xref: /linux/fs/nilfs2/dir.c (revision 2c1ed907520c50326b8f604907a8478b27881a2e)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * NILFS directory entry operations
4  *
5  * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
6  *
7  * Modified for NILFS by Amagai Yoshiji.
8  */
9 /*
10  *  linux/fs/ext2/dir.c
11  *
12  * Copyright (C) 1992, 1993, 1994, 1995
13  * Remy Card (card@masi.ibp.fr)
14  * Laboratoire MASI - Institut Blaise Pascal
15  * Universite Pierre et Marie Curie (Paris VI)
16  *
17  *  from
18  *
19  *  linux/fs/minix/dir.c
20  *
21  *  Copyright (C) 1991, 1992  Linus Torvalds
22  *
23  *  ext2 directory handling functions
24  *
25  *  Big-endian to little-endian byte-swapping/bitmaps by
26  *        David S. Miller (davem@caip.rutgers.edu), 1995
27  *
28  * All code that works with directory layout had been switched to pagecache
29  * and moved here. AV
30  */
31 
32 #include <linux/pagemap.h>
33 #include "nilfs.h"
34 #include "page.h"
35 
nilfs_rec_len_from_disk(__le16 dlen)36 static inline unsigned int nilfs_rec_len_from_disk(__le16 dlen)
37 {
38 	unsigned int len = le16_to_cpu(dlen);
39 
40 #if (PAGE_SIZE >= 65536)
41 	if (len == NILFS_MAX_REC_LEN)
42 		return 1 << 16;
43 #endif
44 	return len;
45 }
46 
nilfs_rec_len_to_disk(unsigned int len)47 static inline __le16 nilfs_rec_len_to_disk(unsigned int len)
48 {
49 #if (PAGE_SIZE >= 65536)
50 	if (len == (1 << 16))
51 		return cpu_to_le16(NILFS_MAX_REC_LEN);
52 
53 	BUG_ON(len > (1 << 16));
54 #endif
55 	return cpu_to_le16(len);
56 }
57 
58 /*
59  * nilfs uses block-sized chunks. Arguably, sector-sized ones would be
60  * more robust, but we have what we have
61  */
nilfs_chunk_size(struct inode * inode)62 static inline unsigned int nilfs_chunk_size(struct inode *inode)
63 {
64 	return inode->i_sb->s_blocksize;
65 }
66 
67 /*
68  * Return the offset into page `page_nr' of the last valid
69  * byte in that page, plus one.
70  */
nilfs_last_byte(struct inode * inode,unsigned long page_nr)71 static unsigned int nilfs_last_byte(struct inode *inode, unsigned long page_nr)
72 {
73 	u64 last_byte = inode->i_size;
74 
75 	last_byte -= page_nr << PAGE_SHIFT;
76 	if (last_byte > PAGE_SIZE)
77 		last_byte = PAGE_SIZE;
78 	return last_byte;
79 }
80 
nilfs_prepare_chunk(struct folio * folio,unsigned int from,unsigned int to)81 static int nilfs_prepare_chunk(struct folio *folio, unsigned int from,
82 			       unsigned int to)
83 {
84 	loff_t pos = folio_pos(folio) + from;
85 
86 	return __block_write_begin(folio, pos, to - from, nilfs_get_block);
87 }
88 
nilfs_commit_chunk(struct folio * folio,struct address_space * mapping,size_t from,size_t to)89 static void nilfs_commit_chunk(struct folio *folio,
90 		struct address_space *mapping, size_t from, size_t to)
91 {
92 	struct inode *dir = mapping->host;
93 	loff_t pos = folio_pos(folio) + from;
94 	size_t copied, len = to - from;
95 	unsigned int nr_dirty;
96 	int err;
97 
98 	nr_dirty = nilfs_page_count_clean_buffers(folio, from, to);
99 	copied = block_write_end(NULL, mapping, pos, len, len, folio, NULL);
100 	if (pos + copied > dir->i_size)
101 		i_size_write(dir, pos + copied);
102 	if (IS_DIRSYNC(dir))
103 		nilfs_set_transaction_flag(NILFS_TI_SYNC);
104 	err = nilfs_set_file_dirty(dir, nr_dirty);
105 	WARN_ON(err); /* do not happen */
106 	folio_unlock(folio);
107 }
108 
nilfs_check_folio(struct folio * folio,char * kaddr)109 static bool nilfs_check_folio(struct folio *folio, char *kaddr)
110 {
111 	struct inode *dir = folio->mapping->host;
112 	struct super_block *sb = dir->i_sb;
113 	unsigned int chunk_size = nilfs_chunk_size(dir);
114 	size_t offs, rec_len;
115 	size_t limit = folio_size(folio);
116 	struct nilfs_dir_entry *p;
117 	char *error;
118 
119 	if (dir->i_size < folio_pos(folio) + limit) {
120 		limit = dir->i_size - folio_pos(folio);
121 		if (limit & (chunk_size - 1))
122 			goto Ebadsize;
123 		if (!limit)
124 			goto out;
125 	}
126 	for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
127 		p = (struct nilfs_dir_entry *)(kaddr + offs);
128 		rec_len = nilfs_rec_len_from_disk(p->rec_len);
129 
130 		if (rec_len < NILFS_DIR_REC_LEN(1))
131 			goto Eshort;
132 		if (rec_len & 3)
133 			goto Ealign;
134 		if (rec_len < NILFS_DIR_REC_LEN(p->name_len))
135 			goto Enamelen;
136 		if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
137 			goto Espan;
138 		if (unlikely(p->inode &&
139 			     NILFS_PRIVATE_INODE(le64_to_cpu(p->inode))))
140 			goto Einumber;
141 	}
142 	if (offs != limit)
143 		goto Eend;
144 out:
145 	folio_set_checked(folio);
146 	return true;
147 
148 	/* Too bad, we had an error */
149 
150 Ebadsize:
151 	nilfs_error(sb,
152 		    "size of directory #%lu is not a multiple of chunk size",
153 		    dir->i_ino);
154 	goto fail;
155 Eshort:
156 	error = "rec_len is smaller than minimal";
157 	goto bad_entry;
158 Ealign:
159 	error = "unaligned directory entry";
160 	goto bad_entry;
161 Enamelen:
162 	error = "rec_len is too small for name_len";
163 	goto bad_entry;
164 Espan:
165 	error = "directory entry across blocks";
166 	goto bad_entry;
167 Einumber:
168 	error = "disallowed inode number";
169 bad_entry:
170 	nilfs_error(sb,
171 		    "bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%zd, name_len=%d",
172 		    dir->i_ino, error, (folio->index << PAGE_SHIFT) + offs,
173 		    (unsigned long)le64_to_cpu(p->inode),
174 		    rec_len, p->name_len);
175 	goto fail;
176 Eend:
177 	p = (struct nilfs_dir_entry *)(kaddr + offs);
178 	nilfs_error(sb,
179 		    "entry in directory #%lu spans the page boundary offset=%lu, inode=%lu",
180 		    dir->i_ino, (folio->index << PAGE_SHIFT) + offs,
181 		    (unsigned long)le64_to_cpu(p->inode));
182 fail:
183 	return false;
184 }
185 
nilfs_get_folio(struct inode * dir,unsigned long n,struct folio ** foliop)186 static void *nilfs_get_folio(struct inode *dir, unsigned long n,
187 		struct folio **foliop)
188 {
189 	struct address_space *mapping = dir->i_mapping;
190 	struct folio *folio = read_mapping_folio(mapping, n, NULL);
191 	void *kaddr;
192 
193 	if (IS_ERR(folio))
194 		return folio;
195 
196 	kaddr = kmap_local_folio(folio, 0);
197 	if (unlikely(!folio_test_checked(folio))) {
198 		if (!nilfs_check_folio(folio, kaddr))
199 			goto fail;
200 	}
201 
202 	*foliop = folio;
203 	return kaddr;
204 
205 fail:
206 	folio_release_kmap(folio, kaddr);
207 	return ERR_PTR(-EIO);
208 }
209 
210 /*
211  * NOTE! unlike strncmp, nilfs_match returns 1 for success, 0 for failure.
212  *
213  * len <= NILFS_NAME_LEN and de != NULL are guaranteed by caller.
214  */
215 static int
nilfs_match(int len,const unsigned char * name,struct nilfs_dir_entry * de)216 nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *de)
217 {
218 	if (len != de->name_len)
219 		return 0;
220 	if (!de->inode)
221 		return 0;
222 	return !memcmp(name, de->name, len);
223 }
224 
225 /*
226  * p is at least 6 bytes before the end of page
227  */
nilfs_next_entry(struct nilfs_dir_entry * p)228 static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
229 {
230 	return (struct nilfs_dir_entry *)((char *)p +
231 					  nilfs_rec_len_from_disk(p->rec_len));
232 }
233 
nilfs_readdir(struct file * file,struct dir_context * ctx)234 static int nilfs_readdir(struct file *file, struct dir_context *ctx)
235 {
236 	loff_t pos = ctx->pos;
237 	struct inode *inode = file_inode(file);
238 	struct super_block *sb = inode->i_sb;
239 	unsigned int offset = pos & ~PAGE_MASK;
240 	unsigned long n = pos >> PAGE_SHIFT;
241 	unsigned long npages = dir_pages(inode);
242 
243 	if (pos > inode->i_size - NILFS_DIR_REC_LEN(1))
244 		return 0;
245 
246 	for ( ; n < npages; n++, offset = 0) {
247 		char *kaddr, *limit;
248 		struct nilfs_dir_entry *de;
249 		struct folio *folio;
250 
251 		kaddr = nilfs_get_folio(inode, n, &folio);
252 		if (IS_ERR(kaddr)) {
253 			nilfs_error(sb, "bad page in #%lu", inode->i_ino);
254 			ctx->pos += PAGE_SIZE - offset;
255 			return -EIO;
256 		}
257 		de = (struct nilfs_dir_entry *)(kaddr + offset);
258 		limit = kaddr + nilfs_last_byte(inode, n) -
259 			NILFS_DIR_REC_LEN(1);
260 		for ( ; (char *)de <= limit; de = nilfs_next_entry(de)) {
261 			if (de->rec_len == 0) {
262 				nilfs_error(sb, "zero-length directory entry");
263 				folio_release_kmap(folio, kaddr);
264 				return -EIO;
265 			}
266 			if (de->inode) {
267 				unsigned char t;
268 
269 				t = fs_ftype_to_dtype(de->file_type);
270 
271 				if (!dir_emit(ctx, de->name, de->name_len,
272 						le64_to_cpu(de->inode), t)) {
273 					folio_release_kmap(folio, kaddr);
274 					return 0;
275 				}
276 			}
277 			ctx->pos += nilfs_rec_len_from_disk(de->rec_len);
278 		}
279 		folio_release_kmap(folio, kaddr);
280 	}
281 	return 0;
282 }
283 
284 /*
285  * nilfs_find_entry()
286  *
287  * Finds an entry in the specified directory with the wanted name. It
288  * returns the folio in which the entry was found, and the entry itself.
289  * The folio is mapped and unlocked.  When the caller is finished with
290  * the entry, it should call folio_release_kmap().
291  *
292  * On failure, returns an error pointer and the caller should ignore foliop.
293  */
nilfs_find_entry(struct inode * dir,const struct qstr * qstr,struct folio ** foliop)294 struct nilfs_dir_entry *nilfs_find_entry(struct inode *dir,
295 		const struct qstr *qstr, struct folio **foliop)
296 {
297 	const unsigned char *name = qstr->name;
298 	int namelen = qstr->len;
299 	unsigned int reclen = NILFS_DIR_REC_LEN(namelen);
300 	unsigned long start, n;
301 	unsigned long npages = dir_pages(dir);
302 	struct nilfs_inode_info *ei = NILFS_I(dir);
303 	struct nilfs_dir_entry *de;
304 
305 	if (npages == 0)
306 		goto out;
307 
308 	start = ei->i_dir_start_lookup;
309 	if (start >= npages)
310 		start = 0;
311 	n = start;
312 	do {
313 		char *kaddr = nilfs_get_folio(dir, n, foliop);
314 
315 		if (IS_ERR(kaddr))
316 			return ERR_CAST(kaddr);
317 
318 		de = (struct nilfs_dir_entry *)kaddr;
319 		kaddr += nilfs_last_byte(dir, n) - reclen;
320 		while ((char *)de <= kaddr) {
321 			if (de->rec_len == 0) {
322 				nilfs_error(dir->i_sb,
323 					    "zero-length directory entry");
324 				folio_release_kmap(*foliop, kaddr);
325 				goto out;
326 			}
327 			if (nilfs_match(namelen, name, de))
328 				goto found;
329 			de = nilfs_next_entry(de);
330 		}
331 		folio_release_kmap(*foliop, kaddr);
332 
333 		if (++n >= npages)
334 			n = 0;
335 		/* next folio is past the blocks we've got */
336 		if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {
337 			nilfs_error(dir->i_sb,
338 			       "dir %lu size %lld exceeds block count %llu",
339 			       dir->i_ino, dir->i_size,
340 			       (unsigned long long)dir->i_blocks);
341 			goto out;
342 		}
343 	} while (n != start);
344 out:
345 	return ERR_PTR(-ENOENT);
346 
347 found:
348 	ei->i_dir_start_lookup = n;
349 	return de;
350 }
351 
nilfs_dotdot(struct inode * dir,struct folio ** foliop)352 struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct folio **foliop)
353 {
354 	struct folio *folio;
355 	struct nilfs_dir_entry *de, *next_de;
356 	size_t limit;
357 	char *msg;
358 
359 	de = nilfs_get_folio(dir, 0, &folio);
360 	if (IS_ERR(de))
361 		return NULL;
362 
363 	limit = nilfs_last_byte(dir, 0);  /* is a multiple of chunk size */
364 	if (unlikely(!limit || le64_to_cpu(de->inode) != dir->i_ino ||
365 		     !nilfs_match(1, ".", de))) {
366 		msg = "missing '.'";
367 		goto fail;
368 	}
369 
370 	next_de = nilfs_next_entry(de);
371 	/*
372 	 * If "next_de" has not reached the end of the chunk, there is
373 	 * at least one more record.  Check whether it matches "..".
374 	 */
375 	if (unlikely((char *)next_de == (char *)de + nilfs_chunk_size(dir) ||
376 		     !nilfs_match(2, "..", next_de))) {
377 		msg = "missing '..'";
378 		goto fail;
379 	}
380 	*foliop = folio;
381 	return next_de;
382 
383 fail:
384 	nilfs_error(dir->i_sb, "directory #%lu %s", dir->i_ino, msg);
385 	folio_release_kmap(folio, de);
386 	return NULL;
387 }
388 
nilfs_inode_by_name(struct inode * dir,const struct qstr * qstr,ino_t * ino)389 int nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr, ino_t *ino)
390 {
391 	struct nilfs_dir_entry *de;
392 	struct folio *folio;
393 
394 	de = nilfs_find_entry(dir, qstr, &folio);
395 	if (IS_ERR(de))
396 		return PTR_ERR(de);
397 
398 	*ino = le64_to_cpu(de->inode);
399 	folio_release_kmap(folio, de);
400 	return 0;
401 }
402 
nilfs_set_link(struct inode * dir,struct nilfs_dir_entry * de,struct folio * folio,struct inode * inode)403 int nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
404 		    struct folio *folio, struct inode *inode)
405 {
406 	size_t from = offset_in_folio(folio, de);
407 	size_t to = from + nilfs_rec_len_from_disk(de->rec_len);
408 	struct address_space *mapping = folio->mapping;
409 	int err;
410 
411 	folio_lock(folio);
412 	err = nilfs_prepare_chunk(folio, from, to);
413 	if (unlikely(err)) {
414 		folio_unlock(folio);
415 		return err;
416 	}
417 	de->inode = cpu_to_le64(inode->i_ino);
418 	de->file_type = fs_umode_to_ftype(inode->i_mode);
419 	nilfs_commit_chunk(folio, mapping, from, to);
420 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
421 	return 0;
422 }
423 
424 /*
425  *	Parent is locked.
426  */
nilfs_add_link(struct dentry * dentry,struct inode * inode)427 int nilfs_add_link(struct dentry *dentry, struct inode *inode)
428 {
429 	struct inode *dir = d_inode(dentry->d_parent);
430 	const unsigned char *name = dentry->d_name.name;
431 	int namelen = dentry->d_name.len;
432 	unsigned int chunk_size = nilfs_chunk_size(dir);
433 	unsigned int reclen = NILFS_DIR_REC_LEN(namelen);
434 	unsigned short rec_len, name_len;
435 	struct folio *folio = NULL;
436 	struct nilfs_dir_entry *de;
437 	unsigned long npages = dir_pages(dir);
438 	unsigned long n;
439 	size_t from, to;
440 	int err;
441 
442 	/*
443 	 * We take care of directory expansion in the same loop.
444 	 * This code plays outside i_size, so it locks the folio
445 	 * to protect that region.
446 	 */
447 	for (n = 0; n <= npages; n++) {
448 		char *kaddr = nilfs_get_folio(dir, n, &folio);
449 		char *dir_end;
450 
451 		if (IS_ERR(kaddr))
452 			return PTR_ERR(kaddr);
453 		folio_lock(folio);
454 		dir_end = kaddr + nilfs_last_byte(dir, n);
455 		de = (struct nilfs_dir_entry *)kaddr;
456 		kaddr += folio_size(folio) - reclen;
457 		while ((char *)de <= kaddr) {
458 			if ((char *)de == dir_end) {
459 				/* We hit i_size */
460 				name_len = 0;
461 				rec_len = chunk_size;
462 				de->rec_len = nilfs_rec_len_to_disk(chunk_size);
463 				de->inode = 0;
464 				goto got_it;
465 			}
466 			if (de->rec_len == 0) {
467 				nilfs_error(dir->i_sb,
468 					    "zero-length directory entry");
469 				err = -EIO;
470 				goto out_unlock;
471 			}
472 			err = -EEXIST;
473 			if (nilfs_match(namelen, name, de))
474 				goto out_unlock;
475 			name_len = NILFS_DIR_REC_LEN(de->name_len);
476 			rec_len = nilfs_rec_len_from_disk(de->rec_len);
477 			if (!de->inode && rec_len >= reclen)
478 				goto got_it;
479 			if (rec_len >= name_len + reclen)
480 				goto got_it;
481 			de = (struct nilfs_dir_entry *)((char *)de + rec_len);
482 		}
483 		folio_unlock(folio);
484 		folio_release_kmap(folio, kaddr);
485 	}
486 	BUG();
487 	return -EINVAL;
488 
489 got_it:
490 	from = offset_in_folio(folio, de);
491 	to = from + rec_len;
492 	err = nilfs_prepare_chunk(folio, from, to);
493 	if (err)
494 		goto out_unlock;
495 	if (de->inode) {
496 		struct nilfs_dir_entry *de1;
497 
498 		de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
499 		de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
500 		de->rec_len = nilfs_rec_len_to_disk(name_len);
501 		de = de1;
502 	}
503 	de->name_len = namelen;
504 	memcpy(de->name, name, namelen);
505 	de->inode = cpu_to_le64(inode->i_ino);
506 	de->file_type = fs_umode_to_ftype(inode->i_mode);
507 	nilfs_commit_chunk(folio, folio->mapping, from, to);
508 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
509 	nilfs_mark_inode_dirty(dir);
510 	/* OFFSET_CACHE */
511 out_put:
512 	folio_release_kmap(folio, de);
513 	return err;
514 out_unlock:
515 	folio_unlock(folio);
516 	goto out_put;
517 }
518 
519 /*
520  * nilfs_delete_entry deletes a directory entry by merging it with the
521  * previous entry. Folio is up-to-date.
522  */
nilfs_delete_entry(struct nilfs_dir_entry * dir,struct folio * folio)523 int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct folio *folio)
524 {
525 	struct address_space *mapping = folio->mapping;
526 	struct inode *inode = mapping->host;
527 	char *kaddr = (char *)((unsigned long)dir & ~(folio_size(folio) - 1));
528 	size_t from, to;
529 	struct nilfs_dir_entry *de, *pde = NULL;
530 	int err;
531 
532 	from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
533 	to = ((char *)dir - kaddr) + nilfs_rec_len_from_disk(dir->rec_len);
534 	de = (struct nilfs_dir_entry *)(kaddr + from);
535 
536 	while ((char *)de < (char *)dir) {
537 		if (de->rec_len == 0) {
538 			nilfs_error(inode->i_sb,
539 				    "zero-length directory entry");
540 			err = -EIO;
541 			goto out;
542 		}
543 		pde = de;
544 		de = nilfs_next_entry(de);
545 	}
546 	if (pde)
547 		from = (char *)pde - kaddr;
548 	folio_lock(folio);
549 	err = nilfs_prepare_chunk(folio, from, to);
550 	if (unlikely(err)) {
551 		folio_unlock(folio);
552 		goto out;
553 	}
554 	if (pde)
555 		pde->rec_len = nilfs_rec_len_to_disk(to - from);
556 	dir->inode = 0;
557 	nilfs_commit_chunk(folio, mapping, from, to);
558 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
559 out:
560 	return err;
561 }
562 
563 /*
564  * Set the first fragment of directory.
565  */
nilfs_make_empty(struct inode * inode,struct inode * parent)566 int nilfs_make_empty(struct inode *inode, struct inode *parent)
567 {
568 	struct address_space *mapping = inode->i_mapping;
569 	struct folio *folio = filemap_grab_folio(mapping, 0);
570 	unsigned int chunk_size = nilfs_chunk_size(inode);
571 	struct nilfs_dir_entry *de;
572 	int err;
573 	void *kaddr;
574 
575 	if (IS_ERR(folio))
576 		return PTR_ERR(folio);
577 
578 	err = nilfs_prepare_chunk(folio, 0, chunk_size);
579 	if (unlikely(err)) {
580 		folio_unlock(folio);
581 		goto fail;
582 	}
583 	kaddr = kmap_local_folio(folio, 0);
584 	memset(kaddr, 0, chunk_size);
585 	de = (struct nilfs_dir_entry *)kaddr;
586 	de->name_len = 1;
587 	de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
588 	memcpy(de->name, ".\0\0", 4);
589 	de->inode = cpu_to_le64(inode->i_ino);
590 	de->file_type = fs_umode_to_ftype(inode->i_mode);
591 
592 	de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
593 	de->name_len = 2;
594 	de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
595 	de->inode = cpu_to_le64(parent->i_ino);
596 	memcpy(de->name, "..\0", 4);
597 	de->file_type = fs_umode_to_ftype(inode->i_mode);
598 	kunmap_local(kaddr);
599 	nilfs_commit_chunk(folio, mapping, 0, chunk_size);
600 fail:
601 	folio_put(folio);
602 	return err;
603 }
604 
605 /*
606  * routine to check that the specified directory is empty (for rmdir)
607  */
nilfs_empty_dir(struct inode * inode)608 int nilfs_empty_dir(struct inode *inode)
609 {
610 	struct folio *folio = NULL;
611 	char *kaddr;
612 	unsigned long i, npages = dir_pages(inode);
613 
614 	for (i = 0; i < npages; i++) {
615 		struct nilfs_dir_entry *de;
616 
617 		kaddr = nilfs_get_folio(inode, i, &folio);
618 		if (IS_ERR(kaddr))
619 			return 0;
620 
621 		de = (struct nilfs_dir_entry *)kaddr;
622 		kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);
623 
624 		while ((char *)de <= kaddr) {
625 			if (de->rec_len == 0) {
626 				nilfs_error(inode->i_sb,
627 					    "zero-length directory entry (kaddr=%p, de=%p)",
628 					    kaddr, de);
629 				goto not_empty;
630 			}
631 			if (de->inode != 0) {
632 				/* check for . and .. */
633 				if (de->name[0] != '.')
634 					goto not_empty;
635 				if (de->name_len > 2)
636 					goto not_empty;
637 				if (de->name_len < 2) {
638 					if (de->inode !=
639 					    cpu_to_le64(inode->i_ino))
640 						goto not_empty;
641 				} else if (de->name[1] != '.')
642 					goto not_empty;
643 			}
644 			de = nilfs_next_entry(de);
645 		}
646 		folio_release_kmap(folio, kaddr);
647 	}
648 	return 1;
649 
650 not_empty:
651 	folio_release_kmap(folio, kaddr);
652 	return 0;
653 }
654 
655 const struct file_operations nilfs_dir_operations = {
656 	.llseek		= generic_file_llseek,
657 	.read		= generic_read_dir,
658 	.iterate_shared	= nilfs_readdir,
659 	.unlocked_ioctl	= nilfs_ioctl,
660 #ifdef CONFIG_COMPAT
661 	.compat_ioctl	= nilfs_compat_ioctl,
662 #endif	/* CONFIG_COMPAT */
663 	.fsync		= nilfs_sync_file,
664 
665 };
666