xref: /openbmc/linux/fs/libfs.c (revision fd589a8f)
1 /*
2  *	fs/libfs.c
3  *	Library for filesystems writers.
4  */
5 
6 #include <linux/module.h>
7 #include <linux/pagemap.h>
8 #include <linux/mount.h>
9 #include <linux/vfs.h>
10 #include <linux/mutex.h>
11 #include <linux/exportfs.h>
12 #include <linux/writeback.h>
13 #include <linux/buffer_head.h>
14 
15 #include <asm/uaccess.h>
16 
17 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
18 		   struct kstat *stat)
19 {
20 	struct inode *inode = dentry->d_inode;
21 	generic_fillattr(inode, stat);
22 	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
23 	return 0;
24 }
25 
26 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
27 {
28 	buf->f_type = dentry->d_sb->s_magic;
29 	buf->f_bsize = PAGE_CACHE_SIZE;
30 	buf->f_namelen = NAME_MAX;
31 	return 0;
32 }
33 
34 /*
35  * Retaining negative dentries for an in-memory filesystem just wastes
36  * memory and lookup time: arrange for them to be deleted immediately.
37  */
38 static int simple_delete_dentry(struct dentry *dentry)
39 {
40 	return 1;
41 }
42 
43 /*
44  * Lookup the data. This is trivial - if the dentry didn't already
45  * exist, we know it is negative.  Set d_op to delete negative dentries.
46  */
47 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
48 {
49 	static const struct dentry_operations simple_dentry_operations = {
50 		.d_delete = simple_delete_dentry,
51 	};
52 
53 	if (dentry->d_name.len > NAME_MAX)
54 		return ERR_PTR(-ENAMETOOLONG);
55 	dentry->d_op = &simple_dentry_operations;
56 	d_add(dentry, NULL);
57 	return NULL;
58 }
59 
60 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
61 {
62 	return 0;
63 }
64 
65 int dcache_dir_open(struct inode *inode, struct file *file)
66 {
67 	static struct qstr cursor_name = {.len = 1, .name = "."};
68 
69 	file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
70 
71 	return file->private_data ? 0 : -ENOMEM;
72 }
73 
74 int dcache_dir_close(struct inode *inode, struct file *file)
75 {
76 	dput(file->private_data);
77 	return 0;
78 }
79 
80 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
81 {
82 	mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
83 	switch (origin) {
84 		case 1:
85 			offset += file->f_pos;
86 		case 0:
87 			if (offset >= 0)
88 				break;
89 		default:
90 			mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
91 			return -EINVAL;
92 	}
93 	if (offset != file->f_pos) {
94 		file->f_pos = offset;
95 		if (file->f_pos >= 2) {
96 			struct list_head *p;
97 			struct dentry *cursor = file->private_data;
98 			loff_t n = file->f_pos - 2;
99 
100 			spin_lock(&dcache_lock);
101 			list_del(&cursor->d_u.d_child);
102 			p = file->f_path.dentry->d_subdirs.next;
103 			while (n && p != &file->f_path.dentry->d_subdirs) {
104 				struct dentry *next;
105 				next = list_entry(p, struct dentry, d_u.d_child);
106 				if (!d_unhashed(next) && next->d_inode)
107 					n--;
108 				p = p->next;
109 			}
110 			list_add_tail(&cursor->d_u.d_child, p);
111 			spin_unlock(&dcache_lock);
112 		}
113 	}
114 	mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
115 	return offset;
116 }
117 
118 /* Relationship between i_mode and the DT_xxx types */
119 static inline unsigned char dt_type(struct inode *inode)
120 {
121 	return (inode->i_mode >> 12) & 15;
122 }
123 
124 /*
125  * Directory is locked and all positive dentries in it are safe, since
126  * for ramfs-type trees they can't go away without unlink() or rmdir(),
127  * both impossible due to the lock on directory.
128  */
129 
130 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
131 {
132 	struct dentry *dentry = filp->f_path.dentry;
133 	struct dentry *cursor = filp->private_data;
134 	struct list_head *p, *q = &cursor->d_u.d_child;
135 	ino_t ino;
136 	int i = filp->f_pos;
137 
138 	switch (i) {
139 		case 0:
140 			ino = dentry->d_inode->i_ino;
141 			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
142 				break;
143 			filp->f_pos++;
144 			i++;
145 			/* fallthrough */
146 		case 1:
147 			ino = parent_ino(dentry);
148 			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
149 				break;
150 			filp->f_pos++;
151 			i++;
152 			/* fallthrough */
153 		default:
154 			spin_lock(&dcache_lock);
155 			if (filp->f_pos == 2)
156 				list_move(q, &dentry->d_subdirs);
157 
158 			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
159 				struct dentry *next;
160 				next = list_entry(p, struct dentry, d_u.d_child);
161 				if (d_unhashed(next) || !next->d_inode)
162 					continue;
163 
164 				spin_unlock(&dcache_lock);
165 				if (filldir(dirent, next->d_name.name,
166 					    next->d_name.len, filp->f_pos,
167 					    next->d_inode->i_ino,
168 					    dt_type(next->d_inode)) < 0)
169 					return 0;
170 				spin_lock(&dcache_lock);
171 				/* next is still alive */
172 				list_move(q, p);
173 				p = q;
174 				filp->f_pos++;
175 			}
176 			spin_unlock(&dcache_lock);
177 	}
178 	return 0;
179 }
180 
181 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
182 {
183 	return -EISDIR;
184 }
185 
186 const struct file_operations simple_dir_operations = {
187 	.open		= dcache_dir_open,
188 	.release	= dcache_dir_close,
189 	.llseek		= dcache_dir_lseek,
190 	.read		= generic_read_dir,
191 	.readdir	= dcache_readdir,
192 	.fsync		= simple_sync_file,
193 };
194 
195 const struct inode_operations simple_dir_inode_operations = {
196 	.lookup		= simple_lookup,
197 };
198 
199 static const struct super_operations simple_super_operations = {
200 	.statfs		= simple_statfs,
201 };
202 
203 /*
204  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
205  * will never be mountable)
206  */
207 int get_sb_pseudo(struct file_system_type *fs_type, char *name,
208 	const struct super_operations *ops, unsigned long magic,
209 	struct vfsmount *mnt)
210 {
211 	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
212 	struct dentry *dentry;
213 	struct inode *root;
214 	struct qstr d_name = {.name = name, .len = strlen(name)};
215 
216 	if (IS_ERR(s))
217 		return PTR_ERR(s);
218 
219 	s->s_flags = MS_NOUSER;
220 	s->s_maxbytes = MAX_LFS_FILESIZE;
221 	s->s_blocksize = PAGE_SIZE;
222 	s->s_blocksize_bits = PAGE_SHIFT;
223 	s->s_magic = magic;
224 	s->s_op = ops ? ops : &simple_super_operations;
225 	s->s_time_gran = 1;
226 	root = new_inode(s);
227 	if (!root)
228 		goto Enomem;
229 	/*
230 	 * since this is the first inode, make it number 1. New inodes created
231 	 * after this must take care not to collide with it (by passing
232 	 * max_reserved of 1 to iunique).
233 	 */
234 	root->i_ino = 1;
235 	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
236 	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
237 	dentry = d_alloc(NULL, &d_name);
238 	if (!dentry) {
239 		iput(root);
240 		goto Enomem;
241 	}
242 	dentry->d_sb = s;
243 	dentry->d_parent = dentry;
244 	d_instantiate(dentry, root);
245 	s->s_root = dentry;
246 	s->s_flags |= MS_ACTIVE;
247 	simple_set_mnt(mnt, s);
248 	return 0;
249 
250 Enomem:
251 	deactivate_locked_super(s);
252 	return -ENOMEM;
253 }
254 
255 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
256 {
257 	struct inode *inode = old_dentry->d_inode;
258 
259 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
260 	inc_nlink(inode);
261 	atomic_inc(&inode->i_count);
262 	dget(dentry);
263 	d_instantiate(dentry, inode);
264 	return 0;
265 }
266 
267 static inline int simple_positive(struct dentry *dentry)
268 {
269 	return dentry->d_inode && !d_unhashed(dentry);
270 }
271 
272 int simple_empty(struct dentry *dentry)
273 {
274 	struct dentry *child;
275 	int ret = 0;
276 
277 	spin_lock(&dcache_lock);
278 	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
279 		if (simple_positive(child))
280 			goto out;
281 	ret = 1;
282 out:
283 	spin_unlock(&dcache_lock);
284 	return ret;
285 }
286 
287 int simple_unlink(struct inode *dir, struct dentry *dentry)
288 {
289 	struct inode *inode = dentry->d_inode;
290 
291 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
292 	drop_nlink(inode);
293 	dput(dentry);
294 	return 0;
295 }
296 
297 int simple_rmdir(struct inode *dir, struct dentry *dentry)
298 {
299 	if (!simple_empty(dentry))
300 		return -ENOTEMPTY;
301 
302 	drop_nlink(dentry->d_inode);
303 	simple_unlink(dir, dentry);
304 	drop_nlink(dir);
305 	return 0;
306 }
307 
308 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
309 		struct inode *new_dir, struct dentry *new_dentry)
310 {
311 	struct inode *inode = old_dentry->d_inode;
312 	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
313 
314 	if (!simple_empty(new_dentry))
315 		return -ENOTEMPTY;
316 
317 	if (new_dentry->d_inode) {
318 		simple_unlink(new_dir, new_dentry);
319 		if (they_are_dirs)
320 			drop_nlink(old_dir);
321 	} else if (they_are_dirs) {
322 		drop_nlink(old_dir);
323 		inc_nlink(new_dir);
324 	}
325 
326 	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
327 		new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
328 
329 	return 0;
330 }
331 
332 int simple_readpage(struct file *file, struct page *page)
333 {
334 	clear_highpage(page);
335 	flush_dcache_page(page);
336 	SetPageUptodate(page);
337 	unlock_page(page);
338 	return 0;
339 }
340 
341 int simple_prepare_write(struct file *file, struct page *page,
342 			unsigned from, unsigned to)
343 {
344 	if (!PageUptodate(page)) {
345 		if (to - from != PAGE_CACHE_SIZE)
346 			zero_user_segments(page,
347 				0, from,
348 				to, PAGE_CACHE_SIZE);
349 	}
350 	return 0;
351 }
352 
353 int simple_write_begin(struct file *file, struct address_space *mapping,
354 			loff_t pos, unsigned len, unsigned flags,
355 			struct page **pagep, void **fsdata)
356 {
357 	struct page *page;
358 	pgoff_t index;
359 	unsigned from;
360 
361 	index = pos >> PAGE_CACHE_SHIFT;
362 	from = pos & (PAGE_CACHE_SIZE - 1);
363 
364 	page = grab_cache_page_write_begin(mapping, index, flags);
365 	if (!page)
366 		return -ENOMEM;
367 
368 	*pagep = page;
369 
370 	return simple_prepare_write(file, page, from, from+len);
371 }
372 
373 static int simple_commit_write(struct file *file, struct page *page,
374 			       unsigned from, unsigned to)
375 {
376 	struct inode *inode = page->mapping->host;
377 	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
378 
379 	if (!PageUptodate(page))
380 		SetPageUptodate(page);
381 	/*
382 	 * No need to use i_size_read() here, the i_size
383 	 * cannot change under us because we hold the i_mutex.
384 	 */
385 	if (pos > inode->i_size)
386 		i_size_write(inode, pos);
387 	set_page_dirty(page);
388 	return 0;
389 }
390 
391 int simple_write_end(struct file *file, struct address_space *mapping,
392 			loff_t pos, unsigned len, unsigned copied,
393 			struct page *page, void *fsdata)
394 {
395 	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
396 
397 	/* zero the stale part of the page if we did a short copy */
398 	if (copied < len) {
399 		void *kaddr = kmap_atomic(page, KM_USER0);
400 		memset(kaddr + from + copied, 0, len - copied);
401 		flush_dcache_page(page);
402 		kunmap_atomic(kaddr, KM_USER0);
403 	}
404 
405 	simple_commit_write(file, page, from, from+copied);
406 
407 	unlock_page(page);
408 	page_cache_release(page);
409 
410 	return copied;
411 }
412 
413 /*
414  * the inodes created here are not hashed. If you use iunique to generate
415  * unique inode values later for this filesystem, then you must take care
416  * to pass it an appropriate max_reserved value to avoid collisions.
417  */
418 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
419 {
420 	struct inode *inode;
421 	struct dentry *root;
422 	struct dentry *dentry;
423 	int i;
424 
425 	s->s_blocksize = PAGE_CACHE_SIZE;
426 	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
427 	s->s_magic = magic;
428 	s->s_op = &simple_super_operations;
429 	s->s_time_gran = 1;
430 
431 	inode = new_inode(s);
432 	if (!inode)
433 		return -ENOMEM;
434 	/*
435 	 * because the root inode is 1, the files array must not contain an
436 	 * entry at index 1
437 	 */
438 	inode->i_ino = 1;
439 	inode->i_mode = S_IFDIR | 0755;
440 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
441 	inode->i_op = &simple_dir_inode_operations;
442 	inode->i_fop = &simple_dir_operations;
443 	inode->i_nlink = 2;
444 	root = d_alloc_root(inode);
445 	if (!root) {
446 		iput(inode);
447 		return -ENOMEM;
448 	}
449 	for (i = 0; !files->name || files->name[0]; i++, files++) {
450 		if (!files->name)
451 			continue;
452 
453 		/* warn if it tries to conflict with the root inode */
454 		if (unlikely(i == 1))
455 			printk(KERN_WARNING "%s: %s passed in a files array"
456 				"with an index of 1!\n", __func__,
457 				s->s_type->name);
458 
459 		dentry = d_alloc_name(root, files->name);
460 		if (!dentry)
461 			goto out;
462 		inode = new_inode(s);
463 		if (!inode)
464 			goto out;
465 		inode->i_mode = S_IFREG | files->mode;
466 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
467 		inode->i_fop = files->ops;
468 		inode->i_ino = i;
469 		d_add(dentry, inode);
470 	}
471 	s->s_root = root;
472 	return 0;
473 out:
474 	d_genocide(root);
475 	dput(root);
476 	return -ENOMEM;
477 }
478 
479 static DEFINE_SPINLOCK(pin_fs_lock);
480 
481 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
482 {
483 	struct vfsmount *mnt = NULL;
484 	spin_lock(&pin_fs_lock);
485 	if (unlikely(!*mount)) {
486 		spin_unlock(&pin_fs_lock);
487 		mnt = vfs_kern_mount(type, 0, type->name, NULL);
488 		if (IS_ERR(mnt))
489 			return PTR_ERR(mnt);
490 		spin_lock(&pin_fs_lock);
491 		if (!*mount)
492 			*mount = mnt;
493 	}
494 	mntget(*mount);
495 	++*count;
496 	spin_unlock(&pin_fs_lock);
497 	mntput(mnt);
498 	return 0;
499 }
500 
501 void simple_release_fs(struct vfsmount **mount, int *count)
502 {
503 	struct vfsmount *mnt;
504 	spin_lock(&pin_fs_lock);
505 	mnt = *mount;
506 	if (!--*count)
507 		*mount = NULL;
508 	spin_unlock(&pin_fs_lock);
509 	mntput(mnt);
510 }
511 
512 /**
513  * simple_read_from_buffer - copy data from the buffer to user space
514  * @to: the user space buffer to read to
515  * @count: the maximum number of bytes to read
516  * @ppos: the current position in the buffer
517  * @from: the buffer to read from
518  * @available: the size of the buffer
519  *
520  * The simple_read_from_buffer() function reads up to @count bytes from the
521  * buffer @from at offset @ppos into the user space address starting at @to.
522  *
523  * On success, the number of bytes read is returned and the offset @ppos is
524  * advanced by this number, or negative value is returned on error.
525  **/
526 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
527 				const void *from, size_t available)
528 {
529 	loff_t pos = *ppos;
530 	if (pos < 0)
531 		return -EINVAL;
532 	if (pos >= available)
533 		return 0;
534 	if (count > available - pos)
535 		count = available - pos;
536 	if (copy_to_user(to, from + pos, count))
537 		return -EFAULT;
538 	*ppos = pos + count;
539 	return count;
540 }
541 
542 /**
543  * memory_read_from_buffer - copy data from the buffer
544  * @to: the kernel space buffer to read to
545  * @count: the maximum number of bytes to read
546  * @ppos: the current position in the buffer
547  * @from: the buffer to read from
548  * @available: the size of the buffer
549  *
550  * The memory_read_from_buffer() function reads up to @count bytes from the
551  * buffer @from at offset @ppos into the kernel space address starting at @to.
552  *
553  * On success, the number of bytes read is returned and the offset @ppos is
554  * advanced by this number, or negative value is returned on error.
555  **/
556 ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
557 				const void *from, size_t available)
558 {
559 	loff_t pos = *ppos;
560 
561 	if (pos < 0)
562 		return -EINVAL;
563 	if (pos >= available)
564 		return 0;
565 	if (count > available - pos)
566 		count = available - pos;
567 	memcpy(to, from + pos, count);
568 	*ppos = pos + count;
569 
570 	return count;
571 }
572 
573 /*
574  * Transaction based IO.
575  * The file expects a single write which triggers the transaction, and then
576  * possibly a read which collects the result - which is stored in a
577  * file-local buffer.
578  */
579 
580 void simple_transaction_set(struct file *file, size_t n)
581 {
582 	struct simple_transaction_argresp *ar = file->private_data;
583 
584 	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
585 
586 	/*
587 	 * The barrier ensures that ar->size will really remain zero until
588 	 * ar->data is ready for reading.
589 	 */
590 	smp_mb();
591 	ar->size = n;
592 }
593 
594 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
595 {
596 	struct simple_transaction_argresp *ar;
597 	static DEFINE_SPINLOCK(simple_transaction_lock);
598 
599 	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
600 		return ERR_PTR(-EFBIG);
601 
602 	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
603 	if (!ar)
604 		return ERR_PTR(-ENOMEM);
605 
606 	spin_lock(&simple_transaction_lock);
607 
608 	/* only one write allowed per open */
609 	if (file->private_data) {
610 		spin_unlock(&simple_transaction_lock);
611 		free_page((unsigned long)ar);
612 		return ERR_PTR(-EBUSY);
613 	}
614 
615 	file->private_data = ar;
616 
617 	spin_unlock(&simple_transaction_lock);
618 
619 	if (copy_from_user(ar->data, buf, size))
620 		return ERR_PTR(-EFAULT);
621 
622 	return ar->data;
623 }
624 
625 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
626 {
627 	struct simple_transaction_argresp *ar = file->private_data;
628 
629 	if (!ar)
630 		return 0;
631 	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
632 }
633 
634 int simple_transaction_release(struct inode *inode, struct file *file)
635 {
636 	free_page((unsigned long)file->private_data);
637 	return 0;
638 }
639 
640 /* Simple attribute files */
641 
642 struct simple_attr {
643 	int (*get)(void *, u64 *);
644 	int (*set)(void *, u64);
645 	char get_buf[24];	/* enough to store a u64 and "\n\0" */
646 	char set_buf[24];
647 	void *data;
648 	const char *fmt;	/* format for read operation */
649 	struct mutex mutex;	/* protects access to these buffers */
650 };
651 
652 /* simple_attr_open is called by an actual attribute open file operation
653  * to set the attribute specific access operations. */
654 int simple_attr_open(struct inode *inode, struct file *file,
655 		     int (*get)(void *, u64 *), int (*set)(void *, u64),
656 		     const char *fmt)
657 {
658 	struct simple_attr *attr;
659 
660 	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
661 	if (!attr)
662 		return -ENOMEM;
663 
664 	attr->get = get;
665 	attr->set = set;
666 	attr->data = inode->i_private;
667 	attr->fmt = fmt;
668 	mutex_init(&attr->mutex);
669 
670 	file->private_data = attr;
671 
672 	return nonseekable_open(inode, file);
673 }
674 
675 int simple_attr_release(struct inode *inode, struct file *file)
676 {
677 	kfree(file->private_data);
678 	return 0;
679 }
680 
681 /* read from the buffer that is filled with the get function */
682 ssize_t simple_attr_read(struct file *file, char __user *buf,
683 			 size_t len, loff_t *ppos)
684 {
685 	struct simple_attr *attr;
686 	size_t size;
687 	ssize_t ret;
688 
689 	attr = file->private_data;
690 
691 	if (!attr->get)
692 		return -EACCES;
693 
694 	ret = mutex_lock_interruptible(&attr->mutex);
695 	if (ret)
696 		return ret;
697 
698 	if (*ppos) {		/* continued read */
699 		size = strlen(attr->get_buf);
700 	} else {		/* first read */
701 		u64 val;
702 		ret = attr->get(attr->data, &val);
703 		if (ret)
704 			goto out;
705 
706 		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
707 				 attr->fmt, (unsigned long long)val);
708 	}
709 
710 	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
711 out:
712 	mutex_unlock(&attr->mutex);
713 	return ret;
714 }
715 
716 /* interpret the buffer as a number to call the set function with */
717 ssize_t simple_attr_write(struct file *file, const char __user *buf,
718 			  size_t len, loff_t *ppos)
719 {
720 	struct simple_attr *attr;
721 	u64 val;
722 	size_t size;
723 	ssize_t ret;
724 
725 	attr = file->private_data;
726 	if (!attr->set)
727 		return -EACCES;
728 
729 	ret = mutex_lock_interruptible(&attr->mutex);
730 	if (ret)
731 		return ret;
732 
733 	ret = -EFAULT;
734 	size = min(sizeof(attr->set_buf) - 1, len);
735 	if (copy_from_user(attr->set_buf, buf, size))
736 		goto out;
737 
738 	ret = len; /* claim we got the whole input */
739 	attr->set_buf[size] = '\0';
740 	val = simple_strtol(attr->set_buf, NULL, 0);
741 	attr->set(attr->data, val);
742 out:
743 	mutex_unlock(&attr->mutex);
744 	return ret;
745 }
746 
747 /**
748  * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
749  * @sb:		filesystem to do the file handle conversion on
750  * @fid:	file handle to convert
751  * @fh_len:	length of the file handle in bytes
752  * @fh_type:	type of file handle
753  * @get_inode:	filesystem callback to retrieve inode
754  *
755  * This function decodes @fid as long as it has one of the well-known
756  * Linux filehandle types and calls @get_inode on it to retrieve the
757  * inode for the object specified in the file handle.
758  */
759 struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
760 		int fh_len, int fh_type, struct inode *(*get_inode)
761 			(struct super_block *sb, u64 ino, u32 gen))
762 {
763 	struct inode *inode = NULL;
764 
765 	if (fh_len < 2)
766 		return NULL;
767 
768 	switch (fh_type) {
769 	case FILEID_INO32_GEN:
770 	case FILEID_INO32_GEN_PARENT:
771 		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
772 		break;
773 	}
774 
775 	return d_obtain_alias(inode);
776 }
777 EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
778 
779 /**
780  * generic_fh_to_dentry - generic helper for the fh_to_parent export operation
781  * @sb:		filesystem to do the file handle conversion on
782  * @fid:	file handle to convert
783  * @fh_len:	length of the file handle in bytes
784  * @fh_type:	type of file handle
785  * @get_inode:	filesystem callback to retrieve inode
786  *
787  * This function decodes @fid as long as it has one of the well-known
788  * Linux filehandle types and calls @get_inode on it to retrieve the
789  * inode for the _parent_ object specified in the file handle if it
790  * is specified in the file handle, or NULL otherwise.
791  */
792 struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
793 		int fh_len, int fh_type, struct inode *(*get_inode)
794 			(struct super_block *sb, u64 ino, u32 gen))
795 {
796 	struct inode *inode = NULL;
797 
798 	if (fh_len <= 2)
799 		return NULL;
800 
801 	switch (fh_type) {
802 	case FILEID_INO32_GEN_PARENT:
803 		inode = get_inode(sb, fid->i32.parent_ino,
804 				  (fh_len > 3 ? fid->i32.parent_gen : 0));
805 		break;
806 	}
807 
808 	return d_obtain_alias(inode);
809 }
810 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
811 
812 int simple_fsync(struct file *file, struct dentry *dentry, int datasync)
813 {
814 	struct writeback_control wbc = {
815 		.sync_mode = WB_SYNC_ALL,
816 		.nr_to_write = 0, /* metadata-only; caller takes care of data */
817 	};
818 	struct inode *inode = dentry->d_inode;
819 	int err;
820 	int ret;
821 
822 	ret = sync_mapping_buffers(inode->i_mapping);
823 	if (!(inode->i_state & I_DIRTY))
824 		return ret;
825 	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
826 		return ret;
827 
828 	err = sync_inode(inode, &wbc);
829 	if (ret == 0)
830 		ret = err;
831 	return ret;
832 }
833 EXPORT_SYMBOL(simple_fsync);
834 
835 EXPORT_SYMBOL(dcache_dir_close);
836 EXPORT_SYMBOL(dcache_dir_lseek);
837 EXPORT_SYMBOL(dcache_dir_open);
838 EXPORT_SYMBOL(dcache_readdir);
839 EXPORT_SYMBOL(generic_read_dir);
840 EXPORT_SYMBOL(get_sb_pseudo);
841 EXPORT_SYMBOL(simple_write_begin);
842 EXPORT_SYMBOL(simple_write_end);
843 EXPORT_SYMBOL(simple_dir_inode_operations);
844 EXPORT_SYMBOL(simple_dir_operations);
845 EXPORT_SYMBOL(simple_empty);
846 EXPORT_SYMBOL(d_alloc_name);
847 EXPORT_SYMBOL(simple_fill_super);
848 EXPORT_SYMBOL(simple_getattr);
849 EXPORT_SYMBOL(simple_link);
850 EXPORT_SYMBOL(simple_lookup);
851 EXPORT_SYMBOL(simple_pin_fs);
852 EXPORT_UNUSED_SYMBOL(simple_prepare_write);
853 EXPORT_SYMBOL(simple_readpage);
854 EXPORT_SYMBOL(simple_release_fs);
855 EXPORT_SYMBOL(simple_rename);
856 EXPORT_SYMBOL(simple_rmdir);
857 EXPORT_SYMBOL(simple_statfs);
858 EXPORT_SYMBOL(simple_sync_file);
859 EXPORT_SYMBOL(simple_unlink);
860 EXPORT_SYMBOL(simple_read_from_buffer);
861 EXPORT_SYMBOL(memory_read_from_buffer);
862 EXPORT_SYMBOL(simple_transaction_set);
863 EXPORT_SYMBOL(simple_transaction_get);
864 EXPORT_SYMBOL(simple_transaction_read);
865 EXPORT_SYMBOL(simple_transaction_release);
866 EXPORT_SYMBOL_GPL(simple_attr_open);
867 EXPORT_SYMBOL_GPL(simple_attr_release);
868 EXPORT_SYMBOL_GPL(simple_attr_read);
869 EXPORT_SYMBOL_GPL(simple_attr_write);
870