xref: /openbmc/linux/fs/libfs.c (revision b18d2847)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *	fs/libfs.c
4  *	Library for filesystems writers.
5  */
6 
7 #include <linux/blkdev.h>
8 #include <linux/export.h>
9 #include <linux/pagemap.h>
10 #include <linux/slab.h>
11 #include <linux/cred.h>
12 #include <linux/mount.h>
13 #include <linux/vfs.h>
14 #include <linux/quotaops.h>
15 #include <linux/mutex.h>
16 #include <linux/namei.h>
17 #include <linux/exportfs.h>
18 #include <linux/writeback.h>
19 #include <linux/buffer_head.h> /* sync_mapping_buffers */
20 #include <linux/fs_context.h>
21 #include <linux/pseudo_fs.h>
22 #include <linux/fsnotify.h>
23 #include <linux/unicode.h>
24 #include <linux/fscrypt.h>
25 
26 #include <linux/uaccess.h>
27 
28 #include "internal.h"
29 
30 int simple_getattr(struct user_namespace *mnt_userns, const struct path *path,
31 		   struct kstat *stat, u32 request_mask,
32 		   unsigned int query_flags)
33 {
34 	struct inode *inode = d_inode(path->dentry);
35 	generic_fillattr(&init_user_ns, inode, stat);
36 	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
37 	return 0;
38 }
39 EXPORT_SYMBOL(simple_getattr);
40 
41 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
42 {
43 	buf->f_type = dentry->d_sb->s_magic;
44 	buf->f_bsize = PAGE_SIZE;
45 	buf->f_namelen = NAME_MAX;
46 	return 0;
47 }
48 EXPORT_SYMBOL(simple_statfs);
49 
50 /*
51  * Retaining negative dentries for an in-memory filesystem just wastes
52  * memory and lookup time: arrange for them to be deleted immediately.
53  */
54 int always_delete_dentry(const struct dentry *dentry)
55 {
56 	return 1;
57 }
58 EXPORT_SYMBOL(always_delete_dentry);
59 
60 const struct dentry_operations simple_dentry_operations = {
61 	.d_delete = always_delete_dentry,
62 };
63 EXPORT_SYMBOL(simple_dentry_operations);
64 
65 /*
66  * Lookup the data. This is trivial - if the dentry didn't already
67  * exist, we know it is negative.  Set d_op to delete negative dentries.
68  */
69 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
70 {
71 	if (dentry->d_name.len > NAME_MAX)
72 		return ERR_PTR(-ENAMETOOLONG);
73 	if (!dentry->d_sb->s_d_op)
74 		d_set_d_op(dentry, &simple_dentry_operations);
75 	d_add(dentry, NULL);
76 	return NULL;
77 }
78 EXPORT_SYMBOL(simple_lookup);
79 
80 int dcache_dir_open(struct inode *inode, struct file *file)
81 {
82 	file->private_data = d_alloc_cursor(file->f_path.dentry);
83 
84 	return file->private_data ? 0 : -ENOMEM;
85 }
86 EXPORT_SYMBOL(dcache_dir_open);
87 
88 int dcache_dir_close(struct inode *inode, struct file *file)
89 {
90 	dput(file->private_data);
91 	return 0;
92 }
93 EXPORT_SYMBOL(dcache_dir_close);
94 
95 /* parent is locked at least shared */
96 /*
97  * Returns an element of siblings' list.
98  * We are looking for <count>th positive after <p>; if
99  * found, dentry is grabbed and returned to caller.
100  * If no such element exists, NULL is returned.
101  */
102 static struct dentry *scan_positives(struct dentry *cursor,
103 					struct list_head *p,
104 					loff_t count,
105 					struct dentry *last)
106 {
107 	struct dentry *dentry = cursor->d_parent, *found = NULL;
108 
109 	spin_lock(&dentry->d_lock);
110 	while ((p = p->next) != &dentry->d_subdirs) {
111 		struct dentry *d = list_entry(p, struct dentry, d_child);
112 		// we must at least skip cursors, to avoid livelocks
113 		if (d->d_flags & DCACHE_DENTRY_CURSOR)
114 			continue;
115 		if (simple_positive(d) && !--count) {
116 			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
117 			if (simple_positive(d))
118 				found = dget_dlock(d);
119 			spin_unlock(&d->d_lock);
120 			if (likely(found))
121 				break;
122 			count = 1;
123 		}
124 		if (need_resched()) {
125 			list_move(&cursor->d_child, p);
126 			p = &cursor->d_child;
127 			spin_unlock(&dentry->d_lock);
128 			cond_resched();
129 			spin_lock(&dentry->d_lock);
130 		}
131 	}
132 	spin_unlock(&dentry->d_lock);
133 	dput(last);
134 	return found;
135 }
136 
137 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
138 {
139 	struct dentry *dentry = file->f_path.dentry;
140 	switch (whence) {
141 		case 1:
142 			offset += file->f_pos;
143 			fallthrough;
144 		case 0:
145 			if (offset >= 0)
146 				break;
147 			fallthrough;
148 		default:
149 			return -EINVAL;
150 	}
151 	if (offset != file->f_pos) {
152 		struct dentry *cursor = file->private_data;
153 		struct dentry *to = NULL;
154 
155 		inode_lock_shared(dentry->d_inode);
156 
157 		if (offset > 2)
158 			to = scan_positives(cursor, &dentry->d_subdirs,
159 					    offset - 2, NULL);
160 		spin_lock(&dentry->d_lock);
161 		if (to)
162 			list_move(&cursor->d_child, &to->d_child);
163 		else
164 			list_del_init(&cursor->d_child);
165 		spin_unlock(&dentry->d_lock);
166 		dput(to);
167 
168 		file->f_pos = offset;
169 
170 		inode_unlock_shared(dentry->d_inode);
171 	}
172 	return offset;
173 }
174 EXPORT_SYMBOL(dcache_dir_lseek);
175 
176 /* Relationship between i_mode and the DT_xxx types */
177 static inline unsigned char dt_type(struct inode *inode)
178 {
179 	return (inode->i_mode >> 12) & 15;
180 }
181 
182 /*
183  * Directory is locked and all positive dentries in it are safe, since
184  * for ramfs-type trees they can't go away without unlink() or rmdir(),
185  * both impossible due to the lock on directory.
186  */
187 
188 int dcache_readdir(struct file *file, struct dir_context *ctx)
189 {
190 	struct dentry *dentry = file->f_path.dentry;
191 	struct dentry *cursor = file->private_data;
192 	struct list_head *anchor = &dentry->d_subdirs;
193 	struct dentry *next = NULL;
194 	struct list_head *p;
195 
196 	if (!dir_emit_dots(file, ctx))
197 		return 0;
198 
199 	if (ctx->pos == 2)
200 		p = anchor;
201 	else if (!list_empty(&cursor->d_child))
202 		p = &cursor->d_child;
203 	else
204 		return 0;
205 
206 	while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
207 		if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
208 			      d_inode(next)->i_ino, dt_type(d_inode(next))))
209 			break;
210 		ctx->pos++;
211 		p = &next->d_child;
212 	}
213 	spin_lock(&dentry->d_lock);
214 	if (next)
215 		list_move_tail(&cursor->d_child, &next->d_child);
216 	else
217 		list_del_init(&cursor->d_child);
218 	spin_unlock(&dentry->d_lock);
219 	dput(next);
220 
221 	return 0;
222 }
223 EXPORT_SYMBOL(dcache_readdir);
224 
225 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
226 {
227 	return -EISDIR;
228 }
229 EXPORT_SYMBOL(generic_read_dir);
230 
231 const struct file_operations simple_dir_operations = {
232 	.open		= dcache_dir_open,
233 	.release	= dcache_dir_close,
234 	.llseek		= dcache_dir_lseek,
235 	.read		= generic_read_dir,
236 	.iterate_shared	= dcache_readdir,
237 	.fsync		= noop_fsync,
238 };
239 EXPORT_SYMBOL(simple_dir_operations);
240 
241 const struct inode_operations simple_dir_inode_operations = {
242 	.lookup		= simple_lookup,
243 };
244 EXPORT_SYMBOL(simple_dir_inode_operations);
245 
246 static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
247 {
248 	struct dentry *child = NULL;
249 	struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
250 
251 	spin_lock(&parent->d_lock);
252 	while ((p = p->next) != &parent->d_subdirs) {
253 		struct dentry *d = container_of(p, struct dentry, d_child);
254 		if (simple_positive(d)) {
255 			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
256 			if (simple_positive(d))
257 				child = dget_dlock(d);
258 			spin_unlock(&d->d_lock);
259 			if (likely(child))
260 				break;
261 		}
262 	}
263 	spin_unlock(&parent->d_lock);
264 	dput(prev);
265 	return child;
266 }
267 
268 void simple_recursive_removal(struct dentry *dentry,
269                               void (*callback)(struct dentry *))
270 {
271 	struct dentry *this = dget(dentry);
272 	while (true) {
273 		struct dentry *victim = NULL, *child;
274 		struct inode *inode = this->d_inode;
275 
276 		inode_lock(inode);
277 		if (d_is_dir(this))
278 			inode->i_flags |= S_DEAD;
279 		while ((child = find_next_child(this, victim)) == NULL) {
280 			// kill and ascend
281 			// update metadata while it's still locked
282 			inode->i_ctime = current_time(inode);
283 			clear_nlink(inode);
284 			inode_unlock(inode);
285 			victim = this;
286 			this = this->d_parent;
287 			inode = this->d_inode;
288 			inode_lock(inode);
289 			if (simple_positive(victim)) {
290 				d_invalidate(victim);	// avoid lost mounts
291 				if (d_is_dir(victim))
292 					fsnotify_rmdir(inode, victim);
293 				else
294 					fsnotify_unlink(inode, victim);
295 				if (callback)
296 					callback(victim);
297 				dput(victim);		// unpin it
298 			}
299 			if (victim == dentry) {
300 				inode->i_ctime = inode->i_mtime =
301 					current_time(inode);
302 				if (d_is_dir(dentry))
303 					drop_nlink(inode);
304 				inode_unlock(inode);
305 				dput(dentry);
306 				return;
307 			}
308 		}
309 		inode_unlock(inode);
310 		this = child;
311 	}
312 }
313 EXPORT_SYMBOL(simple_recursive_removal);
314 
315 static const struct super_operations simple_super_operations = {
316 	.statfs		= simple_statfs,
317 };
318 
319 static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
320 {
321 	struct pseudo_fs_context *ctx = fc->fs_private;
322 	struct inode *root;
323 
324 	s->s_maxbytes = MAX_LFS_FILESIZE;
325 	s->s_blocksize = PAGE_SIZE;
326 	s->s_blocksize_bits = PAGE_SHIFT;
327 	s->s_magic = ctx->magic;
328 	s->s_op = ctx->ops ?: &simple_super_operations;
329 	s->s_xattr = ctx->xattr;
330 	s->s_time_gran = 1;
331 	root = new_inode(s);
332 	if (!root)
333 		return -ENOMEM;
334 
335 	/*
336 	 * since this is the first inode, make it number 1. New inodes created
337 	 * after this must take care not to collide with it (by passing
338 	 * max_reserved of 1 to iunique).
339 	 */
340 	root->i_ino = 1;
341 	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
342 	root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
343 	s->s_root = d_make_root(root);
344 	if (!s->s_root)
345 		return -ENOMEM;
346 	s->s_d_op = ctx->dops;
347 	return 0;
348 }
349 
350 static int pseudo_fs_get_tree(struct fs_context *fc)
351 {
352 	return get_tree_nodev(fc, pseudo_fs_fill_super);
353 }
354 
355 static void pseudo_fs_free(struct fs_context *fc)
356 {
357 	kfree(fc->fs_private);
358 }
359 
360 static const struct fs_context_operations pseudo_fs_context_ops = {
361 	.free		= pseudo_fs_free,
362 	.get_tree	= pseudo_fs_get_tree,
363 };
364 
365 /*
366  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
367  * will never be mountable)
368  */
369 struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
370 					unsigned long magic)
371 {
372 	struct pseudo_fs_context *ctx;
373 
374 	ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
375 	if (likely(ctx)) {
376 		ctx->magic = magic;
377 		fc->fs_private = ctx;
378 		fc->ops = &pseudo_fs_context_ops;
379 		fc->sb_flags |= SB_NOUSER;
380 		fc->global = true;
381 	}
382 	return ctx;
383 }
384 EXPORT_SYMBOL(init_pseudo);
385 
386 int simple_open(struct inode *inode, struct file *file)
387 {
388 	if (inode->i_private)
389 		file->private_data = inode->i_private;
390 	return 0;
391 }
392 EXPORT_SYMBOL(simple_open);
393 
394 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
395 {
396 	struct inode *inode = d_inode(old_dentry);
397 
398 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
399 	inc_nlink(inode);
400 	ihold(inode);
401 	dget(dentry);
402 	d_instantiate(dentry, inode);
403 	return 0;
404 }
405 EXPORT_SYMBOL(simple_link);
406 
407 int simple_empty(struct dentry *dentry)
408 {
409 	struct dentry *child;
410 	int ret = 0;
411 
412 	spin_lock(&dentry->d_lock);
413 	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
414 		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
415 		if (simple_positive(child)) {
416 			spin_unlock(&child->d_lock);
417 			goto out;
418 		}
419 		spin_unlock(&child->d_lock);
420 	}
421 	ret = 1;
422 out:
423 	spin_unlock(&dentry->d_lock);
424 	return ret;
425 }
426 EXPORT_SYMBOL(simple_empty);
427 
428 int simple_unlink(struct inode *dir, struct dentry *dentry)
429 {
430 	struct inode *inode = d_inode(dentry);
431 
432 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
433 	drop_nlink(inode);
434 	dput(dentry);
435 	return 0;
436 }
437 EXPORT_SYMBOL(simple_unlink);
438 
439 int simple_rmdir(struct inode *dir, struct dentry *dentry)
440 {
441 	if (!simple_empty(dentry))
442 		return -ENOTEMPTY;
443 
444 	drop_nlink(d_inode(dentry));
445 	simple_unlink(dir, dentry);
446 	drop_nlink(dir);
447 	return 0;
448 }
449 EXPORT_SYMBOL(simple_rmdir);
450 
451 int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
452 			   struct inode *new_dir, struct dentry *new_dentry)
453 {
454 	bool old_is_dir = d_is_dir(old_dentry);
455 	bool new_is_dir = d_is_dir(new_dentry);
456 
457 	if (old_dir != new_dir && old_is_dir != new_is_dir) {
458 		if (old_is_dir) {
459 			drop_nlink(old_dir);
460 			inc_nlink(new_dir);
461 		} else {
462 			drop_nlink(new_dir);
463 			inc_nlink(old_dir);
464 		}
465 	}
466 	old_dir->i_ctime = old_dir->i_mtime =
467 	new_dir->i_ctime = new_dir->i_mtime =
468 	d_inode(old_dentry)->i_ctime =
469 	d_inode(new_dentry)->i_ctime = current_time(old_dir);
470 
471 	return 0;
472 }
473 EXPORT_SYMBOL_GPL(simple_rename_exchange);
474 
475 int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
476 		  struct dentry *old_dentry, struct inode *new_dir,
477 		  struct dentry *new_dentry, unsigned int flags)
478 {
479 	struct inode *inode = d_inode(old_dentry);
480 	int they_are_dirs = d_is_dir(old_dentry);
481 
482 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
483 		return -EINVAL;
484 
485 	if (flags & RENAME_EXCHANGE)
486 		return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
487 
488 	if (!simple_empty(new_dentry))
489 		return -ENOTEMPTY;
490 
491 	if (d_really_is_positive(new_dentry)) {
492 		simple_unlink(new_dir, new_dentry);
493 		if (they_are_dirs) {
494 			drop_nlink(d_inode(new_dentry));
495 			drop_nlink(old_dir);
496 		}
497 	} else if (they_are_dirs) {
498 		drop_nlink(old_dir);
499 		inc_nlink(new_dir);
500 	}
501 
502 	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
503 		new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
504 
505 	return 0;
506 }
507 EXPORT_SYMBOL(simple_rename);
508 
509 /**
510  * simple_setattr - setattr for simple filesystem
511  * @mnt_userns: user namespace of the target mount
512  * @dentry: dentry
513  * @iattr: iattr structure
514  *
515  * Returns 0 on success, -error on failure.
516  *
517  * simple_setattr is a simple ->setattr implementation without a proper
518  * implementation of size changes.
519  *
520  * It can either be used for in-memory filesystems or special files
521  * on simple regular filesystems.  Anything that needs to change on-disk
522  * or wire state on size changes needs its own setattr method.
523  */
524 int simple_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
525 		   struct iattr *iattr)
526 {
527 	struct inode *inode = d_inode(dentry);
528 	int error;
529 
530 	error = setattr_prepare(mnt_userns, dentry, iattr);
531 	if (error)
532 		return error;
533 
534 	if (iattr->ia_valid & ATTR_SIZE)
535 		truncate_setsize(inode, iattr->ia_size);
536 	setattr_copy(mnt_userns, inode, iattr);
537 	mark_inode_dirty(inode);
538 	return 0;
539 }
540 EXPORT_SYMBOL(simple_setattr);
541 
542 static int simple_readpage(struct file *file, struct page *page)
543 {
544 	clear_highpage(page);
545 	flush_dcache_page(page);
546 	SetPageUptodate(page);
547 	unlock_page(page);
548 	return 0;
549 }
550 
551 int simple_write_begin(struct file *file, struct address_space *mapping,
552 			loff_t pos, unsigned len, unsigned flags,
553 			struct page **pagep, void **fsdata)
554 {
555 	struct page *page;
556 	pgoff_t index;
557 
558 	index = pos >> PAGE_SHIFT;
559 
560 	page = grab_cache_page_write_begin(mapping, index, flags);
561 	if (!page)
562 		return -ENOMEM;
563 
564 	*pagep = page;
565 
566 	if (!PageUptodate(page) && (len != PAGE_SIZE)) {
567 		unsigned from = pos & (PAGE_SIZE - 1);
568 
569 		zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
570 	}
571 	return 0;
572 }
573 EXPORT_SYMBOL(simple_write_begin);
574 
575 /**
576  * simple_write_end - .write_end helper for non-block-device FSes
577  * @file: See .write_end of address_space_operations
578  * @mapping: 		"
579  * @pos: 		"
580  * @len: 		"
581  * @copied: 		"
582  * @page: 		"
583  * @fsdata: 		"
584  *
585  * simple_write_end does the minimum needed for updating a page after writing is
586  * done. It has the same API signature as the .write_end of
587  * address_space_operations vector. So it can just be set onto .write_end for
588  * FSes that don't need any other processing. i_mutex is assumed to be held.
589  * Block based filesystems should use generic_write_end().
590  * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
591  * is not called, so a filesystem that actually does store data in .write_inode
592  * should extend on what's done here with a call to mark_inode_dirty() in the
593  * case that i_size has changed.
594  *
595  * Use *ONLY* with simple_readpage()
596  */
597 static int simple_write_end(struct file *file, struct address_space *mapping,
598 			loff_t pos, unsigned len, unsigned copied,
599 			struct page *page, void *fsdata)
600 {
601 	struct inode *inode = page->mapping->host;
602 	loff_t last_pos = pos + copied;
603 
604 	/* zero the stale part of the page if we did a short copy */
605 	if (!PageUptodate(page)) {
606 		if (copied < len) {
607 			unsigned from = pos & (PAGE_SIZE - 1);
608 
609 			zero_user(page, from + copied, len - copied);
610 		}
611 		SetPageUptodate(page);
612 	}
613 	/*
614 	 * No need to use i_size_read() here, the i_size
615 	 * cannot change under us because we hold the i_mutex.
616 	 */
617 	if (last_pos > inode->i_size)
618 		i_size_write(inode, last_pos);
619 
620 	set_page_dirty(page);
621 	unlock_page(page);
622 	put_page(page);
623 
624 	return copied;
625 }
626 
627 /*
628  * Provides ramfs-style behavior: data in the pagecache, but no writeback.
629  */
630 const struct address_space_operations ram_aops = {
631 	.readpage	= simple_readpage,
632 	.write_begin	= simple_write_begin,
633 	.write_end	= simple_write_end,
634 	.dirty_folio	= noop_dirty_folio,
635 };
636 EXPORT_SYMBOL(ram_aops);
637 
638 /*
639  * the inodes created here are not hashed. If you use iunique to generate
640  * unique inode values later for this filesystem, then you must take care
641  * to pass it an appropriate max_reserved value to avoid collisions.
642  */
643 int simple_fill_super(struct super_block *s, unsigned long magic,
644 		      const struct tree_descr *files)
645 {
646 	struct inode *inode;
647 	struct dentry *root;
648 	struct dentry *dentry;
649 	int i;
650 
651 	s->s_blocksize = PAGE_SIZE;
652 	s->s_blocksize_bits = PAGE_SHIFT;
653 	s->s_magic = magic;
654 	s->s_op = &simple_super_operations;
655 	s->s_time_gran = 1;
656 
657 	inode = new_inode(s);
658 	if (!inode)
659 		return -ENOMEM;
660 	/*
661 	 * because the root inode is 1, the files array must not contain an
662 	 * entry at index 1
663 	 */
664 	inode->i_ino = 1;
665 	inode->i_mode = S_IFDIR | 0755;
666 	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
667 	inode->i_op = &simple_dir_inode_operations;
668 	inode->i_fop = &simple_dir_operations;
669 	set_nlink(inode, 2);
670 	root = d_make_root(inode);
671 	if (!root)
672 		return -ENOMEM;
673 	for (i = 0; !files->name || files->name[0]; i++, files++) {
674 		if (!files->name)
675 			continue;
676 
677 		/* warn if it tries to conflict with the root inode */
678 		if (unlikely(i == 1))
679 			printk(KERN_WARNING "%s: %s passed in a files array"
680 				"with an index of 1!\n", __func__,
681 				s->s_type->name);
682 
683 		dentry = d_alloc_name(root, files->name);
684 		if (!dentry)
685 			goto out;
686 		inode = new_inode(s);
687 		if (!inode) {
688 			dput(dentry);
689 			goto out;
690 		}
691 		inode->i_mode = S_IFREG | files->mode;
692 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
693 		inode->i_fop = files->ops;
694 		inode->i_ino = i;
695 		d_add(dentry, inode);
696 	}
697 	s->s_root = root;
698 	return 0;
699 out:
700 	d_genocide(root);
701 	shrink_dcache_parent(root);
702 	dput(root);
703 	return -ENOMEM;
704 }
705 EXPORT_SYMBOL(simple_fill_super);
706 
707 static DEFINE_SPINLOCK(pin_fs_lock);
708 
709 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
710 {
711 	struct vfsmount *mnt = NULL;
712 	spin_lock(&pin_fs_lock);
713 	if (unlikely(!*mount)) {
714 		spin_unlock(&pin_fs_lock);
715 		mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
716 		if (IS_ERR(mnt))
717 			return PTR_ERR(mnt);
718 		spin_lock(&pin_fs_lock);
719 		if (!*mount)
720 			*mount = mnt;
721 	}
722 	mntget(*mount);
723 	++*count;
724 	spin_unlock(&pin_fs_lock);
725 	mntput(mnt);
726 	return 0;
727 }
728 EXPORT_SYMBOL(simple_pin_fs);
729 
730 void simple_release_fs(struct vfsmount **mount, int *count)
731 {
732 	struct vfsmount *mnt;
733 	spin_lock(&pin_fs_lock);
734 	mnt = *mount;
735 	if (!--*count)
736 		*mount = NULL;
737 	spin_unlock(&pin_fs_lock);
738 	mntput(mnt);
739 }
740 EXPORT_SYMBOL(simple_release_fs);
741 
742 /**
743  * simple_read_from_buffer - copy data from the buffer to user space
744  * @to: the user space buffer to read to
745  * @count: the maximum number of bytes to read
746  * @ppos: the current position in the buffer
747  * @from: the buffer to read from
748  * @available: the size of the buffer
749  *
750  * The simple_read_from_buffer() function reads up to @count bytes from the
751  * buffer @from at offset @ppos into the user space address starting at @to.
752  *
753  * On success, the number of bytes read is returned and the offset @ppos is
754  * advanced by this number, or negative value is returned on error.
755  **/
756 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
757 				const void *from, size_t available)
758 {
759 	loff_t pos = *ppos;
760 	size_t ret;
761 
762 	if (pos < 0)
763 		return -EINVAL;
764 	if (pos >= available || !count)
765 		return 0;
766 	if (count > available - pos)
767 		count = available - pos;
768 	ret = copy_to_user(to, from + pos, count);
769 	if (ret == count)
770 		return -EFAULT;
771 	count -= ret;
772 	*ppos = pos + count;
773 	return count;
774 }
775 EXPORT_SYMBOL(simple_read_from_buffer);
776 
777 /**
778  * simple_write_to_buffer - copy data from user space to the buffer
779  * @to: the buffer to write to
780  * @available: the size of the buffer
781  * @ppos: the current position in the buffer
782  * @from: the user space buffer to read from
783  * @count: the maximum number of bytes to read
784  *
785  * The simple_write_to_buffer() function reads up to @count bytes from the user
786  * space address starting at @from into the buffer @to at offset @ppos.
787  *
788  * On success, the number of bytes written is returned and the offset @ppos is
789  * advanced by this number, or negative value is returned on error.
790  **/
791 ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
792 		const void __user *from, size_t count)
793 {
794 	loff_t pos = *ppos;
795 	size_t res;
796 
797 	if (pos < 0)
798 		return -EINVAL;
799 	if (pos >= available || !count)
800 		return 0;
801 	if (count > available - pos)
802 		count = available - pos;
803 	res = copy_from_user(to + pos, from, count);
804 	if (res == count)
805 		return -EFAULT;
806 	count -= res;
807 	*ppos = pos + count;
808 	return count;
809 }
810 EXPORT_SYMBOL(simple_write_to_buffer);
811 
812 /**
813  * memory_read_from_buffer - copy data from the buffer
814  * @to: the kernel space buffer to read to
815  * @count: the maximum number of bytes to read
816  * @ppos: the current position in the buffer
817  * @from: the buffer to read from
818  * @available: the size of the buffer
819  *
820  * The memory_read_from_buffer() function reads up to @count bytes from the
821  * buffer @from at offset @ppos into the kernel space address starting at @to.
822  *
823  * On success, the number of bytes read is returned and the offset @ppos is
824  * advanced by this number, or negative value is returned on error.
825  **/
826 ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
827 				const void *from, size_t available)
828 {
829 	loff_t pos = *ppos;
830 
831 	if (pos < 0)
832 		return -EINVAL;
833 	if (pos >= available)
834 		return 0;
835 	if (count > available - pos)
836 		count = available - pos;
837 	memcpy(to, from + pos, count);
838 	*ppos = pos + count;
839 
840 	return count;
841 }
842 EXPORT_SYMBOL(memory_read_from_buffer);
843 
844 /*
845  * Transaction based IO.
846  * The file expects a single write which triggers the transaction, and then
847  * possibly a read which collects the result - which is stored in a
848  * file-local buffer.
849  */
850 
851 void simple_transaction_set(struct file *file, size_t n)
852 {
853 	struct simple_transaction_argresp *ar = file->private_data;
854 
855 	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
856 
857 	/*
858 	 * The barrier ensures that ar->size will really remain zero until
859 	 * ar->data is ready for reading.
860 	 */
861 	smp_mb();
862 	ar->size = n;
863 }
864 EXPORT_SYMBOL(simple_transaction_set);
865 
866 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
867 {
868 	struct simple_transaction_argresp *ar;
869 	static DEFINE_SPINLOCK(simple_transaction_lock);
870 
871 	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
872 		return ERR_PTR(-EFBIG);
873 
874 	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
875 	if (!ar)
876 		return ERR_PTR(-ENOMEM);
877 
878 	spin_lock(&simple_transaction_lock);
879 
880 	/* only one write allowed per open */
881 	if (file->private_data) {
882 		spin_unlock(&simple_transaction_lock);
883 		free_page((unsigned long)ar);
884 		return ERR_PTR(-EBUSY);
885 	}
886 
887 	file->private_data = ar;
888 
889 	spin_unlock(&simple_transaction_lock);
890 
891 	if (copy_from_user(ar->data, buf, size))
892 		return ERR_PTR(-EFAULT);
893 
894 	return ar->data;
895 }
896 EXPORT_SYMBOL(simple_transaction_get);
897 
898 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
899 {
900 	struct simple_transaction_argresp *ar = file->private_data;
901 
902 	if (!ar)
903 		return 0;
904 	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
905 }
906 EXPORT_SYMBOL(simple_transaction_read);
907 
908 int simple_transaction_release(struct inode *inode, struct file *file)
909 {
910 	free_page((unsigned long)file->private_data);
911 	return 0;
912 }
913 EXPORT_SYMBOL(simple_transaction_release);
914 
915 /* Simple attribute files */
916 
917 struct simple_attr {
918 	int (*get)(void *, u64 *);
919 	int (*set)(void *, u64);
920 	char get_buf[24];	/* enough to store a u64 and "\n\0" */
921 	char set_buf[24];
922 	void *data;
923 	const char *fmt;	/* format for read operation */
924 	struct mutex mutex;	/* protects access to these buffers */
925 };
926 
927 /* simple_attr_open is called by an actual attribute open file operation
928  * to set the attribute specific access operations. */
929 int simple_attr_open(struct inode *inode, struct file *file,
930 		     int (*get)(void *, u64 *), int (*set)(void *, u64),
931 		     const char *fmt)
932 {
933 	struct simple_attr *attr;
934 
935 	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
936 	if (!attr)
937 		return -ENOMEM;
938 
939 	attr->get = get;
940 	attr->set = set;
941 	attr->data = inode->i_private;
942 	attr->fmt = fmt;
943 	mutex_init(&attr->mutex);
944 
945 	file->private_data = attr;
946 
947 	return nonseekable_open(inode, file);
948 }
949 EXPORT_SYMBOL_GPL(simple_attr_open);
950 
951 int simple_attr_release(struct inode *inode, struct file *file)
952 {
953 	kfree(file->private_data);
954 	return 0;
955 }
956 EXPORT_SYMBOL_GPL(simple_attr_release);	/* GPL-only?  This?  Really? */
957 
958 /* read from the buffer that is filled with the get function */
959 ssize_t simple_attr_read(struct file *file, char __user *buf,
960 			 size_t len, loff_t *ppos)
961 {
962 	struct simple_attr *attr;
963 	size_t size;
964 	ssize_t ret;
965 
966 	attr = file->private_data;
967 
968 	if (!attr->get)
969 		return -EACCES;
970 
971 	ret = mutex_lock_interruptible(&attr->mutex);
972 	if (ret)
973 		return ret;
974 
975 	if (*ppos && attr->get_buf[0]) {
976 		/* continued read */
977 		size = strlen(attr->get_buf);
978 	} else {
979 		/* first read */
980 		u64 val;
981 		ret = attr->get(attr->data, &val);
982 		if (ret)
983 			goto out;
984 
985 		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
986 				 attr->fmt, (unsigned long long)val);
987 	}
988 
989 	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
990 out:
991 	mutex_unlock(&attr->mutex);
992 	return ret;
993 }
994 EXPORT_SYMBOL_GPL(simple_attr_read);
995 
996 /* interpret the buffer as a number to call the set function with */
997 ssize_t simple_attr_write(struct file *file, const char __user *buf,
998 			  size_t len, loff_t *ppos)
999 {
1000 	struct simple_attr *attr;
1001 	unsigned long long val;
1002 	size_t size;
1003 	ssize_t ret;
1004 
1005 	attr = file->private_data;
1006 	if (!attr->set)
1007 		return -EACCES;
1008 
1009 	ret = mutex_lock_interruptible(&attr->mutex);
1010 	if (ret)
1011 		return ret;
1012 
1013 	ret = -EFAULT;
1014 	size = min(sizeof(attr->set_buf) - 1, len);
1015 	if (copy_from_user(attr->set_buf, buf, size))
1016 		goto out;
1017 
1018 	attr->set_buf[size] = '\0';
1019 	ret = kstrtoull(attr->set_buf, 0, &val);
1020 	if (ret)
1021 		goto out;
1022 	ret = attr->set(attr->data, val);
1023 	if (ret == 0)
1024 		ret = len; /* on success, claim we got the whole input */
1025 out:
1026 	mutex_unlock(&attr->mutex);
1027 	return ret;
1028 }
1029 EXPORT_SYMBOL_GPL(simple_attr_write);
1030 
1031 /**
1032  * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
1033  * @sb:		filesystem to do the file handle conversion on
1034  * @fid:	file handle to convert
1035  * @fh_len:	length of the file handle in bytes
1036  * @fh_type:	type of file handle
1037  * @get_inode:	filesystem callback to retrieve inode
1038  *
1039  * This function decodes @fid as long as it has one of the well-known
1040  * Linux filehandle types and calls @get_inode on it to retrieve the
1041  * inode for the object specified in the file handle.
1042  */
1043 struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1044 		int fh_len, int fh_type, struct inode *(*get_inode)
1045 			(struct super_block *sb, u64 ino, u32 gen))
1046 {
1047 	struct inode *inode = NULL;
1048 
1049 	if (fh_len < 2)
1050 		return NULL;
1051 
1052 	switch (fh_type) {
1053 	case FILEID_INO32_GEN:
1054 	case FILEID_INO32_GEN_PARENT:
1055 		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1056 		break;
1057 	}
1058 
1059 	return d_obtain_alias(inode);
1060 }
1061 EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1062 
1063 /**
1064  * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1065  * @sb:		filesystem to do the file handle conversion on
1066  * @fid:	file handle to convert
1067  * @fh_len:	length of the file handle in bytes
1068  * @fh_type:	type of file handle
1069  * @get_inode:	filesystem callback to retrieve inode
1070  *
1071  * This function decodes @fid as long as it has one of the well-known
1072  * Linux filehandle types and calls @get_inode on it to retrieve the
1073  * inode for the _parent_ object specified in the file handle if it
1074  * is specified in the file handle, or NULL otherwise.
1075  */
1076 struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1077 		int fh_len, int fh_type, struct inode *(*get_inode)
1078 			(struct super_block *sb, u64 ino, u32 gen))
1079 {
1080 	struct inode *inode = NULL;
1081 
1082 	if (fh_len <= 2)
1083 		return NULL;
1084 
1085 	switch (fh_type) {
1086 	case FILEID_INO32_GEN_PARENT:
1087 		inode = get_inode(sb, fid->i32.parent_ino,
1088 				  (fh_len > 3 ? fid->i32.parent_gen : 0));
1089 		break;
1090 	}
1091 
1092 	return d_obtain_alias(inode);
1093 }
1094 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1095 
1096 /**
1097  * __generic_file_fsync - generic fsync implementation for simple filesystems
1098  *
1099  * @file:	file to synchronize
1100  * @start:	start offset in bytes
1101  * @end:	end offset in bytes (inclusive)
1102  * @datasync:	only synchronize essential metadata if true
1103  *
1104  * This is a generic implementation of the fsync method for simple
1105  * filesystems which track all non-inode metadata in the buffers list
1106  * hanging off the address_space structure.
1107  */
1108 int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1109 				 int datasync)
1110 {
1111 	struct inode *inode = file->f_mapping->host;
1112 	int err;
1113 	int ret;
1114 
1115 	err = file_write_and_wait_range(file, start, end);
1116 	if (err)
1117 		return err;
1118 
1119 	inode_lock(inode);
1120 	ret = sync_mapping_buffers(inode->i_mapping);
1121 	if (!(inode->i_state & I_DIRTY_ALL))
1122 		goto out;
1123 	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1124 		goto out;
1125 
1126 	err = sync_inode_metadata(inode, 1);
1127 	if (ret == 0)
1128 		ret = err;
1129 
1130 out:
1131 	inode_unlock(inode);
1132 	/* check and advance again to catch errors after syncing out buffers */
1133 	err = file_check_and_advance_wb_err(file);
1134 	if (ret == 0)
1135 		ret = err;
1136 	return ret;
1137 }
1138 EXPORT_SYMBOL(__generic_file_fsync);
1139 
1140 /**
1141  * generic_file_fsync - generic fsync implementation for simple filesystems
1142  *			with flush
1143  * @file:	file to synchronize
1144  * @start:	start offset in bytes
1145  * @end:	end offset in bytes (inclusive)
1146  * @datasync:	only synchronize essential metadata if true
1147  *
1148  */
1149 
1150 int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1151 		       int datasync)
1152 {
1153 	struct inode *inode = file->f_mapping->host;
1154 	int err;
1155 
1156 	err = __generic_file_fsync(file, start, end, datasync);
1157 	if (err)
1158 		return err;
1159 	return blkdev_issue_flush(inode->i_sb->s_bdev);
1160 }
1161 EXPORT_SYMBOL(generic_file_fsync);
1162 
1163 /**
1164  * generic_check_addressable - Check addressability of file system
1165  * @blocksize_bits:	log of file system block size
1166  * @num_blocks:		number of blocks in file system
1167  *
1168  * Determine whether a file system with @num_blocks blocks (and a
1169  * block size of 2**@blocksize_bits) is addressable by the sector_t
1170  * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
1171  */
1172 int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1173 {
1174 	u64 last_fs_block = num_blocks - 1;
1175 	u64 last_fs_page =
1176 		last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1177 
1178 	if (unlikely(num_blocks == 0))
1179 		return 0;
1180 
1181 	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1182 		return -EINVAL;
1183 
1184 	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1185 	    (last_fs_page > (pgoff_t)(~0ULL))) {
1186 		return -EFBIG;
1187 	}
1188 	return 0;
1189 }
1190 EXPORT_SYMBOL(generic_check_addressable);
1191 
1192 /*
1193  * No-op implementation of ->fsync for in-memory filesystems.
1194  */
1195 int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1196 {
1197 	return 0;
1198 }
1199 EXPORT_SYMBOL(noop_fsync);
1200 
1201 ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1202 {
1203 	/*
1204 	 * iomap based filesystems support direct I/O without need for
1205 	 * this callback. However, it still needs to be set in
1206 	 * inode->a_ops so that open/fcntl know that direct I/O is
1207 	 * generally supported.
1208 	 */
1209 	return -EINVAL;
1210 }
1211 EXPORT_SYMBOL_GPL(noop_direct_IO);
1212 
1213 /* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1214 void kfree_link(void *p)
1215 {
1216 	kfree(p);
1217 }
1218 EXPORT_SYMBOL(kfree_link);
1219 
1220 struct inode *alloc_anon_inode(struct super_block *s)
1221 {
1222 	static const struct address_space_operations anon_aops = {
1223 		.dirty_folio	= noop_dirty_folio,
1224 	};
1225 	struct inode *inode = new_inode_pseudo(s);
1226 
1227 	if (!inode)
1228 		return ERR_PTR(-ENOMEM);
1229 
1230 	inode->i_ino = get_next_ino();
1231 	inode->i_mapping->a_ops = &anon_aops;
1232 
1233 	/*
1234 	 * Mark the inode dirty from the very beginning,
1235 	 * that way it will never be moved to the dirty
1236 	 * list because mark_inode_dirty() will think
1237 	 * that it already _is_ on the dirty list.
1238 	 */
1239 	inode->i_state = I_DIRTY;
1240 	inode->i_mode = S_IRUSR | S_IWUSR;
1241 	inode->i_uid = current_fsuid();
1242 	inode->i_gid = current_fsgid();
1243 	inode->i_flags |= S_PRIVATE;
1244 	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1245 	return inode;
1246 }
1247 EXPORT_SYMBOL(alloc_anon_inode);
1248 
1249 /**
1250  * simple_nosetlease - generic helper for prohibiting leases
1251  * @filp: file pointer
1252  * @arg: type of lease to obtain
1253  * @flp: new lease supplied for insertion
1254  * @priv: private data for lm_setup operation
1255  *
1256  * Generic helper for filesystems that do not wish to allow leases to be set.
1257  * All arguments are ignored and it just returns -EINVAL.
1258  */
1259 int
1260 simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1261 		  void **priv)
1262 {
1263 	return -EINVAL;
1264 }
1265 EXPORT_SYMBOL(simple_nosetlease);
1266 
1267 /**
1268  * simple_get_link - generic helper to get the target of "fast" symlinks
1269  * @dentry: not used here
1270  * @inode: the symlink inode
1271  * @done: not used here
1272  *
1273  * Generic helper for filesystems to use for symlink inodes where a pointer to
1274  * the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
1275  * since as an optimization the path lookup code uses any non-NULL ->i_link
1276  * directly, without calling ->get_link().  But ->get_link() still must be set,
1277  * to mark the inode_operations as being for a symlink.
1278  *
1279  * Return: the symlink target
1280  */
1281 const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1282 			    struct delayed_call *done)
1283 {
1284 	return inode->i_link;
1285 }
1286 EXPORT_SYMBOL(simple_get_link);
1287 
1288 const struct inode_operations simple_symlink_inode_operations = {
1289 	.get_link = simple_get_link,
1290 };
1291 EXPORT_SYMBOL(simple_symlink_inode_operations);
1292 
1293 /*
1294  * Operations for a permanently empty directory.
1295  */
1296 static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1297 {
1298 	return ERR_PTR(-ENOENT);
1299 }
1300 
1301 static int empty_dir_getattr(struct user_namespace *mnt_userns,
1302 			     const struct path *path, struct kstat *stat,
1303 			     u32 request_mask, unsigned int query_flags)
1304 {
1305 	struct inode *inode = d_inode(path->dentry);
1306 	generic_fillattr(&init_user_ns, inode, stat);
1307 	return 0;
1308 }
1309 
1310 static int empty_dir_setattr(struct user_namespace *mnt_userns,
1311 			     struct dentry *dentry, struct iattr *attr)
1312 {
1313 	return -EPERM;
1314 }
1315 
1316 static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1317 {
1318 	return -EOPNOTSUPP;
1319 }
1320 
1321 static const struct inode_operations empty_dir_inode_operations = {
1322 	.lookup		= empty_dir_lookup,
1323 	.permission	= generic_permission,
1324 	.setattr	= empty_dir_setattr,
1325 	.getattr	= empty_dir_getattr,
1326 	.listxattr	= empty_dir_listxattr,
1327 };
1328 
1329 static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1330 {
1331 	/* An empty directory has two entries . and .. at offsets 0 and 1 */
1332 	return generic_file_llseek_size(file, offset, whence, 2, 2);
1333 }
1334 
1335 static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1336 {
1337 	dir_emit_dots(file, ctx);
1338 	return 0;
1339 }
1340 
1341 static const struct file_operations empty_dir_operations = {
1342 	.llseek		= empty_dir_llseek,
1343 	.read		= generic_read_dir,
1344 	.iterate_shared	= empty_dir_readdir,
1345 	.fsync		= noop_fsync,
1346 };
1347 
1348 
1349 void make_empty_dir_inode(struct inode *inode)
1350 {
1351 	set_nlink(inode, 2);
1352 	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1353 	inode->i_uid = GLOBAL_ROOT_UID;
1354 	inode->i_gid = GLOBAL_ROOT_GID;
1355 	inode->i_rdev = 0;
1356 	inode->i_size = 0;
1357 	inode->i_blkbits = PAGE_SHIFT;
1358 	inode->i_blocks = 0;
1359 
1360 	inode->i_op = &empty_dir_inode_operations;
1361 	inode->i_opflags &= ~IOP_XATTR;
1362 	inode->i_fop = &empty_dir_operations;
1363 }
1364 
1365 bool is_empty_dir_inode(struct inode *inode)
1366 {
1367 	return (inode->i_fop == &empty_dir_operations) &&
1368 		(inode->i_op == &empty_dir_inode_operations);
1369 }
1370 
1371 #if IS_ENABLED(CONFIG_UNICODE)
1372 /*
1373  * Determine if the name of a dentry should be casefolded.
1374  *
1375  * Return: if names will need casefolding
1376  */
1377 static bool needs_casefold(const struct inode *dir)
1378 {
1379 	return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
1380 }
1381 
1382 /**
1383  * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1384  * @dentry:	dentry whose name we are checking against
1385  * @len:	len of name of dentry
1386  * @str:	str pointer to name of dentry
1387  * @name:	Name to compare against
1388  *
1389  * Return: 0 if names match, 1 if mismatch, or -ERRNO
1390  */
1391 static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1392 				const char *str, const struct qstr *name)
1393 {
1394 	const struct dentry *parent = READ_ONCE(dentry->d_parent);
1395 	const struct inode *dir = READ_ONCE(parent->d_inode);
1396 	const struct super_block *sb = dentry->d_sb;
1397 	const struct unicode_map *um = sb->s_encoding;
1398 	struct qstr qstr = QSTR_INIT(str, len);
1399 	char strbuf[DNAME_INLINE_LEN];
1400 	int ret;
1401 
1402 	if (!dir || !needs_casefold(dir))
1403 		goto fallback;
1404 	/*
1405 	 * If the dentry name is stored in-line, then it may be concurrently
1406 	 * modified by a rename.  If this happens, the VFS will eventually retry
1407 	 * the lookup, so it doesn't matter what ->d_compare() returns.
1408 	 * However, it's unsafe to call utf8_strncasecmp() with an unstable
1409 	 * string.  Therefore, we have to copy the name into a temporary buffer.
1410 	 */
1411 	if (len <= DNAME_INLINE_LEN - 1) {
1412 		memcpy(strbuf, str, len);
1413 		strbuf[len] = 0;
1414 		qstr.name = strbuf;
1415 		/* prevent compiler from optimizing out the temporary buffer */
1416 		barrier();
1417 	}
1418 	ret = utf8_strncasecmp(um, name, &qstr);
1419 	if (ret >= 0)
1420 		return ret;
1421 
1422 	if (sb_has_strict_encoding(sb))
1423 		return -EINVAL;
1424 fallback:
1425 	if (len != name->len)
1426 		return 1;
1427 	return !!memcmp(str, name->name, len);
1428 }
1429 
1430 /**
1431  * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1432  * @dentry:	dentry of the parent directory
1433  * @str:	qstr of name whose hash we should fill in
1434  *
1435  * Return: 0 if hash was successful or unchanged, and -EINVAL on error
1436  */
1437 static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1438 {
1439 	const struct inode *dir = READ_ONCE(dentry->d_inode);
1440 	struct super_block *sb = dentry->d_sb;
1441 	const struct unicode_map *um = sb->s_encoding;
1442 	int ret = 0;
1443 
1444 	if (!dir || !needs_casefold(dir))
1445 		return 0;
1446 
1447 	ret = utf8_casefold_hash(um, dentry, str);
1448 	if (ret < 0 && sb_has_strict_encoding(sb))
1449 		return -EINVAL;
1450 	return 0;
1451 }
1452 
1453 static const struct dentry_operations generic_ci_dentry_ops = {
1454 	.d_hash = generic_ci_d_hash,
1455 	.d_compare = generic_ci_d_compare,
1456 };
1457 #endif
1458 
1459 #ifdef CONFIG_FS_ENCRYPTION
1460 static const struct dentry_operations generic_encrypted_dentry_ops = {
1461 	.d_revalidate = fscrypt_d_revalidate,
1462 };
1463 #endif
1464 
1465 #if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1466 static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
1467 	.d_hash = generic_ci_d_hash,
1468 	.d_compare = generic_ci_d_compare,
1469 	.d_revalidate = fscrypt_d_revalidate,
1470 };
1471 #endif
1472 
1473 /**
1474  * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
1475  * @dentry:	dentry to set ops on
1476  *
1477  * Casefolded directories need d_hash and d_compare set, so that the dentries
1478  * contained in them are handled case-insensitively.  Note that these operations
1479  * are needed on the parent directory rather than on the dentries in it, and
1480  * while the casefolding flag can be toggled on and off on an empty directory,
1481  * dentry_operations can't be changed later.  As a result, if the filesystem has
1482  * casefolding support enabled at all, we have to give all dentries the
1483  * casefolding operations even if their inode doesn't have the casefolding flag
1484  * currently (and thus the casefolding ops would be no-ops for now).
1485  *
1486  * Encryption works differently in that the only dentry operation it needs is
1487  * d_revalidate, which it only needs on dentries that have the no-key name flag.
1488  * The no-key flag can't be set "later", so we don't have to worry about that.
1489  *
1490  * Finally, to maximize compatibility with overlayfs (which isn't compatible
1491  * with certain dentry operations) and to avoid taking an unnecessary
1492  * performance hit, we use custom dentry_operations for each possible
1493  * combination rather than always installing all operations.
1494  */
1495 void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
1496 {
1497 #ifdef CONFIG_FS_ENCRYPTION
1498 	bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
1499 #endif
1500 #if IS_ENABLED(CONFIG_UNICODE)
1501 	bool needs_ci_ops = dentry->d_sb->s_encoding;
1502 #endif
1503 #if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1504 	if (needs_encrypt_ops && needs_ci_ops) {
1505 		d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
1506 		return;
1507 	}
1508 #endif
1509 #ifdef CONFIG_FS_ENCRYPTION
1510 	if (needs_encrypt_ops) {
1511 		d_set_d_op(dentry, &generic_encrypted_dentry_ops);
1512 		return;
1513 	}
1514 #endif
1515 #if IS_ENABLED(CONFIG_UNICODE)
1516 	if (needs_ci_ops) {
1517 		d_set_d_op(dentry, &generic_ci_dentry_ops);
1518 		return;
1519 	}
1520 #endif
1521 }
1522 EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
1523