xref: /openbmc/linux/fs/ext2/dir.c (revision 96de0e252cedffad61b3cb5e05662c591898e69a)
1 /*
2  *  linux/fs/ext2/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  *  ext2 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  * All code that works with directory layout had been switched to pagecache
21  * and moved here. AV
22  */
23 
24 #include "ext2.h"
25 #include <linux/buffer_head.h>
26 #include <linux/pagemap.h>
27 #include <linux/swap.h>
28 
29 typedef struct ext2_dir_entry_2 ext2_dirent;
30 
31 /*
32  * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
33  * more robust, but we have what we have
34  */
35 static inline unsigned ext2_chunk_size(struct inode *inode)
36 {
37 	return inode->i_sb->s_blocksize;
38 }
39 
40 static inline void ext2_put_page(struct page *page)
41 {
42 	kunmap(page);
43 	page_cache_release(page);
44 }
45 
46 static inline unsigned long dir_pages(struct inode *inode)
47 {
48 	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
49 }
50 
51 /*
52  * Return the offset into page `page_nr' of the last valid
53  * byte in that page, plus one.
54  */
55 static unsigned
56 ext2_last_byte(struct inode *inode, unsigned long page_nr)
57 {
58 	unsigned last_byte = inode->i_size;
59 
60 	last_byte -= page_nr << PAGE_CACHE_SHIFT;
61 	if (last_byte > PAGE_CACHE_SIZE)
62 		last_byte = PAGE_CACHE_SIZE;
63 	return last_byte;
64 }
65 
66 static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
67 {
68 	struct address_space *mapping = page->mapping;
69 	struct inode *dir = mapping->host;
70 	int err = 0;
71 
72 	dir->i_version++;
73 	block_write_end(NULL, mapping, pos, len, len, page, NULL);
74 
75 	if (pos+len > dir->i_size) {
76 		i_size_write(dir, pos+len);
77 		mark_inode_dirty(dir);
78 	}
79 
80 	if (IS_DIRSYNC(dir))
81 		err = write_one_page(page, 1);
82 	else
83 		unlock_page(page);
84 
85 	return err;
86 }
87 
88 static void ext2_check_page(struct page *page)
89 {
90 	struct inode *dir = page->mapping->host;
91 	struct super_block *sb = dir->i_sb;
92 	unsigned chunk_size = ext2_chunk_size(dir);
93 	char *kaddr = page_address(page);
94 	u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
95 	unsigned offs, rec_len;
96 	unsigned limit = PAGE_CACHE_SIZE;
97 	ext2_dirent *p;
98 	char *error;
99 
100 	if ((dir->i_size >> PAGE_CACHE_SHIFT) == page->index) {
101 		limit = dir->i_size & ~PAGE_CACHE_MASK;
102 		if (limit & (chunk_size - 1))
103 			goto Ebadsize;
104 		if (!limit)
105 			goto out;
106 	}
107 	for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
108 		p = (ext2_dirent *)(kaddr + offs);
109 		rec_len = le16_to_cpu(p->rec_len);
110 
111 		if (rec_len < EXT2_DIR_REC_LEN(1))
112 			goto Eshort;
113 		if (rec_len & 3)
114 			goto Ealign;
115 		if (rec_len < EXT2_DIR_REC_LEN(p->name_len))
116 			goto Enamelen;
117 		if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
118 			goto Espan;
119 		if (le32_to_cpu(p->inode) > max_inumber)
120 			goto Einumber;
121 	}
122 	if (offs != limit)
123 		goto Eend;
124 out:
125 	SetPageChecked(page);
126 	return;
127 
128 	/* Too bad, we had an error */
129 
130 Ebadsize:
131 	ext2_error(sb, "ext2_check_page",
132 		"size of directory #%lu is not a multiple of chunk size",
133 		dir->i_ino
134 	);
135 	goto fail;
136 Eshort:
137 	error = "rec_len is smaller than minimal";
138 	goto bad_entry;
139 Ealign:
140 	error = "unaligned directory entry";
141 	goto bad_entry;
142 Enamelen:
143 	error = "rec_len is too small for name_len";
144 	goto bad_entry;
145 Espan:
146 	error = "directory entry across blocks";
147 	goto bad_entry;
148 Einumber:
149 	error = "inode out of bounds";
150 bad_entry:
151 	ext2_error (sb, "ext2_check_page", "bad entry in directory #%lu: %s - "
152 		"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
153 		dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
154 		(unsigned long) le32_to_cpu(p->inode),
155 		rec_len, p->name_len);
156 	goto fail;
157 Eend:
158 	p = (ext2_dirent *)(kaddr + offs);
159 	ext2_error (sb, "ext2_check_page",
160 		"entry in directory #%lu spans the page boundary"
161 		"offset=%lu, inode=%lu",
162 		dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs,
163 		(unsigned long) le32_to_cpu(p->inode));
164 fail:
165 	SetPageChecked(page);
166 	SetPageError(page);
167 }
168 
169 static struct page * ext2_get_page(struct inode *dir, unsigned long n)
170 {
171 	struct address_space *mapping = dir->i_mapping;
172 	struct page *page = read_mapping_page(mapping, n, NULL);
173 	if (!IS_ERR(page)) {
174 		kmap(page);
175 		if (!PageChecked(page))
176 			ext2_check_page(page);
177 		if (PageError(page))
178 			goto fail;
179 	}
180 	return page;
181 
182 fail:
183 	ext2_put_page(page);
184 	return ERR_PTR(-EIO);
185 }
186 
187 /*
188  * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
189  *
190  * len <= EXT2_NAME_LEN and de != NULL are guaranteed by caller.
191  */
192 static inline int ext2_match (int len, const char * const name,
193 					struct ext2_dir_entry_2 * de)
194 {
195 	if (len != de->name_len)
196 		return 0;
197 	if (!de->inode)
198 		return 0;
199 	return !memcmp(name, de->name, len);
200 }
201 
202 /*
203  * p is at least 6 bytes before the end of page
204  */
205 static inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
206 {
207 	return (ext2_dirent *)((char*)p + le16_to_cpu(p->rec_len));
208 }
209 
210 static inline unsigned
211 ext2_validate_entry(char *base, unsigned offset, unsigned mask)
212 {
213 	ext2_dirent *de = (ext2_dirent*)(base + offset);
214 	ext2_dirent *p = (ext2_dirent*)(base + (offset&mask));
215 	while ((char*)p < (char*)de) {
216 		if (p->rec_len == 0)
217 			break;
218 		p = ext2_next_entry(p);
219 	}
220 	return (char *)p - base;
221 }
222 
223 static unsigned char ext2_filetype_table[EXT2_FT_MAX] = {
224 	[EXT2_FT_UNKNOWN]	= DT_UNKNOWN,
225 	[EXT2_FT_REG_FILE]	= DT_REG,
226 	[EXT2_FT_DIR]		= DT_DIR,
227 	[EXT2_FT_CHRDEV]	= DT_CHR,
228 	[EXT2_FT_BLKDEV]	= DT_BLK,
229 	[EXT2_FT_FIFO]		= DT_FIFO,
230 	[EXT2_FT_SOCK]		= DT_SOCK,
231 	[EXT2_FT_SYMLINK]	= DT_LNK,
232 };
233 
234 #define S_SHIFT 12
235 static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
236 	[S_IFREG >> S_SHIFT]	= EXT2_FT_REG_FILE,
237 	[S_IFDIR >> S_SHIFT]	= EXT2_FT_DIR,
238 	[S_IFCHR >> S_SHIFT]	= EXT2_FT_CHRDEV,
239 	[S_IFBLK >> S_SHIFT]	= EXT2_FT_BLKDEV,
240 	[S_IFIFO >> S_SHIFT]	= EXT2_FT_FIFO,
241 	[S_IFSOCK >> S_SHIFT]	= EXT2_FT_SOCK,
242 	[S_IFLNK >> S_SHIFT]	= EXT2_FT_SYMLINK,
243 };
244 
245 static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
246 {
247 	mode_t mode = inode->i_mode;
248 	if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
249 		de->file_type = ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
250 	else
251 		de->file_type = 0;
252 }
253 
254 static int
255 ext2_readdir (struct file * filp, void * dirent, filldir_t filldir)
256 {
257 	loff_t pos = filp->f_pos;
258 	struct inode *inode = filp->f_path.dentry->d_inode;
259 	struct super_block *sb = inode->i_sb;
260 	unsigned int offset = pos & ~PAGE_CACHE_MASK;
261 	unsigned long n = pos >> PAGE_CACHE_SHIFT;
262 	unsigned long npages = dir_pages(inode);
263 	unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);
264 	unsigned char *types = NULL;
265 	int need_revalidate = filp->f_version != inode->i_version;
266 
267 	if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))
268 		return 0;
269 
270 	if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
271 		types = ext2_filetype_table;
272 
273 	for ( ; n < npages; n++, offset = 0) {
274 		char *kaddr, *limit;
275 		ext2_dirent *de;
276 		struct page *page = ext2_get_page(inode, n);
277 
278 		if (IS_ERR(page)) {
279 			ext2_error(sb, __FUNCTION__,
280 				   "bad page in #%lu",
281 				   inode->i_ino);
282 			filp->f_pos += PAGE_CACHE_SIZE - offset;
283 			return -EIO;
284 		}
285 		kaddr = page_address(page);
286 		if (unlikely(need_revalidate)) {
287 			if (offset) {
288 				offset = ext2_validate_entry(kaddr, offset, chunk_mask);
289 				filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset;
290 			}
291 			filp->f_version = inode->i_version;
292 			need_revalidate = 0;
293 		}
294 		de = (ext2_dirent *)(kaddr+offset);
295 		limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);
296 		for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {
297 			if (de->rec_len == 0) {
298 				ext2_error(sb, __FUNCTION__,
299 					"zero-length directory entry");
300 				ext2_put_page(page);
301 				return -EIO;
302 			}
303 			if (de->inode) {
304 				int over;
305 				unsigned char d_type = DT_UNKNOWN;
306 
307 				if (types && de->file_type < EXT2_FT_MAX)
308 					d_type = types[de->file_type];
309 
310 				offset = (char *)de - kaddr;
311 				over = filldir(dirent, de->name, de->name_len,
312 						(n<<PAGE_CACHE_SHIFT) | offset,
313 						le32_to_cpu(de->inode), d_type);
314 				if (over) {
315 					ext2_put_page(page);
316 					return 0;
317 				}
318 			}
319 			filp->f_pos += le16_to_cpu(de->rec_len);
320 		}
321 		ext2_put_page(page);
322 	}
323 	return 0;
324 }
325 
326 /*
327  *	ext2_find_entry()
328  *
329  * finds an entry in the specified directory with the wanted name. It
330  * returns the page in which the entry was found, and the entry itself
331  * (as a parameter - res_dir). Page is returned mapped and unlocked.
332  * Entry is guaranteed to be valid.
333  */
334 struct ext2_dir_entry_2 * ext2_find_entry (struct inode * dir,
335 			struct dentry *dentry, struct page ** res_page)
336 {
337 	const char *name = dentry->d_name.name;
338 	int namelen = dentry->d_name.len;
339 	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
340 	unsigned long start, n;
341 	unsigned long npages = dir_pages(dir);
342 	struct page *page = NULL;
343 	struct ext2_inode_info *ei = EXT2_I(dir);
344 	ext2_dirent * de;
345 
346 	if (npages == 0)
347 		goto out;
348 
349 	/* OFFSET_CACHE */
350 	*res_page = NULL;
351 
352 	start = ei->i_dir_start_lookup;
353 	if (start >= npages)
354 		start = 0;
355 	n = start;
356 	do {
357 		char *kaddr;
358 		page = ext2_get_page(dir, n);
359 		if (!IS_ERR(page)) {
360 			kaddr = page_address(page);
361 			de = (ext2_dirent *) kaddr;
362 			kaddr += ext2_last_byte(dir, n) - reclen;
363 			while ((char *) de <= kaddr) {
364 				if (de->rec_len == 0) {
365 					ext2_error(dir->i_sb, __FUNCTION__,
366 						"zero-length directory entry");
367 					ext2_put_page(page);
368 					goto out;
369 				}
370 				if (ext2_match (namelen, name, de))
371 					goto found;
372 				de = ext2_next_entry(de);
373 			}
374 			ext2_put_page(page);
375 		}
376 		if (++n >= npages)
377 			n = 0;
378 		/* next page is past the blocks we've got */
379 		if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
380 			ext2_error(dir->i_sb, __FUNCTION__,
381 				"dir %lu size %lld exceeds block count %llu",
382 				dir->i_ino, dir->i_size,
383 				(unsigned long long)dir->i_blocks);
384 			goto out;
385 		}
386 	} while (n != start);
387 out:
388 	return NULL;
389 
390 found:
391 	*res_page = page;
392 	ei->i_dir_start_lookup = n;
393 	return de;
394 }
395 
396 struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
397 {
398 	struct page *page = ext2_get_page(dir, 0);
399 	ext2_dirent *de = NULL;
400 
401 	if (!IS_ERR(page)) {
402 		de = ext2_next_entry((ext2_dirent *) page_address(page));
403 		*p = page;
404 	}
405 	return de;
406 }
407 
408 ino_t ext2_inode_by_name(struct inode * dir, struct dentry *dentry)
409 {
410 	ino_t res = 0;
411 	struct ext2_dir_entry_2 * de;
412 	struct page *page;
413 
414 	de = ext2_find_entry (dir, dentry, &page);
415 	if (de) {
416 		res = le32_to_cpu(de->inode);
417 		ext2_put_page(page);
418 	}
419 	return res;
420 }
421 
422 /* Releases the page */
423 void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
424 			struct page *page, struct inode *inode)
425 {
426 	loff_t pos = page_offset(page) +
427 			(char *) de - (char *) page_address(page);
428 	unsigned len = le16_to_cpu(de->rec_len);
429 	int err;
430 
431 	lock_page(page);
432 	err = __ext2_write_begin(NULL, page->mapping, pos, len,
433 				AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
434 	BUG_ON(err);
435 	de->inode = cpu_to_le32(inode->i_ino);
436 	ext2_set_de_type(de, inode);
437 	err = ext2_commit_chunk(page, pos, len);
438 	ext2_put_page(page);
439 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
440 	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
441 	mark_inode_dirty(dir);
442 }
443 
444 /*
445  *	Parent is locked.
446  */
447 int ext2_add_link (struct dentry *dentry, struct inode *inode)
448 {
449 	struct inode *dir = dentry->d_parent->d_inode;
450 	const char *name = dentry->d_name.name;
451 	int namelen = dentry->d_name.len;
452 	unsigned chunk_size = ext2_chunk_size(dir);
453 	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
454 	unsigned short rec_len, name_len;
455 	struct page *page = NULL;
456 	ext2_dirent * de;
457 	unsigned long npages = dir_pages(dir);
458 	unsigned long n;
459 	char *kaddr;
460 	loff_t pos;
461 	int err;
462 
463 	/*
464 	 * We take care of directory expansion in the same loop.
465 	 * This code plays outside i_size, so it locks the page
466 	 * to protect that region.
467 	 */
468 	for (n = 0; n <= npages; n++) {
469 		char *dir_end;
470 
471 		page = ext2_get_page(dir, n);
472 		err = PTR_ERR(page);
473 		if (IS_ERR(page))
474 			goto out;
475 		lock_page(page);
476 		kaddr = page_address(page);
477 		dir_end = kaddr + ext2_last_byte(dir, n);
478 		de = (ext2_dirent *)kaddr;
479 		kaddr += PAGE_CACHE_SIZE - reclen;
480 		while ((char *)de <= kaddr) {
481 			if ((char *)de == dir_end) {
482 				/* We hit i_size */
483 				name_len = 0;
484 				rec_len = chunk_size;
485 				de->rec_len = cpu_to_le16(chunk_size);
486 				de->inode = 0;
487 				goto got_it;
488 			}
489 			if (de->rec_len == 0) {
490 				ext2_error(dir->i_sb, __FUNCTION__,
491 					"zero-length directory entry");
492 				err = -EIO;
493 				goto out_unlock;
494 			}
495 			err = -EEXIST;
496 			if (ext2_match (namelen, name, de))
497 				goto out_unlock;
498 			name_len = EXT2_DIR_REC_LEN(de->name_len);
499 			rec_len = le16_to_cpu(de->rec_len);
500 			if (!de->inode && rec_len >= reclen)
501 				goto got_it;
502 			if (rec_len >= name_len + reclen)
503 				goto got_it;
504 			de = (ext2_dirent *) ((char *) de + rec_len);
505 		}
506 		unlock_page(page);
507 		ext2_put_page(page);
508 	}
509 	BUG();
510 	return -EINVAL;
511 
512 got_it:
513 	pos = page_offset(page) +
514 		(char*)de - (char*)page_address(page);
515 	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
516 							&page, NULL);
517 	if (err)
518 		goto out_unlock;
519 	if (de->inode) {
520 		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
521 		de1->rec_len = cpu_to_le16(rec_len - name_len);
522 		de->rec_len = cpu_to_le16(name_len);
523 		de = de1;
524 	}
525 	de->name_len = namelen;
526 	memcpy(de->name, name, namelen);
527 	de->inode = cpu_to_le32(inode->i_ino);
528 	ext2_set_de_type (de, inode);
529 	err = ext2_commit_chunk(page, pos, rec_len);
530 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
531 	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
532 	mark_inode_dirty(dir);
533 	/* OFFSET_CACHE */
534 out_put:
535 	ext2_put_page(page);
536 out:
537 	return err;
538 out_unlock:
539 	unlock_page(page);
540 	goto out_put;
541 }
542 
543 /*
544  * ext2_delete_entry deletes a directory entry by merging it with the
545  * previous entry. Page is up-to-date. Releases the page.
546  */
547 int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
548 {
549 	struct address_space *mapping = page->mapping;
550 	struct inode *inode = mapping->host;
551 	char *kaddr = page_address(page);
552 	unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
553 	unsigned to = ((char*)dir - kaddr) + le16_to_cpu(dir->rec_len);
554 	loff_t pos;
555 	ext2_dirent * pde = NULL;
556 	ext2_dirent * de = (ext2_dirent *) (kaddr + from);
557 	int err;
558 
559 	while ((char*)de < (char*)dir) {
560 		if (de->rec_len == 0) {
561 			ext2_error(inode->i_sb, __FUNCTION__,
562 				"zero-length directory entry");
563 			err = -EIO;
564 			goto out;
565 		}
566 		pde = de;
567 		de = ext2_next_entry(de);
568 	}
569 	if (pde)
570 		from = (char*)pde - (char*)page_address(page);
571 	pos = page_offset(page) + from;
572 	lock_page(page);
573 	err = __ext2_write_begin(NULL, page->mapping, pos, to - from, 0,
574 							&page, NULL);
575 	BUG_ON(err);
576 	if (pde)
577 		pde->rec_len = cpu_to_le16(to - from);
578 	dir->inode = 0;
579 	err = ext2_commit_chunk(page, pos, to - from);
580 	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
581 	EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
582 	mark_inode_dirty(inode);
583 out:
584 	ext2_put_page(page);
585 	return err;
586 }
587 
588 /*
589  * Set the first fragment of directory.
590  */
591 int ext2_make_empty(struct inode *inode, struct inode *parent)
592 {
593 	struct address_space *mapping = inode->i_mapping;
594 	struct page *page = grab_cache_page(mapping, 0);
595 	unsigned chunk_size = ext2_chunk_size(inode);
596 	struct ext2_dir_entry_2 * de;
597 	int err;
598 	void *kaddr;
599 
600 	if (!page)
601 		return -ENOMEM;
602 
603 	err = __ext2_write_begin(NULL, page->mapping, 0, chunk_size, 0,
604 							&page, NULL);
605 	if (err) {
606 		unlock_page(page);
607 		goto fail;
608 	}
609 	kaddr = kmap_atomic(page, KM_USER0);
610 	memset(kaddr, 0, chunk_size);
611 	de = (struct ext2_dir_entry_2 *)kaddr;
612 	de->name_len = 1;
613 	de->rec_len = cpu_to_le16(EXT2_DIR_REC_LEN(1));
614 	memcpy (de->name, ".\0\0", 4);
615 	de->inode = cpu_to_le32(inode->i_ino);
616 	ext2_set_de_type (de, inode);
617 
618 	de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
619 	de->name_len = 2;
620 	de->rec_len = cpu_to_le16(chunk_size - EXT2_DIR_REC_LEN(1));
621 	de->inode = cpu_to_le32(parent->i_ino);
622 	memcpy (de->name, "..\0", 4);
623 	ext2_set_de_type (de, inode);
624 	kunmap_atomic(kaddr, KM_USER0);
625 	err = ext2_commit_chunk(page, 0, chunk_size);
626 fail:
627 	page_cache_release(page);
628 	return err;
629 }
630 
631 /*
632  * routine to check that the specified directory is empty (for rmdir)
633  */
634 int ext2_empty_dir (struct inode * inode)
635 {
636 	struct page *page = NULL;
637 	unsigned long i, npages = dir_pages(inode);
638 
639 	for (i = 0; i < npages; i++) {
640 		char *kaddr;
641 		ext2_dirent * de;
642 		page = ext2_get_page(inode, i);
643 
644 		if (IS_ERR(page))
645 			continue;
646 
647 		kaddr = page_address(page);
648 		de = (ext2_dirent *)kaddr;
649 		kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
650 
651 		while ((char *)de <= kaddr) {
652 			if (de->rec_len == 0) {
653 				ext2_error(inode->i_sb, __FUNCTION__,
654 					"zero-length directory entry");
655 				printk("kaddr=%p, de=%p\n", kaddr, de);
656 				goto not_empty;
657 			}
658 			if (de->inode != 0) {
659 				/* check for . and .. */
660 				if (de->name[0] != '.')
661 					goto not_empty;
662 				if (de->name_len > 2)
663 					goto not_empty;
664 				if (de->name_len < 2) {
665 					if (de->inode !=
666 					    cpu_to_le32(inode->i_ino))
667 						goto not_empty;
668 				} else if (de->name[1] != '.')
669 					goto not_empty;
670 			}
671 			de = ext2_next_entry(de);
672 		}
673 		ext2_put_page(page);
674 	}
675 	return 1;
676 
677 not_empty:
678 	ext2_put_page(page);
679 	return 0;
680 }
681 
682 const struct file_operations ext2_dir_operations = {
683 	.llseek		= generic_file_llseek,
684 	.read		= generic_read_dir,
685 	.readdir	= ext2_readdir,
686 	.ioctl		= ext2_ioctl,
687 #ifdef CONFIG_COMPAT
688 	.compat_ioctl	= ext2_compat_ioctl,
689 #endif
690 	.fsync		= ext2_sync_file,
691 };
692