libfs.c 15.3 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
/*
 *	fs/libfs.c
 *	Library for filesystems writers.
 */

#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <asm/uaccess.h>

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;
}

int simple_statfs(struct super_block *sb, struct kstatfs *buf)
{
	buf->f_type = sb->s_magic;
	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.
 */
static int simple_delete_dentry(struct dentry *dentry)
{
	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)
{
	static struct dentry_operations simple_dentry_operations = {
		.d_delete = simple_delete_dentry,
	};

	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	dentry->d_op = &simple_dentry_operations;
	d_add(dentry, NULL);
	return NULL;
}

int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
{
	return 0;
}
 
int dcache_dir_open(struct inode *inode, struct file *file)
{
	static struct qstr cursor_name = {.len = 1, .name = "."};

	file->private_data = d_alloc(file->f_dentry, &cursor_name);

	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)
{
	down(&file->f_dentry->d_inode->i_sem);
	switch (origin) {
		case 1:
			offset += file->f_pos;
		case 0:
			if (offset >= 0)
				break;
		default:
			up(&file->f_dentry->d_inode->i_sem);
			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;

			spin_lock(&dcache_lock);
E
Eric Dumazet 已提交
96
			list_del(&cursor->d_u.d_child);
L
Linus Torvalds 已提交
97 98 99
			p = file->f_dentry->d_subdirs.next;
			while (n && p != &file->f_dentry->d_subdirs) {
				struct dentry *next;
E
Eric Dumazet 已提交
100
				next = list_entry(p, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
101 102 103 104
				if (!d_unhashed(next) && next->d_inode)
					n--;
				p = p->next;
			}
E
Eric Dumazet 已提交
105
			list_add_tail(&cursor->d_u.d_child, p);
L
Linus Torvalds 已提交
106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128
			spin_unlock(&dcache_lock);
		}
	}
	up(&file->f_dentry->d_inode->i_sem);
	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)
{
	struct dentry *dentry = filp->f_dentry;
	struct dentry *cursor = filp->private_data;
E
Eric Dumazet 已提交
129
	struct list_head *p, *q = &cursor->d_u.d_child;
L
Linus Torvalds 已提交
130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155
	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:
			spin_lock(&dcache_lock);
			if (filp->f_pos == 2) {
				list_del(q);
				list_add(q, &dentry->d_subdirs);
			}
			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
				struct dentry *next;
E
Eric Dumazet 已提交
156
				next = list_entry(p, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185
				if (d_unhashed(next) || !next->d_inode)
					continue;

				spin_unlock(&dcache_lock);
				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)
					return 0;
				spin_lock(&dcache_lock);
				/* next is still alive */
				list_del(q);
				list_add(q, p);
				p = q;
				filp->f_pos++;
			}
			spin_unlock(&dcache_lock);
	}
	return 0;
}

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

struct file_operations simple_dir_operations = {
	.open		= dcache_dir_open,
	.release	= dcache_dir_close,
	.llseek		= dcache_dir_lseek,
	.read		= generic_read_dir,
	.readdir	= dcache_readdir,
186
	.fsync		= simple_sync_file,
L
Linus Torvalds 已提交
187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263
};

struct inode_operations simple_dir_inode_operations = {
	.lookup		= simple_lookup,
};

/*
 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 * will never be mountable)
 */
struct super_block *
get_sb_pseudo(struct file_system_type *fs_type, char *name,
	struct super_operations *ops, unsigned long magic)
{
	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
	static struct super_operations default_ops = {.statfs = simple_statfs};
	struct dentry *dentry;
	struct inode *root;
	struct qstr d_name = {.name = name, .len = strlen(name)};

	if (IS_ERR(s))
		return s;

	s->s_flags = MS_NOUSER;
	s->s_maxbytes = ~0ULL;
	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = magic;
	s->s_op = ops ? ops : &default_ops;
	s->s_time_gran = 1;
	root = new_inode(s);
	if (!root)
		goto Enomem;
	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
	root->i_uid = root->i_gid = 0;
	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
	dentry = d_alloc(NULL, &d_name);
	if (!dentry) {
		iput(root);
		goto Enomem;
	}
	dentry->d_sb = s;
	dentry->d_parent = dentry;
	d_instantiate(dentry, root);
	s->s_root = dentry;
	s->s_flags |= MS_ACTIVE;
	return s;

Enomem:
	up_write(&s->s_umount);
	deactivate_super(s);
	return ERR_PTR(-ENOMEM);
}

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;
	inode->i_nlink++;
	atomic_inc(&inode->i_count);
	dget(dentry);
	d_instantiate(dentry, inode);
	return 0;
}

static inline int simple_positive(struct dentry *dentry)
{
	return dentry->d_inode && !d_unhashed(dentry);
}

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

	spin_lock(&dcache_lock);
E
Eric Dumazet 已提交
264
	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
L
Linus Torvalds 已提交
265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522
		if (simple_positive(child))
			goto out;
	ret = 1;
out:
	spin_unlock(&dcache_lock);
	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;
	inode->i_nlink--;
	dput(dentry);
	return 0;
}

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

	dentry->d_inode->i_nlink--;
	simple_unlink(dir, dentry);
	dir->i_nlink--;
	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);
		if (they_are_dirs)
			old_dir->i_nlink--;
	} else if (they_are_dirs) {
		old_dir->i_nlink--;
		new_dir->i_nlink++;
	}

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

	return 0;
}

int simple_readpage(struct file *file, struct page *page)
{
	void *kaddr;

	if (PageUptodate(page))
		goto out;

	kaddr = kmap_atomic(page, KM_USER0);
	memset(kaddr, 0, PAGE_CACHE_SIZE);
	kunmap_atomic(kaddr, KM_USER0);
	flush_dcache_page(page);
	SetPageUptodate(page);
out:
	unlock_page(page);
	return 0;
}

int simple_prepare_write(struct file *file, struct page *page,
			unsigned from, unsigned to)
{
	if (!PageUptodate(page)) {
		if (to - from != PAGE_CACHE_SIZE) {
			void *kaddr = kmap_atomic(page, KM_USER0);
			memset(kaddr, 0, from);
			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
			flush_dcache_page(page);
			kunmap_atomic(kaddr, KM_USER0);
		}
		SetPageUptodate(page);
	}
	return 0;
}

int simple_commit_write(struct file *file, struct page *page,
			unsigned offset, unsigned to)
{
	struct inode *inode = page->mapping->host;
	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;

	/*
	 * No need to use i_size_read() here, the i_size
	 * cannot change under us because we hold the i_sem.
	 */
	if (pos > inode->i_size)
		i_size_write(inode, pos);
	set_page_dirty(page);
	return 0;
}

int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
{
	static struct super_operations s_ops = {.statfs = simple_statfs};
	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;
	s->s_op = &s_ops;
	s->s_time_gran = 1;

	inode = new_inode(s);
	if (!inode)
		return -ENOMEM;
	inode->i_mode = S_IFDIR | 0755;
	inode->i_uid = inode->i_gid = 0;
	inode->i_blksize = PAGE_CACHE_SIZE;
	inode->i_blocks = 0;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->i_op = &simple_dir_inode_operations;
	inode->i_fop = &simple_dir_operations;
	root = d_alloc_root(inode);
	if (!root) {
		iput(inode);
		return -ENOMEM;
	}
	for (i = 0; !files->name || files->name[0]; i++, files++) {
		if (!files->name)
			continue;
		dentry = d_alloc_name(root, files->name);
		if (!dentry)
			goto out;
		inode = new_inode(s);
		if (!inode)
			goto out;
		inode->i_mode = S_IFREG | files->mode;
		inode->i_uid = inode->i_gid = 0;
		inode->i_blksize = PAGE_CACHE_SIZE;
		inode->i_blocks = 0;
		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);

int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
{
	struct vfsmount *mnt = NULL;
	spin_lock(&pin_fs_lock);
	if (unlikely(!*mount)) {
		spin_unlock(&pin_fs_lock);
		mnt = do_kern_mount(name, 0, name, NULL);
		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);
}

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

/*
 * 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.
 */
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;
}

523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618
/* Simple attribute files */

struct simple_attr {
	u64 (*get)(void *);
	void (*set)(void *, u64);
	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 */
	struct semaphore sem;	/* protects access to these buffers */
};

/* 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,
		     u64 (*get)(void *), void (*set)(void *, u64),
		     const char *fmt)
{
	struct simple_attr *attr;

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

	attr->get = get;
	attr->set = set;
	attr->data = inode->u.generic_ip;
	attr->fmt = fmt;
	init_MUTEX(&attr->sem);

	file->private_data = attr;

	return nonseekable_open(inode, file);
}

int simple_attr_close(struct inode *inode, struct file *file)
{
	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;

	down(&attr->sem);
	if (*ppos) /* continued read */
		size = strlen(attr->get_buf);
	else	  /* first read */
		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
				 attr->fmt,
				 (unsigned long long)attr->get(attr->data));

	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
	up(&attr->sem);
	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;

	down(&attr->sem);
	ret = -EFAULT;
	size = min(sizeof(attr->set_buf) - 1, len);
	if (copy_from_user(attr->set_buf, buf, size))
		goto out;

	ret = len; /* claim we got the whole input */
	attr->set_buf[size] = '\0';
	val = simple_strtol(attr->set_buf, NULL, 0);
	attr->set(attr->data, val);
out:
	up(&attr->sem);
	return ret;
}

L
Linus Torvalds 已提交
619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646
EXPORT_SYMBOL(dcache_dir_close);
EXPORT_SYMBOL(dcache_dir_lseek);
EXPORT_SYMBOL(dcache_dir_open);
EXPORT_SYMBOL(dcache_readdir);
EXPORT_SYMBOL(generic_read_dir);
EXPORT_SYMBOL(get_sb_pseudo);
EXPORT_SYMBOL(simple_commit_write);
EXPORT_SYMBOL(simple_dir_inode_operations);
EXPORT_SYMBOL(simple_dir_operations);
EXPORT_SYMBOL(simple_empty);
EXPORT_SYMBOL(d_alloc_name);
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_prepare_write);
EXPORT_SYMBOL(simple_readpage);
EXPORT_SYMBOL(simple_release_fs);
EXPORT_SYMBOL(simple_rename);
EXPORT_SYMBOL(simple_rmdir);
EXPORT_SYMBOL(simple_statfs);
EXPORT_SYMBOL(simple_sync_file);
EXPORT_SYMBOL(simple_unlink);
EXPORT_SYMBOL(simple_read_from_buffer);
EXPORT_SYMBOL(simple_transaction_get);
EXPORT_SYMBOL(simple_transaction_read);
EXPORT_SYMBOL(simple_transaction_release);
647 648 649 650
EXPORT_SYMBOL_GPL(simple_attr_open);
EXPORT_SYMBOL_GPL(simple_attr_close);
EXPORT_SYMBOL_GPL(simple_attr_read);
EXPORT_SYMBOL_GPL(simple_attr_write);