xref: /linux/fs/exfat/dir.c (revision 1b78070aaef63512688aebfbc82365ef9d6660f1)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
4  */
5 
6 #include <linux/slab.h>
7 #include <linux/compat.h>
8 #include <linux/bio.h>
9 #include <linux/buffer_head.h>
10 #include <linux/filelock.h>
11 
12 #include "exfat_raw.h"
13 #include "exfat_fs.h"
14 
15 static int exfat_extract_uni_name(struct exfat_dentry *ep,
16 		unsigned short *uniname)
17 {
18 	int i, len = 0;
19 
20 	for (i = 0; i < EXFAT_FILE_NAME_LEN; i++) {
21 		*uniname = le16_to_cpu(ep->dentry.name.unicode_0_14[i]);
22 		if (*uniname == 0x0)
23 			return len;
24 		uniname++;
25 		len++;
26 	}
27 
28 	*uniname = 0x0;
29 	return len;
30 
31 }
32 
33 static int exfat_get_uniname_from_ext_entry(struct super_block *sb,
34 		struct exfat_chain *p_dir, int entry, unsigned short *uniname)
35 {
36 	int i, err;
37 	struct exfat_entry_set_cache es;
38 	unsigned int uni_len = 0, len;
39 
40 	err = exfat_get_dentry_set(&es, sb, p_dir, entry, ES_ALL_ENTRIES);
41 	if (err)
42 		return err;
43 
44 	/*
45 	 * First entry  : file entry
46 	 * Second entry : stream-extension entry
47 	 * Third entry  : first file-name entry
48 	 * So, the index of first file-name dentry should start from 2.
49 	 */
50 	for (i = ES_IDX_FIRST_FILENAME; i < es.num_entries; i++) {
51 		struct exfat_dentry *ep = exfat_get_dentry_cached(&es, i);
52 
53 		/* end of name entry */
54 		if (exfat_get_entry_type(ep) != TYPE_EXTEND)
55 			break;
56 
57 		len = exfat_extract_uni_name(ep, uniname);
58 		uni_len += len;
59 		if (len != EXFAT_FILE_NAME_LEN || uni_len >= MAX_NAME_LENGTH)
60 			break;
61 		uniname += EXFAT_FILE_NAME_LEN;
62 	}
63 
64 	exfat_put_dentry_set(&es, false);
65 	return 0;
66 }
67 
68 /* read a directory entry from the opened directory */
69 static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_entry *dir_entry)
70 {
71 	int i, dentries_per_clu, num_ext, err;
72 	unsigned int type, clu_offset, max_dentries;
73 	struct exfat_chain dir, clu;
74 	struct exfat_uni_name uni_name;
75 	struct exfat_dentry *ep;
76 	struct super_block *sb = inode->i_sb;
77 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
78 	struct exfat_inode_info *ei = EXFAT_I(inode);
79 	unsigned int dentry = exfat_bytes_to_dentries(*cpos) & 0xFFFFFFFF;
80 	struct buffer_head *bh;
81 
82 	/* check if the given file ID is opened */
83 	if (ei->type != TYPE_DIR)
84 		return -EPERM;
85 
86 	exfat_chain_set(&dir, ei->start_clu,
87 		exfat_bytes_to_cluster(sbi, i_size_read(inode)), ei->flags);
88 
89 	dentries_per_clu = sbi->dentries_per_clu;
90 	max_dentries = (unsigned int)min_t(u64, MAX_EXFAT_DENTRIES,
91 			exfat_cluster_to_dentries(sbi, sbi->num_clusters));
92 
93 	clu_offset = exfat_dentries_to_cluster(sbi, dentry);
94 	exfat_chain_dup(&clu, &dir);
95 
96 	if (clu.flags == ALLOC_FAT_CHAIN) {
97 		/* hint_information */
98 		if (clu_offset > 0 && ei->hint_bmap.off != EXFAT_EOF_CLUSTER &&
99 		    ei->hint_bmap.off > 0 && clu_offset >= ei->hint_bmap.off) {
100 			clu_offset -= ei->hint_bmap.off;
101 			clu.dir = ei->hint_bmap.clu;
102 			clu.size -= ei->hint_bmap.off;
103 		}
104 	}
105 
106 	if (exfat_chain_advance(sb, &clu, clu_offset))
107 		return -EIO;
108 
109 	while (clu.dir != EXFAT_EOF_CLUSTER && dentry < max_dentries) {
110 		i = dentry & (dentries_per_clu - 1);
111 
112 		for ( ; i < dentries_per_clu; i++, dentry++) {
113 			ep = exfat_get_dentry(sb, &clu, i, &bh);
114 			if (!ep)
115 				return -EIO;
116 
117 			type = exfat_get_entry_type(ep);
118 			if (type == TYPE_UNUSED) {
119 				brelse(bh);
120 				goto out;
121 			}
122 
123 			if (type != TYPE_FILE && type != TYPE_DIR) {
124 				brelse(bh);
125 				continue;
126 			}
127 
128 			num_ext = ep->dentry.file.num_ext;
129 			dir_entry->attr = le16_to_cpu(ep->dentry.file.attr);
130 
131 			*uni_name.name = 0x0;
132 			err = exfat_get_uniname_from_ext_entry(sb, &clu, i,
133 				uni_name.name);
134 			if (err) {
135 				brelse(bh);
136 				continue;
137 			}
138 			exfat_utf16_to_nls(sb, &uni_name,
139 				dir_entry->namebuf.lfn,
140 				dir_entry->namebuf.lfnbuf_len);
141 			brelse(bh);
142 
143 			ep = exfat_get_dentry(sb, &clu, i + 1, &bh);
144 			if (!ep)
145 				return -EIO;
146 			dir_entry->entry = i;
147 			dir_entry->dir = clu;
148 			brelse(bh);
149 
150 			ei->hint_bmap.off = exfat_dentries_to_cluster(sbi, dentry);
151 			ei->hint_bmap.clu = clu.dir;
152 
153 			*cpos = exfat_dentries_to_bytes(dentry + 1 + num_ext);
154 			return 0;
155 		}
156 
157 		if (exfat_chain_advance(sb, &clu, 1))
158 			return -EIO;
159 	}
160 
161 out:
162 	dir_entry->namebuf.lfn[0] = '\0';
163 	*cpos = exfat_dentries_to_bytes(dentry);
164 	return 0;
165 }
166 
167 static void exfat_init_namebuf(struct exfat_dentry_namebuf *nb)
168 {
169 	nb->lfn = NULL;
170 	nb->lfnbuf_len = 0;
171 }
172 
173 static int exfat_alloc_namebuf(struct exfat_dentry_namebuf *nb)
174 {
175 	nb->lfn = __getname();
176 	if (!nb->lfn)
177 		return -ENOMEM;
178 	nb->lfnbuf_len = MAX_VFSNAME_BUF_SIZE;
179 	return 0;
180 }
181 
182 static void exfat_free_namebuf(struct exfat_dentry_namebuf *nb)
183 {
184 	if (!nb->lfn)
185 		return;
186 
187 	__putname(nb->lfn);
188 	exfat_init_namebuf(nb);
189 }
190 
191 /*
192  * Before calling dir_emit*(), sbi->s_lock should be released
193  * because page fault can occur in dir_emit*().
194  */
195 #define ITER_POS_FILLED_DOTS    (2)
196 static int exfat_iterate(struct file *file, struct dir_context *ctx)
197 {
198 	struct inode *inode = file_inode(file);
199 	struct super_block *sb = inode->i_sb;
200 	struct inode *tmp;
201 	struct exfat_dir_entry de;
202 	struct exfat_dentry_namebuf *nb = &(de.namebuf);
203 	struct exfat_inode_info *ei = EXFAT_I(inode);
204 	unsigned long inum;
205 	loff_t cpos, i_pos;
206 	int err = 0, fake_offset = 0;
207 
208 	exfat_init_namebuf(nb);
209 
210 	cpos = ctx->pos;
211 	if (!dir_emit_dots(file, ctx))
212 		goto out;
213 
214 	if (ctx->pos == ITER_POS_FILLED_DOTS) {
215 		cpos = 0;
216 		fake_offset = 1;
217 	}
218 
219 	cpos = round_up(cpos, DENTRY_SIZE);
220 
221 	/* name buffer should be allocated before use */
222 	err = exfat_alloc_namebuf(nb);
223 	if (err)
224 		goto out;
225 get_new:
226 	mutex_lock(&EXFAT_SB(sb)->s_lock);
227 
228 	if (ei->flags == ALLOC_NO_FAT_CHAIN && cpos >= i_size_read(inode))
229 		goto end_of_dir;
230 
231 	err = exfat_readdir(inode, &cpos, &de);
232 	if (err) {
233 		/*
234 		 * At least we tried to read a sector.
235 		 * Move cpos to next sector position (should be aligned).
236 		 */
237 		if (err == -EIO) {
238 			cpos += 1 << (sb->s_blocksize_bits);
239 			cpos &= ~(loff_t)(sb->s_blocksize - 1);
240 		}
241 
242 		err = -EIO;
243 		goto end_of_dir;
244 	}
245 
246 	if (!nb->lfn[0])
247 		goto end_of_dir;
248 
249 	i_pos = ((loff_t)de.dir.dir << 32) | (de.entry & 0xffffffff);
250 	tmp = exfat_iget(sb, i_pos);
251 	if (tmp) {
252 		inum = tmp->i_ino;
253 		iput(tmp);
254 	} else {
255 		inum = iunique(sb, EXFAT_ROOT_INO);
256 	}
257 
258 	mutex_unlock(&EXFAT_SB(sb)->s_lock);
259 	if (!dir_emit(ctx, nb->lfn, strlen(nb->lfn), inum,
260 			(de.attr & EXFAT_ATTR_SUBDIR) ? DT_DIR : DT_REG))
261 		goto out;
262 	ctx->pos = cpos;
263 	goto get_new;
264 
265 end_of_dir:
266 	if (!cpos && fake_offset)
267 		cpos = ITER_POS_FILLED_DOTS;
268 	ctx->pos = cpos;
269 	mutex_unlock(&EXFAT_SB(sb)->s_lock);
270 out:
271 	/*
272 	 * To improve performance, free namebuf after unlock sb_lock.
273 	 * If namebuf is not allocated, this function do nothing
274 	 */
275 	exfat_free_namebuf(nb);
276 	return err;
277 }
278 
279 WRAP_DIR_ITER(exfat_iterate) // FIXME!
280 const struct file_operations exfat_dir_operations = {
281 	.llseek		= generic_file_llseek,
282 	.read		= generic_read_dir,
283 	.iterate_shared	= shared_exfat_iterate,
284 	.unlocked_ioctl = exfat_ioctl,
285 #ifdef CONFIG_COMPAT
286 	.compat_ioctl = exfat_compat_ioctl,
287 #endif
288 	.fsync		= exfat_file_fsync,
289 	.setlease	= generic_setlease,
290 };
291 
292 int exfat_alloc_new_dir(struct inode *inode, struct exfat_chain *clu)
293 {
294 	int ret;
295 
296 	exfat_chain_set(clu, EXFAT_EOF_CLUSTER, 0, ALLOC_NO_FAT_CHAIN);
297 
298 	ret = exfat_alloc_cluster(inode, 1, clu, IS_DIRSYNC(inode), false);
299 	if (ret)
300 		return ret;
301 
302 	ret = exfat_zeroed_cluster(inode, clu->dir);
303 	if (ret) {
304 		exfat_free_cluster(inode, clu);
305 		return ret;
306 	}
307 
308 	return 0;
309 }
310 
311 int exfat_calc_num_entries(struct exfat_uni_name *p_uniname)
312 {
313 	int len;
314 
315 	len = p_uniname->name_len;
316 	if (len == 0)
317 		return -EINVAL;
318 
319 	/* 1 file entry + 1 stream entry + name entries */
320 	return ES_ENTRY_NUM(len);
321 }
322 
323 unsigned int exfat_get_entry_type(struct exfat_dentry *ep)
324 {
325 	if (ep->type == EXFAT_UNUSED)
326 		return TYPE_UNUSED;
327 	if (IS_EXFAT_DELETED(ep->type))
328 		return TYPE_DELETED;
329 	if (ep->type == EXFAT_INVAL)
330 		return TYPE_INVALID;
331 	if (IS_EXFAT_CRITICAL_PRI(ep->type)) {
332 		if (ep->type == EXFAT_BITMAP)
333 			return TYPE_BITMAP;
334 		if (ep->type == EXFAT_UPCASE)
335 			return TYPE_UPCASE;
336 		if (ep->type == EXFAT_VOLUME)
337 			return TYPE_VOLUME;
338 		if (ep->type == EXFAT_FILE) {
339 			if (le16_to_cpu(ep->dentry.file.attr) & EXFAT_ATTR_SUBDIR)
340 				return TYPE_DIR;
341 			return TYPE_FILE;
342 		}
343 		return TYPE_CRITICAL_PRI;
344 	}
345 	if (IS_EXFAT_BENIGN_PRI(ep->type)) {
346 		if (ep->type == EXFAT_GUID)
347 			return TYPE_GUID;
348 		if (ep->type == EXFAT_PADDING)
349 			return TYPE_PADDING;
350 		if (ep->type == EXFAT_ACLTAB)
351 			return TYPE_ACLTAB;
352 		return TYPE_BENIGN_PRI;
353 	}
354 	if (IS_EXFAT_CRITICAL_SEC(ep->type)) {
355 		if (ep->type == EXFAT_STREAM)
356 			return TYPE_STREAM;
357 		if (ep->type == EXFAT_NAME)
358 			return TYPE_EXTEND;
359 		if (ep->type == EXFAT_ACL)
360 			return TYPE_ACL;
361 		return TYPE_CRITICAL_SEC;
362 	}
363 
364 	if (ep->type == EXFAT_VENDOR_EXT)
365 		return TYPE_VENDOR_EXT;
366 	if (ep->type == EXFAT_VENDOR_ALLOC)
367 		return TYPE_VENDOR_ALLOC;
368 
369 	return TYPE_BENIGN_SEC;
370 }
371 
372 static void exfat_set_entry_type(struct exfat_dentry *ep, unsigned int type)
373 {
374 	if (type == TYPE_UNUSED) {
375 		ep->type = EXFAT_UNUSED;
376 	} else if (type == TYPE_DELETED) {
377 		ep->type &= EXFAT_DELETE;
378 	} else if (type == TYPE_STREAM) {
379 		ep->type = EXFAT_STREAM;
380 	} else if (type == TYPE_EXTEND) {
381 		ep->type = EXFAT_NAME;
382 	} else if (type == TYPE_BITMAP) {
383 		ep->type = EXFAT_BITMAP;
384 	} else if (type == TYPE_UPCASE) {
385 		ep->type = EXFAT_UPCASE;
386 	} else if (type == TYPE_VOLUME) {
387 		ep->type = EXFAT_VOLUME;
388 	} else if (type == TYPE_DIR) {
389 		ep->type = EXFAT_FILE;
390 		ep->dentry.file.attr = cpu_to_le16(EXFAT_ATTR_SUBDIR);
391 	} else if (type == TYPE_FILE) {
392 		ep->type = EXFAT_FILE;
393 		ep->dentry.file.attr = cpu_to_le16(EXFAT_ATTR_ARCHIVE);
394 	}
395 }
396 
397 static void exfat_init_stream_entry(struct exfat_dentry *ep,
398 		unsigned int start_clu, unsigned long long size)
399 {
400 	memset(ep, 0, sizeof(*ep));
401 	exfat_set_entry_type(ep, TYPE_STREAM);
402 	if (size == 0)
403 		ep->dentry.stream.flags = ALLOC_FAT_CHAIN;
404 	else
405 		ep->dentry.stream.flags = ALLOC_NO_FAT_CHAIN;
406 	ep->dentry.stream.start_clu = cpu_to_le32(start_clu);
407 	ep->dentry.stream.valid_size = cpu_to_le64(size);
408 	ep->dentry.stream.size = cpu_to_le64(size);
409 }
410 
411 static void exfat_init_name_entry(struct exfat_dentry *ep,
412 		unsigned short *uniname)
413 {
414 	int i;
415 
416 	exfat_set_entry_type(ep, TYPE_EXTEND);
417 	ep->dentry.name.flags = 0x0;
418 
419 	for (i = 0; i < EXFAT_FILE_NAME_LEN; i++) {
420 		if (*uniname != 0x0) {
421 			ep->dentry.name.unicode_0_14[i] = cpu_to_le16(*uniname);
422 			uniname++;
423 		} else {
424 			ep->dentry.name.unicode_0_14[i] = 0x0;
425 		}
426 	}
427 }
428 
429 void exfat_init_dir_entry(struct exfat_entry_set_cache *es,
430 		unsigned int type, unsigned int start_clu,
431 		unsigned long long size, struct timespec64 *ts)
432 {
433 	struct super_block *sb = es->sb;
434 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
435 	struct exfat_dentry *ep;
436 
437 	ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
438 	memset(ep, 0, sizeof(*ep));
439 	exfat_set_entry_type(ep, type);
440 	exfat_set_entry_time(sbi, ts,
441 			&ep->dentry.file.create_tz,
442 			&ep->dentry.file.create_time,
443 			&ep->dentry.file.create_date,
444 			&ep->dentry.file.create_time_cs);
445 	exfat_set_entry_time(sbi, ts,
446 			&ep->dentry.file.modify_tz,
447 			&ep->dentry.file.modify_time,
448 			&ep->dentry.file.modify_date,
449 			&ep->dentry.file.modify_time_cs);
450 	exfat_set_entry_time(sbi, ts,
451 			&ep->dentry.file.access_tz,
452 			&ep->dentry.file.access_time,
453 			&ep->dentry.file.access_date,
454 			NULL);
455 
456 	ep = exfat_get_dentry_cached(es, ES_IDX_STREAM);
457 	exfat_init_stream_entry(ep, start_clu, size);
458 }
459 
460 static void exfat_free_benign_secondary_clusters(struct inode *inode,
461 		struct exfat_dentry *ep)
462 {
463 	struct super_block *sb = inode->i_sb;
464 	struct exfat_chain dir;
465 	unsigned int start_clu =
466 		le32_to_cpu(ep->dentry.generic_secondary.start_clu);
467 	u64 size = le64_to_cpu(ep->dentry.generic_secondary.size);
468 	unsigned char flags = ep->dentry.generic_secondary.flags;
469 
470 	if (!(flags & ALLOC_POSSIBLE) || !start_clu || !size)
471 		return;
472 
473 	exfat_chain_set(&dir, start_clu,
474 			exfat_bytes_to_cluster_round_up(EXFAT_SB(sb), size),
475 			flags);
476 	exfat_free_cluster(inode, &dir);
477 }
478 
479 /*
480  * exfat_init_ext_entry - initialize extension entries in a directory entry set
481  * @es:          target entry set
482  * @num_entries: number of entries excluding benign secondary entries
483  * @p_uniname:   filename to store
484  * @old_es:      optional source entry set with benign secondary entries, or NULL
485  * @num_extra:   number of benign secondary entries to copy from @old_es
486  *
487  * Set up the file, stream extension, and filename entries in @es, optionally
488  * preserving @num_extra benign secondary entries from @old_es.  @es and @old_es
489  * may refer to the same entry set; excess entries are marked as deleted.
490  */
491 void exfat_init_ext_entry(struct exfat_entry_set_cache *es, int num_entries,
492 		struct exfat_uni_name *p_uniname,
493 		struct exfat_entry_set_cache *old_es, int num_extra)
494 {
495 	int i, src_start = 0, old_num;
496 	unsigned short *uniname = p_uniname->name;
497 	struct exfat_dentry *ep;
498 
499 	if (WARN_ON(num_extra < 0 || (num_extra && (!old_es ||
500 		    old_es->num_entries < ES_IDX_FIRST_FILENAME + num_extra))))
501 		num_extra = 0;
502 
503 	/*
504 	 * Save old entry count and source position before modifying
505 	 * es->num_entries, since old_es and es may point to the same
506 	 * entry set.
507 	 */
508 	old_num = es->num_entries;
509 	if (old_es && num_extra > 0)
510 		src_start = old_es->num_entries - num_extra;
511 
512 	es->num_entries = num_entries + num_extra;
513 	ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
514 	ep->dentry.file.num_ext = (unsigned char)(num_entries - 1 + num_extra);
515 
516 	ep = exfat_get_dentry_cached(es, ES_IDX_STREAM);
517 	ep->dentry.stream.name_len = p_uniname->name_len;
518 	ep->dentry.stream.name_hash = cpu_to_le16(p_uniname->name_hash);
519 
520 	if (old_es && num_extra > 0) {
521 		for (i = 0; i < num_extra; i++)
522 			*exfat_get_dentry_cached(es, num_entries + i) =
523 				*exfat_get_dentry_cached(old_es, src_start + i);
524 	}
525 
526 	for (i = ES_IDX_FIRST_FILENAME; i < num_entries; i++) {
527 		ep = exfat_get_dentry_cached(es, i);
528 		exfat_init_name_entry(ep, uniname);
529 		uniname += EXFAT_FILE_NAME_LEN;
530 	}
531 
532 	/* Mark excess old entries as deleted (in-place shrink) */
533 	for (i = num_entries + num_extra; i < old_num; i++) {
534 		ep = exfat_get_dentry_cached(es, i);
535 		exfat_set_entry_type(ep, TYPE_DELETED);
536 	}
537 
538 	exfat_update_dir_chksum(es);
539 }
540 
541 void exfat_remove_entries(struct inode *inode, struct exfat_entry_set_cache *es,
542 		int order, bool free_benign)
543 {
544 	int i;
545 	struct exfat_dentry *ep;
546 
547 	for (i = order; i < es->num_entries; i++) {
548 		ep = exfat_get_dentry_cached(es, i);
549 
550 		if (free_benign && (exfat_get_entry_type(ep) & TYPE_BENIGN_SEC))
551 			exfat_free_benign_secondary_clusters(inode, ep);
552 
553 		exfat_set_entry_type(ep, TYPE_DELETED);
554 	}
555 
556 	if (order < es->num_entries)
557 		es->modified = true;
558 }
559 
560 void exfat_update_dir_chksum(struct exfat_entry_set_cache *es)
561 {
562 	int chksum_type = CS_DIR_ENTRY, i;
563 	unsigned short chksum = 0;
564 	struct exfat_dentry *ep;
565 
566 	for (i = ES_IDX_FILE; i < es->num_entries; i++) {
567 		ep = exfat_get_dentry_cached(es, i);
568 		chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
569 					     chksum_type);
570 		chksum_type = CS_DEFAULT;
571 	}
572 	ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
573 	ep->dentry.file.checksum = cpu_to_le16(chksum);
574 	es->modified = true;
575 }
576 
577 int exfat_put_dentry_set(struct exfat_entry_set_cache *es, int sync)
578 {
579 	int i, err = 0;
580 
581 	if (es->modified)
582 		err = exfat_update_bhs(es->bh, es->num_bh, sync);
583 
584 	for (i = 0; i < es->num_bh; i++)
585 		if (err)
586 			bforget(es->bh[i]);
587 		else
588 			brelse(es->bh[i]);
589 
590 	if (IS_DYNAMIC_ES(es))
591 		kfree(es->bh);
592 
593 	return err;
594 }
595 
596 static int exfat_find_location(struct super_block *sb, struct exfat_chain *p_dir,
597 			       int entry, sector_t *sector, int *offset)
598 {
599 	int ret;
600 	unsigned int off, clu = 0;
601 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
602 
603 	off = exfat_dentries_to_bytes(entry);
604 
605 	clu = p_dir->dir;
606 	ret = exfat_cluster_walk(sb, &clu, exfat_bytes_to_cluster(sbi, off),
607 			p_dir->flags);
608 	if (ret)
609 		return ret;
610 
611 	if (clu == EXFAT_EOF_CLUSTER) {
612 		exfat_fs_error(sb,
613 			"unexpected early break in cluster chain (clu : %u, len : %d)",
614 			p_dir->dir,
615 			exfat_bytes_to_cluster(sbi, off));
616 		return -EIO;
617 	}
618 
619 	if (!exfat_test_bitmap(sb, clu)) {
620 		exfat_err(sb, "failed to test cluster bit(%u)", clu);
621 		return -EIO;
622 	}
623 
624 	/* byte offset in cluster */
625 	off = exfat_cluster_offset(sbi, off);
626 
627 	/* byte offset in sector    */
628 	*offset = exfat_block_offset(sb, off);
629 
630 	/* sector offset in cluster */
631 	*sector = exfat_bytes_to_block(sb, off);
632 	*sector += exfat_cluster_to_sector(sbi, clu);
633 	return 0;
634 }
635 
636 struct exfat_dentry *exfat_get_dentry(struct super_block *sb,
637 		struct exfat_chain *p_dir, int entry, struct buffer_head **bh)
638 {
639 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
640 	unsigned int sect_per_clus = sbi->sect_per_clus;
641 	unsigned int dentries_per_page = exfat_bytes_to_dentries(PAGE_SIZE);
642 	int off;
643 	sector_t sec;
644 
645 	if (p_dir->dir == DIR_DELETED) {
646 		exfat_err(sb, "abnormal access to deleted dentry");
647 		return NULL;
648 	}
649 
650 	if (exfat_find_location(sb, p_dir, entry, &sec, &off))
651 		return NULL;
652 
653 	if (sect_per_clus > 1 &&
654 	    (entry & (dentries_per_page - 1)) == 0) {
655 		sector_t ra = sec;
656 		blkcnt_t cnt = 0;
657 		unsigned int ra_count = sect_per_clus;
658 
659 		/* Not sector aligned with ra_count, resize ra_count to page size */
660 		if ((sec - sbi->data_start_sector) & (ra_count - 1))
661 			ra_count = PAGE_SIZE >> sb->s_blocksize_bits;
662 
663 		exfat_blk_readahead(sb, sec, &ra, &cnt, sec + ra_count - 1);
664 	}
665 
666 	*bh = sb_bread(sb, sec);
667 	if (!*bh)
668 		return NULL;
669 
670 	return (struct exfat_dentry *)((*bh)->b_data + off);
671 }
672 
673 enum exfat_validate_dentry_mode {
674 	ES_MODE_GET_FILE_ENTRY,
675 	ES_MODE_GET_STRM_ENTRY,
676 	ES_MODE_GET_NAME_ENTRY,
677 	ES_MODE_GET_CRITICAL_SEC_ENTRY,
678 	ES_MODE_GET_BENIGN_SEC_ENTRY,
679 };
680 
681 static bool exfat_validate_entry(unsigned int type,
682 		enum exfat_validate_dentry_mode *mode)
683 {
684 	if (type == TYPE_UNUSED || type == TYPE_DELETED)
685 		return false;
686 
687 	switch (*mode) {
688 	case ES_MODE_GET_FILE_ENTRY:
689 		if (type != TYPE_STREAM)
690 			return false;
691 		*mode = ES_MODE_GET_STRM_ENTRY;
692 		break;
693 	case ES_MODE_GET_STRM_ENTRY:
694 		if (type != TYPE_EXTEND)
695 			return false;
696 		*mode = ES_MODE_GET_NAME_ENTRY;
697 		break;
698 	case ES_MODE_GET_NAME_ENTRY:
699 		if (type & TYPE_BENIGN_SEC)
700 			*mode = ES_MODE_GET_BENIGN_SEC_ENTRY;
701 		else if (type != TYPE_EXTEND)
702 			return false;
703 		break;
704 	case ES_MODE_GET_BENIGN_SEC_ENTRY:
705 		/* Assume unreconized benign secondary entry */
706 		if (!(type & TYPE_BENIGN_SEC))
707 			return false;
708 		break;
709 	default:
710 		return false;
711 	}
712 
713 	return true;
714 }
715 
716 struct exfat_dentry *exfat_get_dentry_cached(
717 	struct exfat_entry_set_cache *es, int num)
718 {
719 	int off = es->start_off + num * DENTRY_SIZE;
720 	struct buffer_head *bh = es->bh[exfat_bytes_to_block(es->sb, off)];
721 	char *p = bh->b_data + exfat_block_offset(es->sb, off);
722 
723 	return (struct exfat_dentry *)p;
724 }
725 
726 /*
727  * Returns a set of dentries.
728  *
729  * Note It provides a direct pointer to bh->data via exfat_get_dentry_cached().
730  * User should call exfat_get_dentry_set() after setting 'modified' to apply
731  * changes made in this entry set to the real device.
732  *
733  * in:
734  *   sb+p_dir+entry: indicates a file/dir
735  *   num_entries: specifies how many dentries should be included.
736  *                It will be set to es->num_entries if it is not 0.
737  *                If num_entries is 0, es->num_entries will be obtained
738  *                from the first dentry.
739  * out:
740  *   es: pointer of entry set on success.
741  * return:
742  *   0 on success
743  *   -error code on failure
744  */
745 static int __exfat_get_dentry_set(struct exfat_entry_set_cache *es,
746 		struct super_block *sb, struct exfat_chain *p_dir, int entry,
747 		unsigned int num_entries)
748 {
749 	int ret, i, num_bh;
750 	unsigned int off;
751 	sector_t sec;
752 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
753 	struct buffer_head *bh;
754 
755 	if (p_dir->dir == DIR_DELETED) {
756 		exfat_err(sb, "access to deleted dentry");
757 		return -EIO;
758 	}
759 
760 	ret = exfat_find_location(sb, p_dir, entry, &sec, &off);
761 	if (ret)
762 		return ret;
763 
764 	memset(es, 0, sizeof(*es));
765 	es->sb = sb;
766 	es->modified = false;
767 	es->start_off = off;
768 	es->bh = es->__bh;
769 
770 	bh = sb_bread(sb, sec);
771 	if (!bh)
772 		return -EIO;
773 	es->bh[es->num_bh++] = bh;
774 
775 	if (num_entries == ES_ALL_ENTRIES) {
776 		struct exfat_dentry *ep;
777 
778 		ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
779 		if (ep->type != EXFAT_FILE) {
780 			brelse(bh);
781 			return -EIO;
782 		}
783 
784 		num_entries = ep->dentry.file.num_ext + 1;
785 	}
786 
787 	es->num_entries = num_entries;
788 
789 	num_bh = exfat_bytes_to_block_round_up(sb, off + num_entries * DENTRY_SIZE);
790 	if (num_bh > ARRAY_SIZE(es->__bh)) {
791 		es->bh = kmalloc_objs(*es->bh, num_bh, GFP_NOFS);
792 		if (!es->bh) {
793 			brelse(bh);
794 			return -ENOMEM;
795 		}
796 		es->bh[0] = bh;
797 	}
798 
799 	for (i = 1; i < num_bh; i++) {
800 		/* get the next sector */
801 		if (exfat_is_last_sector_in_cluster(sbi, sec)) {
802 			unsigned int clu = exfat_sector_to_cluster(sbi, sec);
803 
804 			if (exfat_cluster_walk(sb, &clu, 1, p_dir->flags))
805 				goto put_es;
806 			sec = exfat_cluster_to_sector(sbi, clu);
807 		} else {
808 			sec++;
809 		}
810 
811 		bh = sb_bread(sb, sec);
812 		if (!bh)
813 			goto put_es;
814 		es->bh[es->num_bh++] = bh;
815 	}
816 
817 	return 0;
818 
819 put_es:
820 	exfat_put_dentry_set(es, false);
821 	return -EIO;
822 }
823 
824 int exfat_get_dentry_set(struct exfat_entry_set_cache *es,
825 		struct super_block *sb, struct exfat_chain *p_dir,
826 		int entry, unsigned int num_entries)
827 {
828 	int ret, i;
829 	struct exfat_dentry *ep;
830 	enum exfat_validate_dentry_mode mode = ES_MODE_GET_FILE_ENTRY;
831 
832 	ret = __exfat_get_dentry_set(es, sb, p_dir, entry, num_entries);
833 	if (ret < 0)
834 		return ret;
835 
836 	/* validate cached dentries */
837 	for (i = ES_IDX_STREAM; i < es->num_entries; i++) {
838 		ep = exfat_get_dentry_cached(es, i);
839 		if (!exfat_validate_entry(exfat_get_entry_type(ep), &mode))
840 			goto put_es;
841 	}
842 	return 0;
843 
844 put_es:
845 	exfat_put_dentry_set(es, false);
846 	return -EIO;
847 }
848 
849 static int exfat_validate_empty_dentry_set(struct exfat_entry_set_cache *es)
850 {
851 	struct exfat_dentry *ep;
852 	struct buffer_head *bh;
853 	int i, off;
854 	bool unused_hit = false;
855 
856 	/*
857 	 * ONLY UNUSED OR DELETED DENTRIES ARE ALLOWED:
858 	 * Although it violates the specification for a deleted entry to
859 	 * follow an unused entry, some exFAT implementations could work
860 	 * like this. Therefore, to improve compatibility, let's allow it.
861 	 */
862 	for (i = 0; i < es->num_entries; i++) {
863 		ep = exfat_get_dentry_cached(es, i);
864 		if (ep->type == EXFAT_UNUSED) {
865 			unused_hit = true;
866 		} else if (!IS_EXFAT_DELETED(ep->type)) {
867 			if (unused_hit)
868 				goto err_used_follow_unused;
869 			i++;
870 			goto count_skip_entries;
871 		}
872 	}
873 
874 	return 0;
875 
876 err_used_follow_unused:
877 	off = es->start_off + (i << DENTRY_SIZE_BITS);
878 	bh = es->bh[exfat_bytes_to_block(es->sb, off)];
879 
880 	exfat_fs_error(es->sb,
881 		"in sector %lld, dentry %d should be unused, but 0x%x",
882 		bh->b_blocknr, off >> DENTRY_SIZE_BITS, ep->type);
883 
884 	return -EIO;
885 
886 count_skip_entries:
887 	es->num_entries =
888 		exfat_bytes_to_dentries(exfat_block_to_bytes(es->sb, es->num_bh) - es->start_off);
889 	for (; i < es->num_entries; i++) {
890 		ep = exfat_get_dentry_cached(es, i);
891 		if (IS_EXFAT_DELETED(ep->type))
892 			break;
893 	}
894 
895 	return i;
896 }
897 
898 /*
899  * Get an empty dentry set.
900  *
901  * in:
902  *   sb+p_dir+entry: indicates the empty dentry location
903  *   num_entries: specifies how many empty dentries should be included.
904  * out:
905  *   es: pointer of empty dentry set on success.
906  * return:
907  *   0  : on success
908  *   >0 : the dentries are not empty, the return value is the number of
909  *        dentries to be skipped for the next lookup.
910  *   <0 : on failure
911  */
912 int exfat_get_empty_dentry_set(struct exfat_entry_set_cache *es,
913 		struct super_block *sb, struct exfat_chain *p_dir,
914 		int entry, unsigned int num_entries)
915 {
916 	int ret;
917 
918 	ret = __exfat_get_dentry_set(es, sb, p_dir, entry, num_entries);
919 	if (ret < 0)
920 		return ret;
921 
922 	ret = exfat_validate_empty_dentry_set(es);
923 	if (ret)
924 		exfat_put_dentry_set(es, false);
925 
926 	return ret;
927 }
928 
929 static inline void exfat_reset_empty_hint(struct exfat_hint_femp *hint_femp)
930 {
931 	hint_femp->eidx = EXFAT_HINT_NONE;
932 	hint_femp->count = 0;
933 }
934 
935 static inline void exfat_set_empty_hint(struct exfat_inode_info *ei,
936 		struct exfat_hint_femp *candi_empty, struct exfat_chain *clu,
937 		int dentry, int num_entries, int entry_type)
938 {
939 	if (ei->hint_femp.eidx == EXFAT_HINT_NONE ||
940 	    ei->hint_femp.eidx > dentry) {
941 		int total_entries = exfat_bytes_to_dentries(i_size_read(&ei->vfs_inode));
942 
943 		if (candi_empty->count == 0) {
944 			candi_empty->cur = *clu;
945 			candi_empty->eidx = dentry;
946 		}
947 
948 		if (entry_type == TYPE_UNUSED)
949 			candi_empty->count += total_entries - dentry;
950 		else
951 			candi_empty->count++;
952 
953 		if (candi_empty->count == num_entries ||
954 		    candi_empty->count + candi_empty->eidx == total_entries)
955 			ei->hint_femp = *candi_empty;
956 	}
957 }
958 
959 enum {
960 	DIRENT_STEP_FILE,
961 	DIRENT_STEP_STRM,
962 	DIRENT_STEP_NAME,
963 	DIRENT_STEP_SECD,
964 };
965 
966 /*
967  * @ei:         inode info of parent directory
968  * @p_dir:      directory structure of parent directory
969  * @num_entries:entry size of p_uniname
970  * @hint_opt:   If p_uniname is found, filled with optimized dir/entry
971  *              for traversing cluster chain.
972  * @return:
973  *   >= 0:      file directory entry position where the name exists
974  *   -ENOENT:   entry with the name does not exist
975  *   -EIO:      I/O error
976  */
977 int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,
978 		struct exfat_chain *p_dir, struct exfat_uni_name *p_uniname,
979 		struct exfat_hint *hint_opt)
980 {
981 	int i, rewind = 0, dentry = 0, end_eidx = 0, num_ext = 0, len;
982 	int order, step, name_len = 0;
983 	int dentries_per_clu;
984 	unsigned int entry_type;
985 	unsigned short *uniname = NULL;
986 	struct exfat_chain clu;
987 	struct exfat_hint *hint_stat = &ei->hint_stat;
988 	struct exfat_hint_femp candi_empty;
989 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
990 	int num_entries = exfat_calc_num_entries(p_uniname);
991 	unsigned int clu_count = 0;
992 
993 	if (num_entries < 0)
994 		return num_entries;
995 
996 	dentries_per_clu = sbi->dentries_per_clu;
997 
998 	exfat_chain_dup(&clu, p_dir);
999 
1000 	if (hint_stat->eidx) {
1001 		clu.dir = hint_stat->clu;
1002 		dentry = hint_stat->eidx;
1003 		end_eidx = dentry;
1004 	}
1005 
1006 	exfat_reset_empty_hint(&ei->hint_femp);
1007 
1008 rewind:
1009 	order = 0;
1010 	step = DIRENT_STEP_FILE;
1011 	exfat_reset_empty_hint(&candi_empty);
1012 
1013 	while (clu.dir != EXFAT_EOF_CLUSTER) {
1014 		i = dentry & (dentries_per_clu - 1);
1015 		for (; i < dentries_per_clu; i++, dentry++) {
1016 			struct exfat_dentry *ep;
1017 			struct buffer_head *bh;
1018 
1019 			if (rewind && dentry == end_eidx)
1020 				goto not_found;
1021 
1022 			ep = exfat_get_dentry(sb, &clu, i, &bh);
1023 			if (!ep)
1024 				return -EIO;
1025 
1026 			entry_type = exfat_get_entry_type(ep);
1027 
1028 			if (entry_type == TYPE_UNUSED ||
1029 			    entry_type == TYPE_DELETED) {
1030 				step = DIRENT_STEP_FILE;
1031 
1032 				exfat_set_empty_hint(ei, &candi_empty, &clu,
1033 						dentry, num_entries,
1034 						entry_type);
1035 
1036 				brelse(bh);
1037 				if (entry_type == TYPE_UNUSED)
1038 					goto not_found;
1039 				continue;
1040 			}
1041 
1042 			exfat_reset_empty_hint(&candi_empty);
1043 
1044 			if (entry_type == TYPE_FILE || entry_type == TYPE_DIR) {
1045 				step = DIRENT_STEP_FILE;
1046 				hint_opt->clu = clu.dir;
1047 				hint_opt->eidx = i;
1048 				num_ext = ep->dentry.file.num_ext;
1049 				step = DIRENT_STEP_STRM;
1050 				brelse(bh);
1051 				continue;
1052 			}
1053 
1054 			if (entry_type == TYPE_STREAM) {
1055 				u16 name_hash;
1056 
1057 				if (step != DIRENT_STEP_STRM) {
1058 					step = DIRENT_STEP_FILE;
1059 					brelse(bh);
1060 					continue;
1061 				}
1062 				step = DIRENT_STEP_FILE;
1063 				name_hash = le16_to_cpu(
1064 						ep->dentry.stream.name_hash);
1065 				if (p_uniname->name_hash == name_hash &&
1066 				    p_uniname->name_len ==
1067 						ep->dentry.stream.name_len) {
1068 					step = DIRENT_STEP_NAME;
1069 					order = 1;
1070 					name_len = 0;
1071 				}
1072 				brelse(bh);
1073 				continue;
1074 			}
1075 
1076 			if (entry_type == TYPE_EXTEND) {
1077 				unsigned short entry_uniname[16], unichar;
1078 				unsigned int offset;
1079 
1080 				if (step != DIRENT_STEP_NAME ||
1081 				    name_len >= MAX_NAME_LENGTH) {
1082 					brelse(bh);
1083 					step = DIRENT_STEP_FILE;
1084 					continue;
1085 				}
1086 
1087 				offset = (++order - 2) * EXFAT_FILE_NAME_LEN;
1088 				len = exfat_extract_uni_name(ep, entry_uniname);
1089 				brelse(bh);
1090 				if (offset > MAX_NAME_LENGTH ||
1091 				    len > MAX_NAME_LENGTH - offset) {
1092 					step = DIRENT_STEP_FILE;
1093 					continue;
1094 				}
1095 				uniname = p_uniname->name + offset;
1096 				name_len += len;
1097 
1098 				unichar = *(uniname+len);
1099 				*(uniname+len) = 0x0;
1100 
1101 				if (exfat_uniname_ncmp(sb, uniname,
1102 					entry_uniname, len)) {
1103 					step = DIRENT_STEP_FILE;
1104 				} else if (p_uniname->name_len == name_len) {
1105 					if (order == num_ext)
1106 						goto found;
1107 					step = DIRENT_STEP_SECD;
1108 				}
1109 
1110 				*(uniname+len) = unichar;
1111 				continue;
1112 			}
1113 
1114 			brelse(bh);
1115 			if (entry_type &
1116 					(TYPE_CRITICAL_SEC | TYPE_BENIGN_SEC)) {
1117 				if (step == DIRENT_STEP_SECD) {
1118 					if (++order == num_ext)
1119 						goto found;
1120 					continue;
1121 				}
1122 			}
1123 			step = DIRENT_STEP_FILE;
1124 		}
1125 
1126 		if (exfat_chain_advance(sb, &clu, 1))
1127 			return -EIO;
1128 
1129 		/* break if the cluster chain includes a loop */
1130 		if (unlikely(++clu_count > EXFAT_DATA_CLUSTER_COUNT(sbi)))
1131 			goto not_found;
1132 	}
1133 
1134 not_found:
1135 	/*
1136 	 * We started at not 0 index,so we should try to find target
1137 	 * from 0 index to the index we started at.
1138 	 */
1139 	if (!rewind && end_eidx) {
1140 		rewind = 1;
1141 		dentry = 0;
1142 		clu.dir = p_dir->dir;
1143 		goto rewind;
1144 	}
1145 
1146 	/*
1147 	 * set the EXFAT_EOF_CLUSTER flag to avoid search
1148 	 * from the beginning again when allocated a new cluster
1149 	 */
1150 	if (ei->hint_femp.eidx == EXFAT_HINT_NONE) {
1151 		ei->hint_femp.cur.dir = EXFAT_EOF_CLUSTER;
1152 		ei->hint_femp.eidx = p_dir->size * dentries_per_clu;
1153 		ei->hint_femp.count = 0;
1154 	}
1155 
1156 	/* initialized hint_stat */
1157 	hint_stat->clu = p_dir->dir;
1158 	hint_stat->eidx = 0;
1159 	return -ENOENT;
1160 
1161 found:
1162 	/* next dentry we'll find is out of this cluster */
1163 	if (!((dentry + 1) & (dentries_per_clu - 1))) {
1164 		int ret = 0;
1165 
1166 		ret = exfat_chain_advance(sb, &clu, 1);
1167 
1168 		if (ret || clu.dir == EXFAT_EOF_CLUSTER) {
1169 			/* just initialized hint_stat */
1170 			hint_stat->clu = p_dir->dir;
1171 			hint_stat->eidx = 0;
1172 			return (dentry - num_ext);
1173 		}
1174 	}
1175 
1176 	hint_stat->clu = clu.dir;
1177 	hint_stat->eidx = dentry + 1;
1178 	return dentry - num_ext;
1179 }
1180 
1181 int exfat_count_dir_entries(struct super_block *sb, struct exfat_chain *p_dir)
1182 {
1183 	int i, count = 0;
1184 	int dentries_per_clu;
1185 	unsigned int entry_type;
1186 	unsigned int clu_count = 0;
1187 	struct exfat_chain clu;
1188 	struct exfat_dentry *ep;
1189 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
1190 	struct buffer_head *bh;
1191 
1192 	dentries_per_clu = sbi->dentries_per_clu;
1193 
1194 	exfat_chain_dup(&clu, p_dir);
1195 
1196 	while (clu.dir != EXFAT_EOF_CLUSTER) {
1197 		for (i = 0; i < dentries_per_clu; i++) {
1198 			ep = exfat_get_dentry(sb, &clu, i, &bh);
1199 			if (!ep)
1200 				return -EIO;
1201 			entry_type = exfat_get_entry_type(ep);
1202 			brelse(bh);
1203 
1204 			if (entry_type == TYPE_UNUSED)
1205 				return count;
1206 			if (entry_type != TYPE_DIR)
1207 				continue;
1208 			count++;
1209 		}
1210 
1211 		if (exfat_chain_advance(sb, &clu, 1))
1212 			return -EIO;
1213 
1214 		if (unlikely(++clu_count > sbi->used_clusters)) {
1215 			exfat_fs_error(sb, "FAT or bitmap is corrupted");
1216 			return -EIO;
1217 		}
1218 	}
1219 
1220 	return count;
1221 }
1222 
1223 static int exfat_get_volume_label_dentry(struct super_block *sb,
1224 		struct exfat_entry_set_cache *es)
1225 {
1226 	int i;
1227 	int dentry = 0;
1228 	unsigned int type;
1229 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
1230 	struct exfat_hint_femp hint_femp;
1231 	struct exfat_inode_info *ei = EXFAT_I(sb->s_root->d_inode);
1232 	struct exfat_chain clu;
1233 	struct exfat_dentry *ep;
1234 	struct buffer_head *bh;
1235 
1236 	hint_femp.eidx = EXFAT_HINT_NONE;
1237 	exfat_chain_set(&clu, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
1238 
1239 	while (clu.dir != EXFAT_EOF_CLUSTER) {
1240 		for (i = 0; i < sbi->dentries_per_clu; i++, dentry++) {
1241 			ep = exfat_get_dentry(sb, &clu, i, &bh);
1242 			if (!ep)
1243 				return -EIO;
1244 
1245 			type = exfat_get_entry_type(ep);
1246 			if (hint_femp.eidx == EXFAT_HINT_NONE) {
1247 				if (type == TYPE_DELETED || type == TYPE_UNUSED) {
1248 					hint_femp.cur = clu;
1249 					hint_femp.eidx = dentry;
1250 					hint_femp.count = 1;
1251 				}
1252 			}
1253 
1254 			if (type == TYPE_UNUSED) {
1255 				brelse(bh);
1256 				goto not_found;
1257 			}
1258 
1259 			if (type != TYPE_VOLUME) {
1260 				brelse(bh);
1261 				continue;
1262 			}
1263 
1264 			memset(es, 0, sizeof(*es));
1265 			es->sb = sb;
1266 			es->bh = es->__bh;
1267 			es->bh[0] = bh;
1268 			es->num_bh = 1;
1269 			es->start_off = exfat_dentries_to_bytes(i) % sb->s_blocksize;
1270 
1271 			return 0;
1272 		}
1273 
1274 		if (exfat_get_next_cluster(sb, &(clu.dir)))
1275 			return -EIO;
1276 	}
1277 
1278 not_found:
1279 	if (hint_femp.eidx == EXFAT_HINT_NONE) {
1280 		hint_femp.cur.dir = EXFAT_EOF_CLUSTER;
1281 		hint_femp.eidx = dentry;
1282 		hint_femp.count = 0;
1283 	}
1284 
1285 	ei->hint_femp = hint_femp;
1286 
1287 	return -ENOENT;
1288 }
1289 
1290 int exfat_read_volume_label(struct super_block *sb, struct exfat_uni_name *label_out)
1291 {
1292 	int ret, i;
1293 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
1294 	struct exfat_entry_set_cache es;
1295 	struct exfat_dentry *ep;
1296 
1297 	mutex_lock(&sbi->s_lock);
1298 
1299 	memset(label_out, 0, sizeof(*label_out));
1300 	ret = exfat_get_volume_label_dentry(sb, &es);
1301 	if (ret < 0) {
1302 		/*
1303 		 * ENOENT signifies that a volume label dentry doesn't exist
1304 		 * We will treat this as an empty volume label and not fail.
1305 		 */
1306 		if (ret == -ENOENT)
1307 			ret = 0;
1308 
1309 		goto unlock;
1310 	}
1311 
1312 	ep = exfat_get_dentry_cached(&es, 0);
1313 	label_out->name_len = ep->dentry.volume_label.char_count;
1314 	if (label_out->name_len > EXFAT_VOLUME_LABEL_LEN) {
1315 		ret = -EIO;
1316 		exfat_put_dentry_set(&es, false);
1317 		goto unlock;
1318 	}
1319 
1320 	for (i = 0; i < label_out->name_len; i++)
1321 		label_out->name[i] = le16_to_cpu(ep->dentry.volume_label.volume_label[i]);
1322 
1323 	exfat_put_dentry_set(&es, false);
1324 unlock:
1325 	mutex_unlock(&sbi->s_lock);
1326 	return ret;
1327 }
1328 
1329 int exfat_write_volume_label(struct super_block *sb,
1330 			     struct exfat_uni_name *label)
1331 {
1332 	int ret, i;
1333 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
1334 	struct inode *root_inode = sb->s_root->d_inode;
1335 	struct exfat_entry_set_cache es;
1336 	struct exfat_chain clu;
1337 	struct exfat_dentry *ep;
1338 
1339 	if (label->name_len > EXFAT_VOLUME_LABEL_LEN)
1340 		return -EINVAL;
1341 
1342 	mutex_lock(&sbi->s_lock);
1343 
1344 	ret = exfat_get_volume_label_dentry(sb, &es);
1345 	if (ret == -ENOENT) {
1346 		if (label->name_len == 0) {
1347 			/* No volume label dentry, no need to clear */
1348 			ret = 0;
1349 			goto unlock;
1350 		}
1351 
1352 		ret = exfat_find_empty_entry(root_inode, &clu, 1, &es);
1353 	}
1354 
1355 	if (ret < 0)
1356 		goto unlock;
1357 
1358 	ep = exfat_get_dentry_cached(&es, 0);
1359 
1360 	if (label->name_len == 0 && ep->dentry.volume_label.char_count == 0) {
1361 		/* volume label had been cleared */
1362 		exfat_put_dentry_set(&es, 0);
1363 		goto unlock;
1364 	}
1365 
1366 	memset(ep, 0, sizeof(*ep));
1367 	ep->type = EXFAT_VOLUME;
1368 
1369 	for (i = 0; i < label->name_len; i++)
1370 		ep->dentry.volume_label.volume_label[i] =
1371 			cpu_to_le16(label->name[i]);
1372 
1373 	ep->dentry.volume_label.char_count = label->name_len;
1374 	es.modified = true;
1375 
1376 	ret = exfat_put_dentry_set(&es, IS_DIRSYNC(root_inode));
1377 
1378 unlock:
1379 	mutex_unlock(&sbi->s_lock);
1380 	return ret;
1381 }
1382