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
27	#include <linux/uaccess.h>
28
29	#include "internal.h"
30
31	int simple_getattr(struct mnt_idmap *idmap, const struct path *path,
32	struct kstat *stat, u32 request_mask,
33	unsigned int query_flags)
34	{
35	struct inode *inode = d_inode(dentry: path->dentry);
36	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
37	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
38	return 0;
39	}
40	EXPORT_SYMBOL(simple_getattr);
41
42	int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
43	{
44	u64 id = huge_encode_dev(dev: dentry->d_sb->s_dev);
45
46	buf->f_fsid = u64_to_fsid(v: id);
47	buf->f_type = dentry->d_sb->s_magic;
48	buf->f_bsize = PAGE_SIZE;
49	buf->f_namelen = NAME_MAX;
50	return 0;
51	}
52	EXPORT_SYMBOL(simple_statfs);
53
54	/*
55	* Retaining negative dentries for an in-memory filesystem just wastes
56	* memory and lookup time: arrange for them to be deleted immediately.
57	*/
58	int always_delete_dentry(const struct dentry *dentry)
59	{
60	return 1;
61	}
62	EXPORT_SYMBOL(always_delete_dentry);
63
64	const struct dentry_operations simple_dentry_operations = {
65	.d_delete = always_delete_dentry,
66	};
67	EXPORT_SYMBOL(simple_dentry_operations);
68
69	/*
70	* Lookup the data. This is trivial - if the dentry didn't already
71	* exist, we know it is negative. Set d_op to delete negative dentries.
72	*/
73	struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
74	{
75	if (dentry->d_name.len > NAME_MAX)
76	return ERR_PTR(error: -ENAMETOOLONG);
77	if (!dentry->d_sb->s_d_op)
78	d_set_d_op(dentry, op: &simple_dentry_operations);
79	d_add(dentry, NULL);
80	return NULL;
81	}
82	EXPORT_SYMBOL(simple_lookup);
83
84	int dcache_dir_open(struct inode *inode, struct file *file)
85	{
86	file->private_data = d_alloc_cursor(file->f_path.dentry);
87
88	return file->private_data ? 0 : -ENOMEM;
89	}
90	EXPORT_SYMBOL(dcache_dir_open);
91
92	int dcache_dir_close(struct inode *inode, struct file *file)
93	{
94	dput(file->private_data);
95	return 0;
96	}
97	EXPORT_SYMBOL(dcache_dir_close);
98
99	/* parent is locked at least shared */
100	/*
101	* Returns an element of siblings' list.
102	* We are looking for <count>th positive after <p>; if
103	* found, dentry is grabbed and returned to caller.
104	* If no such element exists, NULL is returned.
105	*/
106	static struct dentry *scan_positives(struct dentry *cursor,
107	struct list_head *p,
108	loff_t count,
109	struct dentry *last)
110	{
111	struct dentry *dentry = cursor->d_parent, *found = NULL;
112
113	spin_lock(lock: &dentry->d_lock);
114	while ((p = p->next) != &dentry->d_subdirs) {
115	struct dentry *d = list_entry(p, struct dentry, d_child);
116	// we must at least skip cursors, to avoid livelocks
117	if (d->d_flags & DCACHE_DENTRY_CURSOR)
118	continue;
119	if (simple_positive(dentry: d) && !--count) {
120	spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
121	if (simple_positive(dentry: d))
122	found = dget_dlock(dentry: d);
123	spin_unlock(lock: &d->d_lock);
124	if (likely(found))
125	break;
126	count = 1;
127	}
128	if (need_resched()) {
129	list_move(list: &cursor->d_child, head: p);
130	p = &cursor->d_child;
131	spin_unlock(lock: &dentry->d_lock);
132	cond_resched();
133	spin_lock(lock: &dentry->d_lock);
134	}
135	}
136	spin_unlock(lock: &dentry->d_lock);
137	dput(last);
138	return found;
139	}
140
141	loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
142	{
143	struct dentry *dentry = file->f_path.dentry;
144	switch (whence) {
145	case 1:
146	offset += file->f_pos;
147	fallthrough;
148	case 0:
149	if (offset >= 0)
150	break;
151	fallthrough;
152	default:
153	return -EINVAL;
154	}
155	if (offset != file->f_pos) {
156	struct dentry *cursor = file->private_data;
157	struct dentry *to = NULL;
158
159	inode_lock_shared(inode: dentry->d_inode);
160
161	if (offset > 2)
162	to = scan_positives(cursor, p: &dentry->d_subdirs,
163	count: offset - 2, NULL);
164	spin_lock(lock: &dentry->d_lock);
165	if (to)
166	list_move(list: &cursor->d_child, head: &to->d_child);
167	else
168	list_del_init(entry: &cursor->d_child);
169	spin_unlock(lock: &dentry->d_lock);
170	dput(to);
171
172	file->f_pos = offset;
173
174	inode_unlock_shared(inode: dentry->d_inode);
175	}
176	return offset;
177	}
178	EXPORT_SYMBOL(dcache_dir_lseek);
179
180	/*
181	* Directory is locked and all positive dentries in it are safe, since
182	* for ramfs-type trees they can't go away without unlink() or rmdir(),
183	* both impossible due to the lock on directory.
184	*/
185
186	int dcache_readdir(struct file *file, struct dir_context *ctx)
187	{
188	struct dentry *dentry = file->f_path.dentry;
189	struct dentry *cursor = file->private_data;
190	struct list_head *anchor = &dentry->d_subdirs;
191	struct dentry *next = NULL;
192	struct list_head *p;
193
194	if (!dir_emit_dots(file, ctx))
195	return 0;
196
197	if (ctx->pos == 2)
198	p = anchor;
199	else if (!list_empty(head: &cursor->d_child))
200	p = &cursor->d_child;
201	else
202	return 0;
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_child;
211	}
212	spin_lock(lock: &dentry->d_lock);
213	if (next)
214	list_move_tail(list: &cursor->d_child, head: &next->d_child);
215	else
216	list_del_init(entry: &cursor->d_child);
217	spin_unlock(lock: &dentry->d_lock);
218	dput(next);
219
220	return 0;
221	}
222	EXPORT_SYMBOL(dcache_readdir);
223
224	ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
225	{
226	return -EISDIR;
227	}
228	EXPORT_SYMBOL(generic_read_dir);
229
230	const struct file_operations simple_dir_operations = {
231	.open = dcache_dir_open,
232	.release = dcache_dir_close,
233	.llseek = dcache_dir_lseek,
234	.read = generic_read_dir,
235	.iterate_shared = dcache_readdir,
236	.fsync = noop_fsync,
237	};
238	EXPORT_SYMBOL(simple_dir_operations);
239
240	const struct inode_operations simple_dir_inode_operations = {
241	.lookup = simple_lookup,
242	};
243	EXPORT_SYMBOL(simple_dir_inode_operations);
244
245	static void offset_set(struct dentry *dentry, u32 offset)
246	{
247	dentry->d_fsdata = (void *)((uintptr_t)(offset));
248	}
249
250	static u32 dentry2offset(struct dentry *dentry)
251	{
252	return (u32)((uintptr_t)(dentry->d_fsdata));
253	}
254
255	static struct lock_class_key simple_offset_xa_lock;
256
257	/**
258	* simple_offset_init - initialize an offset_ctx
259	* @octx: directory offset map to be initialized
260	*
261	*/
262	void simple_offset_init(struct offset_ctx *octx)
263	{
264	xa_init_flags(xa: &octx->xa, XA_FLAGS_ALLOC1);
265	lockdep_set_class(&octx->xa.xa_lock, &simple_offset_xa_lock);
266
267	/* 0 is '.', 1 is '..', so always start with offset 2 */
268	octx->next_offset = 2;
269	}
270
271	/**
272	* simple_offset_add - Add an entry to a directory's offset map
273	* @octx: directory offset ctx to be updated
274	* @dentry: new dentry being added
275	*
276	* Returns zero on success. @so_ctx and the dentry offset are updated.
277	* Otherwise, a negative errno value is returned.
278	*/
279	int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
280	{
281	static const struct xa_limit limit = XA_LIMIT(2, U32_MAX);
282	u32 offset;
283	int ret;
284
285	if (dentry2offset(dentry) != 0)
286	return -EBUSY;
287
288	ret = xa_alloc_cyclic(xa: &octx->xa, id: &offset, entry: dentry, limit,
289	next: &octx->next_offset, GFP_KERNEL);
290	if (ret < 0)
291	return ret;
292
293	offset_set(dentry, offset);
294	return 0;
295	}
296
297	/**
298	* simple_offset_remove - Remove an entry to a directory's offset map
299	* @octx: directory offset ctx to be updated
300	* @dentry: dentry being removed
301	*
302	*/
303	void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
304	{
305	u32 offset;
306
307	offset = dentry2offset(dentry);
308	if (offset == 0)
309	return;
310
311	xa_erase(&octx->xa, index: offset);
312	offset_set(dentry, offset: 0);
313	}
314
315	/**
316	* simple_offset_rename_exchange - exchange rename with directory offsets
317	* @old_dir: parent of dentry being moved
318	* @old_dentry: dentry being moved
319	* @new_dir: destination parent
320	* @new_dentry: destination dentry
321	*
322	* Returns zero on success. Otherwise a negative errno is returned and the
323	* rename is rolled back.
324	*/
325	int simple_offset_rename_exchange(struct inode *old_dir,
326	struct dentry *old_dentry,
327	struct inode *new_dir,
328	struct dentry *new_dentry)
329	{
330	struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
331	struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
332	u32 old_index = dentry2offset(dentry: old_dentry);
333	u32 new_index = dentry2offset(dentry: new_dentry);
334	int ret;
335
336	simple_offset_remove(octx: old_ctx, dentry: old_dentry);
337	simple_offset_remove(octx: new_ctx, dentry: new_dentry);
338
339	ret = simple_offset_add(octx: new_ctx, dentry: old_dentry);
340	if (ret)
341	goto out_restore;
342
343	ret = simple_offset_add(octx: old_ctx, dentry: new_dentry);
344	if (ret) {
345	simple_offset_remove(octx: new_ctx, dentry: old_dentry);
346	goto out_restore;
347	}
348
349	ret = simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
350	if (ret) {
351	simple_offset_remove(octx: new_ctx, dentry: old_dentry);
352	simple_offset_remove(octx: old_ctx, dentry: new_dentry);
353	goto out_restore;
354	}
355	return 0;
356
357	out_restore:
358	offset_set(dentry: old_dentry, offset: old_index);
359	xa_store(&old_ctx->xa, index: old_index, entry: old_dentry, GFP_KERNEL);
360	offset_set(dentry: new_dentry, offset: new_index);
361	xa_store(&new_ctx->xa, index: new_index, entry: new_dentry, GFP_KERNEL);
362	return ret;
363	}
364
365	/**
366	* simple_offset_destroy - Release offset map
367	* @octx: directory offset ctx that is about to be destroyed
368	*
369	* During fs teardown (eg. umount), a directory's offset map might still
370	* contain entries. xa_destroy() cleans out anything that remains.
371	*/
372	void simple_offset_destroy(struct offset_ctx *octx)
373	{
374	xa_destroy(&octx->xa);
375	}
376
377	/**
378	* offset_dir_llseek - Advance the read position of a directory descriptor
379	* @file: an open directory whose position is to be updated
380	* @offset: a byte offset
381	* @whence: enumerator describing the starting position for this update
382	*
383	* SEEK_END, SEEK_DATA, and SEEK_HOLE are not supported for directories.
384	*
385	* Returns the updated read position if successful; otherwise a
386	* negative errno is returned and the read position remains unchanged.
387	*/
388	static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
389	{
390	switch (whence) {
391	case SEEK_CUR:
392	offset += file->f_pos;
393	fallthrough;
394	case SEEK_SET:
395	if (offset >= 0)
396	break;
397	fallthrough;
398	default:
399	return -EINVAL;
400	}
401
402	return vfs_setpos(file, offset, U32_MAX);
403	}
404
405	static struct dentry *offset_find_next(struct xa_state *xas)
406	{
407	struct dentry *child, *found = NULL;
408
409	rcu_read_lock();
410	child = xas_next_entry(xas, U32_MAX);
411	if (!child)
412	goto out;
413	spin_lock(lock: &child->d_lock);
414	if (simple_positive(dentry: child))
415	found = dget_dlock(dentry: child);
416	spin_unlock(lock: &child->d_lock);
417	out:
418	rcu_read_unlock();
419	return found;
420	}
421
422	static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
423	{
424	u32 offset = dentry2offset(dentry);
425	struct inode *inode = d_inode(dentry);
426
427	return ctx->actor(ctx, dentry->d_name.name, dentry->d_name.len, offset,
428	inode->i_ino, fs_umode_to_dtype(mode: inode->i_mode));
429	}
430
431	static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
432	{
433	struct offset_ctx *so_ctx = inode->i_op->get_offset_ctx(inode);
434	XA_STATE(xas, &so_ctx->xa, ctx->pos);
435	struct dentry *dentry;
436
437	while (true) {
438	dentry = offset_find_next(xas: &xas);
439	if (!dentry)
440	break;
441
442	if (!offset_dir_emit(ctx, dentry)) {
443	dput(dentry);
444	break;
445	}
446
447	dput(dentry);
448	ctx->pos = xas.xa_index + 1;
449	}
450	}
451
452	/**
453	* offset_readdir - Emit entries starting at offset @ctx->pos
454	* @file: an open directory to iterate over
455	* @ctx: directory iteration context
456	*
457	* Caller must hold @file's i_rwsem to prevent insertion or removal of
458	* entries during this call.
459	*
460	* On entry, @ctx->pos contains an offset that represents the first entry
461	* to be read from the directory.
462	*
463	* The operation continues until there are no more entries to read, or
464	* until the ctx->actor indicates there is no more space in the caller's
465	* output buffer.
466	*
467	* On return, @ctx->pos contains an offset that will read the next entry
468	* in this directory when offset_readdir() is called again with @ctx.
469	*
470	* Return values:
471	* %0 - Complete
472	*/
473	static int offset_readdir(struct file *file, struct dir_context *ctx)
474	{
475	struct dentry *dir = file->f_path.dentry;
476
477	lockdep_assert_held(&d_inode(dir)->i_rwsem);
478
479	if (!dir_emit_dots(file, ctx))
480	return 0;
481
482	offset_iterate_dir(inode: d_inode(dentry: dir), ctx);
483	return 0;
484	}
485
486	const struct file_operations simple_offset_dir_operations = {
487	.llseek = offset_dir_llseek,
488	.iterate_shared = offset_readdir,
489	.read = generic_read_dir,
490	.fsync = noop_fsync,
491	};
492
493	static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
494	{
495	struct dentry *child = NULL;
496	struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
497
498	spin_lock(lock: &parent->d_lock);
499	while ((p = p->next) != &parent->d_subdirs) {
500	struct dentry *d = container_of(p, struct dentry, d_child);
501	if (simple_positive(dentry: d)) {
502	spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
503	if (simple_positive(dentry: d))
504	child = dget_dlock(dentry: d);
505	spin_unlock(lock: &d->d_lock);
506	if (likely(child))
507	break;
508	}
509	}
510	spin_unlock(lock: &parent->d_lock);
511	dput(prev);
512	return child;
513	}
514
515	void simple_recursive_removal(struct dentry *dentry,
516	void (*callback)(struct dentry *))
517	{
518	struct dentry *this = dget(dentry);
519	while (true) {
520	struct dentry *victim = NULL, *child;
521	struct inode *inode = this->d_inode;
522
523	inode_lock(inode);
524	if (d_is_dir(dentry: this))
525	inode->i_flags |= S_DEAD;
526	while ((child = find_next_child(parent: this, prev: victim)) == NULL) {
527	// kill and ascend
528	// update metadata while it's still locked
529	inode_set_ctime_current(inode);
530	clear_nlink(inode);
531	inode_unlock(inode);
532	victim = this;
533	this = this->d_parent;
534	inode = this->d_inode;
535	inode_lock(inode);
536	if (simple_positive(dentry: victim)) {
537	d_invalidate(victim); // avoid lost mounts
538	if (d_is_dir(dentry: victim))
539	fsnotify_rmdir(dir: inode, dentry: victim);
540	else
541	fsnotify_unlink(dir: inode, dentry: victim);
542	if (callback)
543	callback(victim);
544	dput(victim); // unpin it
545	}
546	if (victim == dentry) {
547	inode_set_mtime_to_ts(inode,
548	ts: inode_set_ctime_current(inode));
549	if (d_is_dir(dentry))
550	drop_nlink(inode);
551	inode_unlock(inode);
552	dput(dentry);
553	return;
554	}
555	}
556	inode_unlock(inode);
557	this = child;
558	}
559	}
560	EXPORT_SYMBOL(simple_recursive_removal);
561
562	static const struct super_operations simple_super_operations = {
563	.statfs = simple_statfs,
564	};
565
566	static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
567	{
568	struct pseudo_fs_context *ctx = fc->fs_private;
569	struct inode *root;
570
571	s->s_maxbytes = MAX_LFS_FILESIZE;
572	s->s_blocksize = PAGE_SIZE;
573	s->s_blocksize_bits = PAGE_SHIFT;
574	s->s_magic = ctx->magic;
575	s->s_op = ctx->ops ?: &simple_super_operations;
576	s->s_xattr = ctx->xattr;
577	s->s_time_gran = 1;
578	root = new_inode(sb: s);
579	if (!root)
580	return -ENOMEM;
581
582	/*
583	* since this is the first inode, make it number 1. New inodes created
584	* after this must take care not to collide with it (by passing
585	* max_reserved of 1 to iunique).
586	*/
587	root->i_ino = 1;
588	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
589	simple_inode_init_ts(inode: root);
590	s->s_root = d_make_root(root);
591	if (!s->s_root)
592	return -ENOMEM;
593	s->s_d_op = ctx->dops;
594	return 0;
595	}
596
597	static int pseudo_fs_get_tree(struct fs_context *fc)
598	{
599	return get_tree_nodev(fc, fill_super: pseudo_fs_fill_super);
600	}
601
602	static void pseudo_fs_free(struct fs_context *fc)
603	{
604	kfree(objp: fc->fs_private);
605	}
606
607	static const struct fs_context_operations pseudo_fs_context_ops = {
608	.free = pseudo_fs_free,
609	.get_tree = pseudo_fs_get_tree,
610	};
611
612	/*
613	* Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
614	* will never be mountable)
615	*/
616	struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
617	unsigned long magic)
618	{
619	struct pseudo_fs_context *ctx;
620
621	ctx = kzalloc(size: sizeof(struct pseudo_fs_context), GFP_KERNEL);
622	if (likely(ctx)) {
623	ctx->magic = magic;
624	fc->fs_private = ctx;
625	fc->ops = &pseudo_fs_context_ops;
626	fc->sb_flags |= SB_NOUSER;
627	fc->global = true;
628	}
629	return ctx;
630	}
631	EXPORT_SYMBOL(init_pseudo);
632
633	int simple_open(struct inode *inode, struct file *file)
634	{
635	if (inode->i_private)
636	file->private_data = inode->i_private;
637	return 0;
638	}
639	EXPORT_SYMBOL(simple_open);
640
641	int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
642	{
643	struct inode *inode = d_inode(dentry: old_dentry);
644
645	inode_set_mtime_to_ts(inode: dir,
646	ts: inode_set_ctime_to_ts(inode: dir, ts: inode_set_ctime_current(inode)));
647	inc_nlink(inode);
648	ihold(inode);
649	dget(dentry);
650	d_instantiate(dentry, inode);
651	return 0;
652	}
653	EXPORT_SYMBOL(simple_link);
654
655	int simple_empty(struct dentry *dentry)
656	{
657	struct dentry *child;
658	int ret = 0;
659
660	spin_lock(lock: &dentry->d_lock);
661	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
662	spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
663	if (simple_positive(dentry: child)) {
664	spin_unlock(lock: &child->d_lock);
665	goto out;
666	}
667	spin_unlock(lock: &child->d_lock);
668	}
669	ret = 1;
670	out:
671	spin_unlock(lock: &dentry->d_lock);
672	return ret;
673	}
674	EXPORT_SYMBOL(simple_empty);
675
676	int simple_unlink(struct inode *dir, struct dentry *dentry)
677	{
678	struct inode *inode = d_inode(dentry);
679
680	inode_set_mtime_to_ts(inode: dir,
681	ts: inode_set_ctime_to_ts(inode: dir, ts: inode_set_ctime_current(inode)));
682	drop_nlink(inode);
683	dput(dentry);
684	return 0;
685	}
686	EXPORT_SYMBOL(simple_unlink);
687
688	int simple_rmdir(struct inode *dir, struct dentry *dentry)
689	{
690	if (!simple_empty(dentry))
691	return -ENOTEMPTY;
692
693	drop_nlink(inode: d_inode(dentry));
694	simple_unlink(dir, dentry);
695	drop_nlink(inode: dir);
696	return 0;
697	}
698	EXPORT_SYMBOL(simple_rmdir);
699
700	/**
701	* simple_rename_timestamp - update the various inode timestamps for rename
702	* @old_dir: old parent directory
703	* @old_dentry: dentry that is being renamed
704	* @new_dir: new parent directory
705	* @new_dentry: target for rename
706	*
707	* POSIX mandates that the old and new parent directories have their ctime and
708	* mtime updated, and that inodes of @old_dentry and @new_dentry (if any), have
709	* their ctime updated.
710	*/
711	void simple_rename_timestamp(struct inode *old_dir, struct dentry *old_dentry,
712	struct inode *new_dir, struct dentry *new_dentry)
713	{
714	struct inode *newino = d_inode(dentry: new_dentry);
715
716	inode_set_mtime_to_ts(inode: old_dir, ts: inode_set_ctime_current(inode: old_dir));
717	if (new_dir != old_dir)
718	inode_set_mtime_to_ts(inode: new_dir,
719	ts: inode_set_ctime_current(inode: new_dir));
720	inode_set_ctime_current(inode: d_inode(dentry: old_dentry));
721	if (newino)
722	inode_set_ctime_current(inode: newino);
723	}
724	EXPORT_SYMBOL_GPL(simple_rename_timestamp);
725
726	int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
727	struct inode *new_dir, struct dentry *new_dentry)
728	{
729	bool old_is_dir = d_is_dir(dentry: old_dentry);
730	bool new_is_dir = d_is_dir(dentry: new_dentry);
731
732	if (old_dir != new_dir && old_is_dir != new_is_dir) {
733	if (old_is_dir) {
734	drop_nlink(inode: old_dir);
735	inc_nlink(inode: new_dir);
736	} else {
737	drop_nlink(inode: new_dir);
738	inc_nlink(inode: old_dir);
739	}
740	}
741	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
742	return 0;
743	}
744	EXPORT_SYMBOL_GPL(simple_rename_exchange);
745
746	int simple_rename(struct mnt_idmap *idmap, struct inode *old_dir,
747	struct dentry *old_dentry, struct inode *new_dir,
748	struct dentry *new_dentry, unsigned int flags)
749	{
750	int they_are_dirs = d_is_dir(dentry: old_dentry);
751
752	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
753	return -EINVAL;
754
755	if (flags & RENAME_EXCHANGE)
756	return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
757
758	if (!simple_empty(new_dentry))
759	return -ENOTEMPTY;
760
761	if (d_really_is_positive(dentry: new_dentry)) {
762	simple_unlink(new_dir, new_dentry);
763	if (they_are_dirs) {
764	drop_nlink(inode: d_inode(dentry: new_dentry));
765	drop_nlink(inode: old_dir);
766	}
767	} else if (they_are_dirs) {
768	drop_nlink(inode: old_dir);
769	inc_nlink(inode: new_dir);
770	}
771
772	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
773	return 0;
774	}
775	EXPORT_SYMBOL(simple_rename);
776
777	/**
778	* simple_setattr - setattr for simple filesystem
779	* @idmap: idmap of the target mount
780	* @dentry: dentry
781	* @iattr: iattr structure
782	*
783	* Returns 0 on success, -error on failure.
784	*
785	* simple_setattr is a simple ->setattr implementation without a proper
786	* implementation of size changes.
787	*
788	* It can either be used for in-memory filesystems or special files
789	* on simple regular filesystems. Anything that needs to change on-disk
790	* or wire state on size changes needs its own setattr method.
791	*/
792	int simple_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
793	struct iattr *iattr)
794	{
795	struct inode *inode = d_inode(dentry);
796	int error;
797
798	error = setattr_prepare(idmap, dentry, iattr);
799	if (error)
800	return error;
801
802	if (iattr->ia_valid & ATTR_SIZE)
803	truncate_setsize(inode, newsize: iattr->ia_size);
804	setattr_copy(idmap, inode, attr: iattr);
805	mark_inode_dirty(inode);
806	return 0;
807	}
808	EXPORT_SYMBOL(simple_setattr);
809
810	static int simple_read_folio(struct file *file, struct folio *folio)
811	{
812	folio_zero_range(folio, start: 0, length: folio_size(folio));
813	flush_dcache_folio(folio);
814	folio_mark_uptodate(folio);
815	folio_unlock(folio);
816	return 0;
817	}
818
819	int simple_write_begin(struct file *file, struct address_space *mapping,
820	loff_t pos, unsigned len,
821	struct page **pagep, void **fsdata)
822	{
823	struct folio *folio;
824
825	folio = __filemap_get_folio(mapping, index: pos / PAGE_SIZE, FGP_WRITEBEGIN,
826	gfp: mapping_gfp_mask(mapping));
827	if (IS_ERR(ptr: folio))
828	return PTR_ERR(ptr: folio);
829
830	*pagep = &folio->page;
831
832	if (!folio_test_uptodate(folio) && (len != folio_size(folio))) {
833	size_t from = offset_in_folio(folio, pos);
834
835	folio_zero_segments(folio, start1: 0, xend1: from,
836	start2: from + len, xend2: folio_size(folio));
837	}
838	return 0;
839	}
840	EXPORT_SYMBOL(simple_write_begin);
841
842	/**
843	* simple_write_end - .write_end helper for non-block-device FSes
844	* @file: See .write_end of address_space_operations
845	* @mapping: "
846	* @pos: "
847	* @len: "
848	* @copied: "
849	* @page: "
850	* @fsdata: "
851	*
852	* simple_write_end does the minimum needed for updating a page after writing is
853	* done. It has the same API signature as the .write_end of
854	* address_space_operations vector. So it can just be set onto .write_end for
855	* FSes that don't need any other processing. i_mutex is assumed to be held.
856	* Block based filesystems should use generic_write_end().
857	* NOTE: Even though i_size might get updated by this function, mark_inode_dirty
858	* is not called, so a filesystem that actually does store data in .write_inode
859	* should extend on what's done here with a call to mark_inode_dirty() in the
860	* case that i_size has changed.
861	*
862	* Use *ONLY* with simple_read_folio()
863	*/
864	static int simple_write_end(struct file *file, struct address_space *mapping,
865	loff_t pos, unsigned len, unsigned copied,
866	struct page *page, void *fsdata)
867	{
868	struct folio *folio = page_folio(page);
869	struct inode *inode = folio->mapping->host;
870	loff_t last_pos = pos + copied;
871
872	/* zero the stale part of the folio if we did a short copy */
873	if (!folio_test_uptodate(folio)) {
874	if (copied < len) {
875	size_t from = offset_in_folio(folio, pos);
876
877	folio_zero_range(folio, start: from + copied, length: len - copied);
878	}
879	folio_mark_uptodate(folio);
880	}
881	/*
882	* No need to use i_size_read() here, the i_size
883	* cannot change under us because we hold the i_mutex.
884	*/
885	if (last_pos > inode->i_size)
886	i_size_write(inode, i_size: last_pos);
887
888	folio_mark_dirty(folio);
889	folio_unlock(folio);
890	folio_put(folio);
891
892	return copied;
893	}
894
895	/*
896	* Provides ramfs-style behavior: data in the pagecache, but no writeback.
897	*/
898	const struct address_space_operations ram_aops = {
899	.read_folio = simple_read_folio,
900	.write_begin = simple_write_begin,
901	.write_end = simple_write_end,
902	.dirty_folio = noop_dirty_folio,
903	};
904	EXPORT_SYMBOL(ram_aops);
905
906	/*
907	* the inodes created here are not hashed. If you use iunique to generate
908	* unique inode values later for this filesystem, then you must take care
909	* to pass it an appropriate max_reserved value to avoid collisions.
910	*/
911	int simple_fill_super(struct super_block *s, unsigned long magic,
912	const struct tree_descr *files)
913	{
914	struct inode *inode;
915	struct dentry *root;
916	struct dentry *dentry;
917	int i;
918
919	s->s_blocksize = PAGE_SIZE;
920	s->s_blocksize_bits = PAGE_SHIFT;
921	s->s_magic = magic;
922	s->s_op = &simple_super_operations;
923	s->s_time_gran = 1;
924
925	inode = new_inode(sb: s);
926	if (!inode)
927	return -ENOMEM;
928	/*
929	* because the root inode is 1, the files array must not contain an
930	* entry at index 1
931	*/
932	inode->i_ino = 1;
933	inode->i_mode = S_IFDIR | 0755;
934	simple_inode_init_ts(inode);
935	inode->i_op = &simple_dir_inode_operations;
936	inode->i_fop = &simple_dir_operations;
937	set_nlink(inode, nlink: 2);
938	root = d_make_root(inode);
939	if (!root)
940	return -ENOMEM;
941	for (i = 0; !files->name || files->name[0]; i++, files++) {
942	if (!files->name)
943	continue;
944
945	/* warn if it tries to conflict with the root inode */
946	if (unlikely(i == 1))
947	printk(KERN_WARNING "%s: %s passed in a files array"
948	"with an index of 1!\n", __func__,
949	s->s_type->name);
950
951	dentry = d_alloc_name(root, files->name);
952	if (!dentry)
953	goto out;
954	inode = new_inode(sb: s);
955	if (!inode) {
956	dput(dentry);
957	goto out;
958	}
959	inode->i_mode = S_IFREG | files->mode;
960	simple_inode_init_ts(inode);
961	inode->i_fop = files->ops;
962	inode->i_ino = i;
963	d_add(dentry, inode);
964	}
965	s->s_root = root;
966	return 0;
967	out:
968	d_genocide(root);
969	shrink_dcache_parent(root);
970	dput(root);
971	return -ENOMEM;
972	}
973	EXPORT_SYMBOL(simple_fill_super);
974
975	static DEFINE_SPINLOCK(pin_fs_lock);
976
977	int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
978	{
979	struct vfsmount *mnt = NULL;
980	spin_lock(lock: &pin_fs_lock);
981	if (unlikely(!*mount)) {
982	spin_unlock(lock: &pin_fs_lock);
983	mnt = vfs_kern_mount(type, SB_KERNMOUNT, name: type->name, NULL);
984	if (IS_ERR(ptr: mnt))
985	return PTR_ERR(ptr: mnt);
986	spin_lock(lock: &pin_fs_lock);
987	if (!*mount)
988	*mount = mnt;
989	}
990	mntget(mnt: *mount);
991	++*count;
992	spin_unlock(lock: &pin_fs_lock);
993	mntput(mnt);
994	return 0;
995	}
996	EXPORT_SYMBOL(simple_pin_fs);
997
998	void simple_release_fs(struct vfsmount **mount, int *count)
999	{
1000	struct vfsmount *mnt;
1001	spin_lock(lock: &pin_fs_lock);
1002	mnt = *mount;
1003	if (!--*count)
1004	*mount = NULL;
1005	spin_unlock(lock: &pin_fs_lock);
1006	mntput(mnt);
1007	}
1008	EXPORT_SYMBOL(simple_release_fs);
1009
1010	/**
1011	* simple_read_from_buffer - copy data from the buffer to user space
1012	* @to: the user space buffer to read to
1013	* @count: the maximum number of bytes to read
1014	* @ppos: the current position in the buffer
1015	* @from: the buffer to read from
1016	* @available: the size of the buffer
1017	*
1018	* The simple_read_from_buffer() function reads up to @count bytes from the
1019	* buffer @from at offset @ppos into the user space address starting at @to.
1020	*
1021	* On success, the number of bytes read is returned and the offset @ppos is
1022	* advanced by this number, or negative value is returned on error.
1023	**/
1024	ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
1025	const void *from, size_t available)
1026	{
1027	loff_t pos = *ppos;
1028	size_t ret;
1029
1030	if (pos < 0)
1031	return -EINVAL;
1032	if (pos >= available || !count)
1033	return 0;
1034	if (count > available - pos)
1035	count = available - pos;
1036	ret = copy_to_user(to, from: from + pos, n: count);
1037	if (ret == count)
1038	return -EFAULT;
1039	count -= ret;
1040	*ppos = pos + count;
1041	return count;
1042	}
1043	EXPORT_SYMBOL(simple_read_from_buffer);
1044
1045	/**
1046	* simple_write_to_buffer - copy data from user space to the buffer
1047	* @to: the buffer to write to
1048	* @available: the size of the buffer
1049	* @ppos: the current position in the buffer
1050	* @from: the user space buffer to read from
1051	* @count: the maximum number of bytes to read
1052	*
1053	* The simple_write_to_buffer() function reads up to @count bytes from the user
1054	* space address starting at @from into the buffer @to at offset @ppos.
1055	*
1056	* On success, the number of bytes written is returned and the offset @ppos is
1057	* advanced by this number, or negative value is returned on error.
1058	**/
1059	ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
1060	const void __user *from, size_t count)
1061	{
1062	loff_t pos = *ppos;
1063	size_t res;
1064
1065	if (pos < 0)
1066	return -EINVAL;
1067	if (pos >= available || !count)
1068	return 0;
1069	if (count > available - pos)
1070	count = available - pos;
1071	res = copy_from_user(to: to + pos, from, n: count);
1072	if (res == count)
1073	return -EFAULT;
1074	count -= res;
1075	*ppos = pos + count;
1076	return count;
1077	}
1078	EXPORT_SYMBOL(simple_write_to_buffer);
1079
1080	/**
1081	* memory_read_from_buffer - copy data from the buffer
1082	* @to: the kernel space buffer to read to
1083	* @count: the maximum number of bytes to read
1084	* @ppos: the current position in the buffer
1085	* @from: the buffer to read from
1086	* @available: the size of the buffer
1087	*
1088	* The memory_read_from_buffer() function reads up to @count bytes from the
1089	* buffer @from at offset @ppos into the kernel space address starting at @to.
1090	*
1091	* On success, the number of bytes read is returned and the offset @ppos is
1092	* advanced by this number, or negative value is returned on error.
1093	**/
1094	ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
1095	const void *from, size_t available)
1096	{
1097	loff_t pos = *ppos;
1098
1099	if (pos < 0)
1100	return -EINVAL;
1101	if (pos >= available)
1102	return 0;
1103	if (count > available - pos)
1104	count = available - pos;
1105	memcpy(to, from + pos, count);
1106	*ppos = pos + count;
1107
1108	return count;
1109	}
1110	EXPORT_SYMBOL(memory_read_from_buffer);
1111
1112	/*
1113	* Transaction based IO.
1114	* The file expects a single write which triggers the transaction, and then
1115	* possibly a read which collects the result - which is stored in a
1116	* file-local buffer.
1117	*/
1118
1119	void simple_transaction_set(struct file *file, size_t n)
1120	{
1121	struct simple_transaction_argresp *ar = file->private_data;
1122
1123	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
1124
1125	/*
1126	* The barrier ensures that ar->size will really remain zero until
1127	* ar->data is ready for reading.
1128	*/
1129	smp_mb();
1130	ar->size = n;
1131	}
1132	EXPORT_SYMBOL(simple_transaction_set);
1133
1134	char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
1135	{
1136	struct simple_transaction_argresp *ar;
1137	static DEFINE_SPINLOCK(simple_transaction_lock);
1138
1139	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
1140	return ERR_PTR(error: -EFBIG);
1141
1142	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
1143	if (!ar)
1144	return ERR_PTR(error: -ENOMEM);
1145
1146	spin_lock(lock: &simple_transaction_lock);
1147
1148	/* only one write allowed per open */
1149	if (file->private_data) {
1150	spin_unlock(lock: &simple_transaction_lock);
1151	free_page((unsigned long)ar);
1152	return ERR_PTR(error: -EBUSY);
1153	}
1154
1155	file->private_data = ar;
1156
1157	spin_unlock(lock: &simple_transaction_lock);
1158
1159	if (copy_from_user(to: ar->data, from: buf, n: size))
1160	return ERR_PTR(error: -EFAULT);
1161
1162	return ar->data;
1163	}
1164	EXPORT_SYMBOL(simple_transaction_get);
1165
1166	ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
1167	{
1168	struct simple_transaction_argresp *ar = file->private_data;
1169
1170	if (!ar)
1171	return 0;
1172	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
1173	}
1174	EXPORT_SYMBOL(simple_transaction_read);
1175
1176	int simple_transaction_release(struct inode *inode, struct file *file)
1177	{
1178	free_page((unsigned long)file->private_data);
1179	return 0;
1180	}
1181	EXPORT_SYMBOL(simple_transaction_release);
1182
1183	/* Simple attribute files */
1184
1185	struct simple_attr {
1186	int (*get)(void *, u64 *);
1187	int (*set)(void *, u64);
1188	char get_buf[24]; /* enough to store a u64 and "\n\0" */
1189	char set_buf[24];
1190	void *data;
1191	const char *fmt; /* format for read operation */
1192	struct mutex mutex; /* protects access to these buffers */
1193	};
1194
1195	/* simple_attr_open is called by an actual attribute open file operation
1196	* to set the attribute specific access operations. */
1197	int simple_attr_open(struct inode *inode, struct file *file,
1198	int (*get)(void *, u64 *), int (*set)(void *, u64),
1199	const char *fmt)
1200	{
1201	struct simple_attr *attr;
1202
1203	attr = kzalloc(size: sizeof(*attr), GFP_KERNEL);
1204	if (!attr)
1205	return -ENOMEM;
1206
1207	attr->get = get;
1208	attr->set = set;
1209	attr->data = inode->i_private;
1210	attr->fmt = fmt;
1211	mutex_init(&attr->mutex);
1212
1213	file->private_data = attr;
1214
1215	return nonseekable_open(inode, filp: file);
1216	}
1217	EXPORT_SYMBOL_GPL(simple_attr_open);
1218
1219	int simple_attr_release(struct inode *inode, struct file *file)
1220	{
1221	kfree(objp: file->private_data);
1222	return 0;
1223	}
1224	EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */
1225
1226	/* read from the buffer that is filled with the get function */
1227	ssize_t simple_attr_read(struct file *file, char __user *buf,
1228	size_t len, loff_t *ppos)
1229	{
1230	struct simple_attr *attr;
1231	size_t size;
1232	ssize_t ret;
1233
1234	attr = file->private_data;
1235
1236	if (!attr->get)
1237	return -EACCES;
1238
1239	ret = mutex_lock_interruptible(&attr->mutex);
1240	if (ret)
1241	return ret;
1242
1243	if (*ppos && attr->get_buf[0]) {
1244	/* continued read */
1245	size = strlen(attr->get_buf);
1246	} else {
1247	/* first read */
1248	u64 val;
1249	ret = attr->get(attr->data, &val);
1250	if (ret)
1251	goto out;
1252
1253	size = scnprintf(buf: attr->get_buf, size: sizeof(attr->get_buf),
1254	fmt: attr->fmt, (unsigned long long)val);
1255	}
1256
1257	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
1258	out:
1259	mutex_unlock(lock: &attr->mutex);
1260	return ret;
1261	}
1262	EXPORT_SYMBOL_GPL(simple_attr_read);
1263
1264	/* interpret the buffer as a number to call the set function with */
1265	static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
1266	size_t len, loff_t *ppos, bool is_signed)
1267	{
1268	struct simple_attr *attr;
1269	unsigned long long val;
1270	size_t size;
1271	ssize_t ret;
1272
1273	attr = file->private_data;
1274	if (!attr->set)
1275	return -EACCES;
1276
1277	ret = mutex_lock_interruptible(&attr->mutex);
1278	if (ret)
1279	return ret;
1280
1281	ret = -EFAULT;
1282	size = min(sizeof(attr->set_buf) - 1, len);
1283	if (copy_from_user(to: attr->set_buf, from: buf, n: size))
1284	goto out;
1285
1286	attr->set_buf[size] = '\0';
1287	if (is_signed)
1288	ret = kstrtoll(s: attr->set_buf, base: 0, res: &val);
1289	else
1290	ret = kstrtoull(s: attr->set_buf, base: 0, res: &val);
1291	if (ret)
1292	goto out;
1293	ret = attr->set(attr->data, val);
1294	if (ret == 0)
1295	ret = len; /* on success, claim we got the whole input */
1296	out:
1297	mutex_unlock(lock: &attr->mutex);
1298	return ret;
1299	}
1300
1301	ssize_t simple_attr_write(struct file *file, const char __user *buf,
1302	size_t len, loff_t *ppos)
1303	{
1304	return simple_attr_write_xsigned(file, buf, len, ppos, is_signed: false);
1305	}
1306	EXPORT_SYMBOL_GPL(simple_attr_write);
1307
1308	ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
1309	size_t len, loff_t *ppos)
1310	{
1311	return simple_attr_write_xsigned(file, buf, len, ppos, is_signed: true);
1312	}
1313	EXPORT_SYMBOL_GPL(simple_attr_write_signed);
1314
1315	/**
1316	* generic_encode_ino32_fh - generic export_operations->encode_fh function
1317	* @inode: the object to encode
1318	* @fh: where to store the file handle fragment
1319	* @max_len: maximum length to store there (in 4 byte units)
1320	* @parent: parent directory inode, if wanted
1321	*
1322	* This generic encode_fh function assumes that the 32 inode number
1323	* is suitable for locating an inode, and that the generation number
1324	* can be used to check that it is still valid. It places them in the
1325	* filehandle fragment where export_decode_fh expects to find them.
1326	*/
1327	int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
1328	struct inode *parent)
1329	{
1330	struct fid *fid = (void *)fh;
1331	int len = *max_len;
1332	int type = FILEID_INO32_GEN;
1333
1334	if (parent && (len < 4)) {
1335	*max_len = 4;
1336	return FILEID_INVALID;
1337	} else if (len < 2) {
1338	*max_len = 2;
1339	return FILEID_INVALID;
1340	}
1341
1342	len = 2;
1343	fid->i32.ino = inode->i_ino;
1344	fid->i32.gen = inode->i_generation;
1345	if (parent) {
1346	fid->i32.parent_ino = parent->i_ino;
1347	fid->i32.parent_gen = parent->i_generation;
1348	len = 4;
1349	type = FILEID_INO32_GEN_PARENT;
1350	}
1351	*max_len = len;
1352	return type;
1353	}
1354	EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
1355
1356	/**
1357	* generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
1358	* @sb: filesystem to do the file handle conversion on
1359	* @fid: file handle to convert
1360	* @fh_len: length of the file handle in bytes
1361	* @fh_type: type of file handle
1362	* @get_inode: filesystem callback to retrieve inode
1363	*
1364	* This function decodes @fid as long as it has one of the well-known
1365	* Linux filehandle types and calls @get_inode on it to retrieve the
1366	* inode for the object specified in the file handle.
1367	*/
1368	struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1369	int fh_len, int fh_type, struct inode *(*get_inode)
1370	(struct super_block *sb, u64 ino, u32 gen))
1371	{
1372	struct inode *inode = NULL;
1373
1374	if (fh_len < 2)
1375	return NULL;
1376
1377	switch (fh_type) {
1378	case FILEID_INO32_GEN:
1379	case FILEID_INO32_GEN_PARENT:
1380	inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1381	break;
1382	}
1383
1384	return d_obtain_alias(inode);
1385	}
1386	EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1387
1388	/**
1389	* generic_fh_to_parent - generic helper for the fh_to_parent export operation
1390	* @sb: filesystem to do the file handle conversion on
1391	* @fid: file handle to convert
1392	* @fh_len: length of the file handle in bytes
1393	* @fh_type: type of file handle
1394	* @get_inode: filesystem callback to retrieve inode
1395	*
1396	* This function decodes @fid as long as it has one of the well-known
1397	* Linux filehandle types and calls @get_inode on it to retrieve the
1398	* inode for the _parent_ object specified in the file handle if it
1399	* is specified in the file handle, or NULL otherwise.
1400	*/
1401	struct dentry *generic_fh_to_parent(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_PARENT:
1412	inode = get_inode(sb, fid->i32.parent_ino,
1413	(fh_len > 3 ? fid->i32.parent_gen : 0));
1414	break;
1415	}
1416
1417	return d_obtain_alias(inode);
1418	}
1419	EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1420
1421	/**
1422	* __generic_file_fsync - generic fsync implementation for simple filesystems
1423	*
1424	* @file: file to synchronize
1425	* @start: start offset in bytes
1426	* @end: end offset in bytes (inclusive)
1427	* @datasync: only synchronize essential metadata if true
1428	*
1429	* This is a generic implementation of the fsync method for simple
1430	* filesystems which track all non-inode metadata in the buffers list
1431	* hanging off the address_space structure.
1432	*/
1433	int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1434	int datasync)
1435	{
1436	struct inode *inode = file->f_mapping->host;
1437	int err;
1438	int ret;
1439
1440	err = file_write_and_wait_range(file, start, end);
1441	if (err)
1442	return err;
1443
1444	inode_lock(inode);
1445	ret = sync_mapping_buffers(mapping: inode->i_mapping);
1446	if (!(inode->i_state & I_DIRTY_ALL))
1447	goto out;
1448	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1449	goto out;
1450
1451	err = sync_inode_metadata(inode, wait: 1);
1452	if (ret == 0)
1453	ret = err;
1454
1455	out:
1456	inode_unlock(inode);
1457	/* check and advance again to catch errors after syncing out buffers */
1458	err = file_check_and_advance_wb_err(file);
1459	if (ret == 0)
1460	ret = err;
1461	return ret;
1462	}
1463	EXPORT_SYMBOL(__generic_file_fsync);
1464
1465	/**
1466	* generic_file_fsync - generic fsync implementation for simple filesystems
1467	* with flush
1468	* @file: file to synchronize
1469	* @start: start offset in bytes
1470	* @end: end offset in bytes (inclusive)
1471	* @datasync: only synchronize essential metadata if true
1472	*
1473	*/
1474
1475	int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1476	int datasync)
1477	{
1478	struct inode *inode = file->f_mapping->host;
1479	int err;
1480
1481	err = __generic_file_fsync(file, start, end, datasync);
1482	if (err)
1483	return err;
1484	return blkdev_issue_flush(bdev: inode->i_sb->s_bdev);
1485	}
1486	EXPORT_SYMBOL(generic_file_fsync);
1487
1488	/**
1489	* generic_check_addressable - Check addressability of file system
1490	* @blocksize_bits: log of file system block size
1491	* @num_blocks: number of blocks in file system
1492	*
1493	* Determine whether a file system with @num_blocks blocks (and a
1494	* block size of 2**@blocksize_bits) is addressable by the sector_t
1495	* and page cache of the system. Return 0 if so and -EFBIG otherwise.
1496	*/
1497	int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1498	{
1499	u64 last_fs_block = num_blocks - 1;
1500	u64 last_fs_page =
1501	last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1502
1503	if (unlikely(num_blocks == 0))
1504	return 0;
1505
1506	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1507	return -EINVAL;
1508
1509	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1510	(last_fs_page > (pgoff_t)(~0ULL))) {
1511	return -EFBIG;
1512	}
1513	return 0;
1514	}
1515	EXPORT_SYMBOL(generic_check_addressable);
1516
1517	/*
1518	* No-op implementation of ->fsync for in-memory filesystems.
1519	*/
1520	int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1521	{
1522	return 0;
1523	}
1524	EXPORT_SYMBOL(noop_fsync);
1525
1526	ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1527	{
1528	/*
1529	* iomap based filesystems support direct I/O without need for
1530	* this callback. However, it still needs to be set in
1531	* inode->a_ops so that open/fcntl know that direct I/O is
1532	* generally supported.
1533	*/
1534	return -EINVAL;
1535	}
1536	EXPORT_SYMBOL_GPL(noop_direct_IO);
1537
1538	/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1539	void kfree_link(void *p)
1540	{
1541	kfree(objp: p);
1542	}
1543	EXPORT_SYMBOL(kfree_link);
1544
1545	struct inode *alloc_anon_inode(struct super_block *s)
1546	{
1547	static const struct address_space_operations anon_aops = {
1548	.dirty_folio = noop_dirty_folio,
1549	};
1550	struct inode *inode = new_inode_pseudo(sb: s);
1551
1552	if (!inode)
1553	return ERR_PTR(error: -ENOMEM);
1554
1555	inode->i_ino = get_next_ino();
1556	inode->i_mapping->a_ops = &anon_aops;
1557
1558	/*
1559	* Mark the inode dirty from the very beginning,
1560	* that way it will never be moved to the dirty
1561	* list because mark_inode_dirty() will think
1562	* that it already _is_ on the dirty list.
1563	*/
1564	inode->i_state = I_DIRTY;
1565	inode->i_mode = S_IRUSR | S_IWUSR;
1566	inode->i_uid = current_fsuid();
1567	inode->i_gid = current_fsgid();
1568	inode->i_flags |= S_PRIVATE;
1569	simple_inode_init_ts(inode);
1570	return inode;
1571	}
1572	EXPORT_SYMBOL(alloc_anon_inode);
1573
1574	/**
1575	* simple_nosetlease - generic helper for prohibiting leases
1576	* @filp: file pointer
1577	* @arg: type of lease to obtain
1578	* @flp: new lease supplied for insertion
1579	* @priv: private data for lm_setup operation
1580	*
1581	* Generic helper for filesystems that do not wish to allow leases to be set.
1582	* All arguments are ignored and it just returns -EINVAL.
1583	*/
1584	int
1585	simple_nosetlease(struct file *filp, int arg, struct file_lock **flp,
1586	void **priv)
1587	{
1588	return -EINVAL;
1589	}
1590	EXPORT_SYMBOL(simple_nosetlease);
1591
1592	/**
1593	* simple_get_link - generic helper to get the target of "fast" symlinks
1594	* @dentry: not used here
1595	* @inode: the symlink inode
1596	* @done: not used here
1597	*
1598	* Generic helper for filesystems to use for symlink inodes where a pointer to
1599	* the symlink target is stored in ->i_link. NOTE: this isn't normally called,
1600	* since as an optimization the path lookup code uses any non-NULL ->i_link
1601	* directly, without calling ->get_link(). But ->get_link() still must be set,
1602	* to mark the inode_operations as being for a symlink.
1603	*
1604	* Return: the symlink target
1605	*/
1606	const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1607	struct delayed_call *done)
1608	{
1609	return inode->i_link;
1610	}
1611	EXPORT_SYMBOL(simple_get_link);
1612
1613	const struct inode_operations simple_symlink_inode_operations = {
1614	.get_link = simple_get_link,
1615	};
1616	EXPORT_SYMBOL(simple_symlink_inode_operations);
1617
1618	/*
1619	* Operations for a permanently empty directory.
1620	*/
1621	static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1622	{
1623	return ERR_PTR(error: -ENOENT);
1624	}
1625
1626	static int empty_dir_getattr(struct mnt_idmap *idmap,
1627	const struct path *path, struct kstat *stat,
1628	u32 request_mask, unsigned int query_flags)
1629	{
1630	struct inode *inode = d_inode(dentry: path->dentry);
1631	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
1632	return 0;
1633	}
1634
1635	static int empty_dir_setattr(struct mnt_idmap *idmap,
1636	struct dentry *dentry, struct iattr *attr)
1637	{
1638	return -EPERM;
1639	}
1640
1641	static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1642	{
1643	return -EOPNOTSUPP;
1644	}
1645
1646	static const struct inode_operations empty_dir_inode_operations = {
1647	.lookup = empty_dir_lookup,
1648	.permission = generic_permission,
1649	.setattr = empty_dir_setattr,
1650	.getattr = empty_dir_getattr,
1651	.listxattr = empty_dir_listxattr,
1652	};
1653
1654	static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1655	{
1656	/* An empty directory has two entries . and .. at offsets 0 and 1 */
1657	return generic_file_llseek_size(file, offset, whence, maxsize: 2, eof: 2);
1658	}
1659
1660	static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1661	{
1662	dir_emit_dots(file, ctx);
1663	return 0;
1664	}
1665
1666	static const struct file_operations empty_dir_operations = {
1667	.llseek = empty_dir_llseek,
1668	.read = generic_read_dir,
1669	.iterate_shared = empty_dir_readdir,
1670	.fsync = noop_fsync,
1671	};
1672
1673
1674	void make_empty_dir_inode(struct inode *inode)
1675	{
1676	set_nlink(inode, nlink: 2);
1677	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1678	inode->i_uid = GLOBAL_ROOT_UID;
1679	inode->i_gid = GLOBAL_ROOT_GID;
1680	inode->i_rdev = 0;
1681	inode->i_size = 0;
1682	inode->i_blkbits = PAGE_SHIFT;
1683	inode->i_blocks = 0;
1684
1685	inode->i_op = &empty_dir_inode_operations;
1686	inode->i_opflags &= ~IOP_XATTR;
1687	inode->i_fop = &empty_dir_operations;
1688	}
1689
1690	bool is_empty_dir_inode(struct inode *inode)
1691	{
1692	return (inode->i_fop == &empty_dir_operations) &&
1693	(inode->i_op == &empty_dir_inode_operations);
1694	}
1695
1696	#if IS_ENABLED(CONFIG_UNICODE)
1697	/**
1698	* generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1699	* @dentry: dentry whose name we are checking against
1700	* @len: len of name of dentry
1701	* @str: str pointer to name of dentry
1702	* @name: Name to compare against
1703	*
1704	* Return: 0 if names match, 1 if mismatch, or -ERRNO
1705	*/
1706	static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1707	const char *str, const struct qstr *name)
1708	{
1709	const struct dentry *parent = READ_ONCE(dentry->d_parent);
1710	const struct inode *dir = READ_ONCE(parent->d_inode);
1711	const struct super_block *sb = dentry->d_sb;
1712	const struct unicode_map *um = sb->s_encoding;
1713	struct qstr qstr = QSTR_INIT(str, len);
1714	char strbuf[DNAME_INLINE_LEN];
1715	int ret;
1716
1717	if (!dir || !IS_CASEFOLDED(dir))
1718	goto fallback;
1719	/*
1720	* If the dentry name is stored in-line, then it may be concurrently
1721	* modified by a rename. If this happens, the VFS will eventually retry
1722	* the lookup, so it doesn't matter what ->d_compare() returns.
1723	* However, it's unsafe to call utf8_strncasecmp() with an unstable
1724	* string. Therefore, we have to copy the name into a temporary buffer.
1725	*/
1726	if (len <= DNAME_INLINE_LEN - 1) {
1727	memcpy(strbuf, str, len);
1728	strbuf[len] = 0;
1729	qstr.name = strbuf;
1730	/* prevent compiler from optimizing out the temporary buffer */
1731	barrier();
1732	}
1733	ret = utf8_strncasecmp(um, s1: name, s2: &qstr);
1734	if (ret >= 0)
1735	return ret;
1736
1737	if (sb_has_strict_encoding(sb))
1738	return -EINVAL;
1739	fallback:
1740	if (len != name->len)
1741	return 1;
1742	return !!memcmp(p: str, q: name->name, size: len);
1743	}
1744
1745	/**
1746	* generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1747	* @dentry: dentry of the parent directory
1748	* @str: qstr of name whose hash we should fill in
1749	*
1750	* Return: 0 if hash was successful or unchanged, and -EINVAL on error
1751	*/
1752	static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1753	{
1754	const struct inode *dir = READ_ONCE(dentry->d_inode);
1755	struct super_block *sb = dentry->d_sb;
1756	const struct unicode_map *um = sb->s_encoding;
1757	int ret = 0;
1758
1759	if (!dir || !IS_CASEFOLDED(dir))
1760	return 0;
1761
1762	ret = utf8_casefold_hash(um, salt: dentry, str);
1763	if (ret < 0 && sb_has_strict_encoding(sb))
1764	return -EINVAL;
1765	return 0;
1766	}
1767
1768	static const struct dentry_operations generic_ci_dentry_ops = {
1769	.d_hash = generic_ci_d_hash,
1770	.d_compare = generic_ci_d_compare,
1771	};
1772	#endif
1773
1774	#ifdef CONFIG_FS_ENCRYPTION
1775	static const struct dentry_operations generic_encrypted_dentry_ops = {
1776	.d_revalidate = fscrypt_d_revalidate,
1777	};
1778	#endif
1779
1780	#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1781	static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
1782	.d_hash = generic_ci_d_hash,
1783	.d_compare = generic_ci_d_compare,
1784	.d_revalidate = fscrypt_d_revalidate,
1785	};
1786	#endif
1787
1788	/**
1789	* generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
1790	* @dentry: dentry to set ops on
1791	*
1792	* Casefolded directories need d_hash and d_compare set, so that the dentries
1793	* contained in them are handled case-insensitively. Note that these operations
1794	* are needed on the parent directory rather than on the dentries in it, and
1795	* while the casefolding flag can be toggled on and off on an empty directory,
1796	* dentry_operations can't be changed later. As a result, if the filesystem has
1797	* casefolding support enabled at all, we have to give all dentries the
1798	* casefolding operations even if their inode doesn't have the casefolding flag
1799	* currently (and thus the casefolding ops would be no-ops for now).
1800	*
1801	* Encryption works differently in that the only dentry operation it needs is
1802	* d_revalidate, which it only needs on dentries that have the no-key name flag.
1803	* The no-key flag can't be set "later", so we don't have to worry about that.
1804	*
1805	* Finally, to maximize compatibility with overlayfs (which isn't compatible
1806	* with certain dentry operations) and to avoid taking an unnecessary
1807	* performance hit, we use custom dentry_operations for each possible
1808	* combination rather than always installing all operations.
1809	*/
1810	void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
1811	{
1812	#ifdef CONFIG_FS_ENCRYPTION
1813	bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
1814	#endif
1815	#if IS_ENABLED(CONFIG_UNICODE)
1816	bool needs_ci_ops = dentry->d_sb->s_encoding;
1817	#endif
1818	#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1819	if (needs_encrypt_ops && needs_ci_ops) {
1820	d_set_d_op(dentry, op: &generic_encrypted_ci_dentry_ops);
1821	return;
1822	}
1823	#endif
1824	#ifdef CONFIG_FS_ENCRYPTION
1825	if (needs_encrypt_ops) {
1826	d_set_d_op(dentry, op: &generic_encrypted_dentry_ops);
1827	return;
1828	}
1829	#endif
1830	#if IS_ENABLED(CONFIG_UNICODE)
1831	if (needs_ci_ops) {
1832	d_set_d_op(dentry, op: &generic_ci_dentry_ops);
1833	return;
1834	}
1835	#endif
1836	}
1837	EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
1838
1839	/**
1840	* inode_maybe_inc_iversion - increments i_version
1841	* @inode: inode with the i_version that should be updated
1842	* @force: increment the counter even if it's not necessary?
1843	*
1844	* Every time the inode is modified, the i_version field must be seen to have
1845	* changed by any observer.
1846	*
1847	* If "force" is set or the QUERIED flag is set, then ensure that we increment
1848	* the value, and clear the queried flag.
1849	*
1850	* In the common case where neither is set, then we can return "false" without
1851	* updating i_version.
1852	*
1853	* If this function returns false, and no other metadata has changed, then we
1854	* can avoid logging the metadata.
1855	*/
1856	bool inode_maybe_inc_iversion(struct inode *inode, bool force)
1857	{
1858	u64 cur, new;
1859
1860	/*
1861	* The i_version field is not strictly ordered with any other inode
1862	* information, but the legacy inode_inc_iversion code used a spinlock
1863	* to serialize increments.
1864	*
1865	* Here, we add full memory barriers to ensure that any de-facto
1866	* ordering with other info is preserved.
1867	*
1868	* This barrier pairs with the barrier in inode_query_iversion()
1869	*/
1870	smp_mb();
1871	cur = inode_peek_iversion_raw(inode);
1872	do {
1873	/* If flag is clear then we needn't do anything */
1874	if (!force && !(cur & I_VERSION_QUERIED))
1875	return false;
1876
1877	/* Since lowest bit is flag, add 2 to avoid it */
1878	new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
1879	} while (!atomic64_try_cmpxchg(v: &inode->i_version, old: &cur, new));
1880	return true;
1881	}
1882	EXPORT_SYMBOL(inode_maybe_inc_iversion);
1883
1884	/**
1885	* inode_query_iversion - read i_version for later use
1886	* @inode: inode from which i_version should be read
1887	*
1888	* Read the inode i_version counter. This should be used by callers that wish
1889	* to store the returned i_version for later comparison. This will guarantee
1890	* that a later query of the i_version will result in a different value if
1891	* anything has changed.
1892	*
1893	* In this implementation, we fetch the current value, set the QUERIED flag and
1894	* then try to swap it into place with a cmpxchg, if it wasn't already set. If
1895	* that fails, we try again with the newly fetched value from the cmpxchg.
1896	*/
1897	u64 inode_query_iversion(struct inode *inode)
1898	{
1899	u64 cur, new;
1900
1901	cur = inode_peek_iversion_raw(inode);
1902	do {
1903	/* If flag is already set, then no need to swap */
1904	if (cur & I_VERSION_QUERIED) {
1905	/*
1906	* This barrier (and the implicit barrier in the
1907	* cmpxchg below) pairs with the barrier in
1908	* inode_maybe_inc_iversion().
1909	*/
1910	smp_mb();
1911	break;
1912	}
1913
1914	new = cur | I_VERSION_QUERIED;
1915	} while (!atomic64_try_cmpxchg(v: &inode->i_version, old: &cur, new));
1916	return cur >> I_VERSION_QUERIED_SHIFT;
1917	}
1918	EXPORT_SYMBOL(inode_query_iversion);
1919
1920	ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
1921	ssize_t direct_written, ssize_t buffered_written)
1922	{
1923	struct address_space *mapping = iocb->ki_filp->f_mapping;
1924	loff_t pos = iocb->ki_pos - buffered_written;
1925	loff_t end = iocb->ki_pos - 1;
1926	int err;
1927
1928	/*
1929	* If the buffered write fallback returned an error, we want to return
1930	* the number of bytes which were written by direct I/O, or the error
1931	* code if that was zero.
1932	*
1933	* Note that this differs from normal direct-io semantics, which will
1934	* return -EFOO even if some bytes were written.
1935	*/
1936	if (unlikely(buffered_written < 0)) {
1937	if (direct_written)
1938	return direct_written;
1939	return buffered_written;
1940	}
1941
1942	/*
1943	* We need to ensure that the page cache pages are written to disk and
1944	* invalidated to preserve the expected O_DIRECT semantics.
1945	*/
1946	err = filemap_write_and_wait_range(mapping, lstart: pos, lend: end);
1947	if (err < 0) {
1948	/*
1949	* We don't know how much we wrote, so just return the number of
1950	* bytes which were direct-written
1951	*/
1952	iocb->ki_pos -= buffered_written;
1953	if (direct_written)
1954	return direct_written;
1955	return err;
1956	}
1957	invalidate_mapping_pages(mapping, start: pos >> PAGE_SHIFT, end: end >> PAGE_SHIFT);
1958	return direct_written + buffered_written;
1959	}
1960	EXPORT_SYMBOL_GPL(direct_write_fallback);
1961
1962	/**
1963	* simple_inode_init_ts - initialize the timestamps for a new inode
1964	* @inode: inode to be initialized
1965	*
1966	* When a new inode is created, most filesystems set the timestamps to the
1967	* current time. Add a helper to do this.
1968	*/
1969	struct timespec64 simple_inode_init_ts(struct inode *inode)
1970	{
1971	struct timespec64 ts = inode_set_ctime_current(inode);
1972
1973	inode_set_atime_to_ts(inode, ts);
1974	inode_set_mtime_to_ts(inode, ts);
1975	return ts;
1976	}
1977	EXPORT_SYMBOL(simple_inode_init_ts);
1978