xref: /openbmc/linux/fs/ext4/dir.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  *  linux/fs/ext4/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  *  ext4 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/jbd2.h>
26 #include <linux/ext4_fs.h>
27 #include <linux/buffer_head.h>
28 #include <linux/slab.h>
29 #include <linux/rbtree.h>
30 
31 static unsigned char ext4_filetype_table[] = {
32 	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
33 };
34 
35 static int ext4_readdir(struct file *, void *, filldir_t);
36 static int ext4_dx_readdir(struct file * filp,
37 			   void * dirent, filldir_t filldir);
38 static int ext4_release_dir (struct inode * inode,
39 				struct file * filp);
40 
41 const struct file_operations ext4_dir_operations = {
42 	.llseek		= generic_file_llseek,
43 	.read		= generic_read_dir,
44 	.readdir	= ext4_readdir,		/* we take BKL. needed?*/
45 	.ioctl		= ext4_ioctl,		/* BKL held */
46 #ifdef CONFIG_COMPAT
47 	.compat_ioctl	= ext4_compat_ioctl,
48 #endif
49 	.fsync		= ext4_sync_file,	/* BKL held */
50 #ifdef CONFIG_EXT4_INDEX
51 	.release	= ext4_release_dir,
52 #endif
53 };
54 
55 
56 static unsigned char get_dtype(struct super_block *sb, int filetype)
57 {
58 	if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE) ||
59 	    (filetype >= EXT4_FT_MAX))
60 		return DT_UNKNOWN;
61 
62 	return (ext4_filetype_table[filetype]);
63 }
64 
65 
66 int ext4_check_dir_entry (const char * function, struct inode * dir,
67 			  struct ext4_dir_entry_2 * de,
68 			  struct buffer_head * bh,
69 			  unsigned long offset)
70 {
71 	const char * error_msg = NULL;
72 	const int rlen = le16_to_cpu(de->rec_len);
73 
74 	if (rlen < EXT4_DIR_REC_LEN(1))
75 		error_msg = "rec_len is smaller than minimal";
76 	else if (rlen % 4 != 0)
77 		error_msg = "rec_len % 4 != 0";
78 	else if (rlen < EXT4_DIR_REC_LEN(de->name_len))
79 		error_msg = "rec_len is too small for name_len";
80 	else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
81 		error_msg = "directory entry across blocks";
82 	else if (le32_to_cpu(de->inode) >
83 			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count))
84 		error_msg = "inode out of bounds";
85 
86 	if (error_msg != NULL)
87 		ext4_error (dir->i_sb, function,
88 			"bad entry in directory #%lu: %s - "
89 			"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
90 			dir->i_ino, error_msg, offset,
91 			(unsigned long) le32_to_cpu(de->inode),
92 			rlen, de->name_len);
93 	return error_msg == NULL ? 1 : 0;
94 }
95 
96 static int ext4_readdir(struct file * filp,
97 			 void * dirent, filldir_t filldir)
98 {
99 	int error = 0;
100 	unsigned long offset;
101 	int i, stored;
102 	struct ext4_dir_entry_2 *de;
103 	struct super_block *sb;
104 	int err;
105 	struct inode *inode = filp->f_path.dentry->d_inode;
106 	int ret = 0;
107 
108 	sb = inode->i_sb;
109 
110 #ifdef CONFIG_EXT4_INDEX
111 	if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
112 				    EXT4_FEATURE_COMPAT_DIR_INDEX) &&
113 	    ((EXT4_I(inode)->i_flags & EXT4_INDEX_FL) ||
114 	     ((inode->i_size >> sb->s_blocksize_bits) == 1))) {
115 		err = ext4_dx_readdir(filp, dirent, filldir);
116 		if (err != ERR_BAD_DX_DIR) {
117 			ret = err;
118 			goto out;
119 		}
120 		/*
121 		 * We don't set the inode dirty flag since it's not
122 		 * critical that it get flushed back to the disk.
123 		 */
124 		EXT4_I(filp->f_path.dentry->d_inode)->i_flags &= ~EXT4_INDEX_FL;
125 	}
126 #endif
127 	stored = 0;
128 	offset = filp->f_pos & (sb->s_blocksize - 1);
129 
130 	while (!error && !stored && filp->f_pos < inode->i_size) {
131 		unsigned long blk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
132 		struct buffer_head map_bh;
133 		struct buffer_head *bh = NULL;
134 
135 		map_bh.b_state = 0;
136 		err = ext4_get_blocks_wrap(NULL, inode, blk, 1, &map_bh, 0, 0);
137 		if (err > 0) {
138 			page_cache_readahead(sb->s_bdev->bd_inode->i_mapping,
139 				&filp->f_ra,
140 				filp,
141 				map_bh.b_blocknr >>
142 					(PAGE_CACHE_SHIFT - inode->i_blkbits),
143 				1);
144 			bh = ext4_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 			ext4_error (sb, "ext4_readdir",
153 				"directory #%lu contains a hole at offset %lu",
154 				inode->i_ino, (unsigned long)filp->f_pos);
155 			/* corrupt size?  Maybe no more blocks to read */
156 			if (filp->f_pos > inode->i_blocks << 9)
157 				break;
158 			filp->f_pos += sb->s_blocksize - offset;
159 			continue;
160 		}
161 
162 revalidate:
163 		/* If the dir block has changed since the last call to
164 		 * readdir(2), then we might be pointing to an invalid
165 		 * dirent right now.  Scan from the start of the block
166 		 * to make sure. */
167 		if (filp->f_version != inode->i_version) {
168 			for (i = 0; i < sb->s_blocksize && i < offset; ) {
169 				de = (struct ext4_dir_entry_2 *)
170 					(bh->b_data + i);
171 				/* It's too expensive to do a full
172 				 * dirent test each time round this
173 				 * loop, but we do have to test at
174 				 * least that it is non-zero.  A
175 				 * failure will be detected in the
176 				 * dirent test below. */
177 				if (le16_to_cpu(de->rec_len) <
178 						EXT4_DIR_REC_LEN(1))
179 					break;
180 				i += le16_to_cpu(de->rec_len);
181 			}
182 			offset = i;
183 			filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
184 				| offset;
185 			filp->f_version = inode->i_version;
186 		}
187 
188 		while (!error && filp->f_pos < inode->i_size
189 		       && offset < sb->s_blocksize) {
190 			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
191 			if (!ext4_check_dir_entry ("ext4_readdir", inode, de,
192 						   bh, offset)) {
193 				/*
194 				 * On error, skip the f_pos to the next block
195 				 */
196 				filp->f_pos = (filp->f_pos |
197 						(sb->s_blocksize - 1)) + 1;
198 				brelse (bh);
199 				ret = stored;
200 				goto out;
201 			}
202 			offset += le16_to_cpu(de->rec_len);
203 			if (le32_to_cpu(de->inode)) {
204 				/* We might block in the next section
205 				 * if the data destination is
206 				 * currently swapped out.  So, use a
207 				 * version stamp to detect whether or
208 				 * not the directory has been modified
209 				 * during the copy operation.
210 				 */
211 				unsigned long version = filp->f_version;
212 
213 				error = filldir(dirent, de->name,
214 						de->name_len,
215 						filp->f_pos,
216 						le32_to_cpu(de->inode),
217 						get_dtype(sb, de->file_type));
218 				if (error)
219 					break;
220 				if (version != filp->f_version)
221 					goto revalidate;
222 				stored ++;
223 			}
224 			filp->f_pos += le16_to_cpu(de->rec_len);
225 		}
226 		offset = 0;
227 		brelse (bh);
228 	}
229 out:
230 	return ret;
231 }
232 
233 #ifdef CONFIG_EXT4_INDEX
234 /*
235  * These functions convert from the major/minor hash to an f_pos
236  * value.
237  *
238  * Currently we only use major hash numer.  This is unfortunate, but
239  * on 32-bit machines, the same VFS interface is used for lseek and
240  * llseek, so if we use the 64 bit offset, then the 32-bit versions of
241  * lseek/telldir/seekdir will blow out spectacularly, and from within
242  * the ext2 low-level routine, we don't know if we're being called by
243  * a 64-bit version of the system call or the 32-bit version of the
244  * system call.  Worse yet, NFSv2 only allows for a 32-bit readdir
245  * cookie.  Sigh.
246  */
247 #define hash2pos(major, minor)	(major >> 1)
248 #define pos2maj_hash(pos)	((pos << 1) & 0xffffffff)
249 #define pos2min_hash(pos)	(0)
250 
251 /*
252  * This structure holds the nodes of the red-black tree used to store
253  * the directory entry in hash order.
254  */
255 struct fname {
256 	__u32		hash;
257 	__u32		minor_hash;
258 	struct rb_node	rb_hash;
259 	struct fname	*next;
260 	__u32		inode;
261 	__u8		name_len;
262 	__u8		file_type;
263 	char		name[0];
264 };
265 
266 /*
267  * This functoin implements a non-recursive way of freeing all of the
268  * nodes in the red-black tree.
269  */
270 static void free_rb_tree_fname(struct rb_root *root)
271 {
272 	struct rb_node	*n = root->rb_node;
273 	struct rb_node	*parent;
274 	struct fname	*fname;
275 
276 	while (n) {
277 		/* Do the node's children first */
278 		if ((n)->rb_left) {
279 			n = n->rb_left;
280 			continue;
281 		}
282 		if (n->rb_right) {
283 			n = n->rb_right;
284 			continue;
285 		}
286 		/*
287 		 * The node has no children; free it, and then zero
288 		 * out parent's link to it.  Finally go to the
289 		 * beginning of the loop and try to free the parent
290 		 * node.
291 		 */
292 		parent = rb_parent(n);
293 		fname = rb_entry(n, struct fname, rb_hash);
294 		while (fname) {
295 			struct fname * old = fname;
296 			fname = fname->next;
297 			kfree (old);
298 		}
299 		if (!parent)
300 			root->rb_node = NULL;
301 		else if (parent->rb_left == n)
302 			parent->rb_left = NULL;
303 		else if (parent->rb_right == n)
304 			parent->rb_right = NULL;
305 		n = parent;
306 	}
307 	root->rb_node = NULL;
308 }
309 
310 
311 static struct dir_private_info *create_dir_info(loff_t pos)
312 {
313 	struct dir_private_info *p;
314 
315 	p = kmalloc(sizeof(struct dir_private_info), GFP_KERNEL);
316 	if (!p)
317 		return NULL;
318 	p->root.rb_node = NULL;
319 	p->curr_node = NULL;
320 	p->extra_fname = NULL;
321 	p->last_pos = 0;
322 	p->curr_hash = pos2maj_hash(pos);
323 	p->curr_minor_hash = pos2min_hash(pos);
324 	p->next_hash = 0;
325 	return p;
326 }
327 
328 void ext4_htree_free_dir_info(struct dir_private_info *p)
329 {
330 	free_rb_tree_fname(&p->root);
331 	kfree(p);
332 }
333 
334 /*
335  * Given a directory entry, enter it into the fname rb tree.
336  */
337 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
338 			     __u32 minor_hash,
339 			     struct ext4_dir_entry_2 *dirent)
340 {
341 	struct rb_node **p, *parent = NULL;
342 	struct fname * fname, *new_fn;
343 	struct dir_private_info *info;
344 	int len;
345 
346 	info = (struct dir_private_info *) dir_file->private_data;
347 	p = &info->root.rb_node;
348 
349 	/* Create and allocate the fname structure */
350 	len = sizeof(struct fname) + dirent->name_len + 1;
351 	new_fn = kzalloc(len, GFP_KERNEL);
352 	if (!new_fn)
353 		return -ENOMEM;
354 	new_fn->hash = hash;
355 	new_fn->minor_hash = minor_hash;
356 	new_fn->inode = le32_to_cpu(dirent->inode);
357 	new_fn->name_len = dirent->name_len;
358 	new_fn->file_type = dirent->file_type;
359 	memcpy(new_fn->name, dirent->name, dirent->name_len);
360 	new_fn->name[dirent->name_len] = 0;
361 
362 	while (*p) {
363 		parent = *p;
364 		fname = rb_entry(parent, struct fname, rb_hash);
365 
366 		/*
367 		 * If the hash and minor hash match up, then we put
368 		 * them on a linked list.  This rarely happens...
369 		 */
370 		if ((new_fn->hash == fname->hash) &&
371 		    (new_fn->minor_hash == fname->minor_hash)) {
372 			new_fn->next = fname->next;
373 			fname->next = new_fn;
374 			return 0;
375 		}
376 
377 		if (new_fn->hash < fname->hash)
378 			p = &(*p)->rb_left;
379 		else if (new_fn->hash > fname->hash)
380 			p = &(*p)->rb_right;
381 		else if (new_fn->minor_hash < fname->minor_hash)
382 			p = &(*p)->rb_left;
383 		else /* if (new_fn->minor_hash > fname->minor_hash) */
384 			p = &(*p)->rb_right;
385 	}
386 
387 	rb_link_node(&new_fn->rb_hash, parent, p);
388 	rb_insert_color(&new_fn->rb_hash, &info->root);
389 	return 0;
390 }
391 
392 
393 
394 /*
395  * This is a helper function for ext4_dx_readdir.  It calls filldir
396  * for all entres on the fname linked list.  (Normally there is only
397  * one entry on the linked list, unless there are 62 bit hash collisions.)
398  */
399 static int call_filldir(struct file * filp, void * dirent,
400 			filldir_t filldir, struct fname *fname)
401 {
402 	struct dir_private_info *info = filp->private_data;
403 	loff_t	curr_pos;
404 	struct inode *inode = filp->f_path.dentry->d_inode;
405 	struct super_block * sb;
406 	int error;
407 
408 	sb = inode->i_sb;
409 
410 	if (!fname) {
411 		printk("call_filldir: called with null fname?!?\n");
412 		return 0;
413 	}
414 	curr_pos = hash2pos(fname->hash, fname->minor_hash);
415 	while (fname) {
416 		error = filldir(dirent, fname->name,
417 				fname->name_len, curr_pos,
418 				fname->inode,
419 				get_dtype(sb, fname->file_type));
420 		if (error) {
421 			filp->f_pos = curr_pos;
422 			info->extra_fname = fname->next;
423 			return error;
424 		}
425 		fname = fname->next;
426 	}
427 	return 0;
428 }
429 
430 static int ext4_dx_readdir(struct file * filp,
431 			 void * dirent, filldir_t filldir)
432 {
433 	struct dir_private_info *info = filp->private_data;
434 	struct inode *inode = filp->f_path.dentry->d_inode;
435 	struct fname *fname;
436 	int	ret;
437 
438 	if (!info) {
439 		info = create_dir_info(filp->f_pos);
440 		if (!info)
441 			return -ENOMEM;
442 		filp->private_data = info;
443 	}
444 
445 	if (filp->f_pos == EXT4_HTREE_EOF)
446 		return 0;	/* EOF */
447 
448 	/* Some one has messed with f_pos; reset the world */
449 	if (info->last_pos != filp->f_pos) {
450 		free_rb_tree_fname(&info->root);
451 		info->curr_node = NULL;
452 		info->extra_fname = NULL;
453 		info->curr_hash = pos2maj_hash(filp->f_pos);
454 		info->curr_minor_hash = pos2min_hash(filp->f_pos);
455 	}
456 
457 	/*
458 	 * If there are any leftover names on the hash collision
459 	 * chain, return them first.
460 	 */
461 	if (info->extra_fname &&
462 	    call_filldir(filp, dirent, filldir, info->extra_fname))
463 		goto finished;
464 
465 	if (!info->curr_node)
466 		info->curr_node = rb_first(&info->root);
467 
468 	while (1) {
469 		/*
470 		 * Fill the rbtree if we have no more entries,
471 		 * or the inode has changed since we last read in the
472 		 * cached entries.
473 		 */
474 		if ((!info->curr_node) ||
475 		    (filp->f_version != inode->i_version)) {
476 			info->curr_node = NULL;
477 			free_rb_tree_fname(&info->root);
478 			filp->f_version = inode->i_version;
479 			ret = ext4_htree_fill_tree(filp, info->curr_hash,
480 						   info->curr_minor_hash,
481 						   &info->next_hash);
482 			if (ret < 0)
483 				return ret;
484 			if (ret == 0) {
485 				filp->f_pos = EXT4_HTREE_EOF;
486 				break;
487 			}
488 			info->curr_node = rb_first(&info->root);
489 		}
490 
491 		fname = rb_entry(info->curr_node, struct fname, rb_hash);
492 		info->curr_hash = fname->hash;
493 		info->curr_minor_hash = fname->minor_hash;
494 		if (call_filldir(filp, dirent, filldir, fname))
495 			break;
496 
497 		info->curr_node = rb_next(info->curr_node);
498 		if (!info->curr_node) {
499 			if (info->next_hash == ~0) {
500 				filp->f_pos = EXT4_HTREE_EOF;
501 				break;
502 			}
503 			info->curr_hash = info->next_hash;
504 			info->curr_minor_hash = 0;
505 		}
506 	}
507 finished:
508 	info->last_pos = filp->f_pos;
509 	return 0;
510 }
511 
512 static int ext4_release_dir (struct inode * inode, struct file * filp)
513 {
514 	if (filp->private_data)
515 		ext4_htree_free_dir_info(filp->private_data);
516 
517 	return 0;
518 }
519 
520 #endif
521