        && offset < sb->s_blocksize) {
179                         de = (struct ext3_dir_entry_2 *) (bh->b_data + offset);
180                         if (!ext3_check_dir_entry ("ext3_readdir", inode, de,
181                                                    bh, offset)) {
182                                 /* On error, skip the to the
183                                    next block. */
184                                 ctx->pos = (ctx->pos |
185                                                 (sb->s_blocksize - 1)) + 1;
186                                 break;
187                         }
188                         offset += ext3_rec_len_from_disk(de->rec_len);
189                         if (le32_to_cpu(de->inode)) {
190                                 if (!dir_emit(ctx, de->name, de->name_len,
191                                               le32_to_cpu(de->inode),
192                                               get_dtype(sb, de->file_type))) {
193                                         brelse(bh);
194                                         return 0;
195                                 }
196                         }
197                         ctx->pos += ext3_rec_len_from_disk(de->rec_len);
198                 }
199                 offset = 0;
200                 brelse (bh);
201                 if (ctx->pos < inode->i_size)
202                         if (!dir_relax(inode))
203                                 return 0;
204         }
205         return 0;
206 }
207 
208 static inline int is_32bit_api(void)
209 {
210 #ifdef CONFIG_COMPAT
211         return is_compat_task();
212 #else
213         return (BITS_PER_LONG == 32);
214 #endif
215 }
216 
217 /*
218  * These functions convert from the major/minor hash to an f_pos
219  * value for dx directories
220  *
221  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
222  * FMODE_64BITHASH explicitly. On the other hand, we allow ext3 to be mounted
223  * directly on both 32-bit and 64-bit nodes, under such case, neither
224  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
225  */
226 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
227 {
228         if ((filp->f_mode & FMODE_32BITHASH) ||
229             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
230                 return major >> 1;
231         else
232                 return ((__u64)(major >> 1) << 32) | (__u64)minor;
233 }
234 
235 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
236 {
237         if ((filp->f_mode & FMODE_32BITHASH) ||
238             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
239                 return (pos << 1) & 0xffffffff;
240         else
241                 return ((pos >> 32) << 1) & 0xffffffff;
242 }
243 
244 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
245 {
246         if ((filp->f_mode & FMODE_32BITHASH) ||
247             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
248                 return 0;
249         else
250                 return pos & 0xffffffff;
251 }
252 
253 /*
254  * Return 32- or 64-bit end-of-file for dx directories
255  */
256 static inline loff_t ext3_get_htree_eof(struct file *filp)
257 {
258         if ((filp->f_mode & FMODE_32BITHASH) ||
259             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
260                 return EXT3_HTREE_EOF_32BIT;
261         else
262                 return EXT3_HTREE_EOF_64BIT;
263 }
264 
265 
266 /*
267  * ext3_dir_llseek() calls generic_file_llseek[_size]() to handle both
268  * non-htree and htree directories, where the "offset" is in terms
269  * of the filename hash value instead of the byte offset.
270  *
271  * Because we may return a 64-bit hash that is well beyond s_maxbytes,
272  * we need to pass the max hash as the maximum allowable offset in
273  * the htree directory case.
274  *
275  * NOTE: offsets obtained *before* ext3_set_inode_flag(dir, EXT3_INODE_INDEX)
276  *       will be invalid once the directory was converted into a dx directory
277  */
278 static loff_t ext3_dir_llseek(struct file *file, loff_t offset, int whence)
279 {
280         struct inode *inode = file->f_mapping->host;
281         int dx_dir = is_dx_dir(inode);
282         loff_t htree_max = ext3_get_htree_eof(file);
283 
284         if (likely(dx_dir))
285                 return generic_file_llseek_size(file, offset, whence,
286                                                 htree_max, htree_max);
287         else
288                 return generic_file_llseek(file, offset, whence);
289 }
290 
291 /*
292  * This structure holds the nodes of the red-black tree used to store
293  * the directory entry in hash order.
294  */
295 struct fname {
296         __u32           hash;
297         __u32           minor_hash;
298         struct rb_node  rb_hash;
299         struct fname    *next;
300         __u32           inode;
301         __u8            name_len;
302         __u8            file_type;
303         char            name[0];
304 };
305 
306 /*
307  * This functoin implements a non-recursive way of freeing all of the
308  * nodes in the red-black tree.
309  */
310 static void free_rb_tree_fname(struct rb_root *root)
311 {
312         struct fname *fname, *next;
313 
314         rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
315                 do {
316                         struct fname *old = fname;
317                         fname = fname->next;
318                         kfree(old);
319                 } while (fname);
320 
321         *root = RB_ROOT;
322 }
323 
324 static struct dir_private_info *ext3_htree_create_dir_info(struct file *filp,
325                                                            loff_t pos)
326 {
327         struct dir_private_info *p;
328 
329         p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
330         if (!p)
331                 return NULL;
332         p->curr_hash = pos2maj_hash(filp, pos);
333         p->curr_minor_hash = pos2min_hash(filp, pos);
334         return p;
335 }
336 
337 void ext3_htree_free_dir_info(struct dir_private_info *p)
338 {
339         free_rb_tree_fname(&p->root);
340         kfree(p);
341 }
342 
343 /*
344  * Given a directory entry, enter it into the fname rb tree.
345  */
346 int ext3_htree_store_dirent(struct file *dir_file, __u32 hash,
347                              __u32 minor_hash,
348                              struct ext3_dir_entry_2 *dirent)
349 {
350         struct rb_node **p, *parent = NULL;
351         struct fname * fname, *new_fn;
352         struct dir_private_info *info;
353         int len;
354 
355         info = (struct dir_private_info *) dir_file->private_data;
356         p = &info->root.rb_node;
357 
358         /* Create and allocate the fname structure */
359         len = sizeof(struct fname) + dirent->name_len + 1;
360         new_fn = kzalloc(len, GFP_KERNEL);
361         if (!new_fn)
362                 return -ENOMEM;
363         new_fn->hash = hash;
364         new_fn->minor_hash = minor_hash;
365         new_fn->inode = le32_to_cpu(dirent->inode);
366         new_fn->name_len = dirent->name_len;
367         new_fn->file_type = dirent->file_type;
368         memcpy(new_fn->name, dirent->name, dirent->name_len);
369         new_fn->name[dirent->name_len] = 0;
370 
371         while (*p) {
372                 parent = *p;
373                 fname = rb_entry(parent, struct fname, rb_hash);
374 
375                 /*
376                  * If the hash and minor hash match up, then we put
377                  * them on a linked list.  This rarely happens...
378                  */
379                 if ((new_fn->hash == fname->hash) &&
380                     (new_fn->minor_hash == fname->minor_hash)) {
381                         new_fn->next = fname->next;
382                         fname->next = new_fn;
383                         return 0;
384                 }
385 
386                 if (new_fn->hash < fname->hash)
387                         p = &(*p)->rb_left;
388                 else if (new_fn->hash > fname->hash)
389                         p = &(*p)->rb_right;
390                 else if (new_fn->minor_hash < fname->minor_hash)
391                         p = &(*p)->rb_left;
392                 else /* if (new_fn->minor_hash > fname->minor_hash) */
393                         p = &(*p)->rb_right;
394         }
395 
396         rb_link_node(&new_fn->rb_hash, parent, p);
397         rb_insert_color(&new_fn->rb_hash, &info->root);
398         return 0;
399 }
400 
401 
402 
403 /*
404  * This is a helper function for ext3_dx_readdir.  It calls filldir
405  * for all entres on the fname linked list.  (Normally there is only
406  * one entry on the linked list, unless there are 62 bit hash collisions.)
407  */
408 static bool call_filldir(struct file *file, struct dir_context *ctx,
409                         struct fname *fname)
410 {
411         struct dir_private_info *info = file->private_data;
412         struct inode *inode = file_inode(file);
413         struct super_block *sb = inode->i_sb;
414 
415         if (!fname) {
416                 printk("call_filldir: called with null fname?!?\n");
417                 return true;
418         }
419         ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
420         while (fname) {
421                 if (!dir_emit(ctx, fname->name, fname->name_len,
422                                 fname->inode,
423                                 get_dtype(sb, fname->file_type))) {
424                         info->extra_fname = fname;
425                         return false;
426                 }
427                 fname = fname->next;
428         }
429         return true;
430 }
431 
432 static int ext3_dx_readdir(struct file *file, struct dir_context *ctx)
433 {
434         struct dir_private_info *info = file->private_data;
435         struct inode *inode = file_inode(file);
436         struct fname *fname;
437         int     ret;
438 
439         if (!info) {
440                 info = ext3_htree_create_dir_info(file, ctx->pos);
441                 if (!info)
442                         return -ENOMEM;
443                 file->private_data = info;
444         }
445 
446         if (ctx->pos == ext3_get_htree_eof(file))
447                 return 0;       /* EOF */
448 
449         /* Some one has messed with f_pos; reset the world */
450         if (info->last_pos != ctx->pos) {
451                 free_rb_tree_fname(&info->root);
452                 info->curr_node = NULL;
453                 info->extra_fname = NULL;
454                 info->curr_hash = pos2maj_hash(file, ctx->pos);
455                 info->curr_minor_hash = pos2min_hash(file, ctx->pos);
456         }
457 
458         /*
459          * If there are any leftover names on the hash collision
460          * chain, return them first.
461          */
462         if (info->extra_fname) {
463                 if (!call_filldir(file, ctx, info->extra_fname))
464                         goto finished;
465                 info->extra_fname = NULL;
466                 goto next_node;
467         } else if (!info->curr_node)
468                 info->curr_node = rb_first(&info->root);
469 
470         while (1) {
471                 /*
472                  * Fill the rbtree if we have no more entries,
473                  * or the inode has changed since we last read in the
474                  * cached entries.
475                  */
476                 if ((!info->curr_node) ||
477                     (file->f_version != inode->i_version)) {
478                         info->curr_node = NULL;
479                         free_rb_tree_fname(&info->root);
480                         file->f_version = inode->i_version;
481                         ret = ext3_htree_fill_tree(file, info->curr_hash,
482                                                    info->curr_minor_hash,
483                                                    &info->next_hash);
484                         if (ret < 0)
485                                 return ret;
486                         if (ret == 0) {
487                                 ctx->pos = ext3_get_htree_eof(file);
488                                 break;
489                         }
490                         info->curr_node = rb_first(&info->root);
491                 }
492 
493                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
494                 info->curr_hash = fname->hash;
495                 info->curr_minor_hash = fname->minor_hash;
496                 if (!call_filldir(file, ctx, fname))
497                         break;
498         next_node:
499                 info->curr_node = rb_next(info->curr_node);
500                 if (info->curr_node) {
501                         fname = rb_entry(info->curr_node, struct fname,
502                                          rb_hash);
503                         info->curr_hash = fname->hash;
504                         info->curr_minor_hash = fname->minor_hash;
505                 } else {
506                         if (info->next_hash == ~0) {
507                                 ctx->pos = ext3_get_htree_eof(file);
508                                 break;
509                         }
510                         info->curr_hash = info->next_hash;
511                         info->curr_minor_hash = 0;
512                 }
513         }
514 finished:
515         info->last_pos = ctx->pos;
516         return 0;
517 }
518 
519 static int ext3_release_dir (struct inode * inode, struct file * filp)
520 {
521        if (filp->private_data)
522                 ext3_htree_free_dir_info(filp->private_data);
523 
524         return 0;
525 }
526 
527 const struct file_operations ext3_dir_operations = {
528         .llseek         = ext3_dir_llseek,
529         .read           = generic_read_dir,
530         .iterate        = ext3_readdir,
531         .unlocked_ioctl = ext3_ioctl,
532 #ifdef CONFIG_COMPAT
533         .compat_ioctl   = ext3_compat_ioctl,
534 #endif
535         .fsync          = ext3_sync_file,
536         .release        = ext3_release_dir,
537 };
538 

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