xref: /openbmc/linux/fs/libfs.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 
12 #include <asm/uaccess.h>
13 
14 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
15 		   struct kstat *stat)
16 {
17 	struct inode *inode = dentry->d_inode;
18 	generic_fillattr(inode, stat);
19 	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
20 	return 0;
21 }
22 
23 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
24 {
25 	buf->f_type = dentry->d_sb->s_magic;
26 	buf->f_bsize = PAGE_CACHE_SIZE;
27 	buf->f_namelen = NAME_MAX;
28 	return 0;
29 }
30 
31 /*
32  * Retaining negative dentries for an in-memory filesystem just wastes
33  * memory and lookup time: arrange for them to be deleted immediately.
34  */
35 static int simple_delete_dentry(struct dentry *dentry)
36 {
37 	return 1;
38 }
39 
40 /*
41  * Lookup the data. This is trivial - if the dentry didn't already
42  * exist, we know it is negative.  Set d_op to delete negative dentries.
43  */
44 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
45 {
46 	static struct dentry_operations simple_dentry_operations = {
47 		.d_delete = simple_delete_dentry,
48 	};
49 
50 	if (dentry->d_name.len > NAME_MAX)
51 		return ERR_PTR(-ENAMETOOLONG);
52 	dentry->d_op = &simple_dentry_operations;
53 	d_add(dentry, NULL);
54 	return NULL;
55 }
56 
57 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
58 {
59 	return 0;
60 }
61 
62 int dcache_dir_open(struct inode *inode, struct file *file)
63 {
64 	static struct qstr cursor_name = {.len = 1, .name = "."};
65 
66 	file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
67 
68 	return file->private_data ? 0 : -ENOMEM;
69 }
70 
71 int dcache_dir_close(struct inode *inode, struct file *file)
72 {
73 	dput(file->private_data);
74 	return 0;
75 }
76 
77 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
78 {
79 	mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
80 	switch (origin) {
81 		case 1:
82 			offset += file->f_pos;
83 		case 0:
84 			if (offset >= 0)
85 				break;
86 		default:
87 			mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
88 			return -EINVAL;
89 	}
90 	if (offset != file->f_pos) {
91 		file->f_pos = offset;
92 		if (file->f_pos >= 2) {
93 			struct list_head *p;
94 			struct dentry *cursor = file->private_data;
95 			loff_t n = file->f_pos - 2;
96 
97 			spin_lock(&dcache_lock);
98 			list_del(&cursor->d_u.d_child);
99 			p = file->f_path.dentry->d_subdirs.next;
100 			while (n && p != &file->f_path.dentry->d_subdirs) {
101 				struct dentry *next;
102 				next = list_entry(p, struct dentry, d_u.d_child);
103 				if (!d_unhashed(next) && next->d_inode)
104 					n--;
105 				p = p->next;
106 			}
107 			list_add_tail(&cursor->d_u.d_child, p);
108 			spin_unlock(&dcache_lock);
109 		}
110 	}
111 	mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
112 	return offset;
113 }
114 
115 /* Relationship between i_mode and the DT_xxx types */
116 static inline unsigned char dt_type(struct inode *inode)
117 {
118 	return (inode->i_mode >> 12) & 15;
119 }
120 
121 /*
122  * Directory is locked and all positive dentries in it are safe, since
123  * for ramfs-type trees they can't go away without unlink() or rmdir(),
124  * both impossible due to the lock on directory.
125  */
126 
127 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
128 {
129 	struct dentry *dentry = filp->f_path.dentry;
130 	struct dentry *cursor = filp->private_data;
131 	struct list_head *p, *q = &cursor->d_u.d_child;
132 	ino_t ino;
133 	int i = filp->f_pos;
134 
135 	switch (i) {
136 		case 0:
137 			ino = dentry->d_inode->i_ino;
138 			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
139 				break;
140 			filp->f_pos++;
141 			i++;
142 			/* fallthrough */
143 		case 1:
144 			ino = parent_ino(dentry);
145 			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
146 				break;
147 			filp->f_pos++;
148 			i++;
149 			/* fallthrough */
150 		default:
151 			spin_lock(&dcache_lock);
152 			if (filp->f_pos == 2)
153 				list_move(q, &dentry->d_subdirs);
154 
155 			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
156 				struct dentry *next;
157 				next = list_entry(p, struct dentry, d_u.d_child);
158 				if (d_unhashed(next) || !next->d_inode)
159 					continue;
160 
161 				spin_unlock(&dcache_lock);
162 				if (filldir(dirent, next->d_name.name,
163 					    next->d_name.len, filp->f_pos,
164 					    next->d_inode->i_ino,
165 					    dt_type(next->d_inode)) < 0)
166 					return 0;
167 				spin_lock(&dcache_lock);
168 				/* next is still alive */
169 				list_move(q, p);
170 				p = q;
171 				filp->f_pos++;
172 			}
173 			spin_unlock(&dcache_lock);
174 	}
175 	return 0;
176 }
177 
178 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
179 {
180 	return -EISDIR;
181 }
182 
183 const struct file_operations simple_dir_operations = {
184 	.open		= dcache_dir_open,
185 	.release	= dcache_dir_close,
186 	.llseek		= dcache_dir_lseek,
187 	.read		= generic_read_dir,
188 	.readdir	= dcache_readdir,
189 	.fsync		= simple_sync_file,
190 };
191 
192 const struct inode_operations simple_dir_inode_operations = {
193 	.lookup		= simple_lookup,
194 };
195 
196 static const struct super_operations simple_super_operations = {
197 	.statfs		= simple_statfs,
198 };
199 
200 /*
201  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
202  * will never be mountable)
203  */
204 int get_sb_pseudo(struct file_system_type *fs_type, char *name,
205 	const struct super_operations *ops, unsigned long magic,
206 	struct vfsmount *mnt)
207 {
208 	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
209 	struct dentry *dentry;
210 	struct inode *root;
211 	struct qstr d_name = {.name = name, .len = strlen(name)};
212 
213 	if (IS_ERR(s))
214 		return PTR_ERR(s);
215 
216 	s->s_flags = MS_NOUSER;
217 	s->s_maxbytes = ~0ULL;
218 	s->s_blocksize = 1024;
219 	s->s_blocksize_bits = 10;
220 	s->s_magic = magic;
221 	s->s_op = ops ? ops : &simple_super_operations;
222 	s->s_time_gran = 1;
223 	root = new_inode(s);
224 	if (!root)
225 		goto Enomem;
226 	/*
227 	 * since this is the first inode, make it number 1. New inodes created
228 	 * after this must take care not to collide with it (by passing
229 	 * max_reserved of 1 to iunique).
230 	 */
231 	root->i_ino = 1;
232 	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
233 	root->i_uid = root->i_gid = 0;
234 	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
235 	dentry = d_alloc(NULL, &d_name);
236 	if (!dentry) {
237 		iput(root);
238 		goto Enomem;
239 	}
240 	dentry->d_sb = s;
241 	dentry->d_parent = dentry;
242 	d_instantiate(dentry, root);
243 	s->s_root = dentry;
244 	s->s_flags |= MS_ACTIVE;
245 	return simple_set_mnt(mnt, s);
246 
247 Enomem:
248 	up_write(&s->s_umount);
249 	deactivate_super(s);
250 	return -ENOMEM;
251 }
252 
253 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
254 {
255 	struct inode *inode = old_dentry->d_inode;
256 
257 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
258 	inc_nlink(inode);
259 	atomic_inc(&inode->i_count);
260 	dget(dentry);
261 	d_instantiate(dentry, inode);
262 	return 0;
263 }
264 
265 static inline int simple_positive(struct dentry *dentry)
266 {
267 	return dentry->d_inode && !d_unhashed(dentry);
268 }
269 
270 int simple_empty(struct dentry *dentry)
271 {
272 	struct dentry *child;
273 	int ret = 0;
274 
275 	spin_lock(&dcache_lock);
276 	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
277 		if (simple_positive(child))
278 			goto out;
279 	ret = 1;
280 out:
281 	spin_unlock(&dcache_lock);
282 	return ret;
283 }
284 
285 int simple_unlink(struct inode *dir, struct dentry *dentry)
286 {
287 	struct inode *inode = dentry->d_inode;
288 
289 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
290 	drop_nlink(inode);
291 	dput(dentry);
292 	return 0;
293 }
294 
295 int simple_rmdir(struct inode *dir, struct dentry *dentry)
296 {
297 	if (!simple_empty(dentry))
298 		return -ENOTEMPTY;
299 
300 	drop_nlink(dentry->d_inode);
301 	simple_unlink(dir, dentry);
302 	drop_nlink(dir);
303 	return 0;
304 }
305 
306 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
307 		struct inode *new_dir, struct dentry *new_dentry)
308 {
309 	struct inode *inode = old_dentry->d_inode;
310 	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
311 
312 	if (!simple_empty(new_dentry))
313 		return -ENOTEMPTY;
314 
315 	if (new_dentry->d_inode) {
316 		simple_unlink(new_dir, new_dentry);
317 		if (they_are_dirs)
318 			drop_nlink(old_dir);
319 	} else if (they_are_dirs) {
320 		drop_nlink(old_dir);
321 		inc_nlink(new_dir);
322 	}
323 
324 	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
325 		new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
326 
327 	return 0;
328 }
329 
330 int simple_readpage(struct file *file, struct page *page)
331 {
332 	clear_highpage(page);
333 	flush_dcache_page(page);
334 	SetPageUptodate(page);
335 	unlock_page(page);
336 	return 0;
337 }
338 
339 int simple_prepare_write(struct file *file, struct page *page,
340 			unsigned from, unsigned to)
341 {
342 	if (!PageUptodate(page)) {
343 		if (to - from != PAGE_CACHE_SIZE) {
344 			void *kaddr = kmap_atomic(page, KM_USER0);
345 			memset(kaddr, 0, from);
346 			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
347 			flush_dcache_page(page);
348 			kunmap_atomic(kaddr, KM_USER0);
349 		}
350 	}
351 	return 0;
352 }
353 
354 int simple_commit_write(struct file *file, struct page *page,
355 			unsigned from, unsigned to)
356 {
357 	struct inode *inode = page->mapping->host;
358 	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
359 
360 	if (!PageUptodate(page))
361 		SetPageUptodate(page);
362 	/*
363 	 * No need to use i_size_read() here, the i_size
364 	 * cannot change under us because we hold the i_mutex.
365 	 */
366 	if (pos > inode->i_size)
367 		i_size_write(inode, pos);
368 	set_page_dirty(page);
369 	return 0;
370 }
371 
372 /*
373  * the inodes created here are not hashed. If you use iunique to generate
374  * unique inode values later for this filesystem, then you must take care
375  * to pass it an appropriate max_reserved value to avoid collisions.
376  */
377 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
378 {
379 	struct inode *inode;
380 	struct dentry *root;
381 	struct dentry *dentry;
382 	int i;
383 
384 	s->s_blocksize = PAGE_CACHE_SIZE;
385 	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
386 	s->s_magic = magic;
387 	s->s_op = &simple_super_operations;
388 	s->s_time_gran = 1;
389 
390 	inode = new_inode(s);
391 	if (!inode)
392 		return -ENOMEM;
393 	/*
394 	 * because the root inode is 1, the files array must not contain an
395 	 * entry at index 1
396 	 */
397 	inode->i_ino = 1;
398 	inode->i_mode = S_IFDIR | 0755;
399 	inode->i_uid = inode->i_gid = 0;
400 	inode->i_blocks = 0;
401 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
402 	inode->i_op = &simple_dir_inode_operations;
403 	inode->i_fop = &simple_dir_operations;
404 	inode->i_nlink = 2;
405 	root = d_alloc_root(inode);
406 	if (!root) {
407 		iput(inode);
408 		return -ENOMEM;
409 	}
410 	for (i = 0; !files->name || files->name[0]; i++, files++) {
411 		if (!files->name)
412 			continue;
413 
414 		/* warn if it tries to conflict with the root inode */
415 		if (unlikely(i == 1))
416 			printk(KERN_WARNING "%s: %s passed in a files array"
417 				"with an index of 1!\n", __func__,
418 				s->s_type->name);
419 
420 		dentry = d_alloc_name(root, files->name);
421 		if (!dentry)
422 			goto out;
423 		inode = new_inode(s);
424 		if (!inode)
425 			goto out;
426 		inode->i_mode = S_IFREG | files->mode;
427 		inode->i_uid = inode->i_gid = 0;
428 		inode->i_blocks = 0;
429 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
430 		inode->i_fop = files->ops;
431 		inode->i_ino = i;
432 		d_add(dentry, inode);
433 	}
434 	s->s_root = root;
435 	return 0;
436 out:
437 	d_genocide(root);
438 	dput(root);
439 	return -ENOMEM;
440 }
441 
442 static DEFINE_SPINLOCK(pin_fs_lock);
443 
444 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
445 {
446 	struct vfsmount *mnt = NULL;
447 	spin_lock(&pin_fs_lock);
448 	if (unlikely(!*mount)) {
449 		spin_unlock(&pin_fs_lock);
450 		mnt = vfs_kern_mount(type, 0, type->name, NULL);
451 		if (IS_ERR(mnt))
452 			return PTR_ERR(mnt);
453 		spin_lock(&pin_fs_lock);
454 		if (!*mount)
455 			*mount = mnt;
456 	}
457 	mntget(*mount);
458 	++*count;
459 	spin_unlock(&pin_fs_lock);
460 	mntput(mnt);
461 	return 0;
462 }
463 
464 void simple_release_fs(struct vfsmount **mount, int *count)
465 {
466 	struct vfsmount *mnt;
467 	spin_lock(&pin_fs_lock);
468 	mnt = *mount;
469 	if (!--*count)
470 		*mount = NULL;
471 	spin_unlock(&pin_fs_lock);
472 	mntput(mnt);
473 }
474 
475 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
476 				const void *from, size_t available)
477 {
478 	loff_t pos = *ppos;
479 	if (pos < 0)
480 		return -EINVAL;
481 	if (pos >= available)
482 		return 0;
483 	if (count > available - pos)
484 		count = available - pos;
485 	if (copy_to_user(to, from + pos, count))
486 		return -EFAULT;
487 	*ppos = pos + count;
488 	return count;
489 }
490 
491 /*
492  * Transaction based IO.
493  * The file expects a single write which triggers the transaction, and then
494  * possibly a read which collects the result - which is stored in a
495  * file-local buffer.
496  */
497 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
498 {
499 	struct simple_transaction_argresp *ar;
500 	static DEFINE_SPINLOCK(simple_transaction_lock);
501 
502 	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
503 		return ERR_PTR(-EFBIG);
504 
505 	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
506 	if (!ar)
507 		return ERR_PTR(-ENOMEM);
508 
509 	spin_lock(&simple_transaction_lock);
510 
511 	/* only one write allowed per open */
512 	if (file->private_data) {
513 		spin_unlock(&simple_transaction_lock);
514 		free_page((unsigned long)ar);
515 		return ERR_PTR(-EBUSY);
516 	}
517 
518 	file->private_data = ar;
519 
520 	spin_unlock(&simple_transaction_lock);
521 
522 	if (copy_from_user(ar->data, buf, size))
523 		return ERR_PTR(-EFAULT);
524 
525 	return ar->data;
526 }
527 
528 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
529 {
530 	struct simple_transaction_argresp *ar = file->private_data;
531 
532 	if (!ar)
533 		return 0;
534 	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
535 }
536 
537 int simple_transaction_release(struct inode *inode, struct file *file)
538 {
539 	free_page((unsigned long)file->private_data);
540 	return 0;
541 }
542 
543 /* Simple attribute files */
544 
545 struct simple_attr {
546 	u64 (*get)(void *);
547 	void (*set)(void *, u64);
548 	char get_buf[24];	/* enough to store a u64 and "\n\0" */
549 	char set_buf[24];
550 	void *data;
551 	const char *fmt;	/* format for read operation */
552 	struct mutex mutex;	/* protects access to these buffers */
553 };
554 
555 /* simple_attr_open is called by an actual attribute open file operation
556  * to set the attribute specific access operations. */
557 int simple_attr_open(struct inode *inode, struct file *file,
558 		     u64 (*get)(void *), void (*set)(void *, u64),
559 		     const char *fmt)
560 {
561 	struct simple_attr *attr;
562 
563 	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
564 	if (!attr)
565 		return -ENOMEM;
566 
567 	attr->get = get;
568 	attr->set = set;
569 	attr->data = inode->i_private;
570 	attr->fmt = fmt;
571 	mutex_init(&attr->mutex);
572 
573 	file->private_data = attr;
574 
575 	return nonseekable_open(inode, file);
576 }
577 
578 int simple_attr_close(struct inode *inode, struct file *file)
579 {
580 	kfree(file->private_data);
581 	return 0;
582 }
583 
584 /* read from the buffer that is filled with the get function */
585 ssize_t simple_attr_read(struct file *file, char __user *buf,
586 			 size_t len, loff_t *ppos)
587 {
588 	struct simple_attr *attr;
589 	size_t size;
590 	ssize_t ret;
591 
592 	attr = file->private_data;
593 
594 	if (!attr->get)
595 		return -EACCES;
596 
597 	mutex_lock(&attr->mutex);
598 	if (*ppos) /* continued read */
599 		size = strlen(attr->get_buf);
600 	else	  /* first read */
601 		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
602 				 attr->fmt,
603 				 (unsigned long long)attr->get(attr->data));
604 
605 	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
606 	mutex_unlock(&attr->mutex);
607 	return ret;
608 }
609 
610 /* interpret the buffer as a number to call the set function with */
611 ssize_t simple_attr_write(struct file *file, const char __user *buf,
612 			  size_t len, loff_t *ppos)
613 {
614 	struct simple_attr *attr;
615 	u64 val;
616 	size_t size;
617 	ssize_t ret;
618 
619 	attr = file->private_data;
620 
621 	if (!attr->set)
622 		return -EACCES;
623 
624 	mutex_lock(&attr->mutex);
625 	ret = -EFAULT;
626 	size = min(sizeof(attr->set_buf) - 1, len);
627 	if (copy_from_user(attr->set_buf, buf, size))
628 		goto out;
629 
630 	ret = len; /* claim we got the whole input */
631 	attr->set_buf[size] = '\0';
632 	val = simple_strtol(attr->set_buf, NULL, 0);
633 	attr->set(attr->data, val);
634 out:
635 	mutex_unlock(&attr->mutex);
636 	return ret;
637 }
638 
639 EXPORT_SYMBOL(dcache_dir_close);
640 EXPORT_SYMBOL(dcache_dir_lseek);
641 EXPORT_SYMBOL(dcache_dir_open);
642 EXPORT_SYMBOL(dcache_readdir);
643 EXPORT_SYMBOL(generic_read_dir);
644 EXPORT_SYMBOL(get_sb_pseudo);
645 EXPORT_SYMBOL(simple_commit_write);
646 EXPORT_SYMBOL(simple_dir_inode_operations);
647 EXPORT_SYMBOL(simple_dir_operations);
648 EXPORT_SYMBOL(simple_empty);
649 EXPORT_SYMBOL(d_alloc_name);
650 EXPORT_SYMBOL(simple_fill_super);
651 EXPORT_SYMBOL(simple_getattr);
652 EXPORT_SYMBOL(simple_link);
653 EXPORT_SYMBOL(simple_lookup);
654 EXPORT_SYMBOL(simple_pin_fs);
655 EXPORT_SYMBOL(simple_prepare_write);
656 EXPORT_SYMBOL(simple_readpage);
657 EXPORT_SYMBOL(simple_release_fs);
658 EXPORT_SYMBOL(simple_rename);
659 EXPORT_SYMBOL(simple_rmdir);
660 EXPORT_SYMBOL(simple_statfs);
661 EXPORT_SYMBOL(simple_sync_file);
662 EXPORT_SYMBOL(simple_unlink);
663 EXPORT_SYMBOL(simple_read_from_buffer);
664 EXPORT_SYMBOL(simple_transaction_get);
665 EXPORT_SYMBOL(simple_transaction_read);
666 EXPORT_SYMBOL(simple_transaction_release);
667 EXPORT_SYMBOL_GPL(simple_attr_open);
668 EXPORT_SYMBOL_GPL(simple_attr_close);
669 EXPORT_SYMBOL_GPL(simple_attr_read);
670 EXPORT_SYMBOL_GPL(simple_attr_write);
671