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/iversion.h>
19	#include <linux/writeback.h>
20	#include <linux/buffer_head.h> /* sync_mapping_buffers */
21	#include <linux/fs_context.h>
22	#include <linux/pseudo_fs.h>
23	#include <linux/fsnotify.h>
24	#include <linux/unicode.h>
25	#include <linux/fscrypt.h>
26	#include <linux/pidfs.h>
27
28	#include <linux/uaccess.h>
29
30	#include "internal.h"
31
32	int simple_getattr(struct mnt_idmap *idmap, const struct path *path,
33	struct kstat *stat, u32 request_mask,
34	unsigned int query_flags)
35	{
36	struct inode *inode = d_inode(dentry: path->dentry);
37	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
38	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
39	return 0;
40	}
41	EXPORT_SYMBOL(simple_getattr);
42
43	int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
44	{
45	u64 id = huge_encode_dev(dev: dentry->d_sb->s_dev);
46
47	buf->f_fsid = u64_to_fsid(v: id);
48	buf->f_type = dentry->d_sb->s_magic;
49	buf->f_bsize = PAGE_SIZE;
50	buf->f_namelen = NAME_MAX;
51	return 0;
52	}
53	EXPORT_SYMBOL(simple_statfs);
54
55	/*
56	* Retaining negative dentries for an in-memory filesystem just wastes
57	* memory and lookup time: arrange for them to be deleted immediately.
58	*/
59	int always_delete_dentry(const struct dentry *dentry)
60	{
61	return 1;
62	}
63	EXPORT_SYMBOL(always_delete_dentry);
64
65	const struct dentry_operations simple_dentry_operations = {
66	.d_delete = always_delete_dentry,
67	};
68	EXPORT_SYMBOL(simple_dentry_operations);
69
70	/*
71	* Lookup the data. This is trivial - if the dentry didn't already
72	* exist, we know it is negative. Set d_op to delete negative dentries.
73	*/
74	struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
75	{
76	if (dentry->d_name.len > NAME_MAX)
77	return ERR_PTR(error: -ENAMETOOLONG);
78	if (!dentry->d_sb->s_d_op)
79	d_set_d_op(dentry, op: &simple_dentry_operations);
80	d_add(dentry, NULL);
81	return NULL;
82	}
83	EXPORT_SYMBOL(simple_lookup);
84
85	int dcache_dir_open(struct inode *inode, struct file *file)
86	{
87	file->private_data = d_alloc_cursor(file->f_path.dentry);
88
89	return file->private_data ? 0 : -ENOMEM;
90	}
91	EXPORT_SYMBOL(dcache_dir_open);
92
93	int dcache_dir_close(struct inode *inode, struct file *file)
94	{
95	dput(file->private_data);
96	return 0;
97	}
98	EXPORT_SYMBOL(dcache_dir_close);
99
100	/* parent is locked at least shared */
101	/*
102	* Returns an element of siblings' list.
103	* We are looking for <count>th positive after <p>; if
104	* found, dentry is grabbed and returned to caller.
105	* If no such element exists, NULL is returned.
106	*/
107	static struct dentry *scan_positives(struct dentry *cursor,
108	struct hlist_node **p,
109	loff_t count,
110	struct dentry *last)
111	{
112	struct dentry *dentry = cursor->d_parent, *found = NULL;
113
114	spin_lock(lock: &dentry->d_lock);
115	while (*p) {
116	struct dentry *d = hlist_entry(*p, struct dentry, d_sib);
117	p = &d->d_sib.next;
118	// we must at least skip cursors, to avoid livelocks
119	if (d->d_flags & DCACHE_DENTRY_CURSOR)
120	continue;
121	if (simple_positive(dentry: d) && !--count) {
122	spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
123	if (simple_positive(dentry: d))
124	found = dget_dlock(dentry: d);
125	spin_unlock(lock: &d->d_lock);
126	if (likely(found))
127	break;
128	count = 1;
129	}
130	if (need_resched()) {
131	if (!hlist_unhashed(h: &cursor->d_sib))
132	__hlist_del(n: &cursor->d_sib);
133	hlist_add_behind(n: &cursor->d_sib, prev: &d->d_sib);
134	p = &cursor->d_sib.next;
135	spin_unlock(lock: &dentry->d_lock);
136	cond_resched();
137	spin_lock(lock: &dentry->d_lock);
138	}
139	}
140	spin_unlock(lock: &dentry->d_lock);
141	dput(last);
142	return found;
143	}
144
145	loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
146	{
147	struct dentry *dentry = file->f_path.dentry;
148	switch (whence) {
149	case 1:
150	offset += file->f_pos;
151	fallthrough;
152	case 0:
153	if (offset >= 0)
154	break;
155	fallthrough;
156	default:
157	return -EINVAL;
158	}
159	if (offset != file->f_pos) {
160	struct dentry *cursor = file->private_data;
161	struct dentry *to = NULL;
162
163	inode_lock_shared(inode: dentry->d_inode);
164
165	if (offset > 2)
166	to = scan_positives(cursor, p: &dentry->d_children.first,
167	count: offset - 2, NULL);
168	spin_lock(lock: &dentry->d_lock);
169	hlist_del_init(n: &cursor->d_sib);
170	if (to)
171	hlist_add_behind(n: &cursor->d_sib, prev: &to->d_sib);
172	spin_unlock(lock: &dentry->d_lock);
173	dput(to);
174
175	file->f_pos = offset;
176
177	inode_unlock_shared(inode: dentry->d_inode);
178	}
179	return offset;
180	}
181	EXPORT_SYMBOL(dcache_dir_lseek);
182
183	/*
184	* Directory is locked and all positive dentries in it are safe, since
185	* for ramfs-type trees they can't go away without unlink() or rmdir(),
186	* both impossible due to the lock on directory.
187	*/
188
189	int dcache_readdir(struct file *file, struct dir_context *ctx)
190	{
191	struct dentry *dentry = file->f_path.dentry;
192	struct dentry *cursor = file->private_data;
193	struct dentry *next = NULL;
194	struct hlist_node **p;
195
196	if (!dir_emit_dots(file, ctx))
197	return 0;
198
199	if (ctx->pos == 2)
200	p = &dentry->d_children.first;
201	else
202	p = &cursor->d_sib.next;
203
204	while ((next = scan_positives(cursor, p, count: 1, last: next)) != NULL) {
205	if (!dir_emit(ctx, name: next->d_name.name, namelen: next->d_name.len,
206	ino: d_inode(dentry: next)->i_ino,
207	type: fs_umode_to_dtype(mode: d_inode(dentry: next)->i_mode)))
208	break;
209	ctx->pos++;
210	p = &next->d_sib.next;
211	}
212	spin_lock(lock: &dentry->d_lock);
213	hlist_del_init(n: &cursor->d_sib);
214	if (next)
215	hlist_add_before(n: &cursor->d_sib, next: &next->d_sib);
216	spin_unlock(lock: &dentry->d_lock);
217	dput(next);
218
219	return 0;
220	}
221	EXPORT_SYMBOL(dcache_readdir);
222
223	ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
224	{
225	return -EISDIR;
226	}
227	EXPORT_SYMBOL(generic_read_dir);
228
229	const struct file_operations simple_dir_operations = {
230	.open = dcache_dir_open,
231	.release = dcache_dir_close,
232	.llseek = dcache_dir_lseek,
233	.read = generic_read_dir,
234	.iterate_shared = dcache_readdir,
235	.fsync = noop_fsync,
236	};
237	EXPORT_SYMBOL(simple_dir_operations);
238
239	const struct inode_operations simple_dir_inode_operations = {
240	.lookup = simple_lookup,
241	};
242	EXPORT_SYMBOL(simple_dir_inode_operations);
243
244	/* 0 is '.', 1 is '..', so always start with offset 2 or more */
245	enum {
246	DIR_OFFSET_MIN = 2,
247	};
248
249	static void offset_set(struct dentry *dentry, long offset)
250	{
251	dentry->d_fsdata = (void *)offset;
252	}
253
254	static long dentry2offset(struct dentry *dentry)
255	{
256	return (long)dentry->d_fsdata;
257	}
258
259	static struct lock_class_key simple_offset_lock_class;
260
261	/**
262	* simple_offset_init - initialize an offset_ctx
263	* @octx: directory offset map to be initialized
264	*
265	*/
266	void simple_offset_init(struct offset_ctx *octx)
267	{
268	mt_init_flags(mt: &octx->mt, MT_FLAGS_ALLOC_RANGE);
269	lockdep_set_class(&octx->mt.ma_lock, &simple_offset_lock_class);
270	octx->next_offset = DIR_OFFSET_MIN;
271	}
272
273	/**
274	* simple_offset_add - Add an entry to a directory's offset map
275	* @octx: directory offset ctx to be updated
276	* @dentry: new dentry being added
277	*
278	* Returns zero on success. @octx and the dentry's offset are updated.
279	* Otherwise, a negative errno value is returned.
280	*/
281	int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
282	{
283	unsigned long offset;
284	int ret;
285
286	if (dentry2offset(dentry) != 0)
287	return -EBUSY;
288
289	ret = mtree_alloc_cyclic(mt: &octx->mt, startp: &offset, entry: dentry, range_lo: DIR_OFFSET_MIN,
290	LONG_MAX, next: &octx->next_offset, GFP_KERNEL);
291	if (ret < 0)
292	return ret;
293
294	offset_set(dentry, offset);
295	return 0;
296	}
297
298	/**
299	* simple_offset_remove - Remove an entry to a directory's offset map
300	* @octx: directory offset ctx to be updated
301	* @dentry: dentry being removed
302	*
303	*/
304	void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
305	{
306	long offset;
307
308	offset = dentry2offset(dentry);
309	if (offset == 0)
310	return;
311
312	mtree_erase(mt: &octx->mt, index: offset);
313	offset_set(dentry, offset: 0);
314	}
315
316	/**
317	* simple_offset_empty - Check if a dentry can be unlinked
318	* @dentry: dentry to be tested
319	*
320	* Returns 0 if @dentry is a non-empty directory; otherwise returns 1.
321	*/
322	int simple_offset_empty(struct dentry *dentry)
323	{
324	struct inode *inode = d_inode(dentry);
325	struct offset_ctx *octx;
326	struct dentry *child;
327	unsigned long index;
328	int ret = 1;
329
330	if (!inode || !S_ISDIR(inode->i_mode))
331	return ret;
332
333	index = DIR_OFFSET_MIN;
334	octx = inode->i_op->get_offset_ctx(inode);
335	mt_for_each(&octx->mt, child, index, LONG_MAX) {
336	spin_lock(lock: &child->d_lock);
337	if (simple_positive(dentry: child)) {
338	spin_unlock(lock: &child->d_lock);
339	ret = 0;
340	break;
341	}
342	spin_unlock(lock: &child->d_lock);
343	}
344
345	return ret;
346	}
347
348	/**
349	* simple_offset_rename_exchange - exchange rename with directory offsets
350	* @old_dir: parent of dentry being moved
351	* @old_dentry: dentry being moved
352	* @new_dir: destination parent
353	* @new_dentry: destination dentry
354	*
355	* Returns zero on success. Otherwise a negative errno is returned and the
356	* rename is rolled back.
357	*/
358	int simple_offset_rename_exchange(struct inode *old_dir,
359	struct dentry *old_dentry,
360	struct inode *new_dir,
361	struct dentry *new_dentry)
362	{
363	struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
364	struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
365	long old_index = dentry2offset(dentry: old_dentry);
366	long new_index = dentry2offset(dentry: new_dentry);
367	int ret;
368
369	simple_offset_remove(octx: old_ctx, dentry: old_dentry);
370	simple_offset_remove(octx: new_ctx, dentry: new_dentry);
371
372	ret = simple_offset_add(octx: new_ctx, dentry: old_dentry);
373	if (ret)
374	goto out_restore;
375
376	ret = simple_offset_add(octx: old_ctx, dentry: new_dentry);
377	if (ret) {
378	simple_offset_remove(octx: new_ctx, dentry: old_dentry);
379	goto out_restore;
380	}
381
382	ret = simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
383	if (ret) {
384	simple_offset_remove(octx: new_ctx, dentry: old_dentry);
385	simple_offset_remove(octx: old_ctx, dentry: new_dentry);
386	goto out_restore;
387	}
388	return 0;
389
390	out_restore:
391	offset_set(dentry: old_dentry, offset: old_index);
392	mtree_store(mt: &old_ctx->mt, index: old_index, entry: old_dentry, GFP_KERNEL);
393	offset_set(dentry: new_dentry, offset: new_index);
394	mtree_store(mt: &new_ctx->mt, index: new_index, entry: new_dentry, GFP_KERNEL);
395	return ret;
396	}
397
398	/**
399	* simple_offset_destroy - Release offset map
400	* @octx: directory offset ctx that is about to be destroyed
401	*
402	* During fs teardown (eg. umount), a directory's offset map might still
403	* contain entries. xa_destroy() cleans out anything that remains.
404	*/
405	void simple_offset_destroy(struct offset_ctx *octx)
406	{
407	mtree_destroy(mt: &octx->mt);
408	}
409
410	/**
411	* offset_dir_llseek - Advance the read position of a directory descriptor
412	* @file: an open directory whose position is to be updated
413	* @offset: a byte offset
414	* @whence: enumerator describing the starting position for this update
415	*
416	* SEEK_END, SEEK_DATA, and SEEK_HOLE are not supported for directories.
417	*
418	* Returns the updated read position if successful; otherwise a
419	* negative errno is returned and the read position remains unchanged.
420	*/
421	static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
422	{
423	switch (whence) {
424	case SEEK_CUR:
425	offset += file->f_pos;
426	fallthrough;
427	case SEEK_SET:
428	if (offset >= 0)
429	break;
430	fallthrough;
431	default:
432	return -EINVAL;
433	}
434
435	/* In this case, ->private_data is protected by f_pos_lock */
436	file->private_data = NULL;
437	return vfs_setpos(file, offset, LONG_MAX);
438	}
439
440	static struct dentry *offset_find_next(struct offset_ctx *octx, loff_t offset)
441	{
442	MA_STATE(mas, &octx->mt, offset, offset);
443	struct dentry *child, *found = NULL;
444
445	rcu_read_lock();
446	child = mas_find(mas: &mas, LONG_MAX);
447	if (!child)
448	goto out;
449	spin_lock(lock: &child->d_lock);
450	if (simple_positive(dentry: child))
451	found = dget_dlock(dentry: child);
452	spin_unlock(lock: &child->d_lock);
453	out:
454	rcu_read_unlock();
455	return found;
456	}
457
458	static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
459	{
460	struct inode *inode = d_inode(dentry);
461	long offset = dentry2offset(dentry);
462
463	return ctx->actor(ctx, dentry->d_name.name, dentry->d_name.len, offset,
464	inode->i_ino, fs_umode_to_dtype(mode: inode->i_mode));
465	}
466
467	static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
468	{
469	struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode);
470	struct dentry *dentry;
471
472	while (true) {
473	dentry = offset_find_next(octx, offset: ctx->pos);
474	if (!dentry)
475	return ERR_PTR(error: -ENOENT);
476
477	if (!offset_dir_emit(ctx, dentry)) {
478	dput(dentry);
479	break;
480	}
481
482	ctx->pos = dentry2offset(dentry) + 1;
483	dput(dentry);
484	}
485	return NULL;
486	}
487
488	/**
489	* offset_readdir - Emit entries starting at offset @ctx->pos
490	* @file: an open directory to iterate over
491	* @ctx: directory iteration context
492	*
493	* Caller must hold @file's i_rwsem to prevent insertion or removal of
494	* entries during this call.
495	*
496	* On entry, @ctx->pos contains an offset that represents the first entry
497	* to be read from the directory.
498	*
499	* The operation continues until there are no more entries to read, or
500	* until the ctx->actor indicates there is no more space in the caller's
501	* output buffer.
502	*
503	* On return, @ctx->pos contains an offset that will read the next entry
504	* in this directory when offset_readdir() is called again with @ctx.
505	*
506	* Return values:
507	* %0 - Complete
508	*/
509	static int offset_readdir(struct file *file, struct dir_context *ctx)
510	{
511	struct dentry *dir = file->f_path.dentry;
512
513	lockdep_assert_held(&d_inode(dir)->i_rwsem);
514
515	if (!dir_emit_dots(file, ctx))
516	return 0;
517
518	/* In this case, ->private_data is protected by f_pos_lock */
519	if (ctx->pos == DIR_OFFSET_MIN)
520	file->private_data = NULL;
521	else if (file->private_data == ERR_PTR(error: -ENOENT))
522	return 0;
523	file->private_data = offset_iterate_dir(inode: d_inode(dentry: dir), ctx);
524	return 0;
525	}
526
527	const struct file_operations simple_offset_dir_operations = {
528	.llseek = offset_dir_llseek,
529	.iterate_shared = offset_readdir,
530	.read = generic_read_dir,
531	.fsync = noop_fsync,
532	};
533
534	static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
535	{
536	struct dentry *child = NULL, *d;
537
538	spin_lock(lock: &parent->d_lock);
539	d = prev ? d_next_sibling(dentry: prev) : d_first_child(dentry: parent);
540	hlist_for_each_entry_from(d, d_sib) {
541	if (simple_positive(dentry: d)) {
542	spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
543	if (simple_positive(dentry: d))
544	child = dget_dlock(dentry: d);
545	spin_unlock(lock: &d->d_lock);
546	if (likely(child))
547	break;
548	}
549	}
550	spin_unlock(lock: &parent->d_lock);
551	dput(prev);
552	return child;
553	}
554
555	void simple_recursive_removal(struct dentry *dentry,
556	void (*callback)(struct dentry *))
557	{
558	struct dentry *this = dget(dentry);
559	while (true) {
560	struct dentry *victim = NULL, *child;
561	struct inode *inode = this->d_inode;
562
563	inode_lock(inode);
564	if (d_is_dir(dentry: this))
565	inode->i_flags |= S_DEAD;
566	while ((child = find_next_child(parent: this, prev: victim)) == NULL) {
567	// kill and ascend
568	// update metadata while it's still locked
569	inode_set_ctime_current(inode);
570	clear_nlink(inode);
571	inode_unlock(inode);
572	victim = this;
573	this = this->d_parent;
574	inode = this->d_inode;
575	inode_lock(inode);
576	if (simple_positive(dentry: victim)) {
577	d_invalidate(victim); // avoid lost mounts
578	if (d_is_dir(dentry: victim))
579	fsnotify_rmdir(dir: inode, dentry: victim);
580	else
581	fsnotify_unlink(dir: inode, dentry: victim);
582	if (callback)
583	callback(victim);
584	dput(victim); // unpin it
585	}
586	if (victim == dentry) {
587	inode_set_mtime_to_ts(inode,
588	ts: inode_set_ctime_current(inode));
589	if (d_is_dir(dentry))
590	drop_nlink(inode);
591	inode_unlock(inode);
592	dput(dentry);
593	return;
594	}
595	}
596	inode_unlock(inode);
597	this = child;
598	}
599	}
600	EXPORT_SYMBOL(simple_recursive_removal);
601
602	static const struct super_operations simple_super_operations = {
603	.statfs = simple_statfs,
604	};
605
606	static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
607	{
608	struct pseudo_fs_context *ctx = fc->fs_private;
609	struct inode *root;
610
611	s->s_maxbytes = MAX_LFS_FILESIZE;
612	s->s_blocksize = PAGE_SIZE;
613	s->s_blocksize_bits = PAGE_SHIFT;
614	s->s_magic = ctx->magic;
615	s->s_op = ctx->ops ?: &simple_super_operations;
616	s->s_xattr = ctx->xattr;
617	s->s_time_gran = 1;
618	root = new_inode(sb: s);
619	if (!root)
620	return -ENOMEM;
621
622	/*
623	* since this is the first inode, make it number 1. New inodes created
624	* after this must take care not to collide with it (by passing
625	* max_reserved of 1 to iunique).
626	*/
627	root->i_ino = 1;
628	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
629	simple_inode_init_ts(inode: root);
630	s->s_root = d_make_root(root);
631	if (!s->s_root)
632	return -ENOMEM;
633	s->s_d_op = ctx->dops;
634	return 0;
635	}
636
637	static int pseudo_fs_get_tree(struct fs_context *fc)
638	{
639	return get_tree_nodev(fc, fill_super: pseudo_fs_fill_super);
640	}
641
642	static void pseudo_fs_free(struct fs_context *fc)
643	{
644	kfree(objp: fc->fs_private);
645	}
646
647	static const struct fs_context_operations pseudo_fs_context_ops = {
648	.free = pseudo_fs_free,
649	.get_tree = pseudo_fs_get_tree,
650	};
651
652	/*
653	* Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
654	* will never be mountable)
655	*/
656	struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
657	unsigned long magic)
658	{
659	struct pseudo_fs_context *ctx;
660
661	ctx = kzalloc(size: sizeof(struct pseudo_fs_context), GFP_KERNEL);
662	if (likely(ctx)) {
663	ctx->magic = magic;
664	fc->fs_private = ctx;
665	fc->ops = &pseudo_fs_context_ops;
666	fc->sb_flags |= SB_NOUSER;
667	fc->global = true;
668	}
669	return ctx;
670	}
671	EXPORT_SYMBOL(init_pseudo);
672
673	int simple_open(struct inode *inode, struct file *file)
674	{
675	if (inode->i_private)
676	file->private_data = inode->i_private;
677	return 0;
678	}
679	EXPORT_SYMBOL(simple_open);
680
681	int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
682	{
683	struct inode *inode = d_inode(dentry: old_dentry);
684
685	inode_set_mtime_to_ts(inode: dir,
686	ts: inode_set_ctime_to_ts(inode: dir, ts: inode_set_ctime_current(inode)));
687	inc_nlink(inode);
688	ihold(inode);
689	dget(dentry);
690	d_instantiate(dentry, inode);
691	return 0;
692	}
693	EXPORT_SYMBOL(simple_link);
694
695	int simple_empty(struct dentry *dentry)
696	{
697	struct dentry *child;
698	int ret = 0;
699
700	spin_lock(lock: &dentry->d_lock);
701	hlist_for_each_entry(child, &dentry->d_children, d_sib) {
702	spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
703	if (simple_positive(dentry: child)) {
704	spin_unlock(lock: &child->d_lock);
705	goto out;
706	}
707	spin_unlock(lock: &child->d_lock);
708	}
709	ret = 1;
710	out:
711	spin_unlock(lock: &dentry->d_lock);
712	return ret;
713	}
714	EXPORT_SYMBOL(simple_empty);
715
716	int simple_unlink(struct inode *dir, struct dentry *dentry)
717	{
718	struct inode *inode = d_inode(dentry);
719
720	inode_set_mtime_to_ts(inode: dir,
721	ts: inode_set_ctime_to_ts(inode: dir, ts: inode_set_ctime_current(inode)));
722	drop_nlink(inode);
723	dput(dentry);
724	return 0;
725	}
726	EXPORT_SYMBOL(simple_unlink);
727
728	int simple_rmdir(struct inode *dir, struct dentry *dentry)
729	{
730	if (!simple_empty(dentry))
731	return -ENOTEMPTY;
732
733	drop_nlink(inode: d_inode(dentry));
734	simple_unlink(dir, dentry);
735	drop_nlink(inode: dir);
736	return 0;
737	}
738	EXPORT_SYMBOL(simple_rmdir);
739
740	/**
741	* simple_rename_timestamp - update the various inode timestamps for rename
742	* @old_dir: old parent directory
743	* @old_dentry: dentry that is being renamed
744	* @new_dir: new parent directory
745	* @new_dentry: target for rename
746	*
747	* POSIX mandates that the old and new parent directories have their ctime and
748	* mtime updated, and that inodes of @old_dentry and @new_dentry (if any), have
749	* their ctime updated.
750	*/
751	void simple_rename_timestamp(struct inode *old_dir, struct dentry *old_dentry,
752	struct inode *new_dir, struct dentry *new_dentry)
753	{
754	struct inode *newino = d_inode(dentry: new_dentry);
755
756	inode_set_mtime_to_ts(inode: old_dir, ts: inode_set_ctime_current(inode: old_dir));
757	if (new_dir != old_dir)
758	inode_set_mtime_to_ts(inode: new_dir,
759	ts: inode_set_ctime_current(inode: new_dir));
760	inode_set_ctime_current(inode: d_inode(dentry: old_dentry));
761	if (newino)
762	inode_set_ctime_current(inode: newino);
763	}
764	EXPORT_SYMBOL_GPL(simple_rename_timestamp);
765
766	int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
767	struct inode *new_dir, struct dentry *new_dentry)
768	{
769	bool old_is_dir = d_is_dir(dentry: old_dentry);
770	bool new_is_dir = d_is_dir(dentry: new_dentry);
771
772	if (old_dir != new_dir && old_is_dir != new_is_dir) {
773	if (old_is_dir) {
774	drop_nlink(inode: old_dir);
775	inc_nlink(inode: new_dir);
776	} else {
777	drop_nlink(inode: new_dir);
778	inc_nlink(inode: old_dir);
779	}
780	}
781	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
782	return 0;
783	}
784	EXPORT_SYMBOL_GPL(simple_rename_exchange);
785
786	int simple_rename(struct mnt_idmap *idmap, struct inode *old_dir,
787	struct dentry *old_dentry, struct inode *new_dir,
788	struct dentry *new_dentry, unsigned int flags)
789	{
790	int they_are_dirs = d_is_dir(dentry: old_dentry);
791
792	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
793	return -EINVAL;
794
795	if (flags & RENAME_EXCHANGE)
796	return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
797
798	if (!simple_empty(new_dentry))
799	return -ENOTEMPTY;
800
801	if (d_really_is_positive(dentry: new_dentry)) {
802	simple_unlink(new_dir, new_dentry);
803	if (they_are_dirs) {
804	drop_nlink(inode: d_inode(dentry: new_dentry));
805	drop_nlink(inode: old_dir);
806	}
807	} else if (they_are_dirs) {
808	drop_nlink(inode: old_dir);
809	inc_nlink(inode: new_dir);
810	}
811
812	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
813	return 0;
814	}
815	EXPORT_SYMBOL(simple_rename);
816
817	/**
818	* simple_setattr - setattr for simple filesystem
819	* @idmap: idmap of the target mount
820	* @dentry: dentry
821	* @iattr: iattr structure
822	*
823	* Returns 0 on success, -error on failure.
824	*
825	* simple_setattr is a simple ->setattr implementation without a proper
826	* implementation of size changes.
827	*
828	* It can either be used for in-memory filesystems or special files
829	* on simple regular filesystems. Anything that needs to change on-disk
830	* or wire state on size changes needs its own setattr method.
831	*/
832	int simple_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
833	struct iattr *iattr)
834	{
835	struct inode *inode = d_inode(dentry);
836	int error;
837
838	error = setattr_prepare(idmap, dentry, iattr);
839	if (error)
840	return error;
841
842	if (iattr->ia_valid & ATTR_SIZE)
843	truncate_setsize(inode, newsize: iattr->ia_size);
844	setattr_copy(idmap, inode, attr: iattr);
845	mark_inode_dirty(inode);
846	return 0;
847	}
848	EXPORT_SYMBOL(simple_setattr);
849
850	static int simple_read_folio(struct file *file, struct folio *folio)
851	{
852	folio_zero_range(folio, start: 0, length: folio_size(folio));
853	flush_dcache_folio(folio);
854	folio_mark_uptodate(folio);
855	folio_unlock(folio);
856	return 0;
857	}
858
859	int simple_write_begin(struct file *file, struct address_space *mapping,
860	loff_t pos, unsigned len,
861	struct page **pagep, void **fsdata)
862	{
863	struct folio *folio;
864
865	folio = __filemap_get_folio(mapping, index: pos / PAGE_SIZE, FGP_WRITEBEGIN,
866	gfp: mapping_gfp_mask(mapping));
867	if (IS_ERR(ptr: folio))
868	return PTR_ERR(ptr: folio);
869
870	*pagep = &folio->page;
871
872	if (!folio_test_uptodate(folio) && (len != folio_size(folio))) {
873	size_t from = offset_in_folio(folio, pos);
874
875	folio_zero_segments(folio, start1: 0, xend1: from,
876	start2: from + len, xend2: folio_size(folio));
877	}
878	return 0;
879	}
880	EXPORT_SYMBOL(simple_write_begin);
881
882	/**
883	* simple_write_end - .write_end helper for non-block-device FSes
884	* @file: See .write_end of address_space_operations
885	* @mapping: "
886	* @pos: "
887	* @len: "
888	* @copied: "
889	* @page: "
890	* @fsdata: "
891	*
892	* simple_write_end does the minimum needed for updating a page after writing is
893	* done. It has the same API signature as the .write_end of
894	* address_space_operations vector. So it can just be set onto .write_end for
895	* FSes that don't need any other processing. i_mutex is assumed to be held.
896	* Block based filesystems should use generic_write_end().
897	* NOTE: Even though i_size might get updated by this function, mark_inode_dirty
898	* is not called, so a filesystem that actually does store data in .write_inode
899	* should extend on what's done here with a call to mark_inode_dirty() in the
900	* case that i_size has changed.
901	*
902	* Use *ONLY* with simple_read_folio()
903	*/
904	static int simple_write_end(struct file *file, struct address_space *mapping,
905	loff_t pos, unsigned len, unsigned copied,
906	struct page *page, void *fsdata)
907	{
908	struct folio *folio = page_folio(page);
909	struct inode *inode = folio->mapping->host;
910	loff_t last_pos = pos + copied;
911
912	/* zero the stale part of the folio if we did a short copy */
913	if (!folio_test_uptodate(folio)) {
914	if (copied < len) {
915	size_t from = offset_in_folio(folio, pos);
916
917	folio_zero_range(folio, start: from + copied, length: len - copied);
918	}
919	folio_mark_uptodate(folio);
920	}
921	/*
922	* No need to use i_size_read() here, the i_size
923	* cannot change under us because we hold the i_mutex.
924	*/
925	if (last_pos > inode->i_size)
926	i_size_write(inode, i_size: last_pos);
927
928	folio_mark_dirty(folio);
929	folio_unlock(folio);
930	folio_put(folio);
931
932	return copied;
933	}
934
935	/*
936	* Provides ramfs-style behavior: data in the pagecache, but no writeback.
937	*/
938	const struct address_space_operations ram_aops = {
939	.read_folio = simple_read_folio,
940	.write_begin = simple_write_begin,
941	.write_end = simple_write_end,
942	.dirty_folio = noop_dirty_folio,
943	};
944	EXPORT_SYMBOL(ram_aops);
945
946	/*
947	* the inodes created here are not hashed. If you use iunique to generate
948	* unique inode values later for this filesystem, then you must take care
949	* to pass it an appropriate max_reserved value to avoid collisions.
950	*/
951	int simple_fill_super(struct super_block *s, unsigned long magic,
952	const struct tree_descr *files)
953	{
954	struct inode *inode;
955	struct dentry *dentry;
956	int i;
957
958	s->s_blocksize = PAGE_SIZE;
959	s->s_blocksize_bits = PAGE_SHIFT;
960	s->s_magic = magic;
961	s->s_op = &simple_super_operations;
962	s->s_time_gran = 1;
963
964	inode = new_inode(sb: s);
965	if (!inode)
966	return -ENOMEM;
967	/*
968	* because the root inode is 1, the files array must not contain an
969	* entry at index 1
970	*/
971	inode->i_ino = 1;
972	inode->i_mode = S_IFDIR | 0755;
973	simple_inode_init_ts(inode);
974	inode->i_op = &simple_dir_inode_operations;
975	inode->i_fop = &simple_dir_operations;
976	set_nlink(inode, nlink: 2);
977	s->s_root = d_make_root(inode);
978	if (!s->s_root)
979	return -ENOMEM;
980	for (i = 0; !files->name || files->name[0]; i++, files++) {
981	if (!files->name)
982	continue;
983
984	/* warn if it tries to conflict with the root inode */
985	if (unlikely(i == 1))
986	printk(KERN_WARNING "%s: %s passed in a files array"
987	"with an index of 1!\n", __func__,
988	s->s_type->name);
989
990	dentry = d_alloc_name(s->s_root, files->name);
991	if (!dentry)
992	return -ENOMEM;
993	inode = new_inode(sb: s);
994	if (!inode) {
995	dput(dentry);
996	return -ENOMEM;
997	}
998	inode->i_mode = S_IFREG | files->mode;
999	simple_inode_init_ts(inode);
1000	inode->i_fop = files->ops;
1001	inode->i_ino = i;
1002	d_add(dentry, inode);
1003	}
1004	return 0;
1005	}
1006	EXPORT_SYMBOL(simple_fill_super);
1007
1008	static DEFINE_SPINLOCK(pin_fs_lock);
1009
1010	int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
1011	{
1012	struct vfsmount *mnt = NULL;
1013	spin_lock(lock: &pin_fs_lock);
1014	if (unlikely(!*mount)) {
1015	spin_unlock(lock: &pin_fs_lock);
1016	mnt = vfs_kern_mount(type, SB_KERNMOUNT, name: type->name, NULL);
1017	if (IS_ERR(ptr: mnt))
1018	return PTR_ERR(ptr: mnt);
1019	spin_lock(lock: &pin_fs_lock);
1020	if (!*mount)
1021	*mount = mnt;
1022	}
1023	mntget(mnt: *mount);
1024	++*count;
1025	spin_unlock(lock: &pin_fs_lock);
1026	mntput(mnt);
1027	return 0;
1028	}
1029	EXPORT_SYMBOL(simple_pin_fs);
1030
1031	void simple_release_fs(struct vfsmount **mount, int *count)
1032	{
1033	struct vfsmount *mnt;
1034	spin_lock(lock: &pin_fs_lock);
1035	mnt = *mount;
1036	if (!--*count)
1037	*mount = NULL;
1038	spin_unlock(lock: &pin_fs_lock);
1039	mntput(mnt);
1040	}
1041	EXPORT_SYMBOL(simple_release_fs);
1042
1043	/**
1044	* simple_read_from_buffer - copy data from the buffer to user space
1045	* @to: the user space buffer to read to
1046	* @count: the maximum number of bytes to read
1047	* @ppos: the current position in the buffer
1048	* @from: the buffer to read from
1049	* @available: the size of the buffer
1050	*
1051	* The simple_read_from_buffer() function reads up to @count bytes from the
1052	* buffer @from at offset @ppos into the user space address starting at @to.
1053	*
1054	* On success, the number of bytes read is returned and the offset @ppos is
1055	* advanced by this number, or negative value is returned on error.
1056	**/
1057	ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
1058	const void *from, size_t available)
1059	{
1060	loff_t pos = *ppos;
1061	size_t ret;
1062
1063	if (pos < 0)
1064	return -EINVAL;
1065	if (pos >= available || !count)
1066	return 0;
1067	if (count > available - pos)
1068	count = available - pos;
1069	ret = copy_to_user(to, from: from + pos, n: count);
1070	if (ret == count)
1071	return -EFAULT;
1072	count -= ret;
1073	*ppos = pos + count;
1074	return count;
1075	}
1076	EXPORT_SYMBOL(simple_read_from_buffer);
1077
1078	/**
1079	* simple_write_to_buffer - copy data from user space to the buffer
1080	* @to: the buffer to write to
1081	* @available: the size of the buffer
1082	* @ppos: the current position in the buffer
1083	* @from: the user space buffer to read from
1084	* @count: the maximum number of bytes to read
1085	*
1086	* The simple_write_to_buffer() function reads up to @count bytes from the user
1087	* space address starting at @from into the buffer @to at offset @ppos.
1088	*
1089	* On success, the number of bytes written is returned and the offset @ppos is
1090	* advanced by this number, or negative value is returned on error.
1091	**/
1092	ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
1093	const void __user *from, size_t count)
1094	{
1095	loff_t pos = *ppos;
1096	size_t res;
1097
1098	if (pos < 0)
1099	return -EINVAL;
1100	if (pos >= available || !count)
1101	return 0;
1102	if (count > available - pos)
1103	count = available - pos;
1104	res = copy_from_user(to: to + pos, from, n: count);
1105	if (res == count)
1106	return -EFAULT;
1107	count -= res;
1108	*ppos = pos + count;
1109	return count;
1110	}
1111	EXPORT_SYMBOL(simple_write_to_buffer);
1112
1113	/**
1114	* memory_read_from_buffer - copy data from the buffer
1115	* @to: the kernel space buffer to read to
1116	* @count: the maximum number of bytes to read
1117	* @ppos: the current position in the buffer
1118	* @from: the buffer to read from
1119	* @available: the size of the buffer
1120	*
1121	* The memory_read_from_buffer() function reads up to @count bytes from the
1122	* buffer @from at offset @ppos into the kernel space address starting at @to.
1123	*
1124	* On success, the number of bytes read is returned and the offset @ppos is
1125	* advanced by this number, or negative value is returned on error.
1126	**/
1127	ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
1128	const void *from, size_t available)
1129	{
1130	loff_t pos = *ppos;
1131
1132	if (pos < 0)
1133	return -EINVAL;
1134	if (pos >= available)
1135	return 0;
1136	if (count > available - pos)
1137	count = available - pos;
1138	memcpy(to, from + pos, count);
1139	*ppos = pos + count;
1140
1141	return count;
1142	}
1143	EXPORT_SYMBOL(memory_read_from_buffer);
1144
1145	/*
1146	* Transaction based IO.
1147	* The file expects a single write which triggers the transaction, and then
1148	* possibly a read which collects the result - which is stored in a
1149	* file-local buffer.
1150	*/
1151
1152	void simple_transaction_set(struct file *file, size_t n)
1153	{
1154	struct simple_transaction_argresp *ar = file->private_data;
1155
1156	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
1157
1158	/*
1159	* The barrier ensures that ar->size will really remain zero until
1160	* ar->data is ready for reading.
1161	*/
1162	smp_mb();
1163	ar->size = n;
1164	}
1165	EXPORT_SYMBOL(simple_transaction_set);
1166
1167	char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
1168	{
1169	struct simple_transaction_argresp *ar;
1170	static DEFINE_SPINLOCK(simple_transaction_lock);
1171
1172	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
1173	return ERR_PTR(error: -EFBIG);
1174
1175	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
1176	if (!ar)
1177	return ERR_PTR(error: -ENOMEM);
1178
1179	spin_lock(lock: &simple_transaction_lock);
1180
1181	/* only one write allowed per open */
1182	if (file->private_data) {
1183	spin_unlock(lock: &simple_transaction_lock);
1184	free_page((unsigned long)ar);
1185	return ERR_PTR(error: -EBUSY);
1186	}
1187
1188	file->private_data = ar;
1189
1190	spin_unlock(lock: &simple_transaction_lock);
1191
1192	if (copy_from_user(to: ar->data, from: buf, n: size))
1193	return ERR_PTR(error: -EFAULT);
1194
1195	return ar->data;
1196	}
1197	EXPORT_SYMBOL(simple_transaction_get);
1198
1199	ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
1200	{
1201	struct simple_transaction_argresp *ar = file->private_data;
1202
1203	if (!ar)
1204	return 0;
1205	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
1206	}
1207	EXPORT_SYMBOL(simple_transaction_read);
1208
1209	int simple_transaction_release(struct inode *inode, struct file *file)
1210	{
1211	free_page((unsigned long)file->private_data);
1212	return 0;
1213	}
1214	EXPORT_SYMBOL(simple_transaction_release);
1215
1216	/* Simple attribute files */
1217
1218	struct simple_attr {
1219	int (*get)(void *, u64 *);
1220	int (*set)(void *, u64);
1221	char get_buf[24]; /* enough to store a u64 and "\n\0" */
1222	char set_buf[24];
1223	void *data;
1224	const char *fmt; /* format for read operation */
1225	struct mutex mutex; /* protects access to these buffers */
1226	};
1227
1228	/* simple_attr_open is called by an actual attribute open file operation
1229	* to set the attribute specific access operations. */
1230	int simple_attr_open(struct inode *inode, struct file *file,
1231	int (*get)(void *, u64 *), int (*set)(void *, u64),
1232	const char *fmt)
1233	{
1234	struct simple_attr *attr;
1235
1236	attr = kzalloc(size: sizeof(*attr), GFP_KERNEL);
1237	if (!attr)
1238	return -ENOMEM;
1239
1240	attr->get = get;
1241	attr->set = set;
1242	attr->data = inode->i_private;
1243	attr->fmt = fmt;
1244	mutex_init(&attr->mutex);
1245
1246	file->private_data = attr;
1247
1248	return nonseekable_open(inode, filp: file);
1249	}
1250	EXPORT_SYMBOL_GPL(simple_attr_open);
1251
1252	int simple_attr_release(struct inode *inode, struct file *file)
1253	{
1254	kfree(objp: file->private_data);
1255	return 0;
1256	}
1257	EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */
1258
1259	/* read from the buffer that is filled with the get function */
1260	ssize_t simple_attr_read(struct file *file, char __user *buf,
1261	size_t len, loff_t *ppos)
1262	{
1263	struct simple_attr *attr;
1264	size_t size;
1265	ssize_t ret;
1266
1267	attr = file->private_data;
1268
1269	if (!attr->get)
1270	return -EACCES;
1271
1272	ret = mutex_lock_interruptible(&attr->mutex);
1273	if (ret)
1274	return ret;
1275
1276	if (*ppos && attr->get_buf[0]) {
1277	/* continued read */
1278	size = strlen(attr->get_buf);
1279	} else {
1280	/* first read */
1281	u64 val;
1282	ret = attr->get(attr->data, &val);
1283	if (ret)
1284	goto out;
1285
1286	size = scnprintf(buf: attr->get_buf, size: sizeof(attr->get_buf),
1287	fmt: attr->fmt, (unsigned long long)val);
1288	}
1289
1290	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
1291	out:
1292	mutex_unlock(lock: &attr->mutex);
1293	return ret;
1294	}
1295	EXPORT_SYMBOL_GPL(simple_attr_read);
1296
1297	/* interpret the buffer as a number to call the set function with */
1298	static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
1299	size_t len, loff_t *ppos, bool is_signed)
1300	{
1301	struct simple_attr *attr;
1302	unsigned long long val;
1303	size_t size;
1304	ssize_t ret;
1305
1306	attr = file->private_data;
1307	if (!attr->set)
1308	return -EACCES;
1309
1310	ret = mutex_lock_interruptible(&attr->mutex);
1311	if (ret)
1312	return ret;
1313
1314	ret = -EFAULT;
1315	size = min(sizeof(attr->set_buf) - 1, len);
1316	if (copy_from_user(to: attr->set_buf, from: buf, n: size))
1317	goto out;
1318
1319	attr->set_buf[size] = '\0';
1320	if (is_signed)
1321	ret = kstrtoll(s: attr->set_buf, base: 0, res: &val);
1322	else
1323	ret = kstrtoull(s: attr->set_buf, base: 0, res: &val);
1324	if (ret)
1325	goto out;
1326	ret = attr->set(attr->data, val);
1327	if (ret == 0)
1328	ret = len; /* on success, claim we got the whole input */
1329	out:
1330	mutex_unlock(lock: &attr->mutex);
1331	return ret;
1332	}
1333
1334	ssize_t simple_attr_write(struct file *file, const char __user *buf,
1335	size_t len, loff_t *ppos)
1336	{
1337	return simple_attr_write_xsigned(file, buf, len, ppos, is_signed: false);
1338	}
1339	EXPORT_SYMBOL_GPL(simple_attr_write);
1340
1341	ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
1342	size_t len, loff_t *ppos)
1343	{
1344	return simple_attr_write_xsigned(file, buf, len, ppos, is_signed: true);
1345	}
1346	EXPORT_SYMBOL_GPL(simple_attr_write_signed);
1347
1348	/**
1349	* generic_encode_ino32_fh - generic export_operations->encode_fh function
1350	* @inode: the object to encode
1351	* @fh: where to store the file handle fragment
1352	* @max_len: maximum length to store there (in 4 byte units)
1353	* @parent: parent directory inode, if wanted
1354	*
1355	* This generic encode_fh function assumes that the 32 inode number
1356	* is suitable for locating an inode, and that the generation number
1357	* can be used to check that it is still valid. It places them in the
1358	* filehandle fragment where export_decode_fh expects to find them.
1359	*/
1360	int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
1361	struct inode *parent)
1362	{
1363	struct fid *fid = (void *)fh;
1364	int len = *max_len;
1365	int type = FILEID_INO32_GEN;
1366
1367	if (parent && (len < 4)) {
1368	*max_len = 4;
1369	return FILEID_INVALID;
1370	} else if (len < 2) {
1371	*max_len = 2;
1372	return FILEID_INVALID;
1373	}
1374
1375	len = 2;
1376	fid->i32.ino = inode->i_ino;
1377	fid->i32.gen = inode->i_generation;
1378	if (parent) {
1379	fid->i32.parent_ino = parent->i_ino;
1380	fid->i32.parent_gen = parent->i_generation;
1381	len = 4;
1382	type = FILEID_INO32_GEN_PARENT;
1383	}
1384	*max_len = len;
1385	return type;
1386	}
1387	EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
1388
1389	/**
1390	* generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
1391	* @sb: filesystem to do the file handle conversion on
1392	* @fid: file handle to convert
1393	* @fh_len: length of the file handle in bytes
1394	* @fh_type: type of file handle
1395	* @get_inode: filesystem callback to retrieve inode
1396	*
1397	* This function decodes @fid as long as it has one of the well-known
1398	* Linux filehandle types and calls @get_inode on it to retrieve the
1399	* inode for the object specified in the file handle.
1400	*/
1401	struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1402	int fh_len, int fh_type, struct inode *(*get_inode)
1403	(struct super_block *sb, u64 ino, u32 gen))
1404	{
1405	struct inode *inode = NULL;
1406
1407	if (fh_len < 2)
1408	return NULL;
1409
1410	switch (fh_type) {
1411	case FILEID_INO32_GEN:
1412	case FILEID_INO32_GEN_PARENT:
1413	inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1414	break;
1415	}
1416
1417	return d_obtain_alias(inode);
1418	}
1419	EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1420
1421	/**
1422	* generic_fh_to_parent - generic helper for the fh_to_parent export operation
1423	* @sb: filesystem to do the file handle conversion on
1424	* @fid: file handle to convert
1425	* @fh_len: length of the file handle in bytes
1426	* @fh_type: type of file handle
1427	* @get_inode: filesystem callback to retrieve inode
1428	*
1429	* This function decodes @fid as long as it has one of the well-known
1430	* Linux filehandle types and calls @get_inode on it to retrieve the
1431	* inode for the _parent_ object specified in the file handle if it
1432	* is specified in the file handle, or NULL otherwise.
1433	*/
1434	struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1435	int fh_len, int fh_type, struct inode *(*get_inode)
1436	(struct super_block *sb, u64 ino, u32 gen))
1437	{
1438	struct inode *inode = NULL;
1439
1440	if (fh_len <= 2)
1441	return NULL;
1442
1443	switch (fh_type) {
1444	case FILEID_INO32_GEN_PARENT:
1445	inode = get_inode(sb, fid->i32.parent_ino,
1446	(fh_len > 3 ? fid->i32.parent_gen : 0));
1447	break;
1448	}
1449
1450	return d_obtain_alias(inode);
1451	}
1452	EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1453
1454	/**
1455	* __generic_file_fsync - generic fsync implementation for simple filesystems
1456	*
1457	* @file: file to synchronize
1458	* @start: start offset in bytes
1459	* @end: end offset in bytes (inclusive)
1460	* @datasync: only synchronize essential metadata if true
1461	*
1462	* This is a generic implementation of the fsync method for simple
1463	* filesystems which track all non-inode metadata in the buffers list
1464	* hanging off the address_space structure.
1465	*/
1466	int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1467	int datasync)
1468	{
1469	struct inode *inode = file->f_mapping->host;
1470	int err;
1471	int ret;
1472
1473	err = file_write_and_wait_range(file, start, end);
1474	if (err)
1475	return err;
1476
1477	inode_lock(inode);
1478	ret = sync_mapping_buffers(mapping: inode->i_mapping);
1479	if (!(inode->i_state & I_DIRTY_ALL))
1480	goto out;
1481	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1482	goto out;
1483
1484	err = sync_inode_metadata(inode, wait: 1);
1485	if (ret == 0)
1486	ret = err;
1487
1488	out:
1489	inode_unlock(inode);
1490	/* check and advance again to catch errors after syncing out buffers */
1491	err = file_check_and_advance_wb_err(file);
1492	if (ret == 0)
1493	ret = err;
1494	return ret;
1495	}
1496	EXPORT_SYMBOL(__generic_file_fsync);
1497
1498	/**
1499	* generic_file_fsync - generic fsync implementation for simple filesystems
1500	* with flush
1501	* @file: file to synchronize
1502	* @start: start offset in bytes
1503	* @end: end offset in bytes (inclusive)
1504	* @datasync: only synchronize essential metadata if true
1505	*
1506	*/
1507
1508	int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1509	int datasync)
1510	{
1511	struct inode *inode = file->f_mapping->host;
1512	int err;
1513
1514	err = __generic_file_fsync(file, start, end, datasync);
1515	if (err)
1516	return err;
1517	return blkdev_issue_flush(bdev: inode->i_sb->s_bdev);
1518	}
1519	EXPORT_SYMBOL(generic_file_fsync);
1520
1521	/**
1522	* generic_check_addressable - Check addressability of file system
1523	* @blocksize_bits: log of file system block size
1524	* @num_blocks: number of blocks in file system
1525	*
1526	* Determine whether a file system with @num_blocks blocks (and a
1527	* block size of 2**@blocksize_bits) is addressable by the sector_t
1528	* and page cache of the system. Return 0 if so and -EFBIG otherwise.
1529	*/
1530	int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1531	{
1532	u64 last_fs_block = num_blocks - 1;
1533	u64 last_fs_page =
1534	last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1535
1536	if (unlikely(num_blocks == 0))
1537	return 0;
1538
1539	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1540	return -EINVAL;
1541
1542	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1543	(last_fs_page > (pgoff_t)(~0ULL))) {
1544	return -EFBIG;
1545	}
1546	return 0;
1547	}
1548	EXPORT_SYMBOL(generic_check_addressable);
1549
1550	/*
1551	* No-op implementation of ->fsync for in-memory filesystems.
1552	*/
1553	int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1554	{
1555	return 0;
1556	}
1557	EXPORT_SYMBOL(noop_fsync);
1558
1559	ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1560	{
1561	/*
1562	* iomap based filesystems support direct I/O without need for
1563	* this callback. However, it still needs to be set in
1564	* inode->a_ops so that open/fcntl know that direct I/O is
1565	* generally supported.
1566	*/
1567	return -EINVAL;
1568	}
1569	EXPORT_SYMBOL_GPL(noop_direct_IO);
1570
1571	/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1572	void kfree_link(void *p)
1573	{
1574	kfree(objp: p);
1575	}
1576	EXPORT_SYMBOL(kfree_link);
1577
1578	struct inode *alloc_anon_inode(struct super_block *s)
1579	{
1580	static const struct address_space_operations anon_aops = {
1581	.dirty_folio = noop_dirty_folio,
1582	};
1583	struct inode *inode = new_inode_pseudo(sb: s);
1584
1585	if (!inode)
1586	return ERR_PTR(error: -ENOMEM);
1587
1588	inode->i_ino = get_next_ino();
1589	inode->i_mapping->a_ops = &anon_aops;
1590
1591	/*
1592	* Mark the inode dirty from the very beginning,
1593	* that way it will never be moved to the dirty
1594	* list because mark_inode_dirty() will think
1595	* that it already _is_ on the dirty list.
1596	*/
1597	inode->i_state = I_DIRTY;
1598	inode->i_mode = S_IRUSR | S_IWUSR;
1599	inode->i_uid = current_fsuid();
1600	inode->i_gid = current_fsgid();
1601	inode->i_flags |= S_PRIVATE;
1602	simple_inode_init_ts(inode);
1603	return inode;
1604	}
1605	EXPORT_SYMBOL(alloc_anon_inode);
1606
1607	/**
1608	* simple_nosetlease - generic helper for prohibiting leases
1609	* @filp: file pointer
1610	* @arg: type of lease to obtain
1611	* @flp: new lease supplied for insertion
1612	* @priv: private data for lm_setup operation
1613	*
1614	* Generic helper for filesystems that do not wish to allow leases to be set.
1615	* All arguments are ignored and it just returns -EINVAL.
1616	*/
1617	int
1618	simple_nosetlease(struct file *filp, int arg, struct file_lease **flp,
1619	void **priv)
1620	{
1621	return -EINVAL;
1622	}
1623	EXPORT_SYMBOL(simple_nosetlease);
1624
1625	/**
1626	* simple_get_link - generic helper to get the target of "fast" symlinks
1627	* @dentry: not used here
1628	* @inode: the symlink inode
1629	* @done: not used here
1630	*
1631	* Generic helper for filesystems to use for symlink inodes where a pointer to
1632	* the symlink target is stored in ->i_link. NOTE: this isn't normally called,
1633	* since as an optimization the path lookup code uses any non-NULL ->i_link
1634	* directly, without calling ->get_link(). But ->get_link() still must be set,
1635	* to mark the inode_operations as being for a symlink.
1636	*
1637	* Return: the symlink target
1638	*/
1639	const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1640	struct delayed_call *done)
1641	{
1642	return inode->i_link;
1643	}
1644	EXPORT_SYMBOL(simple_get_link);
1645
1646	const struct inode_operations simple_symlink_inode_operations = {
1647	.get_link = simple_get_link,
1648	};
1649	EXPORT_SYMBOL(simple_symlink_inode_operations);
1650
1651	/*
1652	* Operations for a permanently empty directory.
1653	*/
1654	static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1655	{
1656	return ERR_PTR(error: -ENOENT);
1657	}
1658
1659	static int empty_dir_getattr(struct mnt_idmap *idmap,
1660	const struct path *path, struct kstat *stat,
1661	u32 request_mask, unsigned int query_flags)
1662	{
1663	struct inode *inode = d_inode(dentry: path->dentry);
1664	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
1665	return 0;
1666	}
1667
1668	static int empty_dir_setattr(struct mnt_idmap *idmap,
1669	struct dentry *dentry, struct iattr *attr)
1670	{
1671	return -EPERM;
1672	}
1673
1674	static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1675	{
1676	return -EOPNOTSUPP;
1677	}
1678
1679	static const struct inode_operations empty_dir_inode_operations = {
1680	.lookup = empty_dir_lookup,
1681	.permission = generic_permission,
1682	.setattr = empty_dir_setattr,
1683	.getattr = empty_dir_getattr,
1684	.listxattr = empty_dir_listxattr,
1685	};
1686
1687	static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1688	{
1689	/* An empty directory has two entries . and .. at offsets 0 and 1 */
1690	return generic_file_llseek_size(file, offset, whence, maxsize: 2, eof: 2);
1691	}
1692
1693	static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1694	{
1695	dir_emit_dots(file, ctx);
1696	return 0;
1697	}
1698
1699	static const struct file_operations empty_dir_operations = {
1700	.llseek = empty_dir_llseek,
1701	.read = generic_read_dir,
1702	.iterate_shared = empty_dir_readdir,
1703	.fsync = noop_fsync,
1704	};
1705
1706
1707	void make_empty_dir_inode(struct inode *inode)
1708	{
1709	set_nlink(inode, nlink: 2);
1710	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1711	inode->i_uid = GLOBAL_ROOT_UID;
1712	inode->i_gid = GLOBAL_ROOT_GID;
1713	inode->i_rdev = 0;
1714	inode->i_size = 0;
1715	inode->i_blkbits = PAGE_SHIFT;
1716	inode->i_blocks = 0;
1717
1718	inode->i_op = &empty_dir_inode_operations;
1719	inode->i_opflags &= ~IOP_XATTR;
1720	inode->i_fop = &empty_dir_operations;
1721	}
1722
1723	bool is_empty_dir_inode(struct inode *inode)
1724	{
1725	return (inode->i_fop == &empty_dir_operations) &&
1726	(inode->i_op == &empty_dir_inode_operations);
1727	}
1728
1729	#if IS_ENABLED(CONFIG_UNICODE)
1730	/**
1731	* generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1732	* @dentry: dentry whose name we are checking against
1733	* @len: len of name of dentry
1734	* @str: str pointer to name of dentry
1735	* @name: Name to compare against
1736	*
1737	* Return: 0 if names match, 1 if mismatch, or -ERRNO
1738	*/
1739	static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1740	const char *str, const struct qstr *name)
1741	{
1742	const struct dentry *parent;
1743	const struct inode *dir;
1744	char strbuf[DNAME_INLINE_LEN];
1745	struct qstr qstr;
1746
1747	/*
1748	* Attempt a case-sensitive match first. It is cheaper and
1749	* should cover most lookups, including all the sane
1750	* applications that expect a case-sensitive filesystem.
1751	*
1752	* This comparison is safe under RCU because the caller
1753	* guarantees the consistency between str and len. See
1754	* __d_lookup_rcu_op_compare() for details.
1755	*/
1756	if (len == name->len && !memcmp(p: str, q: name->name, size: len))
1757	return 0;
1758
1759	parent = READ_ONCE(dentry->d_parent);
1760	dir = READ_ONCE(parent->d_inode);
1761	if (!dir || !IS_CASEFOLDED(dir))
1762	return 1;
1763
1764	/*
1765	* If the dentry name is stored in-line, then it may be concurrently
1766	* modified by a rename. If this happens, the VFS will eventually retry
1767	* the lookup, so it doesn't matter what ->d_compare() returns.
1768	* However, it's unsafe to call utf8_strncasecmp() with an unstable
1769	* string. Therefore, we have to copy the name into a temporary buffer.
1770	*/
1771	if (len <= DNAME_INLINE_LEN - 1) {
1772	memcpy(strbuf, str, len);
1773	strbuf[len] = 0;
1774	str = strbuf;
1775	/* prevent compiler from optimizing out the temporary buffer */
1776	barrier();
1777	}
1778	qstr.len = len;
1779	qstr.name = str;
1780
1781	return utf8_strncasecmp(um: dentry->d_sb->s_encoding, s1: name, s2: &qstr);
1782	}
1783
1784	/**
1785	* generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1786	* @dentry: dentry of the parent directory
1787	* @str: qstr of name whose hash we should fill in
1788	*
1789	* Return: 0 if hash was successful or unchanged, and -EINVAL on error
1790	*/
1791	static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1792	{
1793	const struct inode *dir = READ_ONCE(dentry->d_inode);
1794	struct super_block *sb = dentry->d_sb;
1795	const struct unicode_map *um = sb->s_encoding;
1796	int ret;
1797
1798	if (!dir || !IS_CASEFOLDED(dir))
1799	return 0;
1800
1801	ret = utf8_casefold_hash(um, salt: dentry, str);
1802	if (ret < 0 && sb_has_strict_encoding(sb))
1803	return -EINVAL;
1804	return 0;
1805	}
1806
1807	static const struct dentry_operations generic_ci_dentry_ops = {
1808	.d_hash = generic_ci_d_hash,
1809	.d_compare = generic_ci_d_compare,
1810	#ifdef CONFIG_FS_ENCRYPTION
1811	.d_revalidate = fscrypt_d_revalidate,
1812	#endif
1813	};
1814	#endif
1815
1816	#ifdef CONFIG_FS_ENCRYPTION
1817	static const struct dentry_operations generic_encrypted_dentry_ops = {
1818	.d_revalidate = fscrypt_d_revalidate,
1819	};
1820	#endif
1821
1822	/**
1823	* generic_set_sb_d_ops - helper for choosing the set of
1824	* filesystem-wide dentry operations for the enabled features
1825	* @sb: superblock to be configured
1826	*
1827	* Filesystems supporting casefolding and/or fscrypt can call this
1828	* helper at mount-time to configure sb->s_d_op to best set of dentry
1829	* operations required for the enabled features. The helper must be
1830	* called after these have been configured, but before the root dentry
1831	* is created.
1832	*/
1833	void generic_set_sb_d_ops(struct super_block *sb)
1834	{
1835	#if IS_ENABLED(CONFIG_UNICODE)
1836	if (sb->s_encoding) {
1837	sb->s_d_op = &generic_ci_dentry_ops;
1838	return;
1839	}
1840	#endif
1841	#ifdef CONFIG_FS_ENCRYPTION
1842	if (sb->s_cop) {
1843	sb->s_d_op = &generic_encrypted_dentry_ops;
1844	return;
1845	}
1846	#endif
1847	}
1848	EXPORT_SYMBOL(generic_set_sb_d_ops);
1849
1850	/**
1851	* inode_maybe_inc_iversion - increments i_version
1852	* @inode: inode with the i_version that should be updated
1853	* @force: increment the counter even if it's not necessary?
1854	*
1855	* Every time the inode is modified, the i_version field must be seen to have
1856	* changed by any observer.
1857	*
1858	* If "force" is set or the QUERIED flag is set, then ensure that we increment
1859	* the value, and clear the queried flag.
1860	*
1861	* In the common case where neither is set, then we can return "false" without
1862	* updating i_version.
1863	*
1864	* If this function returns false, and no other metadata has changed, then we
1865	* can avoid logging the metadata.
1866	*/
1867	bool inode_maybe_inc_iversion(struct inode *inode, bool force)
1868	{
1869	u64 cur, new;
1870
1871	/*
1872	* The i_version field is not strictly ordered with any other inode
1873	* information, but the legacy inode_inc_iversion code used a spinlock
1874	* to serialize increments.
1875	*
1876	* Here, we add full memory barriers to ensure that any de-facto
1877	* ordering with other info is preserved.
1878	*
1879	* This barrier pairs with the barrier in inode_query_iversion()
1880	*/
1881	smp_mb();
1882	cur = inode_peek_iversion_raw(inode);
1883	do {
1884	/* If flag is clear then we needn't do anything */
1885	if (!force && !(cur & I_VERSION_QUERIED))
1886	return false;
1887
1888	/* Since lowest bit is flag, add 2 to avoid it */
1889	new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
1890	} while (!atomic64_try_cmpxchg(v: &inode->i_version, old: &cur, new));
1891	return true;
1892	}
1893	EXPORT_SYMBOL(inode_maybe_inc_iversion);
1894
1895	/**
1896	* inode_query_iversion - read i_version for later use
1897	* @inode: inode from which i_version should be read
1898	*
1899	* Read the inode i_version counter. This should be used by callers that wish
1900	* to store the returned i_version for later comparison. This will guarantee
1901	* that a later query of the i_version will result in a different value if
1902	* anything has changed.
1903	*
1904	* In this implementation, we fetch the current value, set the QUERIED flag and
1905	* then try to swap it into place with a cmpxchg, if it wasn't already set. If
1906	* that fails, we try again with the newly fetched value from the cmpxchg.
1907	*/
1908	u64 inode_query_iversion(struct inode *inode)
1909	{
1910	u64 cur, new;
1911
1912	cur = inode_peek_iversion_raw(inode);
1913	do {
1914	/* If flag is already set, then no need to swap */
1915	if (cur & I_VERSION_QUERIED) {
1916	/*
1917	* This barrier (and the implicit barrier in the
1918	* cmpxchg below) pairs with the barrier in
1919	* inode_maybe_inc_iversion().
1920	*/
1921	smp_mb();
1922	break;
1923	}
1924
1925	new = cur | I_VERSION_QUERIED;
1926	} while (!atomic64_try_cmpxchg(v: &inode->i_version, old: &cur, new));
1927	return cur >> I_VERSION_QUERIED_SHIFT;
1928	}
1929	EXPORT_SYMBOL(inode_query_iversion);
1930
1931	ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
1932	ssize_t direct_written, ssize_t buffered_written)
1933	{
1934	struct address_space *mapping = iocb->ki_filp->f_mapping;
1935	loff_t pos = iocb->ki_pos - buffered_written;
1936	loff_t end = iocb->ki_pos - 1;
1937	int err;
1938
1939	/*
1940	* If the buffered write fallback returned an error, we want to return
1941	* the number of bytes which were written by direct I/O, or the error
1942	* code if that was zero.
1943	*
1944	* Note that this differs from normal direct-io semantics, which will
1945	* return -EFOO even if some bytes were written.
1946	*/
1947	if (unlikely(buffered_written < 0)) {
1948	if (direct_written)
1949	return direct_written;
1950	return buffered_written;
1951	}
1952
1953	/*
1954	* We need to ensure that the page cache pages are written to disk and
1955	* invalidated to preserve the expected O_DIRECT semantics.
1956	*/
1957	err = filemap_write_and_wait_range(mapping, lstart: pos, lend: end);
1958	if (err < 0) {
1959	/*
1960	* We don't know how much we wrote, so just return the number of
1961	* bytes which were direct-written
1962	*/
1963	iocb->ki_pos -= buffered_written;
1964	if (direct_written)
1965	return direct_written;
1966	return err;
1967	}
1968	invalidate_mapping_pages(mapping, start: pos >> PAGE_SHIFT, end: end >> PAGE_SHIFT);
1969	return direct_written + buffered_written;
1970	}
1971	EXPORT_SYMBOL_GPL(direct_write_fallback);
1972
1973	/**
1974	* simple_inode_init_ts - initialize the timestamps for a new inode
1975	* @inode: inode to be initialized
1976	*
1977	* When a new inode is created, most filesystems set the timestamps to the
1978	* current time. Add a helper to do this.
1979	*/
1980	struct timespec64 simple_inode_init_ts(struct inode *inode)
1981	{
1982	struct timespec64 ts = inode_set_ctime_current(inode);
1983
1984	inode_set_atime_to_ts(inode, ts);
1985	inode_set_mtime_to_ts(inode, ts);
1986	return ts;
1987	}
1988	EXPORT_SYMBOL(simple_inode_init_ts);
1989
1990	static inline struct dentry *get_stashed_dentry(struct dentry *stashed)
1991	{
1992	struct dentry *dentry;
1993
1994	guard(rcu)();
1995	dentry = READ_ONCE(stashed);
1996	if (!dentry)
1997	return NULL;
1998	if (!lockref_get_not_dead(&dentry->d_lockref))
1999	return NULL;
2000	return dentry;
2001	}
2002
2003	static struct dentry *prepare_anon_dentry(struct dentry **stashed,
2004	struct super_block *sb,
2005	void *data)
2006	{
2007	struct dentry *dentry;
2008	struct inode *inode;
2009	const struct stashed_operations *sops = sb->s_fs_info;
2010	int ret;
2011
2012	inode = new_inode_pseudo(sb);
2013	if (!inode) {
2014	sops->put_data(data);
2015	return ERR_PTR(error: -ENOMEM);
2016	}
2017
2018	inode->i_flags |= S_IMMUTABLE;
2019	inode->i_mode = S_IFREG;
2020	simple_inode_init_ts(inode);
2021
2022	ret = sops->init_inode(inode, data);
2023	if (ret < 0) {
2024	iput(inode);
2025	return ERR_PTR(error: ret);
2026	}
2027
2028	/* Notice when this is changed. */
2029	WARN_ON_ONCE(!S_ISREG(inode->i_mode));
2030	WARN_ON_ONCE(!IS_IMMUTABLE(inode));
2031
2032	dentry = d_alloc_anon(sb);
2033	if (!dentry) {
2034	iput(inode);
2035	return ERR_PTR(error: -ENOMEM);
2036	}
2037
2038	/* Store address of location where dentry's supposed to be stashed. */
2039	dentry->d_fsdata = stashed;
2040
2041	/* @data is now owned by the fs */
2042	d_instantiate(dentry, inode);
2043	return dentry;
2044	}
2045
2046	static struct dentry *stash_dentry(struct dentry **stashed,
2047	struct dentry *dentry)
2048	{
2049	guard(rcu)();
2050	for (;;) {
2051	struct dentry *old;
2052
2053	/* Assume any old dentry was cleared out. */
2054	old = cmpxchg(stashed, NULL, dentry);
2055	if (likely(!old))
2056	return dentry;
2057
2058	/* Check if somebody else installed a reusable dentry. */
2059	if (lockref_get_not_dead(&old->d_lockref))
2060	return old;
2061
2062	/* There's an old dead dentry there, try to take it over. */
2063	if (likely(try_cmpxchg(stashed, &old, dentry)))
2064	return dentry;
2065	}
2066	}
2067
2068	/**
2069	* path_from_stashed - create path from stashed or new dentry
2070	* @stashed: where to retrieve or stash dentry
2071	* @mnt: mnt of the filesystems to use
2072	* @data: data to store in inode->i_private
2073	* @path: path to create
2074	*
2075	* The function tries to retrieve a stashed dentry from @stashed. If the dentry
2076	* is still valid then it will be reused. If the dentry isn't able the function
2077	* will allocate a new dentry and inode. It will then check again whether it
2078	* can reuse an existing dentry in case one has been added in the meantime or
2079	* update @stashed with the newly added dentry.
2080	*
2081	* Special-purpose helper for nsfs and pidfs.
2082	*
2083	* Return: On success zero and on failure a negative error is returned.
2084	*/
2085	int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
2086	struct path *path)
2087	{
2088	struct dentry *dentry;
2089	const struct stashed_operations *sops = mnt->mnt_sb->s_fs_info;
2090
2091	/* See if dentry can be reused. */
2092	path->dentry = get_stashed_dentry(stashed: *stashed);
2093	if (path->dentry) {
2094	sops->put_data(data);
2095	goto out_path;
2096	}
2097
2098	/* Allocate a new dentry. */
2099	dentry = prepare_anon_dentry(stashed, sb: mnt->mnt_sb, data);
2100	if (IS_ERR(ptr: dentry))
2101	return PTR_ERR(ptr: dentry);
2102
2103	/* Added a new dentry. @data is now owned by the filesystem. */
2104	path->dentry = stash_dentry(stashed, dentry);
2105	if (path->dentry != dentry)
2106	dput(dentry);
2107
2108	out_path:
2109	WARN_ON_ONCE(path->dentry->d_fsdata != stashed);
2110	WARN_ON_ONCE(d_inode(path->dentry)->i_private != data);
2111	path->mnt = mntget(mnt);
2112	return 0;
2113	}
2114
2115	void stashed_dentry_prune(struct dentry *dentry)
2116	{
2117	struct dentry **stashed = dentry->d_fsdata;
2118	struct inode *inode = d_inode(dentry);
2119
2120	if (WARN_ON_ONCE(!stashed))
2121	return;
2122
2123	if (!inode)
2124	return;
2125
2126	/*
2127	* Only replace our own @dentry as someone else might've
2128	* already cleared out @dentry and stashed their own
2129	* dentry in there.
2130	*/
2131	cmpxchg(stashed, dentry, NULL);
2132	}
2133