1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *	fs/libfs.c
   4 *	Library for filesystems writers.
   5 */
   6
   7#include <linux/blkdev.h>
   8#include <linux/export.h>
   9#include <linux/pagemap.h>
  10#include <linux/slab.h>
  11#include <linux/cred.h>
  12#include <linux/mount.h>
  13#include <linux/vfs.h>
  14#include <linux/quotaops.h>
  15#include <linux/mutex.h>
  16#include <linux/namei.h>
  17#include <linux/exportfs.h>
  18#include <linux/iversion.h>
  19#include <linux/writeback.h>
  20#include <linux/buffer_head.h> /* sync_mapping_buffers */
  21#include <linux/fs_context.h>
  22#include <linux/pseudo_fs.h>
  23#include <linux/fsnotify.h>
  24#include <linux/unicode.h>
  25#include <linux/fscrypt.h>
  26
  27#include <linux/uaccess.h>
  28
  29#include "internal.h"
  30
  31int simple_getattr(struct user_namespace *mnt_userns, const struct path *path,
  32		   struct kstat *stat, u32 request_mask,
  33		   unsigned int query_flags)
  34{
  35	struct inode *inode = d_inode(path->dentry);
  36	generic_fillattr(&init_user_ns, inode, stat);
  37	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
  38	return 0;
  39}
  40EXPORT_SYMBOL(simple_getattr);
  41
  42int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
  43{
  44	buf->f_type = dentry->d_sb->s_magic;
  45	buf->f_bsize = PAGE_SIZE;
  46	buf->f_namelen = NAME_MAX;
  47	return 0;
  48}
  49EXPORT_SYMBOL(simple_statfs);
  50
  51/*
  52 * Retaining negative dentries for an in-memory filesystem just wastes
  53 * memory and lookup time: arrange for them to be deleted immediately.
  54 */
  55int always_delete_dentry(const struct dentry *dentry)
  56{
  57	return 1;
  58}
  59EXPORT_SYMBOL(always_delete_dentry);
  60
  61const struct dentry_operations simple_dentry_operations = {
  62	.d_delete = always_delete_dentry,
  63};
  64EXPORT_SYMBOL(simple_dentry_operations);
  65
  66/*
  67 * Lookup the data. This is trivial - if the dentry didn't already
  68 * exist, we know it is negative.  Set d_op to delete negative dentries.
  69 */
  70struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
  71{
  72	if (dentry->d_name.len > NAME_MAX)
  73		return ERR_PTR(-ENAMETOOLONG);
  74	if (!dentry->d_sb->s_d_op)
  75		d_set_d_op(dentry, &simple_dentry_operations);
  76	d_add(dentry, NULL);
  77	return NULL;
  78}
  79EXPORT_SYMBOL(simple_lookup);
  80
  81int dcache_dir_open(struct inode *inode, struct file *file)
  82{
  83	file->private_data = d_alloc_cursor(file->f_path.dentry);
  84
  85	return file->private_data ? 0 : -ENOMEM;
  86}
  87EXPORT_SYMBOL(dcache_dir_open);
  88
  89int dcache_dir_close(struct inode *inode, struct file *file)
  90{
  91	dput(file->private_data);
  92	return 0;
  93}
  94EXPORT_SYMBOL(dcache_dir_close);
  95
  96/* parent is locked at least shared */
  97/*
  98 * Returns an element of siblings' list.
  99 * We are looking for <count>th positive after <p>; if
 100 * found, dentry is grabbed and returned to caller.
 101 * If no such element exists, NULL is returned.
 102 */
 103static struct dentry *scan_positives(struct dentry *cursor,
 104					struct list_head *p,
 105					loff_t count,
 106					struct dentry *last)
 107{
 108	struct dentry *dentry = cursor->d_parent, *found = NULL;
 109
 110	spin_lock(&dentry->d_lock);
 111	while ((p = p->next) != &dentry->d_subdirs) {
 112		struct dentry *d = list_entry(p, struct dentry, d_child);
 113		// we must at least skip cursors, to avoid livelocks
 114		if (d->d_flags & DCACHE_DENTRY_CURSOR)
 115			continue;
 116		if (simple_positive(d) && !--count) {
 117			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
 118			if (simple_positive(d))
 119				found = dget_dlock(d);
 120			spin_unlock(&d->d_lock);
 121			if (likely(found))
 122				break;
 123			count = 1;
 124		}
 125		if (need_resched()) {
 126			list_move(&cursor->d_child, p);
 127			p = &cursor->d_child;
 128			spin_unlock(&dentry->d_lock);
 129			cond_resched();
 130			spin_lock(&dentry->d_lock);
 131		}
 132	}
 133	spin_unlock(&dentry->d_lock);
 134	dput(last);
 135	return found;
 136}
 137
 138loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
 139{
 140	struct dentry *dentry = file->f_path.dentry;
 141	switch (whence) {
 142		case 1:
 143			offset += file->f_pos;
 144			fallthrough;
 145		case 0:
 146			if (offset >= 0)
 147				break;
 148			fallthrough;
 149		default:
 150			return -EINVAL;
 151	}
 152	if (offset != file->f_pos) {
 153		struct dentry *cursor = file->private_data;
 154		struct dentry *to = NULL;
 155
 156		inode_lock_shared(dentry->d_inode);
 157
 158		if (offset > 2)
 159			to = scan_positives(cursor, &dentry->d_subdirs,
 160					    offset - 2, NULL);
 161		spin_lock(&dentry->d_lock);
 162		if (to)
 163			list_move(&cursor->d_child, &to->d_child);
 164		else
 165			list_del_init(&cursor->d_child);
 166		spin_unlock(&dentry->d_lock);
 167		dput(to);
 168
 169		file->f_pos = offset;
 170
 171		inode_unlock_shared(dentry->d_inode);
 172	}
 173	return offset;
 174}
 175EXPORT_SYMBOL(dcache_dir_lseek);
 176
 177/* Relationship between i_mode and the DT_xxx types */
 178static inline unsigned char dt_type(struct inode *inode)
 179{
 180	return (inode->i_mode >> 12) & 15;
 181}
 182
 183/*
 184 * Directory is locked and all positive dentries in it are safe, since
 185 * for ramfs-type trees they can't go away without unlink() or rmdir(),
 186 * both impossible due to the lock on directory.
 187 */
 188
 189int dcache_readdir(struct file *file, struct dir_context *ctx)
 190{
 191	struct dentry *dentry = file->f_path.dentry;
 192	struct dentry *cursor = file->private_data;
 193	struct list_head *anchor = &dentry->d_subdirs;
 194	struct dentry *next = NULL;
 195	struct list_head *p;
 196
 197	if (!dir_emit_dots(file, ctx))
 198		return 0;
 199
 200	if (ctx->pos == 2)
 201		p = anchor;
 202	else if (!list_empty(&cursor->d_child))
 203		p = &cursor->d_child;
 204	else
 205		return 0;
 206
 207	while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
 208		if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
 209			      d_inode(next)->i_ino, dt_type(d_inode(next))))
 210			break;
 211		ctx->pos++;
 212		p = &next->d_child;
 213	}
 214	spin_lock(&dentry->d_lock);
 215	if (next)
 216		list_move_tail(&cursor->d_child, &next->d_child);
 217	else
 218		list_del_init(&cursor->d_child);
 219	spin_unlock(&dentry->d_lock);
 220	dput(next);
 221
 222	return 0;
 223}
 224EXPORT_SYMBOL(dcache_readdir);
 225
 226ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 227{
 228	return -EISDIR;
 229}
 230EXPORT_SYMBOL(generic_read_dir);
 231
 232const struct file_operations simple_dir_operations = {
 233	.open		= dcache_dir_open,
 234	.release	= dcache_dir_close,
 235	.llseek		= dcache_dir_lseek,
 236	.read		= generic_read_dir,
 237	.iterate_shared	= dcache_readdir,
 238	.fsync		= noop_fsync,
 239};
 240EXPORT_SYMBOL(simple_dir_operations);
 241
 242const struct inode_operations simple_dir_inode_operations = {
 243	.lookup		= simple_lookup,
 244};
 245EXPORT_SYMBOL(simple_dir_inode_operations);
 246
 247static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
 248{
 249	struct dentry *child = NULL;
 250	struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
 251
 252	spin_lock(&parent->d_lock);
 253	while ((p = p->next) != &parent->d_subdirs) {
 254		struct dentry *d = container_of(p, struct dentry, d_child);
 255		if (simple_positive(d)) {
 256			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
 257			if (simple_positive(d))
 258				child = dget_dlock(d);
 259			spin_unlock(&d->d_lock);
 260			if (likely(child))
 261				break;
 262		}
 263	}
 264	spin_unlock(&parent->d_lock);
 265	dput(prev);
 266	return child;
 267}
 268
 269void simple_recursive_removal(struct dentry *dentry,
 270                              void (*callback)(struct dentry *))
 271{
 272	struct dentry *this = dget(dentry);
 273	while (true) {
 274		struct dentry *victim = NULL, *child;
 275		struct inode *inode = this->d_inode;
 276
 277		inode_lock(inode);
 278		if (d_is_dir(this))
 279			inode->i_flags |= S_DEAD;
 280		while ((child = find_next_child(this, victim)) == NULL) {
 281			// kill and ascend
 282			// update metadata while it's still locked
 283			inode->i_ctime = current_time(inode);
 284			clear_nlink(inode);
 285			inode_unlock(inode);
 286			victim = this;
 287			this = this->d_parent;
 288			inode = this->d_inode;
 289			inode_lock(inode);
 290			if (simple_positive(victim)) {
 291				d_invalidate(victim);	// avoid lost mounts
 292				if (d_is_dir(victim))
 293					fsnotify_rmdir(inode, victim);
 294				else
 295					fsnotify_unlink(inode, victim);
 296				if (callback)
 297					callback(victim);
 298				dput(victim);		// unpin it
 299			}
 300			if (victim == dentry) {
 301				inode->i_ctime = inode->i_mtime =
 302					current_time(inode);
 303				if (d_is_dir(dentry))
 304					drop_nlink(inode);
 305				inode_unlock(inode);
 306				dput(dentry);
 307				return;
 308			}
 309		}
 310		inode_unlock(inode);
 311		this = child;
 312	}
 313}
 314EXPORT_SYMBOL(simple_recursive_removal);
 315
 316static const struct super_operations simple_super_operations = {
 317	.statfs		= simple_statfs,
 318};
 319
 320static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
 321{
 322	struct pseudo_fs_context *ctx = fc->fs_private;
 323	struct inode *root;
 324
 325	s->s_maxbytes = MAX_LFS_FILESIZE;
 326	s->s_blocksize = PAGE_SIZE;
 327	s->s_blocksize_bits = PAGE_SHIFT;
 328	s->s_magic = ctx->magic;
 329	s->s_op = ctx->ops ?: &simple_super_operations;
 330	s->s_xattr = ctx->xattr;
 331	s->s_time_gran = 1;
 332	root = new_inode(s);
 333	if (!root)
 334		return -ENOMEM;
 335
 336	/*
 337	 * since this is the first inode, make it number 1. New inodes created
 338	 * after this must take care not to collide with it (by passing
 339	 * max_reserved of 1 to iunique).
 340	 */
 341	root->i_ino = 1;
 342	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 343	root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
 344	s->s_root = d_make_root(root);
 345	if (!s->s_root)
 346		return -ENOMEM;
 347	s->s_d_op = ctx->dops;
 348	return 0;
 349}
 350
 351static int pseudo_fs_get_tree(struct fs_context *fc)
 352{
 353	return get_tree_nodev(fc, pseudo_fs_fill_super);
 354}
 355
 356static void pseudo_fs_free(struct fs_context *fc)
 357{
 358	kfree(fc->fs_private);
 359}
 360
 361static const struct fs_context_operations pseudo_fs_context_ops = {
 362	.free		= pseudo_fs_free,
 363	.get_tree	= pseudo_fs_get_tree,
 364};
 365
 366/*
 367 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 368 * will never be mountable)
 369 */
 370struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
 371					unsigned long magic)
 372{
 373	struct pseudo_fs_context *ctx;
 374
 375	ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
 376	if (likely(ctx)) {
 377		ctx->magic = magic;
 378		fc->fs_private = ctx;
 379		fc->ops = &pseudo_fs_context_ops;
 380		fc->sb_flags |= SB_NOUSER;
 381		fc->global = true;
 382	}
 383	return ctx;
 384}
 385EXPORT_SYMBOL(init_pseudo);
 386
 387int simple_open(struct inode *inode, struct file *file)
 388{
 389	if (inode->i_private)
 390		file->private_data = inode->i_private;
 391	return 0;
 392}
 393EXPORT_SYMBOL(simple_open);
 394
 395int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 396{
 397	struct inode *inode = d_inode(old_dentry);
 398
 399	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
 400	inc_nlink(inode);
 401	ihold(inode);
 402	dget(dentry);
 403	d_instantiate(dentry, inode);
 404	return 0;
 405}
 406EXPORT_SYMBOL(simple_link);
 407
 408int simple_empty(struct dentry *dentry)
 409{
 410	struct dentry *child;
 411	int ret = 0;
 412
 413	spin_lock(&dentry->d_lock);
 414	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
 415		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 416		if (simple_positive(child)) {
 417			spin_unlock(&child->d_lock);
 418			goto out;
 419		}
 420		spin_unlock(&child->d_lock);
 421	}
 422	ret = 1;
 423out:
 424	spin_unlock(&dentry->d_lock);
 425	return ret;
 426}
 427EXPORT_SYMBOL(simple_empty);
 428
 429int simple_unlink(struct inode *dir, struct dentry *dentry)
 430{
 431	struct inode *inode = d_inode(dentry);
 432
 433	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
 434	drop_nlink(inode);
 435	dput(dentry);
 436	return 0;
 437}
 438EXPORT_SYMBOL(simple_unlink);
 439
 440int simple_rmdir(struct inode *dir, struct dentry *dentry)
 441{
 442	if (!simple_empty(dentry))
 443		return -ENOTEMPTY;
 444
 445	drop_nlink(d_inode(dentry));
 446	simple_unlink(dir, dentry);
 447	drop_nlink(dir);
 448	return 0;
 449}
 450EXPORT_SYMBOL(simple_rmdir);
 451
 452int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
 453			   struct inode *new_dir, struct dentry *new_dentry)
 454{
 455	bool old_is_dir = d_is_dir(old_dentry);
 456	bool new_is_dir = d_is_dir(new_dentry);
 457
 458	if (old_dir != new_dir && old_is_dir != new_is_dir) {
 459		if (old_is_dir) {
 460			drop_nlink(old_dir);
 461			inc_nlink(new_dir);
 462		} else {
 463			drop_nlink(new_dir);
 464			inc_nlink(old_dir);
 465		}
 466	}
 467	old_dir->i_ctime = old_dir->i_mtime =
 468	new_dir->i_ctime = new_dir->i_mtime =
 469	d_inode(old_dentry)->i_ctime =
 470	d_inode(new_dentry)->i_ctime = current_time(old_dir);
 471
 472	return 0;
 473}
 474EXPORT_SYMBOL_GPL(simple_rename_exchange);
 475
 476int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 477		  struct dentry *old_dentry, struct inode *new_dir,
 478		  struct dentry *new_dentry, unsigned int flags)
 479{
 480	struct inode *inode = d_inode(old_dentry);
 481	int they_are_dirs = d_is_dir(old_dentry);
 482
 483	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
 484		return -EINVAL;
 485
 486	if (flags & RENAME_EXCHANGE)
 487		return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
 488
 489	if (!simple_empty(new_dentry))
 490		return -ENOTEMPTY;
 491
 492	if (d_really_is_positive(new_dentry)) {
 493		simple_unlink(new_dir, new_dentry);
 494		if (they_are_dirs) {
 495			drop_nlink(d_inode(new_dentry));
 496			drop_nlink(old_dir);
 497		}
 498	} else if (they_are_dirs) {
 499		drop_nlink(old_dir);
 500		inc_nlink(new_dir);
 501	}
 502
 503	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 504		new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
 505
 506	return 0;
 507}
 508EXPORT_SYMBOL(simple_rename);
 509
 510/**
 511 * simple_setattr - setattr for simple filesystem
 512 * @mnt_userns: user namespace of the target mount
 513 * @dentry: dentry
 514 * @iattr: iattr structure
 515 *
 516 * Returns 0 on success, -error on failure.
 517 *
 518 * simple_setattr is a simple ->setattr implementation without a proper
 519 * implementation of size changes.
 520 *
 521 * It can either be used for in-memory filesystems or special files
 522 * on simple regular filesystems.  Anything that needs to change on-disk
 523 * or wire state on size changes needs its own setattr method.
 524 */
 525int simple_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 526		   struct iattr *iattr)
 527{
 528	struct inode *inode = d_inode(dentry);
 529	int error;
 530
 531	error = setattr_prepare(mnt_userns, dentry, iattr);
 532	if (error)
 533		return error;
 534
 535	if (iattr->ia_valid & ATTR_SIZE)
 536		truncate_setsize(inode, iattr->ia_size);
 537	setattr_copy(mnt_userns, inode, iattr);
 538	mark_inode_dirty(inode);
 539	return 0;
 540}
 541EXPORT_SYMBOL(simple_setattr);
 542
 543static int simple_read_folio(struct file *file, struct folio *folio)
 544{
 545	folio_zero_range(folio, 0, folio_size(folio));
 546	flush_dcache_folio(folio);
 547	folio_mark_uptodate(folio);
 548	folio_unlock(folio);
 549	return 0;
 550}
 551
 552int simple_write_begin(struct file *file, struct address_space *mapping,
 553			loff_t pos, unsigned len,
 554			struct page **pagep, void **fsdata)
 555{
 556	struct page *page;
 557	pgoff_t index;
 558
 559	index = pos >> PAGE_SHIFT;
 560
 561	page = grab_cache_page_write_begin(mapping, index);
 562	if (!page)
 563		return -ENOMEM;
 564
 565	*pagep = page;
 566
 567	if (!PageUptodate(page) && (len != PAGE_SIZE)) {
 568		unsigned from = pos & (PAGE_SIZE - 1);
 569
 570		zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
 571	}
 572	return 0;
 573}
 574EXPORT_SYMBOL(simple_write_begin);
 575
 576/**
 577 * simple_write_end - .write_end helper for non-block-device FSes
 578 * @file: See .write_end of address_space_operations
 579 * @mapping: 		"
 580 * @pos: 		"
 581 * @len: 		"
 582 * @copied: 		"
 583 * @page: 		"
 584 * @fsdata: 		"
 585 *
 586 * simple_write_end does the minimum needed for updating a page after writing is
 587 * done. It has the same API signature as the .write_end of
 588 * address_space_operations vector. So it can just be set onto .write_end for
 589 * FSes that don't need any other processing. i_mutex is assumed to be held.
 590 * Block based filesystems should use generic_write_end().
 591 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
 592 * is not called, so a filesystem that actually does store data in .write_inode
 593 * should extend on what's done here with a call to mark_inode_dirty() in the
 594 * case that i_size has changed.
 595 *
 596 * Use *ONLY* with simple_read_folio()
 597 */
 598static int simple_write_end(struct file *file, struct address_space *mapping,
 599			loff_t pos, unsigned len, unsigned copied,
 600			struct page *page, void *fsdata)
 601{
 602	struct inode *inode = page->mapping->host;
 603	loff_t last_pos = pos + copied;
 604
 605	/* zero the stale part of the page if we did a short copy */
 606	if (!PageUptodate(page)) {
 607		if (copied < len) {
 608			unsigned from = pos & (PAGE_SIZE - 1);
 609
 610			zero_user(page, from + copied, len - copied);
 611		}
 612		SetPageUptodate(page);
 613	}
 614	/*
 615	 * No need to use i_size_read() here, the i_size
 616	 * cannot change under us because we hold the i_mutex.
 617	 */
 618	if (last_pos > inode->i_size)
 619		i_size_write(inode, last_pos);
 620
 621	set_page_dirty(page);
 622	unlock_page(page);
 623	put_page(page);
 624
 625	return copied;
 626}
 627
 628/*
 629 * Provides ramfs-style behavior: data in the pagecache, but no writeback.
 630 */
 631const struct address_space_operations ram_aops = {
 632	.read_folio	= simple_read_folio,
 633	.write_begin	= simple_write_begin,
 634	.write_end	= simple_write_end,
 635	.dirty_folio	= noop_dirty_folio,
 636};
 637EXPORT_SYMBOL(ram_aops);
 638
 639/*
 640 * the inodes created here are not hashed. If you use iunique to generate
 641 * unique inode values later for this filesystem, then you must take care
 642 * to pass it an appropriate max_reserved value to avoid collisions.
 643 */
 644int simple_fill_super(struct super_block *s, unsigned long magic,
 645		      const struct tree_descr *files)
 646{
 647	struct inode *inode;
 648	struct dentry *root;
 649	struct dentry *dentry;
 650	int i;
 651
 652	s->s_blocksize = PAGE_SIZE;
 653	s->s_blocksize_bits = PAGE_SHIFT;
 654	s->s_magic = magic;
 655	s->s_op = &simple_super_operations;
 656	s->s_time_gran = 1;
 657
 658	inode = new_inode(s);
 659	if (!inode)
 660		return -ENOMEM;
 661	/*
 662	 * because the root inode is 1, the files array must not contain an
 663	 * entry at index 1
 664	 */
 665	inode->i_ino = 1;
 666	inode->i_mode = S_IFDIR | 0755;
 667	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 668	inode->i_op = &simple_dir_inode_operations;
 669	inode->i_fop = &simple_dir_operations;
 670	set_nlink(inode, 2);
 671	root = d_make_root(inode);
 672	if (!root)
 673		return -ENOMEM;
 674	for (i = 0; !files->name || files->name[0]; i++, files++) {
 675		if (!files->name)
 676			continue;
 677
 678		/* warn if it tries to conflict with the root inode */
 679		if (unlikely(i == 1))
 680			printk(KERN_WARNING "%s: %s passed in a files array"
 681				"with an index of 1!\n", __func__,
 682				s->s_type->name);
 683
 684		dentry = d_alloc_name(root, files->name);
 685		if (!dentry)
 686			goto out;
 687		inode = new_inode(s);
 688		if (!inode) {
 689			dput(dentry);
 690			goto out;
 691		}
 692		inode->i_mode = S_IFREG | files->mode;
 693		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 694		inode->i_fop = files->ops;
 695		inode->i_ino = i;
 696		d_add(dentry, inode);
 697	}
 698	s->s_root = root;
 699	return 0;
 700out:
 701	d_genocide(root);
 702	shrink_dcache_parent(root);
 703	dput(root);
 704	return -ENOMEM;
 705}
 706EXPORT_SYMBOL(simple_fill_super);
 707
 708static DEFINE_SPINLOCK(pin_fs_lock);
 709
 710int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
 711{
 712	struct vfsmount *mnt = NULL;
 713	spin_lock(&pin_fs_lock);
 714	if (unlikely(!*mount)) {
 715		spin_unlock(&pin_fs_lock);
 716		mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
 717		if (IS_ERR(mnt))
 718			return PTR_ERR(mnt);
 719		spin_lock(&pin_fs_lock);
 720		if (!*mount)
 721			*mount = mnt;
 722	}
 723	mntget(*mount);
 724	++*count;
 725	spin_unlock(&pin_fs_lock);
 726	mntput(mnt);
 727	return 0;
 728}
 729EXPORT_SYMBOL(simple_pin_fs);
 730
 731void simple_release_fs(struct vfsmount **mount, int *count)
 732{
 733	struct vfsmount *mnt;
 734	spin_lock(&pin_fs_lock);
 735	mnt = *mount;
 736	if (!--*count)
 737		*mount = NULL;
 738	spin_unlock(&pin_fs_lock);
 739	mntput(mnt);
 740}
 741EXPORT_SYMBOL(simple_release_fs);
 742
 743/**
 744 * simple_read_from_buffer - copy data from the buffer to user space
 745 * @to: the user space buffer to read to
 746 * @count: the maximum number of bytes to read
 747 * @ppos: the current position in the buffer
 748 * @from: the buffer to read from
 749 * @available: the size of the buffer
 750 *
 751 * The simple_read_from_buffer() function reads up to @count bytes from the
 752 * buffer @from at offset @ppos into the user space address starting at @to.
 753 *
 754 * On success, the number of bytes read is returned and the offset @ppos is
 755 * advanced by this number, or negative value is returned on error.
 756 **/
 757ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 758				const void *from, size_t available)
 759{
 760	loff_t pos = *ppos;
 761	size_t ret;
 762
 763	if (pos < 0)
 764		return -EINVAL;
 765	if (pos >= available || !count)
 766		return 0;
 767	if (count > available - pos)
 768		count = available - pos;
 769	ret = copy_to_user(to, from + pos, count);
 770	if (ret == count)
 771		return -EFAULT;
 772	count -= ret;
 773	*ppos = pos + count;
 774	return count;
 775}
 776EXPORT_SYMBOL(simple_read_from_buffer);
 777
 778/**
 779 * simple_write_to_buffer - copy data from user space to the buffer
 780 * @to: the buffer to write to
 781 * @available: the size of the buffer
 782 * @ppos: the current position in the buffer
 783 * @from: the user space buffer to read from
 784 * @count: the maximum number of bytes to read
 785 *
 786 * The simple_write_to_buffer() function reads up to @count bytes from the user
 787 * space address starting at @from into the buffer @to at offset @ppos.
 788 *
 789 * On success, the number of bytes written is returned and the offset @ppos is
 790 * advanced by this number, or negative value is returned on error.
 791 **/
 792ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
 793		const void __user *from, size_t count)
 794{
 795	loff_t pos = *ppos;
 796	size_t res;
 797
 798	if (pos < 0)
 799		return -EINVAL;
 800	if (pos >= available || !count)
 801		return 0;
 802	if (count > available - pos)
 803		count = available - pos;
 804	res = copy_from_user(to + pos, from, count);
 805	if (res == count)
 806		return -EFAULT;
 807	count -= res;
 808	*ppos = pos + count;
 809	return count;
 810}
 811EXPORT_SYMBOL(simple_write_to_buffer);
 812
 813/**
 814 * memory_read_from_buffer - copy data from the buffer
 815 * @to: the kernel space buffer to read to
 816 * @count: the maximum number of bytes to read
 817 * @ppos: the current position in the buffer
 818 * @from: the buffer to read from
 819 * @available: the size of the buffer
 820 *
 821 * The memory_read_from_buffer() function reads up to @count bytes from the
 822 * buffer @from at offset @ppos into the kernel space address starting at @to.
 823 *
 824 * On success, the number of bytes read is returned and the offset @ppos is
 825 * advanced by this number, or negative value is returned on error.
 826 **/
 827ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
 828				const void *from, size_t available)
 829{
 830	loff_t pos = *ppos;
 831
 832	if (pos < 0)
 833		return -EINVAL;
 834	if (pos >= available)
 835		return 0;
 836	if (count > available - pos)
 837		count = available - pos;
 838	memcpy(to, from + pos, count);
 839	*ppos = pos + count;
 840
 841	return count;
 842}
 843EXPORT_SYMBOL(memory_read_from_buffer);
 844
 845/*
 846 * Transaction based IO.
 847 * The file expects a single write which triggers the transaction, and then
 848 * possibly a read which collects the result - which is stored in a
 849 * file-local buffer.
 850 */
 851
 852void simple_transaction_set(struct file *file, size_t n)
 853{
 854	struct simple_transaction_argresp *ar = file->private_data;
 855
 856	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
 857
 858	/*
 859	 * The barrier ensures that ar->size will really remain zero until
 860	 * ar->data is ready for reading.
 861	 */
 862	smp_mb();
 863	ar->size = n;
 864}
 865EXPORT_SYMBOL(simple_transaction_set);
 866
 867char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 868{
 869	struct simple_transaction_argresp *ar;
 870	static DEFINE_SPINLOCK(simple_transaction_lock);
 871
 872	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 873		return ERR_PTR(-EFBIG);
 874
 875	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 876	if (!ar)
 877		return ERR_PTR(-ENOMEM);
 878
 879	spin_lock(&simple_transaction_lock);
 880
 881	/* only one write allowed per open */
 882	if (file->private_data) {
 883		spin_unlock(&simple_transaction_lock);
 884		free_page((unsigned long)ar);
 885		return ERR_PTR(-EBUSY);
 886	}
 887
 888	file->private_data = ar;
 889
 890	spin_unlock(&simple_transaction_lock);
 891
 892	if (copy_from_user(ar->data, buf, size))
 893		return ERR_PTR(-EFAULT);
 894
 895	return ar->data;
 896}
 897EXPORT_SYMBOL(simple_transaction_get);
 898
 899ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 900{
 901	struct simple_transaction_argresp *ar = file->private_data;
 902
 903	if (!ar)
 904		return 0;
 905	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 906}
 907EXPORT_SYMBOL(simple_transaction_read);
 908
 909int simple_transaction_release(struct inode *inode, struct file *file)
 910{
 911	free_page((unsigned long)file->private_data);
 912	return 0;
 913}
 914EXPORT_SYMBOL(simple_transaction_release);
 915
 916/* Simple attribute files */
 917
 918struct simple_attr {
 919	int (*get)(void *, u64 *);
 920	int (*set)(void *, u64);
 921	char get_buf[24];	/* enough to store a u64 and "\n\0" */
 922	char set_buf[24];
 923	void *data;
 924	const char *fmt;	/* format for read operation */
 925	struct mutex mutex;	/* protects access to these buffers */
 926};
 927
 928/* simple_attr_open is called by an actual attribute open file operation
 929 * to set the attribute specific access operations. */
 930int simple_attr_open(struct inode *inode, struct file *file,
 931		     int (*get)(void *, u64 *), int (*set)(void *, u64),
 932		     const char *fmt)
 933{
 934	struct simple_attr *attr;
 935
 936	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
 937	if (!attr)
 938		return -ENOMEM;
 939
 940	attr->get = get;
 941	attr->set = set;
 942	attr->data = inode->i_private;
 943	attr->fmt = fmt;
 944	mutex_init(&attr->mutex);
 945
 946	file->private_data = attr;
 947
 948	return nonseekable_open(inode, file);
 949}
 950EXPORT_SYMBOL_GPL(simple_attr_open);
 951
 952int simple_attr_release(struct inode *inode, struct file *file)
 953{
 954	kfree(file->private_data);
 955	return 0;
 956}
 957EXPORT_SYMBOL_GPL(simple_attr_release);	/* GPL-only?  This?  Really? */
 958
 959/* read from the buffer that is filled with the get function */
 960ssize_t simple_attr_read(struct file *file, char __user *buf,
 961			 size_t len, loff_t *ppos)
 962{
 963	struct simple_attr *attr;
 964	size_t size;
 965	ssize_t ret;
 966
 967	attr = file->private_data;
 968
 969	if (!attr->get)
 970		return -EACCES;
 971
 972	ret = mutex_lock_interruptible(&attr->mutex);
 973	if (ret)
 974		return ret;
 975
 976	if (*ppos && attr->get_buf[0]) {
 977		/* continued read */
 978		size = strlen(attr->get_buf);
 979	} else {
 980		/* first read */
 981		u64 val;
 982		ret = attr->get(attr->data, &val);
 983		if (ret)
 984			goto out;
 985
 986		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 987				 attr->fmt, (unsigned long long)val);
 988	}
 989
 990	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 991out:
 992	mutex_unlock(&attr->mutex);
 993	return ret;
 994}
 995EXPORT_SYMBOL_GPL(simple_attr_read);
 996
 997/* interpret the buffer as a number to call the set function with */
 998static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
 999			  size_t len, loff_t *ppos, bool is_signed)
1000{
1001	struct simple_attr *attr;
1002	unsigned long long val;
1003	size_t size;
1004	ssize_t ret;
1005
1006	attr = file->private_data;
1007	if (!attr->set)
1008		return -EACCES;
1009
1010	ret = mutex_lock_interruptible(&attr->mutex);
1011	if (ret)
1012		return ret;
1013
1014	ret = -EFAULT;
1015	size = min(sizeof(attr->set_buf) - 1, len);
1016	if (copy_from_user(attr->set_buf, buf, size))
1017		goto out;
1018
1019	attr->set_buf[size] = '\0';
1020	if (is_signed)
1021		ret = kstrtoll(attr->set_buf, 0, &val);
1022	else
1023		ret = kstrtoull(attr->set_buf, 0, &val);
1024	if (ret)
1025		goto out;
1026	ret = attr->set(attr->data, val);
1027	if (ret == 0)
1028		ret = len; /* on success, claim we got the whole input */
1029out:
1030	mutex_unlock(&attr->mutex);
1031	return ret;
1032}
1033
1034ssize_t simple_attr_write(struct file *file, const char __user *buf,
1035			  size_t len, loff_t *ppos)
1036{
1037	return simple_attr_write_xsigned(file, buf, len, ppos, false);
1038}
1039EXPORT_SYMBOL_GPL(simple_attr_write);
1040
1041ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
1042			  size_t len, loff_t *ppos)
1043{
1044	return simple_attr_write_xsigned(file, buf, len, ppos, true);
1045}
1046EXPORT_SYMBOL_GPL(simple_attr_write_signed);
1047
1048/**
1049 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
1050 * @sb:		filesystem to do the file handle conversion on
1051 * @fid:	file handle to convert
1052 * @fh_len:	length of the file handle in bytes
1053 * @fh_type:	type of file handle
1054 * @get_inode:	filesystem callback to retrieve inode
1055 *
1056 * This function decodes @fid as long as it has one of the well-known
1057 * Linux filehandle types and calls @get_inode on it to retrieve the
1058 * inode for the object specified in the file handle.
1059 */
1060struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1061		int fh_len, int fh_type, struct inode *(*get_inode)
1062			(struct super_block *sb, u64 ino, u32 gen))
1063{
1064	struct inode *inode = NULL;
1065
1066	if (fh_len < 2)
1067		return NULL;
1068
1069	switch (fh_type) {
1070	case FILEID_INO32_GEN:
1071	case FILEID_INO32_GEN_PARENT:
1072		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1073		break;
1074	}
1075
1076	return d_obtain_alias(inode);
1077}
1078EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1079
1080/**
1081 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1082 * @sb:		filesystem to do the file handle conversion on
1083 * @fid:	file handle to convert
1084 * @fh_len:	length of the file handle in bytes
1085 * @fh_type:	type of file handle
1086 * @get_inode:	filesystem callback to retrieve inode
1087 *
1088 * This function decodes @fid as long as it has one of the well-known
1089 * Linux filehandle types and calls @get_inode on it to retrieve the
1090 * inode for the _parent_ object specified in the file handle if it
1091 * is specified in the file handle, or NULL otherwise.
1092 */
1093struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1094		int fh_len, int fh_type, struct inode *(*get_inode)
1095			(struct super_block *sb, u64 ino, u32 gen))
1096{
1097	struct inode *inode = NULL;
1098
1099	if (fh_len <= 2)
1100		return NULL;
1101
1102	switch (fh_type) {
1103	case FILEID_INO32_GEN_PARENT:
1104		inode = get_inode(sb, fid->i32.parent_ino,
1105				  (fh_len > 3 ? fid->i32.parent_gen : 0));
1106		break;
1107	}
1108
1109	return d_obtain_alias(inode);
1110}
1111EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1112
1113/**
1114 * __generic_file_fsync - generic fsync implementation for simple filesystems
1115 *
1116 * @file:	file to synchronize
1117 * @start:	start offset in bytes
1118 * @end:	end offset in bytes (inclusive)
1119 * @datasync:	only synchronize essential metadata if true
1120 *
1121 * This is a generic implementation of the fsync method for simple
1122 * filesystems which track all non-inode metadata in the buffers list
1123 * hanging off the address_space structure.
1124 */
1125int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1126				 int datasync)
1127{
1128	struct inode *inode = file->f_mapping->host;
1129	int err;
1130	int ret;
1131
1132	err = file_write_and_wait_range(file, start, end);
1133	if (err)
1134		return err;
1135
1136	inode_lock(inode);
1137	ret = sync_mapping_buffers(inode->i_mapping);
1138	if (!(inode->i_state & I_DIRTY_ALL))
1139		goto out;
1140	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1141		goto out;
1142
1143	err = sync_inode_metadata(inode, 1);
1144	if (ret == 0)
1145		ret = err;
1146
1147out:
1148	inode_unlock(inode);
1149	/* check and advance again to catch errors after syncing out buffers */
1150	err = file_check_and_advance_wb_err(file);
1151	if (ret == 0)
1152		ret = err;
1153	return ret;
1154}
1155EXPORT_SYMBOL(__generic_file_fsync);
1156
1157/**
1158 * generic_file_fsync - generic fsync implementation for simple filesystems
1159 *			with flush
1160 * @file:	file to synchronize
1161 * @start:	start offset in bytes
1162 * @end:	end offset in bytes (inclusive)
1163 * @datasync:	only synchronize essential metadata if true
1164 *
1165 */
1166
1167int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1168		       int datasync)
1169{
1170	struct inode *inode = file->f_mapping->host;
1171	int err;
1172
1173	err = __generic_file_fsync(file, start, end, datasync);
1174	if (err)
1175		return err;
1176	return blkdev_issue_flush(inode->i_sb->s_bdev);
1177}
1178EXPORT_SYMBOL(generic_file_fsync);
1179
1180/**
1181 * generic_check_addressable - Check addressability of file system
1182 * @blocksize_bits:	log of file system block size
1183 * @num_blocks:		number of blocks in file system
1184 *
1185 * Determine whether a file system with @num_blocks blocks (and a
1186 * block size of 2**@blocksize_bits) is addressable by the sector_t
1187 * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
1188 */
1189int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1190{
1191	u64 last_fs_block = num_blocks - 1;
1192	u64 last_fs_page =
1193		last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1194
1195	if (unlikely(num_blocks == 0))
1196		return 0;
1197
1198	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1199		return -EINVAL;
1200
1201	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1202	    (last_fs_page > (pgoff_t)(~0ULL))) {
1203		return -EFBIG;
1204	}
1205	return 0;
1206}
1207EXPORT_SYMBOL(generic_check_addressable);
1208
1209/*
1210 * No-op implementation of ->fsync for in-memory filesystems.
1211 */
1212int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1213{
1214	return 0;
1215}
1216EXPORT_SYMBOL(noop_fsync);
1217
 
 
 
 
 
 
 
 
 
 
 
1218ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1219{
1220	/*
1221	 * iomap based filesystems support direct I/O without need for
1222	 * this callback. However, it still needs to be set in
1223	 * inode->a_ops so that open/fcntl know that direct I/O is
1224	 * generally supported.
1225	 */
1226	return -EINVAL;
1227}
1228EXPORT_SYMBOL_GPL(noop_direct_IO);
1229
1230/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1231void kfree_link(void *p)
1232{
1233	kfree(p);
1234}
1235EXPORT_SYMBOL(kfree_link);
1236
1237struct inode *alloc_anon_inode(struct super_block *s)
1238{
1239	static const struct address_space_operations anon_aops = {
1240		.dirty_folio	= noop_dirty_folio,
1241	};
1242	struct inode *inode = new_inode_pseudo(s);
1243
1244	if (!inode)
1245		return ERR_PTR(-ENOMEM);
1246
1247	inode->i_ino = get_next_ino();
1248	inode->i_mapping->a_ops = &anon_aops;
1249
1250	/*
1251	 * Mark the inode dirty from the very beginning,
1252	 * that way it will never be moved to the dirty
1253	 * list because mark_inode_dirty() will think
1254	 * that it already _is_ on the dirty list.
1255	 */
1256	inode->i_state = I_DIRTY;
1257	inode->i_mode = S_IRUSR | S_IWUSR;
1258	inode->i_uid = current_fsuid();
1259	inode->i_gid = current_fsgid();
1260	inode->i_flags |= S_PRIVATE;
1261	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1262	return inode;
1263}
1264EXPORT_SYMBOL(alloc_anon_inode);
1265
1266/**
1267 * simple_nosetlease - generic helper for prohibiting leases
1268 * @filp: file pointer
1269 * @arg: type of lease to obtain
1270 * @flp: new lease supplied for insertion
1271 * @priv: private data for lm_setup operation
1272 *
1273 * Generic helper for filesystems that do not wish to allow leases to be set.
1274 * All arguments are ignored and it just returns -EINVAL.
1275 */
1276int
1277simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1278		  void **priv)
1279{
1280	return -EINVAL;
1281}
1282EXPORT_SYMBOL(simple_nosetlease);
1283
1284/**
1285 * simple_get_link - generic helper to get the target of "fast" symlinks
1286 * @dentry: not used here
1287 * @inode: the symlink inode
1288 * @done: not used here
1289 *
1290 * Generic helper for filesystems to use for symlink inodes where a pointer to
1291 * the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
1292 * since as an optimization the path lookup code uses any non-NULL ->i_link
1293 * directly, without calling ->get_link().  But ->get_link() still must be set,
1294 * to mark the inode_operations as being for a symlink.
1295 *
1296 * Return: the symlink target
1297 */
1298const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1299			    struct delayed_call *done)
1300{
1301	return inode->i_link;
1302}
1303EXPORT_SYMBOL(simple_get_link);
1304
1305const struct inode_operations simple_symlink_inode_operations = {
1306	.get_link = simple_get_link,
1307};
1308EXPORT_SYMBOL(simple_symlink_inode_operations);
1309
1310/*
1311 * Operations for a permanently empty directory.
1312 */
1313static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1314{
1315	return ERR_PTR(-ENOENT);
1316}
1317
1318static int empty_dir_getattr(struct user_namespace *mnt_userns,
1319			     const struct path *path, struct kstat *stat,
1320			     u32 request_mask, unsigned int query_flags)
1321{
1322	struct inode *inode = d_inode(path->dentry);
1323	generic_fillattr(&init_user_ns, inode, stat);
1324	return 0;
1325}
1326
1327static int empty_dir_setattr(struct user_namespace *mnt_userns,
1328			     struct dentry *dentry, struct iattr *attr)
1329{
1330	return -EPERM;
1331}
1332
1333static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1334{
1335	return -EOPNOTSUPP;
1336}
1337
1338static const struct inode_operations empty_dir_inode_operations = {
1339	.lookup		= empty_dir_lookup,
1340	.permission	= generic_permission,
1341	.setattr	= empty_dir_setattr,
1342	.getattr	= empty_dir_getattr,
1343	.listxattr	= empty_dir_listxattr,
1344};
1345
1346static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1347{
1348	/* An empty directory has two entries . and .. at offsets 0 and 1 */
1349	return generic_file_llseek_size(file, offset, whence, 2, 2);
1350}
1351
1352static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1353{
1354	dir_emit_dots(file, ctx);
1355	return 0;
1356}
1357
1358static const struct file_operations empty_dir_operations = {
1359	.llseek		= empty_dir_llseek,
1360	.read		= generic_read_dir,
1361	.iterate_shared	= empty_dir_readdir,
1362	.fsync		= noop_fsync,
1363};
1364
1365
1366void make_empty_dir_inode(struct inode *inode)
1367{
1368	set_nlink(inode, 2);
1369	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1370	inode->i_uid = GLOBAL_ROOT_UID;
1371	inode->i_gid = GLOBAL_ROOT_GID;
1372	inode->i_rdev = 0;
1373	inode->i_size = 0;
1374	inode->i_blkbits = PAGE_SHIFT;
1375	inode->i_blocks = 0;
1376
1377	inode->i_op = &empty_dir_inode_operations;
1378	inode->i_opflags &= ~IOP_XATTR;
1379	inode->i_fop = &empty_dir_operations;
1380}
1381
1382bool is_empty_dir_inode(struct inode *inode)
1383{
1384	return (inode->i_fop == &empty_dir_operations) &&
1385		(inode->i_op == &empty_dir_inode_operations);
1386}
1387
1388#if IS_ENABLED(CONFIG_UNICODE)
1389/*
1390 * Determine if the name of a dentry should be casefolded.
1391 *
1392 * Return: if names will need casefolding
1393 */
1394static bool needs_casefold(const struct inode *dir)
1395{
1396	return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
1397}
1398
1399/**
1400 * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1401 * @dentry:	dentry whose name we are checking against
1402 * @len:	len of name of dentry
1403 * @str:	str pointer to name of dentry
1404 * @name:	Name to compare against
1405 *
1406 * Return: 0 if names match, 1 if mismatch, or -ERRNO
1407 */
1408static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1409				const char *str, const struct qstr *name)
1410{
1411	const struct dentry *parent = READ_ONCE(dentry->d_parent);
1412	const struct inode *dir = READ_ONCE(parent->d_inode);
1413	const struct super_block *sb = dentry->d_sb;
1414	const struct unicode_map *um = sb->s_encoding;
1415	struct qstr qstr = QSTR_INIT(str, len);
1416	char strbuf[DNAME_INLINE_LEN];
1417	int ret;
1418
1419	if (!dir || !needs_casefold(dir))
1420		goto fallback;
1421	/*
1422	 * If the dentry name is stored in-line, then it may be concurrently
1423	 * modified by a rename.  If this happens, the VFS will eventually retry
1424	 * the lookup, so it doesn't matter what ->d_compare() returns.
1425	 * However, it's unsafe to call utf8_strncasecmp() with an unstable
1426	 * string.  Therefore, we have to copy the name into a temporary buffer.
1427	 */
1428	if (len <= DNAME_INLINE_LEN - 1) {
1429		memcpy(strbuf, str, len);
1430		strbuf[len] = 0;
1431		qstr.name = strbuf;
1432		/* prevent compiler from optimizing out the temporary buffer */
1433		barrier();
1434	}
1435	ret = utf8_strncasecmp(um, name, &qstr);
1436	if (ret >= 0)
1437		return ret;
1438
1439	if (sb_has_strict_encoding(sb))
1440		return -EINVAL;
1441fallback:
1442	if (len != name->len)
1443		return 1;
1444	return !!memcmp(str, name->name, len);
1445}
1446
1447/**
1448 * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1449 * @dentry:	dentry of the parent directory
1450 * @str:	qstr of name whose hash we should fill in
1451 *
1452 * Return: 0 if hash was successful or unchanged, and -EINVAL on error
1453 */
1454static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1455{
1456	const struct inode *dir = READ_ONCE(dentry->d_inode);
1457	struct super_block *sb = dentry->d_sb;
1458	const struct unicode_map *um = sb->s_encoding;
1459	int ret = 0;
1460
1461	if (!dir || !needs_casefold(dir))
1462		return 0;
1463
1464	ret = utf8_casefold_hash(um, dentry, str);
1465	if (ret < 0 && sb_has_strict_encoding(sb))
1466		return -EINVAL;
1467	return 0;
1468}
1469
1470static const struct dentry_operations generic_ci_dentry_ops = {
1471	.d_hash = generic_ci_d_hash,
1472	.d_compare = generic_ci_d_compare,
1473};
1474#endif
1475
1476#ifdef CONFIG_FS_ENCRYPTION
1477static const struct dentry_operations generic_encrypted_dentry_ops = {
1478	.d_revalidate = fscrypt_d_revalidate,
1479};
1480#endif
1481
1482#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1483static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
1484	.d_hash = generic_ci_d_hash,
1485	.d_compare = generic_ci_d_compare,
1486	.d_revalidate = fscrypt_d_revalidate,
1487};
1488#endif
1489
1490/**
1491 * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
1492 * @dentry:	dentry to set ops on
1493 *
1494 * Casefolded directories need d_hash and d_compare set, so that the dentries
1495 * contained in them are handled case-insensitively.  Note that these operations
1496 * are needed on the parent directory rather than on the dentries in it, and
1497 * while the casefolding flag can be toggled on and off on an empty directory,
1498 * dentry_operations can't be changed later.  As a result, if the filesystem has
1499 * casefolding support enabled at all, we have to give all dentries the
1500 * casefolding operations even if their inode doesn't have the casefolding flag
1501 * currently (and thus the casefolding ops would be no-ops for now).
1502 *
1503 * Encryption works differently in that the only dentry operation it needs is
1504 * d_revalidate, which it only needs on dentries that have the no-key name flag.
1505 * The no-key flag can't be set "later", so we don't have to worry about that.
1506 *
1507 * Finally, to maximize compatibility with overlayfs (which isn't compatible
1508 * with certain dentry operations) and to avoid taking an unnecessary
1509 * performance hit, we use custom dentry_operations for each possible
1510 * combination rather than always installing all operations.
1511 */
1512void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
1513{
1514#ifdef CONFIG_FS_ENCRYPTION
1515	bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
1516#endif
1517#if IS_ENABLED(CONFIG_UNICODE)
1518	bool needs_ci_ops = dentry->d_sb->s_encoding;
1519#endif
1520#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1521	if (needs_encrypt_ops && needs_ci_ops) {
1522		d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
1523		return;
1524	}
1525#endif
1526#ifdef CONFIG_FS_ENCRYPTION
1527	if (needs_encrypt_ops) {
1528		d_set_d_op(dentry, &generic_encrypted_dentry_ops);
1529		return;
1530	}
1531#endif
1532#if IS_ENABLED(CONFIG_UNICODE)
1533	if (needs_ci_ops) {
1534		d_set_d_op(dentry, &generic_ci_dentry_ops);
1535		return;
1536	}
1537#endif
1538}
1539EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
1540
1541/**
1542 * inode_maybe_inc_iversion - increments i_version
1543 * @inode: inode with the i_version that should be updated
1544 * @force: increment the counter even if it's not necessary?
1545 *
1546 * Every time the inode is modified, the i_version field must be seen to have
1547 * changed by any observer.
1548 *
1549 * If "force" is set or the QUERIED flag is set, then ensure that we increment
1550 * the value, and clear the queried flag.
1551 *
1552 * In the common case where neither is set, then we can return "false" without
1553 * updating i_version.
1554 *
1555 * If this function returns false, and no other metadata has changed, then we
1556 * can avoid logging the metadata.
1557 */
1558bool inode_maybe_inc_iversion(struct inode *inode, bool force)
1559{
1560	u64 cur, new;
1561
1562	/*
1563	 * The i_version field is not strictly ordered with any other inode
1564	 * information, but the legacy inode_inc_iversion code used a spinlock
1565	 * to serialize increments.
1566	 *
1567	 * Here, we add full memory barriers to ensure that any de-facto
1568	 * ordering with other info is preserved.
1569	 *
1570	 * This barrier pairs with the barrier in inode_query_iversion()
1571	 */
1572	smp_mb();
1573	cur = inode_peek_iversion_raw(inode);
1574	do {
1575		/* If flag is clear then we needn't do anything */
1576		if (!force && !(cur & I_VERSION_QUERIED))
1577			return false;
1578
1579		/* Since lowest bit is flag, add 2 to avoid it */
1580		new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
1581	} while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
1582	return true;
1583}
1584EXPORT_SYMBOL(inode_maybe_inc_iversion);