libfs.c 25.6 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5
/*
 *	fs/libfs.c
 *	Library for filesystems writers.
 */

6
#include <linux/export.h>
L
Linus Torvalds 已提交
7
#include <linux/pagemap.h>
8
#include <linux/slab.h>
L
Linus Torvalds 已提交
9 10
#include <linux/mount.h>
#include <linux/vfs.h>
11
#include <linux/quotaops.h>
I
Ingo Molnar 已提交
12
#include <linux/mutex.h>
C
Christoph Hellwig 已提交
13
#include <linux/exportfs.h>
A
Al Viro 已提交
14
#include <linux/writeback.h>
A
Al Viro 已提交
15
#include <linux/buffer_head.h> /* sync_mapping_buffers */
I
Ingo Molnar 已提交
16

L
Linus Torvalds 已提交
17 18
#include <asm/uaccess.h>

19 20
#include "internal.h"

N
Nick Piggin 已提交
21 22 23 24 25
static inline int simple_positive(struct dentry *dentry)
{
	return dentry->d_inode && !d_unhashed(dentry);
}

L
Linus Torvalds 已提交
26 27 28 29 30 31 32 33 34
int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
		   struct kstat *stat)
{
	struct inode *inode = dentry->d_inode;
	generic_fillattr(inode, stat);
	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
	return 0;
}

35
int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
L
Linus Torvalds 已提交
36
{
37
	buf->f_type = dentry->d_sb->s_magic;
L
Linus Torvalds 已提交
38 39 40 41 42 43 44 45 46
	buf->f_bsize = PAGE_CACHE_SIZE;
	buf->f_namelen = NAME_MAX;
	return 0;
}

/*
 * Retaining negative dentries for an in-memory filesystem just wastes
 * memory and lookup time: arrange for them to be deleted immediately.
 */
N
Nick Piggin 已提交
47
static int simple_delete_dentry(const struct dentry *dentry)
L
Linus Torvalds 已提交
48 49 50 51 52 53 54 55 56 57
{
	return 1;
}

/*
 * Lookup the data. This is trivial - if the dentry didn't already
 * exist, we know it is negative.  Set d_op to delete negative dentries.
 */
struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
A
Al Viro 已提交
58
	static const struct dentry_operations simple_dentry_operations = {
L
Linus Torvalds 已提交
59 60 61 62 63
		.d_delete = simple_delete_dentry,
	};

	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
64
	d_set_d_op(dentry, &simple_dentry_operations);
L
Linus Torvalds 已提交
65 66 67 68 69 70 71 72
	d_add(dentry, NULL);
	return NULL;
}

int dcache_dir_open(struct inode *inode, struct file *file)
{
	static struct qstr cursor_name = {.len = 1, .name = "."};

73
	file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
L
Linus Torvalds 已提交
74 75 76 77 78 79 80 81 82 83 84 85

	return file->private_data ? 0 : -ENOMEM;
}

int dcache_dir_close(struct inode *inode, struct file *file)
{
	dput(file->private_data);
	return 0;
}

loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
{
N
Nick Piggin 已提交
86 87
	struct dentry *dentry = file->f_path.dentry;
	mutex_lock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
88 89 90 91 92 93 94
	switch (origin) {
		case 1:
			offset += file->f_pos;
		case 0:
			if (offset >= 0)
				break;
		default:
N
Nick Piggin 已提交
95
			mutex_unlock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
96 97 98 99 100 101 102 103 104
			return -EINVAL;
	}
	if (offset != file->f_pos) {
		file->f_pos = offset;
		if (file->f_pos >= 2) {
			struct list_head *p;
			struct dentry *cursor = file->private_data;
			loff_t n = file->f_pos - 2;

N
Nick Piggin 已提交
105 106
			spin_lock(&dentry->d_lock);
			/* d_lock not required for cursor */
E
Eric Dumazet 已提交
107
			list_del(&cursor->d_u.d_child);
N
Nick Piggin 已提交
108 109
			p = dentry->d_subdirs.next;
			while (n && p != &dentry->d_subdirs) {
L
Linus Torvalds 已提交
110
				struct dentry *next;
E
Eric Dumazet 已提交
111
				next = list_entry(p, struct dentry, d_u.d_child);
N
Nick Piggin 已提交
112
				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
N
Nick Piggin 已提交
113
				if (simple_positive(next))
L
Linus Torvalds 已提交
114
					n--;
N
Nick Piggin 已提交
115
				spin_unlock(&next->d_lock);
L
Linus Torvalds 已提交
116 117
				p = p->next;
			}
E
Eric Dumazet 已提交
118
			list_add_tail(&cursor->d_u.d_child, p);
N
Nick Piggin 已提交
119
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
120 121
		}
	}
N
Nick Piggin 已提交
122
	mutex_unlock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139
	return offset;
}

/* Relationship between i_mode and the DT_xxx types */
static inline unsigned char dt_type(struct inode *inode)
{
	return (inode->i_mode >> 12) & 15;
}

/*
 * Directory is locked and all positive dentries in it are safe, since
 * for ramfs-type trees they can't go away without unlink() or rmdir(),
 * both impossible due to the lock on directory.
 */

int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
140
	struct dentry *dentry = filp->f_path.dentry;
L
Linus Torvalds 已提交
141
	struct dentry *cursor = filp->private_data;
E
Eric Dumazet 已提交
142
	struct list_head *p, *q = &cursor->d_u.d_child;
L
Linus Torvalds 已提交
143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161
	ino_t ino;
	int i = filp->f_pos;

	switch (i) {
		case 0:
			ino = dentry->d_inode->i_ino;
			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
				break;
			filp->f_pos++;
			i++;
			/* fallthrough */
		case 1:
			ino = parent_ino(dentry);
			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
				break;
			filp->f_pos++;
			i++;
			/* fallthrough */
		default:
N
Nick Piggin 已提交
162
			spin_lock(&dentry->d_lock);
A
Akinobu Mita 已提交
163 164 165
			if (filp->f_pos == 2)
				list_move(q, &dentry->d_subdirs);

L
Linus Torvalds 已提交
166 167
			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
				struct dentry *next;
E
Eric Dumazet 已提交
168
				next = list_entry(p, struct dentry, d_u.d_child);
N
Nick Piggin 已提交
169 170 171
				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
				if (!simple_positive(next)) {
					spin_unlock(&next->d_lock);
L
Linus Torvalds 已提交
172
					continue;
N
Nick Piggin 已提交
173
				}
L
Linus Torvalds 已提交
174

N
Nick Piggin 已提交
175
				spin_unlock(&next->d_lock);
N
Nick Piggin 已提交
176
				spin_unlock(&dentry->d_lock);
177 178 179 180
				if (filldir(dirent, next->d_name.name, 
					    next->d_name.len, filp->f_pos, 
					    next->d_inode->i_ino, 
					    dt_type(next->d_inode)) < 0)
L
Linus Torvalds 已提交
181
					return 0;
N
Nick Piggin 已提交
182 183
				spin_lock(&dentry->d_lock);
				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
184
				/* next is still alive */
A
Akinobu Mita 已提交
185
				list_move(q, p);
N
Nick Piggin 已提交
186
				spin_unlock(&next->d_lock);
L
Linus Torvalds 已提交
187 188 189
				p = q;
				filp->f_pos++;
			}
N
Nick Piggin 已提交
190
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
191 192 193 194 195 196 197 198 199
	}
	return 0;
}

ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
{
	return -EISDIR;
}

200
const struct file_operations simple_dir_operations = {
L
Linus Torvalds 已提交
201 202 203 204 205
	.open		= dcache_dir_open,
	.release	= dcache_dir_close,
	.llseek		= dcache_dir_lseek,
	.read		= generic_read_dir,
	.readdir	= dcache_readdir,
206
	.fsync		= noop_fsync,
L
Linus Torvalds 已提交
207 208
};

209
const struct inode_operations simple_dir_inode_operations = {
L
Linus Torvalds 已提交
210 211 212
	.lookup		= simple_lookup,
};

213 214 215 216
static const struct super_operations simple_super_operations = {
	.statfs		= simple_statfs,
};

L
Linus Torvalds 已提交
217 218 219 220
/*
 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 * will never be mountable)
 */
A
Al Viro 已提交
221
struct dentry *mount_pseudo(struct file_system_type *fs_type, char *name,
222 223
	const struct super_operations *ops,
	const struct dentry_operations *dops, unsigned long magic)
L
Linus Torvalds 已提交
224 225 226 227 228 229 230
{
	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
	struct dentry *dentry;
	struct inode *root;
	struct qstr d_name = {.name = name, .len = strlen(name)};

	if (IS_ERR(s))
A
Al Viro 已提交
231
		return ERR_CAST(s);
L
Linus Torvalds 已提交
232 233

	s->s_flags = MS_NOUSER;
234
	s->s_maxbytes = MAX_LFS_FILESIZE;
235 236
	s->s_blocksize = PAGE_SIZE;
	s->s_blocksize_bits = PAGE_SHIFT;
L
Linus Torvalds 已提交
237
	s->s_magic = magic;
238
	s->s_op = ops ? ops : &simple_super_operations;
L
Linus Torvalds 已提交
239 240 241 242
	s->s_time_gran = 1;
	root = new_inode(s);
	if (!root)
		goto Enomem;
243 244 245 246 247 248
	/*
	 * since this is the first inode, make it number 1. New inodes created
	 * after this must take care not to collide with it (by passing
	 * max_reserved of 1 to iunique).
	 */
	root->i_ino = 1;
L
Linus Torvalds 已提交
249 250
	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
251
	dentry = __d_alloc(s, &d_name);
L
Linus Torvalds 已提交
252 253 254 255 256 257
	if (!dentry) {
		iput(root);
		goto Enomem;
	}
	d_instantiate(dentry, root);
	s->s_root = dentry;
258
	s->s_d_op = dops;
L
Linus Torvalds 已提交
259
	s->s_flags |= MS_ACTIVE;
A
Al Viro 已提交
260
	return dget(s->s_root);
L
Linus Torvalds 已提交
261 262

Enomem:
263
	deactivate_locked_super(s);
A
Al Viro 已提交
264
	return ERR_PTR(-ENOMEM);
L
Linus Torvalds 已提交
265 266 267 268 269 270 271
}

int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
	struct inode *inode = old_dentry->d_inode;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
272
	inc_nlink(inode);
A
Al Viro 已提交
273
	ihold(inode);
L
Linus Torvalds 已提交
274 275 276 277 278 279 280 281 282 283
	dget(dentry);
	d_instantiate(dentry, inode);
	return 0;
}

int simple_empty(struct dentry *dentry)
{
	struct dentry *child;
	int ret = 0;

N
Nick Piggin 已提交
284
	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
285 286 287 288
	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
		if (simple_positive(child)) {
			spin_unlock(&child->d_lock);
L
Linus Torvalds 已提交
289
			goto out;
N
Nick Piggin 已提交
290 291 292
		}
		spin_unlock(&child->d_lock);
	}
L
Linus Torvalds 已提交
293 294
	ret = 1;
out:
N
Nick Piggin 已提交
295
	spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
296 297 298 299 300 301 302 303
	return ret;
}

int simple_unlink(struct inode *dir, struct dentry *dentry)
{
	struct inode *inode = dentry->d_inode;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
304
	drop_nlink(inode);
L
Linus Torvalds 已提交
305 306 307 308 309 310 311 312 313
	dput(dentry);
	return 0;
}

int simple_rmdir(struct inode *dir, struct dentry *dentry)
{
	if (!simple_empty(dentry))
		return -ENOTEMPTY;

314
	drop_nlink(dentry->d_inode);
L
Linus Torvalds 已提交
315
	simple_unlink(dir, dentry);
316
	drop_nlink(dir);
L
Linus Torvalds 已提交
317 318 319 320 321 322 323 324 325 326 327 328 329 330
	return 0;
}

int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
		struct inode *new_dir, struct dentry *new_dentry)
{
	struct inode *inode = old_dentry->d_inode;
	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);

	if (!simple_empty(new_dentry))
		return -ENOTEMPTY;

	if (new_dentry->d_inode) {
		simple_unlink(new_dir, new_dentry);
331 332
		if (they_are_dirs) {
			drop_nlink(new_dentry->d_inode);
333
			drop_nlink(old_dir);
334
		}
L
Linus Torvalds 已提交
335
	} else if (they_are_dirs) {
336
		drop_nlink(old_dir);
337
		inc_nlink(new_dir);
L
Linus Torvalds 已提交
338 339 340 341 342 343 344 345
	}

	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
		new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;

	return 0;
}

346
/**
C
Christoph Hellwig 已提交
347
 * simple_setattr - setattr for simple filesystem
348 349 350 351 352
 * @dentry: dentry
 * @iattr: iattr structure
 *
 * Returns 0 on success, -error on failure.
 *
C
Christoph Hellwig 已提交
353 354 355 356 357 358
 * simple_setattr is a simple ->setattr implementation without a proper
 * implementation of size changes.
 *
 * It can either be used for in-memory filesystems or special files
 * on simple regular filesystems.  Anything that needs to change on-disk
 * or wire state on size changes needs its own setattr method.
359 360 361 362 363 364
 */
int simple_setattr(struct dentry *dentry, struct iattr *iattr)
{
	struct inode *inode = dentry->d_inode;
	int error;

C
Christoph Hellwig 已提交
365 366
	WARN_ON_ONCE(inode->i_op->truncate);

367 368 369 370
	error = inode_change_ok(inode, iattr);
	if (error)
		return error;

371 372
	if (iattr->ia_valid & ATTR_SIZE)
		truncate_setsize(inode, iattr->ia_size);
C
Christoph Hellwig 已提交
373
	setattr_copy(inode, iattr);
C
Christoph Hellwig 已提交
374 375
	mark_inode_dirty(inode);
	return 0;
376 377 378
}
EXPORT_SYMBOL(simple_setattr);

L
Linus Torvalds 已提交
379 380
int simple_readpage(struct file *file, struct page *page)
{
381
	clear_highpage(page);
L
Linus Torvalds 已提交
382 383 384 385 386 387
	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	return 0;
}

388 389 390 391 392 393 394 395 396
int simple_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata)
{
	struct page *page;
	pgoff_t index;

	index = pos >> PAGE_CACHE_SHIFT;

397
	page = grab_cache_page_write_begin(mapping, index, flags);
398 399 400 401 402
	if (!page)
		return -ENOMEM;

	*pagep = page;

403 404 405 406 407 408
	if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
		unsigned from = pos & (PAGE_CACHE_SIZE - 1);

		zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE);
	}
	return 0;
409 410
}

411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431
/**
 * simple_write_end - .write_end helper for non-block-device FSes
 * @available: See .write_end of address_space_operations
 * @file: 		"
 * @mapping: 		"
 * @pos: 		"
 * @len: 		"
 * @copied: 		"
 * @page: 		"
 * @fsdata: 		"
 *
 * simple_write_end does the minimum needed for updating a page after writing is
 * done. It has the same API signature as the .write_end of
 * address_space_operations vector. So it can just be set onto .write_end for
 * FSes that don't need any other processing. i_mutex is assumed to be held.
 * Block based filesystems should use generic_write_end().
 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
 * is not called, so a filesystem that actually does store data in .write_inode
 * should extend on what's done here with a call to mark_inode_dirty() in the
 * case that i_size has changed.
 */
432 433 434 435
int simple_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
436 437
	struct inode *inode = page->mapping->host;
	loff_t last_pos = pos + copied;
438 439 440

	/* zero the stale part of the page if we did a short copy */
	if (copied < len) {
441 442 443
		unsigned from = pos & (PAGE_CACHE_SIZE - 1);

		zero_user(page, from + copied, len - copied);
444 445
	}

446 447 448 449 450 451 452 453
	if (!PageUptodate(page))
		SetPageUptodate(page);
	/*
	 * No need to use i_size_read() here, the i_size
	 * cannot change under us because we hold the i_mutex.
	 */
	if (last_pos > inode->i_size)
		i_size_write(inode, last_pos);
454

455
	set_page_dirty(page);
456 457 458 459 460 461
	unlock_page(page);
	page_cache_release(page);

	return copied;
}

462 463 464 465 466
/*
 * the inodes created here are not hashed. If you use iunique to generate
 * unique inode values later for this filesystem, then you must take care
 * to pass it an appropriate max_reserved value to avoid collisions.
 */
467 468
int simple_fill_super(struct super_block *s, unsigned long magic,
		      struct tree_descr *files)
L
Linus Torvalds 已提交
469 470 471 472 473 474 475 476 477
{
	struct inode *inode;
	struct dentry *root;
	struct dentry *dentry;
	int i;

	s->s_blocksize = PAGE_CACHE_SIZE;
	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
	s->s_magic = magic;
478
	s->s_op = &simple_super_operations;
L
Linus Torvalds 已提交
479 480 481 482 483
	s->s_time_gran = 1;

	inode = new_inode(s);
	if (!inode)
		return -ENOMEM;
484 485 486 487 488
	/*
	 * because the root inode is 1, the files array must not contain an
	 * entry at index 1
	 */
	inode->i_ino = 1;
L
Linus Torvalds 已提交
489 490 491 492
	inode->i_mode = S_IFDIR | 0755;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->i_op = &simple_dir_inode_operations;
	inode->i_fop = &simple_dir_operations;
M
Miklos Szeredi 已提交
493
	set_nlink(inode, 2);
494 495
	root = d_make_root(inode);
	if (!root)
L
Linus Torvalds 已提交
496 497 498 499
		return -ENOMEM;
	for (i = 0; !files->name || files->name[0]; i++, files++) {
		if (!files->name)
			continue;
500 501 502 503 504 505 506

		/* warn if it tries to conflict with the root inode */
		if (unlikely(i == 1))
			printk(KERN_WARNING "%s: %s passed in a files array"
				"with an index of 1!\n", __func__,
				s->s_type->name);

L
Linus Torvalds 已提交
507 508 509 510
		dentry = d_alloc_name(root, files->name);
		if (!dentry)
			goto out;
		inode = new_inode(s);
511 512
		if (!inode) {
			dput(dentry);
L
Linus Torvalds 已提交
513
			goto out;
514
		}
L
Linus Torvalds 已提交
515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530
		inode->i_mode = S_IFREG | files->mode;
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_fop = files->ops;
		inode->i_ino = i;
		d_add(dentry, inode);
	}
	s->s_root = root;
	return 0;
out:
	d_genocide(root);
	dput(root);
	return -ENOMEM;
}

static DEFINE_SPINLOCK(pin_fs_lock);

531
int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
L
Linus Torvalds 已提交
532 533 534 535 536
{
	struct vfsmount *mnt = NULL;
	spin_lock(&pin_fs_lock);
	if (unlikely(!*mount)) {
		spin_unlock(&pin_fs_lock);
537
		mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, NULL);
L
Linus Torvalds 已提交
538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561
		if (IS_ERR(mnt))
			return PTR_ERR(mnt);
		spin_lock(&pin_fs_lock);
		if (!*mount)
			*mount = mnt;
	}
	mntget(*mount);
	++*count;
	spin_unlock(&pin_fs_lock);
	mntput(mnt);
	return 0;
}

void simple_release_fs(struct vfsmount **mount, int *count)
{
	struct vfsmount *mnt;
	spin_lock(&pin_fs_lock);
	mnt = *mount;
	if (!--*count)
		*mount = NULL;
	spin_unlock(&pin_fs_lock);
	mntput(mnt);
}

562 563 564 565 566 567 568 569 570 571 572 573 574 575
/**
 * simple_read_from_buffer - copy data from the buffer to user space
 * @to: the user space buffer to read to
 * @count: the maximum number of bytes to read
 * @ppos: the current position in the buffer
 * @from: the buffer to read from
 * @available: the size of the buffer
 *
 * The simple_read_from_buffer() function reads up to @count bytes from the
 * buffer @from at offset @ppos into the user space address starting at @to.
 *
 * On success, the number of bytes read is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
L
Linus Torvalds 已提交
576 577 578 579
ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
				const void *from, size_t available)
{
	loff_t pos = *ppos;
580 581
	size_t ret;

L
Linus Torvalds 已提交
582 583
	if (pos < 0)
		return -EINVAL;
584
	if (pos >= available || !count)
L
Linus Torvalds 已提交
585 586 587
		return 0;
	if (count > available - pos)
		count = available - pos;
588 589
	ret = copy_to_user(to, from + pos, count);
	if (ret == count)
L
Linus Torvalds 已提交
590
		return -EFAULT;
591
	count -= ret;
L
Linus Torvalds 已提交
592 593 594 595
	*ppos = pos + count;
	return count;
}

596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629
/**
 * simple_write_to_buffer - copy data from user space to the buffer
 * @to: the buffer to write to
 * @available: the size of the buffer
 * @ppos: the current position in the buffer
 * @from: the user space buffer to read from
 * @count: the maximum number of bytes to read
 *
 * The simple_write_to_buffer() function reads up to @count bytes from the user
 * space address starting at @from into the buffer @to at offset @ppos.
 *
 * On success, the number of bytes written is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
		const void __user *from, size_t count)
{
	loff_t pos = *ppos;
	size_t res;

	if (pos < 0)
		return -EINVAL;
	if (pos >= available || !count)
		return 0;
	if (count > available - pos)
		count = available - pos;
	res = copy_from_user(to + pos, from, count);
	if (res == count)
		return -EFAULT;
	count -= res;
	*ppos = pos + count;
	return count;
}

630 631 632 633 634 635 636 637 638 639 640 641 642 643
/**
 * memory_read_from_buffer - copy data from the buffer
 * @to: the kernel space buffer to read to
 * @count: the maximum number of bytes to read
 * @ppos: the current position in the buffer
 * @from: the buffer to read from
 * @available: the size of the buffer
 *
 * The memory_read_from_buffer() function reads up to @count bytes from the
 * buffer @from at offset @ppos into the kernel space address starting at @to.
 *
 * On success, the number of bytes read is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660
ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
				const void *from, size_t available)
{
	loff_t pos = *ppos;

	if (pos < 0)
		return -EINVAL;
	if (pos >= available)
		return 0;
	if (count > available - pos)
		count = available - pos;
	memcpy(to, from + pos, count);
	*ppos = pos + count;

	return count;
}

L
Linus Torvalds 已提交
661 662 663 664 665 666
/*
 * Transaction based IO.
 * The file expects a single write which triggers the transaction, and then
 * possibly a read which collects the result - which is stored in a
 * file-local buffer.
 */
667 668 669 670 671 672 673 674 675 676 677 678 679 680 681

void simple_transaction_set(struct file *file, size_t n)
{
	struct simple_transaction_argresp *ar = file->private_data;

	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);

	/*
	 * The barrier ensures that ar->size will really remain zero until
	 * ar->data is ready for reading.
	 */
	smp_mb();
	ar->size = n;
}

L
Linus Torvalds 已提交
682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727
char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
{
	struct simple_transaction_argresp *ar;
	static DEFINE_SPINLOCK(simple_transaction_lock);

	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
		return ERR_PTR(-EFBIG);

	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
	if (!ar)
		return ERR_PTR(-ENOMEM);

	spin_lock(&simple_transaction_lock);

	/* only one write allowed per open */
	if (file->private_data) {
		spin_unlock(&simple_transaction_lock);
		free_page((unsigned long)ar);
		return ERR_PTR(-EBUSY);
	}

	file->private_data = ar;

	spin_unlock(&simple_transaction_lock);

	if (copy_from_user(ar->data, buf, size))
		return ERR_PTR(-EFAULT);

	return ar->data;
}

ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
{
	struct simple_transaction_argresp *ar = file->private_data;

	if (!ar)
		return 0;
	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
}

int simple_transaction_release(struct inode *inode, struct file *file)
{
	free_page((unsigned long)file->private_data);
	return 0;
}

728 729 730
/* Simple attribute files */

struct simple_attr {
731 732
	int (*get)(void *, u64 *);
	int (*set)(void *, u64);
733 734 735 736
	char get_buf[24];	/* enough to store a u64 and "\n\0" */
	char set_buf[24];
	void *data;
	const char *fmt;	/* format for read operation */
I
Ingo Molnar 已提交
737
	struct mutex mutex;	/* protects access to these buffers */
738 739 740 741 742
};

/* simple_attr_open is called by an actual attribute open file operation
 * to set the attribute specific access operations. */
int simple_attr_open(struct inode *inode, struct file *file,
743
		     int (*get)(void *, u64 *), int (*set)(void *, u64),
744 745 746 747 748 749 750 751 752 753
		     const char *fmt)
{
	struct simple_attr *attr;

	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
	if (!attr)
		return -ENOMEM;

	attr->get = get;
	attr->set = set;
754
	attr->data = inode->i_private;
755
	attr->fmt = fmt;
I
Ingo Molnar 已提交
756
	mutex_init(&attr->mutex);
757 758 759 760 761 762

	file->private_data = attr;

	return nonseekable_open(inode, file);
}

763
int simple_attr_release(struct inode *inode, struct file *file)
764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781
{
	kfree(file->private_data);
	return 0;
}

/* read from the buffer that is filled with the get function */
ssize_t simple_attr_read(struct file *file, char __user *buf,
			 size_t len, loff_t *ppos)
{
	struct simple_attr *attr;
	size_t size;
	ssize_t ret;

	attr = file->private_data;

	if (!attr->get)
		return -EACCES;

782 783 784 785
	ret = mutex_lock_interruptible(&attr->mutex);
	if (ret)
		return ret;

786
	if (*ppos) {		/* continued read */
787
		size = strlen(attr->get_buf);
788 789 790 791 792 793
	} else {		/* first read */
		u64 val;
		ret = attr->get(attr->data, &val);
		if (ret)
			goto out;

794
		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
795 796
				 attr->fmt, (unsigned long long)val);
	}
797 798

	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
799
out:
I
Ingo Molnar 已提交
800
	mutex_unlock(&attr->mutex);
801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816
	return ret;
}

/* interpret the buffer as a number to call the set function with */
ssize_t simple_attr_write(struct file *file, const char __user *buf,
			  size_t len, loff_t *ppos)
{
	struct simple_attr *attr;
	u64 val;
	size_t size;
	ssize_t ret;

	attr = file->private_data;
	if (!attr->set)
		return -EACCES;

817 818 819 820
	ret = mutex_lock_interruptible(&attr->mutex);
	if (ret)
		return ret;

821 822 823 824 825 826
	ret = -EFAULT;
	size = min(sizeof(attr->set_buf) - 1, len);
	if (copy_from_user(attr->set_buf, buf, size))
		goto out;

	attr->set_buf[size] = '\0';
827
	val = simple_strtoll(attr->set_buf, NULL, 0);
828 829 830
	ret = attr->set(attr->data, val);
	if (ret == 0)
		ret = len; /* on success, claim we got the whole input */
831
out:
I
Ingo Molnar 已提交
832
	mutex_unlock(&attr->mutex);
833 834 835
	return ret;
}

C
Christoph Hellwig 已提交
836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863
/**
 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
 * @sb:		filesystem to do the file handle conversion on
 * @fid:	file handle to convert
 * @fh_len:	length of the file handle in bytes
 * @fh_type:	type of file handle
 * @get_inode:	filesystem callback to retrieve inode
 *
 * This function decodes @fid as long as it has one of the well-known
 * Linux filehandle types and calls @get_inode on it to retrieve the
 * inode for the object specified in the file handle.
 */
struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
		int fh_len, int fh_type, struct inode *(*get_inode)
			(struct super_block *sb, u64 ino, u32 gen))
{
	struct inode *inode = NULL;

	if (fh_len < 2)
		return NULL;

	switch (fh_type) {
	case FILEID_INO32_GEN:
	case FILEID_INO32_GEN_PARENT:
		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
		break;
	}

864
	return d_obtain_alias(inode);
C
Christoph Hellwig 已提交
865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896
}
EXPORT_SYMBOL_GPL(generic_fh_to_dentry);

/**
 * generic_fh_to_dentry - generic helper for the fh_to_parent export operation
 * @sb:		filesystem to do the file handle conversion on
 * @fid:	file handle to convert
 * @fh_len:	length of the file handle in bytes
 * @fh_type:	type of file handle
 * @get_inode:	filesystem callback to retrieve inode
 *
 * This function decodes @fid as long as it has one of the well-known
 * Linux filehandle types and calls @get_inode on it to retrieve the
 * inode for the _parent_ object specified in the file handle if it
 * is specified in the file handle, or NULL otherwise.
 */
struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
		int fh_len, int fh_type, struct inode *(*get_inode)
			(struct super_block *sb, u64 ino, u32 gen))
{
	struct inode *inode = NULL;

	if (fh_len <= 2)
		return NULL;

	switch (fh_type) {
	case FILEID_INO32_GEN_PARENT:
		inode = get_inode(sb, fid->i32.parent_ino,
				  (fh_len > 3 ? fid->i32.parent_gen : 0));
		break;
	}

897
	return d_obtain_alias(inode);
C
Christoph Hellwig 已提交
898 899 900
}
EXPORT_SYMBOL_GPL(generic_fh_to_parent);

901 902 903 904 905 906 907 908 909
/**
 * generic_file_fsync - generic fsync implementation for simple filesystems
 * @file:	file to synchronize
 * @datasync:	only synchronize essential metadata if true
 *
 * This is a generic implementation of the fsync method for simple
 * filesystems which track all non-inode metadata in the buffers list
 * hanging off the address_space structure.
 */
910 911
int generic_file_fsync(struct file *file, loff_t start, loff_t end,
		       int datasync)
A
Al Viro 已提交
912
{
913
	struct inode *inode = file->f_mapping->host;
A
Al Viro 已提交
914 915 916
	int err;
	int ret;

917 918 919 920 921
	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
	if (err)
		return err;

	mutex_lock(&inode->i_mutex);
A
Al Viro 已提交
922 923
	ret = sync_mapping_buffers(inode->i_mapping);
	if (!(inode->i_state & I_DIRTY))
924
		goto out;
A
Al Viro 已提交
925
	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
926
		goto out;
A
Al Viro 已提交
927

C
Christoph Hellwig 已提交
928
	err = sync_inode_metadata(inode, 1);
A
Al Viro 已提交
929 930
	if (ret == 0)
		ret = err;
931 932
out:
	mutex_unlock(&inode->i_mutex);
A
Al Viro 已提交
933 934
	return ret;
}
935 936
EXPORT_SYMBOL(generic_file_fsync);

937 938 939 940 941 942 943 944 945 946 947 948
/**
 * generic_check_addressable - Check addressability of file system
 * @blocksize_bits:	log of file system block size
 * @num_blocks:		number of blocks in file system
 *
 * Determine whether a file system with @num_blocks blocks (and a
 * block size of 2**@blocksize_bits) is addressable by the sector_t
 * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
 */
int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
{
	u64 last_fs_block = num_blocks - 1;
949 950
	u64 last_fs_page =
		last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
951 952 953 954 955 956 957

	if (unlikely(num_blocks == 0))
		return 0;

	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
		return -EINVAL;

958 959
	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
	    (last_fs_page > (pgoff_t)(~0ULL))) {
960 961 962 963 964 965
		return -EFBIG;
	}
	return 0;
}
EXPORT_SYMBOL(generic_check_addressable);

966 967 968
/*
 * No-op implementation of ->fsync for in-memory filesystems.
 */
969
int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
970 971 972
{
	return 0;
}
A
Al Viro 已提交
973

L
Linus Torvalds 已提交
974 975 976 977 978
EXPORT_SYMBOL(dcache_dir_close);
EXPORT_SYMBOL(dcache_dir_lseek);
EXPORT_SYMBOL(dcache_dir_open);
EXPORT_SYMBOL(dcache_readdir);
EXPORT_SYMBOL(generic_read_dir);
A
Al Viro 已提交
979
EXPORT_SYMBOL(mount_pseudo);
980 981
EXPORT_SYMBOL(simple_write_begin);
EXPORT_SYMBOL(simple_write_end);
L
Linus Torvalds 已提交
982 983 984 985 986 987 988 989 990 991 992 993 994
EXPORT_SYMBOL(simple_dir_inode_operations);
EXPORT_SYMBOL(simple_dir_operations);
EXPORT_SYMBOL(simple_empty);
EXPORT_SYMBOL(simple_fill_super);
EXPORT_SYMBOL(simple_getattr);
EXPORT_SYMBOL(simple_link);
EXPORT_SYMBOL(simple_lookup);
EXPORT_SYMBOL(simple_pin_fs);
EXPORT_SYMBOL(simple_readpage);
EXPORT_SYMBOL(simple_release_fs);
EXPORT_SYMBOL(simple_rename);
EXPORT_SYMBOL(simple_rmdir);
EXPORT_SYMBOL(simple_statfs);
995
EXPORT_SYMBOL(noop_fsync);
L
Linus Torvalds 已提交
996 997
EXPORT_SYMBOL(simple_unlink);
EXPORT_SYMBOL(simple_read_from_buffer);
998
EXPORT_SYMBOL(simple_write_to_buffer);
999
EXPORT_SYMBOL(memory_read_from_buffer);
1000
EXPORT_SYMBOL(simple_transaction_set);
L
Linus Torvalds 已提交
1001 1002 1003
EXPORT_SYMBOL(simple_transaction_get);
EXPORT_SYMBOL(simple_transaction_read);
EXPORT_SYMBOL(simple_transaction_release);
1004
EXPORT_SYMBOL_GPL(simple_attr_open);
1005
EXPORT_SYMBOL_GPL(simple_attr_release);
1006 1007
EXPORT_SYMBOL_GPL(simple_attr_read);
EXPORT_SYMBOL_GPL(simple_attr_write);