ext3: ensure fast symlinks are NUL-terminated
[linux-2.6.git] / fs / ext3 / dir.c
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/fs.h>
25 #include <linux/jbd.h>
26 #include <linux/ext3_fs.h>
27 #include <linux/buffer_head.h>
28 #include <linux/slab.h>
29 #include <linux/rbtree.h>
30
31 static unsigned char ext3_filetype_table[] = {
32         DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
33 };
34
35 static int ext3_readdir(struct file *, void *, filldir_t);
36 static int ext3_dx_readdir(struct file * filp,
37                            void * dirent, filldir_t filldir);
38 static int ext3_release_dir (struct inode * inode,
39                                 struct file * filp);
40
41 const struct file_operations ext3_dir_operations = {
42         .llseek         = generic_file_llseek,
43         .read           = generic_read_dir,
44         .readdir        = ext3_readdir,         /* we take BKL. needed?*/
45         .ioctl          = ext3_ioctl,           /* BKL held */
46 #ifdef CONFIG_COMPAT
47         .compat_ioctl   = ext3_compat_ioctl,
48 #endif
49         .fsync          = ext3_sync_file,       /* BKL held */
50         .release        = ext3_release_dir,
51 };
52
53
54 static unsigned char get_dtype(struct super_block *sb, int filetype)
55 {
56         if (!EXT3_HAS_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_FILETYPE) ||
57             (filetype >= EXT3_FT_MAX))
58                 return DT_UNKNOWN;
59
60         return (ext3_filetype_table[filetype]);
61 }
62
63
64 int ext3_check_dir_entry (const char * function, struct inode * dir,
65                           struct ext3_dir_entry_2 * de,
66                           struct buffer_head * bh,
67                           unsigned long offset)
68 {
69         const char * error_msg = NULL;
70         const int rlen = ext3_rec_len_from_disk(de->rec_len);
71
72         if (rlen < EXT3_DIR_REC_LEN(1))
73                 error_msg = "rec_len is smaller than minimal";
74         else if (rlen % 4 != 0)
75                 error_msg = "rec_len % 4 != 0";
76         else if (rlen < EXT3_DIR_REC_LEN(de->name_len))
77                 error_msg = "rec_len is too small for name_len";
78         else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
79                 error_msg = "directory entry across blocks";
80         else if (le32_to_cpu(de->inode) >
81                         le32_to_cpu(EXT3_SB(dir->i_sb)->s_es->s_inodes_count))
82                 error_msg = "inode out of bounds";
83
84         if (error_msg != NULL)
85                 ext3_error (dir->i_sb, function,
86                         "bad entry in directory #%lu: %s - "
87                         "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
88                         dir->i_ino, error_msg, offset,
89                         (unsigned long) le32_to_cpu(de->inode),
90                         rlen, de->name_len);
91         return error_msg == NULL ? 1 : 0;
92 }
93
94 static int ext3_readdir(struct file * filp,
95                          void * dirent, filldir_t filldir)
96 {
97         int error = 0;
98         unsigned long offset;
99         int i, stored;
100         struct ext3_dir_entry_2 *de;
101         struct super_block *sb;
102         int err;
103         struct inode *inode = filp->f_path.dentry->d_inode;
104         int ret = 0;
105         int dir_has_error = 0;
106
107         sb = inode->i_sb;
108
109         if (EXT3_HAS_COMPAT_FEATURE(inode->i_sb,
110                                     EXT3_FEATURE_COMPAT_DIR_INDEX) &&
111             ((EXT3_I(inode)->i_flags & EXT3_INDEX_FL) ||
112              ((inode->i_size >> sb->s_blocksize_bits) == 1))) {
113                 err = ext3_dx_readdir(filp, dirent, filldir);
114                 if (err != ERR_BAD_DX_DIR) {
115                         ret = err;
116                         goto out;
117                 }
118                 /*
119                  * We don't set the inode dirty flag since it's not
120                  * critical that it get flushed back to the disk.
121                  */
122                 EXT3_I(filp->f_path.dentry->d_inode)->i_flags &= ~EXT3_INDEX_FL;
123         }
124         stored = 0;
125         offset = filp->f_pos & (sb->s_blocksize - 1);
126
127         while (!error && !stored && filp->f_pos < inode->i_size) {
128                 unsigned long blk = filp->f_pos >> EXT3_BLOCK_SIZE_BITS(sb);
129                 struct buffer_head map_bh;
130                 struct buffer_head *bh = NULL;
131
132                 map_bh.b_state = 0;
133                 err = ext3_get_blocks_handle(NULL, inode, blk, 1,
134                                                 &map_bh, 0, 0);
135                 if (err > 0) {
136                         pgoff_t index = map_bh.b_blocknr >>
137                                         (PAGE_CACHE_SHIFT - inode->i_blkbits);
138                         if (!ra_has_index(&filp->f_ra, index))
139                                 page_cache_sync_readahead(
140                                         sb->s_bdev->bd_inode->i_mapping,
141                                         &filp->f_ra, filp,
142                                         index, 1);
143                         filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
144                         bh = ext3_bread(NULL, inode, blk, 0, &err);
145                 }
146
147                 /*
148                  * We ignore I/O errors on directories so users have a chance
149                  * of recovering data when there's a bad sector
150                  */
151                 if (!bh) {
152                         if (!dir_has_error) {
153                                 ext3_error(sb, __func__, "directory #%lu "
154                                         "contains a hole at offset %lld",
155                                         inode->i_ino, filp->f_pos);
156                                 dir_has_error = 1;
157                         }
158                         /* corrupt size?  Maybe no more blocks to read */
159                         if (filp->f_pos > inode->i_blocks << 9)
160                                 break;
161                         filp->f_pos += sb->s_blocksize - offset;
162                         continue;
163                 }
164
165 revalidate:
166                 /* If the dir block has changed since the last call to
167                  * readdir(2), then we might be pointing to an invalid
168                  * dirent right now.  Scan from the start of the block
169                  * to make sure. */
170                 if (filp->f_version != inode->i_version) {
171                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
172                                 de = (struct ext3_dir_entry_2 *)
173                                         (bh->b_data + i);
174                                 /* It's too expensive to do a full
175                                  * dirent test each time round this
176                                  * loop, but we do have to test at
177                                  * least that it is non-zero.  A
178                                  * failure will be detected in the
179                                  * dirent test below. */
180                                 if (ext3_rec_len_from_disk(de->rec_len) <
181                                                 EXT3_DIR_REC_LEN(1))
182                                         break;
183                                 i += ext3_rec_len_from_disk(de->rec_len);
184                         }
185                         offset = i;
186                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
187                                 | offset;
188                         filp->f_version = inode->i_version;
189                 }
190
191                 while (!error && filp->f_pos < inode->i_size
192                        && offset < sb->s_blocksize) {
193                         de = (struct ext3_dir_entry_2 *) (bh->b_data + offset);
194                         if (!ext3_check_dir_entry ("ext3_readdir", inode, de,
195                                                    bh, offset)) {
196                                 /* On error, skip the f_pos to the
197                                    next block. */
198                                 filp->f_pos = (filp->f_pos |
199                                                 (sb->s_blocksize - 1)) + 1;
200                                 brelse (bh);
201                                 ret = stored;
202                                 goto out;
203                         }
204                         offset += ext3_rec_len_from_disk(de->rec_len);
205                         if (le32_to_cpu(de->inode)) {
206                                 /* We might block in the next section
207                                  * if the data destination is
208                                  * currently swapped out.  So, use a
209                                  * version stamp to detect whether or
210                                  * not the directory has been modified
211                                  * during the copy operation.
212                                  */
213                                 u64 version = filp->f_version;
214
215                                 error = filldir(dirent, de->name,
216                                                 de->name_len,
217                                                 filp->f_pos,
218                                                 le32_to_cpu(de->inode),
219                                                 get_dtype(sb, de->file_type));
220                                 if (error)
221                                         break;
222                                 if (version != filp->f_version)
223                                         goto revalidate;
224                                 stored ++;
225                         }
226                         filp->f_pos += ext3_rec_len_from_disk(de->rec_len);
227                 }
228                 offset = 0;
229                 brelse (bh);
230         }
231 out:
232         return ret;
233 }
234
235 /*
236  * These functions convert from the major/minor hash to an f_pos
237  * value.
238  *
239  * Currently we only use major hash numer.  This is unfortunate, but
240  * on 32-bit machines, the same VFS interface is used for lseek and
241  * llseek, so if we use the 64 bit offset, then the 32-bit versions of
242  * lseek/telldir/seekdir will blow out spectacularly, and from within
243  * the ext2 low-level routine, we don't know if we're being called by
244  * a 64-bit version of the system call or the 32-bit version of the
245  * system call.  Worse yet, NFSv2 only allows for a 32-bit readdir
246  * cookie.  Sigh.
247  */
248 #define hash2pos(major, minor)  (major >> 1)
249 #define pos2maj_hash(pos)       ((pos << 1) & 0xffffffff)
250 #define pos2min_hash(pos)       (0)
251
252 /*
253  * This structure holds the nodes of the red-black tree used to store
254  * the directory entry in hash order.
255  */
256 struct fname {
257         __u32           hash;
258         __u32           minor_hash;
259         struct rb_node  rb_hash;
260         struct fname    *next;
261         __u32           inode;
262         __u8            name_len;
263         __u8            file_type;
264         char            name[0];
265 };
266
267 /*
268  * This functoin implements a non-recursive way of freeing all of the
269  * nodes in the red-black tree.
270  */
271 static void free_rb_tree_fname(struct rb_root *root)
272 {
273         struct rb_node  *n = root->rb_node;
274         struct rb_node  *parent;
275         struct fname    *fname;
276
277         while (n) {
278                 /* Do the node's children first */
279                 if (n->rb_left) {
280                         n = n->rb_left;
281                         continue;
282                 }
283                 if (n->rb_right) {
284                         n = n->rb_right;
285                         continue;
286                 }
287                 /*
288                  * The node has no children; free it, and then zero
289                  * out parent's link to it.  Finally go to the
290                  * beginning of the loop and try to free the parent
291                  * node.
292                  */
293                 parent = rb_parent(n);
294                 fname = rb_entry(n, struct fname, rb_hash);
295                 while (fname) {
296                         struct fname * old = fname;
297                         fname = fname->next;
298                         kfree (old);
299                 }
300                 if (!parent)
301                         root->rb_node = NULL;
302                 else if (parent->rb_left == n)
303                         parent->rb_left = NULL;
304                 else if (parent->rb_right == n)
305                         parent->rb_right = NULL;
306                 n = parent;
307         }
308 }
309
310
311 static struct dir_private_info *ext3_htree_create_dir_info(loff_t pos)
312 {
313         struct dir_private_info *p;
314
315         p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
316         if (!p)
317                 return NULL;
318         p->curr_hash = pos2maj_hash(pos);
319         p->curr_minor_hash = pos2min_hash(pos);
320         return p;
321 }
322
323 void ext3_htree_free_dir_info(struct dir_private_info *p)
324 {
325         free_rb_tree_fname(&p->root);
326         kfree(p);
327 }
328
329 /*
330  * Given a directory entry, enter it into the fname rb tree.
331  */
332 int ext3_htree_store_dirent(struct file *dir_file, __u32 hash,
333                              __u32 minor_hash,
334                              struct ext3_dir_entry_2 *dirent)
335 {
336         struct rb_node **p, *parent = NULL;
337         struct fname * fname, *new_fn;
338         struct dir_private_info *info;
339         int len;
340
341         info = (struct dir_private_info *) dir_file->private_data;
342         p = &info->root.rb_node;
343
344         /* Create and allocate the fname structure */
345         len = sizeof(struct fname) + dirent->name_len + 1;
346         new_fn = kzalloc(len, GFP_KERNEL);
347         if (!new_fn)
348                 return -ENOMEM;
349         new_fn->hash = hash;
350         new_fn->minor_hash = minor_hash;
351         new_fn->inode = le32_to_cpu(dirent->inode);
352         new_fn->name_len = dirent->name_len;
353         new_fn->file_type = dirent->file_type;
354         memcpy(new_fn->name, dirent->name, dirent->name_len);
355         new_fn->name[dirent->name_len] = 0;
356
357         while (*p) {
358                 parent = *p;
359                 fname = rb_entry(parent, struct fname, rb_hash);
360
361                 /*
362                  * If the hash and minor hash match up, then we put
363                  * them on a linked list.  This rarely happens...
364                  */
365                 if ((new_fn->hash == fname->hash) &&
366                     (new_fn->minor_hash == fname->minor_hash)) {
367                         new_fn->next = fname->next;
368                         fname->next = new_fn;
369                         return 0;
370                 }
371
372                 if (new_fn->hash < fname->hash)
373                         p = &(*p)->rb_left;
374                 else if (new_fn->hash > fname->hash)
375                         p = &(*p)->rb_right;
376                 else if (new_fn->minor_hash < fname->minor_hash)
377                         p = &(*p)->rb_left;
378                 else /* if (new_fn->minor_hash > fname->minor_hash) */
379                         p = &(*p)->rb_right;
380         }
381
382         rb_link_node(&new_fn->rb_hash, parent, p);
383         rb_insert_color(&new_fn->rb_hash, &info->root);
384         return 0;
385 }
386
387
388
389 /*
390  * This is a helper function for ext3_dx_readdir.  It calls filldir
391  * for all entres on the fname linked list.  (Normally there is only
392  * one entry on the linked list, unless there are 62 bit hash collisions.)
393  */
394 static int call_filldir(struct file * filp, void * dirent,
395                         filldir_t filldir, struct fname *fname)
396 {
397         struct dir_private_info *info = filp->private_data;
398         loff_t  curr_pos;
399         struct inode *inode = filp->f_path.dentry->d_inode;
400         struct super_block * sb;
401         int error;
402
403         sb = inode->i_sb;
404
405         if (!fname) {
406                 printk("call_filldir: called with null fname?!?\n");
407                 return 0;
408         }
409         curr_pos = hash2pos(fname->hash, fname->minor_hash);
410         while (fname) {
411                 error = filldir(dirent, fname->name,
412                                 fname->name_len, curr_pos,
413                                 fname->inode,
414                                 get_dtype(sb, fname->file_type));
415                 if (error) {
416                         filp->f_pos = curr_pos;
417                         info->extra_fname = fname;
418                         return error;
419                 }
420                 fname = fname->next;
421         }
422         return 0;
423 }
424
425 static int ext3_dx_readdir(struct file * filp,
426                          void * dirent, filldir_t filldir)
427 {
428         struct dir_private_info *info = filp->private_data;
429         struct inode *inode = filp->f_path.dentry->d_inode;
430         struct fname *fname;
431         int     ret;
432
433         if (!info) {
434                 info = ext3_htree_create_dir_info(filp->f_pos);
435                 if (!info)
436                         return -ENOMEM;
437                 filp->private_data = info;
438         }
439
440         if (filp->f_pos == EXT3_HTREE_EOF)
441                 return 0;       /* EOF */
442
443         /* Some one has messed with f_pos; reset the world */
444         if (info->last_pos != filp->f_pos) {
445                 free_rb_tree_fname(&info->root);
446                 info->curr_node = NULL;
447                 info->extra_fname = NULL;
448                 info->curr_hash = pos2maj_hash(filp->f_pos);
449                 info->curr_minor_hash = pos2min_hash(filp->f_pos);
450         }
451
452         /*
453          * If there are any leftover names on the hash collision
454          * chain, return them first.
455          */
456         if (info->extra_fname) {
457                 if (call_filldir(filp, dirent, filldir, info->extra_fname))
458                         goto finished;
459                 info->extra_fname = NULL;
460                 goto next_node;
461         } else if (!info->curr_node)
462                 info->curr_node = rb_first(&info->root);
463
464         while (1) {
465                 /*
466                  * Fill the rbtree if we have no more entries,
467                  * or the inode has changed since we last read in the
468                  * cached entries.
469                  */
470                 if ((!info->curr_node) ||
471                     (filp->f_version != inode->i_version)) {
472                         info->curr_node = NULL;
473                         free_rb_tree_fname(&info->root);
474                         filp->f_version = inode->i_version;
475                         ret = ext3_htree_fill_tree(filp, info->curr_hash,
476                                                    info->curr_minor_hash,
477                                                    &info->next_hash);
478                         if (ret < 0)
479                                 return ret;
480                         if (ret == 0) {
481                                 filp->f_pos = EXT3_HTREE_EOF;
482                                 break;
483                         }
484                         info->curr_node = rb_first(&info->root);
485                 }
486
487                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
488                 info->curr_hash = fname->hash;
489                 info->curr_minor_hash = fname->minor_hash;
490                 if (call_filldir(filp, dirent, filldir, fname))
491                         break;
492         next_node:
493                 info->curr_node = rb_next(info->curr_node);
494                 if (info->curr_node) {
495                         fname = rb_entry(info->curr_node, struct fname,
496                                          rb_hash);
497                         info->curr_hash = fname->hash;
498                         info->curr_minor_hash = fname->minor_hash;
499                 } else {
500                         if (info->next_hash == ~0) {
501                                 filp->f_pos = EXT3_HTREE_EOF;
502                                 break;
503                         }
504                         info->curr_hash = info->next_hash;
505                         info->curr_minor_hash = 0;
506                 }
507         }
508 finished:
509         info->last_pos = filp->f_pos;
510         return 0;
511 }
512
513 static int ext3_release_dir (struct inode * inode, struct file * filp)
514 {
515        if (filp->private_data)
516                 ext3_htree_free_dir_info(filp->private_data);
517
518         return 0;
519 }