xattr.c 25.6 KB
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 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021
/*
 * linux/fs/reiserfs/xattr.c
 *
 * Copyright (c) 2002 by Jeff Mahoney, <jeffm@suse.com>
 *
 */

/*
 * In order to implement EA/ACLs in a clean, backwards compatible manner,
 * they are implemented as files in a "private" directory.
 * Each EA is in it's own file, with the directory layout like so (/ is assumed
 * to be relative to fs root). Inside the /.reiserfs_priv/xattrs directory,
 * directories named using the capital-hex form of the objectid and
 * generation number are used. Inside each directory are individual files
 * named with the name of the extended attribute.
 *
 * So, for objectid 12648430, we could have:
 * /.reiserfs_priv/xattrs/C0FFEE.0/system.posix_acl_access
 * /.reiserfs_priv/xattrs/C0FFEE.0/system.posix_acl_default
 * /.reiserfs_priv/xattrs/C0FFEE.0/user.Content-Type
 * .. or similar.
 *
 * The file contents are the text of the EA. The size is known based on the
 * stat data describing the file.
 *
 * In the case of system.posix_acl_access and system.posix_acl_default, since
 * these are special cases for filesystem ACLs, they are interpreted by the
 * kernel, in addition, they are negatively and positively cached and attached
 * to the inode so that unnecessary lookups are avoided.
 *
 * Locking works like so:
 * Directory components (xattr root, xattr dir) are protectd by their i_mutex.
 * The xattrs themselves are protected by the xattr_sem.
 */

#include "reiserfs.h"
#include <linux/capability.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/xattr.h>
#include "xattr.h"
#include "acl.h"
#include <asm/uaccess.h>
#include <net/checksum.h>
#include <linux/stat.h>
#include <linux/quotaops.h>
#include <linux/security.h>
#include <linux/posix_acl_xattr.h>

#define PRIVROOT_NAME ".reiserfs_priv"
#define XAROOT_NAME   "xattrs"


/* Helpers for inode ops. We do this so that we don't have all the VFS
 * overhead and also for proper i_mutex annotation.
 * dir->i_mutex must be held for all of them. */
#ifdef CONFIG_REISERFS_FS_XATTR
static int xattr_create(struct inode *dir, struct dentry *dentry, int mode)
{
	BUG_ON(!mutex_is_locked(&dir->i_mutex));
	return dir->i_op->create(dir, dentry, mode, true);
}
#endif

static int xattr_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
	BUG_ON(!mutex_is_locked(&dir->i_mutex));
	return dir->i_op->mkdir(dir, dentry, mode);
}

/* We use I_MUTEX_CHILD here to silence lockdep. It's safe because xattr
 * mutation ops aren't called during rename or splace, which are the
 * only other users of I_MUTEX_CHILD. It violates the ordering, but that's
 * better than allocating another subclass just for this code. */
static int xattr_unlink(struct inode *dir, struct dentry *dentry)
{
	int error;
	BUG_ON(!mutex_is_locked(&dir->i_mutex));

	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
	error = dir->i_op->unlink(dir, dentry);
	mutex_unlock(&dentry->d_inode->i_mutex);

	if (!error)
		d_delete(dentry);
	return error;
}

static int xattr_rmdir(struct inode *dir, struct dentry *dentry)
{
	int error;
	BUG_ON(!mutex_is_locked(&dir->i_mutex));

	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
	error = dir->i_op->rmdir(dir, dentry);
	if (!error)
		dentry->d_inode->i_flags |= S_DEAD;
	mutex_unlock(&dentry->d_inode->i_mutex);
	if (!error)
		d_delete(dentry);

	return error;
}

#define xattr_may_create(flags)	(!flags || flags & XATTR_CREATE)

static struct dentry *open_xa_root(struct super_block *sb, int flags)
{
	struct dentry *privroot = REISERFS_SB(sb)->priv_root;
	struct dentry *xaroot;
	if (!privroot->d_inode)
		return ERR_PTR(-ENODATA);

	mutex_lock_nested(&privroot->d_inode->i_mutex, I_MUTEX_XATTR);

	xaroot = dget(REISERFS_SB(sb)->xattr_root);
	if (!xaroot)
		xaroot = ERR_PTR(-ENODATA);
	else if (!xaroot->d_inode) {
		int err = -ENODATA;
		if (xattr_may_create(flags))
			err = xattr_mkdir(privroot->d_inode, xaroot, 0700);
		if (err) {
			dput(xaroot);
			xaroot = ERR_PTR(err);
		}
	}

	mutex_unlock(&privroot->d_inode->i_mutex);
	return xaroot;
}

static struct dentry *open_xa_dir(const struct inode *inode, int flags)
{
	struct dentry *xaroot, *xadir;
	char namebuf[17];

	xaroot = open_xa_root(inode->i_sb, flags);
	if (IS_ERR(xaroot))
		return xaroot;

	snprintf(namebuf, sizeof(namebuf), "%X.%X",
		 le32_to_cpu(INODE_PKEY(inode)->k_objectid),
		 inode->i_generation);

	mutex_lock_nested(&xaroot->d_inode->i_mutex, I_MUTEX_XATTR);

	xadir = lookup_one_len(namebuf, xaroot, strlen(namebuf));
	if (!IS_ERR(xadir) && !xadir->d_inode) {
		int err = -ENODATA;
		if (xattr_may_create(flags))
			err = xattr_mkdir(xaroot->d_inode, xadir, 0700);
		if (err) {
			dput(xadir);
			xadir = ERR_PTR(err);
		}
	}

	mutex_unlock(&xaroot->d_inode->i_mutex);
	dput(xaroot);
	return xadir;
}

/* The following are side effects of other operations that aren't explicitly
 * modifying extended attributes. This includes operations such as permissions
 * or ownership changes, object deletions, etc. */
struct reiserfs_dentry_buf {
	struct dir_context ctx;
	struct dentry *xadir;
	int count;
	struct dentry *dentries[8];
};

static int
fill_with_dentries(void *buf, const char *name, int namelen, loff_t offset,
		    u64 ino, unsigned int d_type)
{
	struct reiserfs_dentry_buf *dbuf = buf;
	struct dentry *dentry;
	WARN_ON_ONCE(!mutex_is_locked(&dbuf->xadir->d_inode->i_mutex));

	if (dbuf->count == ARRAY_SIZE(dbuf->dentries))
		return -ENOSPC;

	if (name[0] == '.' && (namelen < 2 ||
			       (namelen == 2 && name[1] == '.')))
		return 0;

	dentry = lookup_one_len(name, dbuf->xadir, namelen);
	if (IS_ERR(dentry)) {
		return PTR_ERR(dentry);
	} else if (!dentry->d_inode) {
		/* A directory entry exists, but no file? */
		reiserfs_error(dentry->d_sb, "xattr-20003",
			       "Corrupted directory: xattr %s listed but "
			       "not found for file %s.\n",
			       dentry->d_name.name, dbuf->xadir->d_name.name);
		dput(dentry);
		return -EIO;
	}

	dbuf->dentries[dbuf->count++] = dentry;
	return 0;
}

static void
cleanup_dentry_buf(struct reiserfs_dentry_buf *buf)
{
	int i;
	for (i = 0; i < buf->count; i++)
		if (buf->dentries[i])
			dput(buf->dentries[i]);
}

static int reiserfs_for_each_xattr(struct inode *inode,
				   int (*action)(struct dentry *, void *),
				   void *data)
{
	struct dentry *dir;
	int i, err = 0;
	struct reiserfs_dentry_buf buf = {
		.ctx.actor = fill_with_dentries,
	};

	/* Skip out, an xattr has no xattrs associated with it */
	if (IS_PRIVATE(inode) || get_inode_sd_version(inode) == STAT_DATA_V1)
		return 0;

	dir = open_xa_dir(inode, XATTR_REPLACE);
	if (IS_ERR(dir)) {
		err = PTR_ERR(dir);
		goto out;
	} else if (!dir->d_inode) {
		err = 0;
		goto out_dir;
	}

	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_XATTR);

	buf.xadir = dir;
	while (1) {
		err = reiserfs_readdir_inode(dir->d_inode, &buf.ctx);
		if (err)
			break;
		if (!buf.count)
			break;
		for (i = 0; !err && i < buf.count && buf.dentries[i]; i++) {
			struct dentry *dentry = buf.dentries[i];

			if (!S_ISDIR(dentry->d_inode->i_mode))
				err = action(dentry, data);

			dput(dentry);
			buf.dentries[i] = NULL;
		}
		if (err)
			break;
		buf.count = 0;
	}
	mutex_unlock(&dir->d_inode->i_mutex);

	cleanup_dentry_buf(&buf);

	if (!err) {
		/* We start a transaction here to avoid a ABBA situation
		 * between the xattr root's i_mutex and the journal lock.
		 * This doesn't incur much additional overhead since the
		 * new transaction will just nest inside the
		 * outer transaction. */
		int blocks = JOURNAL_PER_BALANCE_CNT * 2 + 2 +
			     4 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb);
		struct reiserfs_transaction_handle th;
		reiserfs_write_lock(inode->i_sb);
		err = journal_begin(&th, inode->i_sb, blocks);
		reiserfs_write_unlock(inode->i_sb);
		if (!err) {
			int jerror;
			mutex_lock_nested(&dir->d_parent->d_inode->i_mutex,
					  I_MUTEX_XATTR);
			err = action(dir, data);
			reiserfs_write_lock(inode->i_sb);
			jerror = journal_end(&th, inode->i_sb, blocks);
			reiserfs_write_unlock(inode->i_sb);
			mutex_unlock(&dir->d_parent->d_inode->i_mutex);
			err = jerror ?: err;
		}
	}
out_dir:
	dput(dir);
out:
	/* -ENODATA isn't an error */
	if (err == -ENODATA)
		err = 0;
	return err;
}

static int delete_one_xattr(struct dentry *dentry, void *data)
{
	struct inode *dir = dentry->d_parent->d_inode;

	/* This is the xattr dir, handle specially. */
	if (S_ISDIR(dentry->d_inode->i_mode))
		return xattr_rmdir(dir, dentry);

	return xattr_unlink(dir, dentry);
}

static int chown_one_xattr(struct dentry *dentry, void *data)
{
	struct iattr *attrs = data;
	int ia_valid = attrs->ia_valid;
	int err;

	/*
	 * We only want the ownership bits. Otherwise, we'll do
	 * things like change a directory to a regular file if
	 * ATTR_MODE is set.
	 */
	attrs->ia_valid &= (ATTR_UID|ATTR_GID);
	err = reiserfs_setattr(dentry, attrs);
	attrs->ia_valid = ia_valid;

	return err;
}

/* No i_mutex, but the inode is unconnected. */
int reiserfs_delete_xattrs(struct inode *inode)
{
	int err = reiserfs_for_each_xattr(inode, delete_one_xattr, NULL);
	if (err)
		reiserfs_warning(inode->i_sb, "jdm-20004",
				 "Couldn't delete all xattrs (%d)\n", err);
	return err;
}

/* inode->i_mutex: down */
int reiserfs_chown_xattrs(struct inode *inode, struct iattr *attrs)
{
	int err = reiserfs_for_each_xattr(inode, chown_one_xattr, attrs);
	if (err)
		reiserfs_warning(inode->i_sb, "jdm-20007",
				 "Couldn't chown all xattrs (%d)\n", err);
	return err;
}

#ifdef CONFIG_REISERFS_FS_XATTR
/* Returns a dentry corresponding to a specific extended attribute file
 * for the inode. If flags allow, the file is created. Otherwise, a
 * valid or negative dentry, or an error is returned. */
static struct dentry *xattr_lookup(struct inode *inode, const char *name,
				    int flags)
{
	struct dentry *xadir, *xafile;
	int err = 0;

	xadir = open_xa_dir(inode, flags);
	if (IS_ERR(xadir))
		return ERR_CAST(xadir);

	mutex_lock_nested(&xadir->d_inode->i_mutex, I_MUTEX_XATTR);
	xafile = lookup_one_len(name, xadir, strlen(name));
	if (IS_ERR(xafile)) {
		err = PTR_ERR(xafile);
		goto out;
	}

	if (xafile->d_inode && (flags & XATTR_CREATE))
		err = -EEXIST;

	if (!xafile->d_inode) {
		err = -ENODATA;
		if (xattr_may_create(flags))
			err = xattr_create(xadir->d_inode, xafile,
					      0700|S_IFREG);
	}

	if (err)
		dput(xafile);
out:
	mutex_unlock(&xadir->d_inode->i_mutex);
	dput(xadir);
	if (err)
		return ERR_PTR(err);
	return xafile;
}

/* Internal operations on file data */
static inline void reiserfs_put_page(struct page *page)
{
	kunmap(page);
	page_cache_release(page);
}

static struct page *reiserfs_get_page(struct inode *dir, size_t n)
{
	struct address_space *mapping = dir->i_mapping;
	struct page *page;
	/* We can deadlock if we try to free dentries,
	   and an unlink/rmdir has just occurred - GFP_NOFS avoids this */
	mapping_set_gfp_mask(mapping, GFP_NOFS);
	page = read_mapping_page(mapping, n >> PAGE_CACHE_SHIFT, NULL);
	if (!IS_ERR(page)) {
		kmap(page);
		if (PageError(page))
			goto fail;
	}
	return page;

      fail:
	reiserfs_put_page(page);
	return ERR_PTR(-EIO);
}

static inline __u32 xattr_hash(const char *msg, int len)
{
	return csum_partial(msg, len, 0);
}

int reiserfs_commit_write(struct file *f, struct page *page,
			  unsigned from, unsigned to);

static void update_ctime(struct inode *inode)
{
	struct timespec now = current_fs_time(inode->i_sb);
	if (inode_unhashed(inode) || !inode->i_nlink ||
	    timespec_equal(&inode->i_ctime, &now))
		return;

	inode->i_ctime = CURRENT_TIME_SEC;
	mark_inode_dirty(inode);
}

static int lookup_and_delete_xattr(struct inode *inode, const char *name)
{
	int err = 0;
	struct dentry *dentry, *xadir;

	xadir = open_xa_dir(inode, XATTR_REPLACE);
	if (IS_ERR(xadir))
		return PTR_ERR(xadir);

	mutex_lock_nested(&xadir->d_inode->i_mutex, I_MUTEX_XATTR);
	dentry = lookup_one_len(name, xadir, strlen(name));
	if (IS_ERR(dentry)) {
		err = PTR_ERR(dentry);
		goto out_dput;
	}

	if (dentry->d_inode) {
		err = xattr_unlink(xadir->d_inode, dentry);
		update_ctime(inode);
	}

	dput(dentry);
out_dput:
	mutex_unlock(&xadir->d_inode->i_mutex);
	dput(xadir);
	return err;
}


/* Generic extended attribute operations that can be used by xa plugins */

/*
 * inode->i_mutex: down
 */
int
reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th,
			  struct inode *inode, const char *name,
			  const void *buffer, size_t buffer_size, int flags)
{
	int err = 0;
	struct dentry *dentry;
	struct page *page;
	char *data;
	size_t file_pos = 0;
	size_t buffer_pos = 0;
	size_t new_size;
	__u32 xahash = 0;

	if (get_inode_sd_version(inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	if (!buffer) {
		err = lookup_and_delete_xattr(inode, name);
		return err;
	}

	dentry = xattr_lookup(inode, name, flags);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	down_write(&REISERFS_I(inode)->i_xattr_sem);

	xahash = xattr_hash(buffer, buffer_size);
	while (buffer_pos < buffer_size || buffer_pos == 0) {
		size_t chunk;
		size_t skip = 0;
		size_t page_offset = (file_pos & (PAGE_CACHE_SIZE - 1));
		if (buffer_size - buffer_pos > PAGE_CACHE_SIZE)
			chunk = PAGE_CACHE_SIZE;
		else
			chunk = buffer_size - buffer_pos;

		page = reiserfs_get_page(dentry->d_inode, file_pos);
		if (IS_ERR(page)) {
			err = PTR_ERR(page);
			goto out_unlock;
		}

		lock_page(page);
		data = page_address(page);

		if (file_pos == 0) {
			struct reiserfs_xattr_header *rxh;
			skip = file_pos = sizeof(struct reiserfs_xattr_header);
			if (chunk + skip > PAGE_CACHE_SIZE)
				chunk = PAGE_CACHE_SIZE - skip;
			rxh = (struct reiserfs_xattr_header *)data;
			rxh->h_magic = cpu_to_le32(REISERFS_XATTR_MAGIC);
			rxh->h_hash = cpu_to_le32(xahash);
		}

		reiserfs_write_lock(inode->i_sb);
		err = __reiserfs_write_begin(page, page_offset, chunk + skip);
		if (!err) {
			if (buffer)
				memcpy(data + skip, buffer + buffer_pos, chunk);
			err = reiserfs_commit_write(NULL, page, page_offset,
						    page_offset + chunk +
						    skip);
		}
		reiserfs_write_unlock(inode->i_sb);
		unlock_page(page);
		reiserfs_put_page(page);
		buffer_pos += chunk;
		file_pos += chunk;
		skip = 0;
		if (err || buffer_size == 0 || !buffer)
			break;
	}

	new_size = buffer_size + sizeof(struct reiserfs_xattr_header);
	if (!err && new_size < i_size_read(dentry->d_inode)) {
		struct iattr newattrs = {
			.ia_ctime = current_fs_time(inode->i_sb),
			.ia_size = new_size,
			.ia_valid = ATTR_SIZE | ATTR_CTIME,
		};

		mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_XATTR);
		inode_dio_wait(dentry->d_inode);

		err = reiserfs_setattr(dentry, &newattrs);
		mutex_unlock(&dentry->d_inode->i_mutex);
	} else
		update_ctime(inode);
out_unlock:
	up_write(&REISERFS_I(inode)->i_xattr_sem);
	dput(dentry);
	return err;
}

/* We need to start a transaction to maintain lock ordering */
int reiserfs_xattr_set(struct inode *inode, const char *name,
		       const void *buffer, size_t buffer_size, int flags)
{

	struct reiserfs_transaction_handle th;
	int error, error2;
	size_t jbegin_count = reiserfs_xattr_nblocks(inode, buffer_size);

	if (!(flags & XATTR_REPLACE))
		jbegin_count += reiserfs_xattr_jcreate_nblocks(inode);

	reiserfs_write_lock(inode->i_sb);
	error = journal_begin(&th, inode->i_sb, jbegin_count);
	reiserfs_write_unlock(inode->i_sb);
	if (error) {
		return error;
	}

	error = reiserfs_xattr_set_handle(&th, inode, name,
					  buffer, buffer_size, flags);

	reiserfs_write_lock(inode->i_sb);
	error2 = journal_end(&th, inode->i_sb, jbegin_count);
	reiserfs_write_unlock(inode->i_sb);
	if (error == 0)
		error = error2;

	return error;
}

/*
 * inode->i_mutex: down
 */
int
reiserfs_xattr_get(struct inode *inode, const char *name, void *buffer,
		   size_t buffer_size)
{
	ssize_t err = 0;
	struct dentry *dentry;
	size_t isize;
	size_t file_pos = 0;
	size_t buffer_pos = 0;
	struct page *page;
	__u32 hash = 0;

	if (name == NULL)
		return -EINVAL;

	/* We can't have xattrs attached to v1 items since they don't have
	 * generation numbers */
	if (get_inode_sd_version(inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	dentry = xattr_lookup(inode, name, XATTR_REPLACE);
	if (IS_ERR(dentry)) {
		err = PTR_ERR(dentry);
		goto out;
	}

	down_read(&REISERFS_I(inode)->i_xattr_sem);

	isize = i_size_read(dentry->d_inode);

	/* Just return the size needed */
	if (buffer == NULL) {
		err = isize - sizeof(struct reiserfs_xattr_header);
		goto out_unlock;
	}

	if (buffer_size < isize - sizeof(struct reiserfs_xattr_header)) {
		err = -ERANGE;
		goto out_unlock;
	}

	while (file_pos < isize) {
		size_t chunk;
		char *data;
		size_t skip = 0;
		if (isize - file_pos > PAGE_CACHE_SIZE)
			chunk = PAGE_CACHE_SIZE;
		else
			chunk = isize - file_pos;

		page = reiserfs_get_page(dentry->d_inode, file_pos);
		if (IS_ERR(page)) {
			err = PTR_ERR(page);
			goto out_unlock;
		}

		lock_page(page);
		data = page_address(page);
		if (file_pos == 0) {
			struct reiserfs_xattr_header *rxh =
			    (struct reiserfs_xattr_header *)data;
			skip = file_pos = sizeof(struct reiserfs_xattr_header);
			chunk -= skip;
			/* Magic doesn't match up.. */
			if (rxh->h_magic != cpu_to_le32(REISERFS_XATTR_MAGIC)) {
				unlock_page(page);
				reiserfs_put_page(page);
				reiserfs_warning(inode->i_sb, "jdm-20001",
						 "Invalid magic for xattr (%s) "
						 "associated with %k", name,
						 INODE_PKEY(inode));
				err = -EIO;
				goto out_unlock;
			}
			hash = le32_to_cpu(rxh->h_hash);
		}
		memcpy(buffer + buffer_pos, data + skip, chunk);
		unlock_page(page);
		reiserfs_put_page(page);
		file_pos += chunk;
		buffer_pos += chunk;
		skip = 0;
	}
	err = isize - sizeof(struct reiserfs_xattr_header);

	if (xattr_hash(buffer, isize - sizeof(struct reiserfs_xattr_header)) !=
	    hash) {
		reiserfs_warning(inode->i_sb, "jdm-20002",
				 "Invalid hash for xattr (%s) associated "
				 "with %k", name, INODE_PKEY(inode));
		err = -EIO;
	}

out_unlock:
	up_read(&REISERFS_I(inode)->i_xattr_sem);
	dput(dentry);

out:
	return err;
}

/*
 * In order to implement different sets of xattr operations for each xattr
 * prefix with the generic xattr API, a filesystem should create a
 * null-terminated array of struct xattr_handler (one for each prefix) and
 * hang a pointer to it off of the s_xattr field of the superblock.
 *
 * The generic_fooxattr() functions will use this list to dispatch xattr
 * operations to the correct xattr_handler.
 */
#define for_each_xattr_handler(handlers, handler)		\
		for ((handler) = *(handlers)++;			\
			(handler) != NULL;			\
			(handler) = *(handlers)++)

/* This is the implementation for the xattr plugin infrastructure */
static inline const struct xattr_handler *
find_xattr_handler_prefix(const struct xattr_handler **handlers,
			   const char *name)
{
	const struct xattr_handler *xah;

	if (!handlers)
		return NULL;

	for_each_xattr_handler(handlers, xah) {
		if (strncmp(xah->prefix, name, strlen(xah->prefix)) == 0)
			break;
	}

	return xah;
}


/*
 * Inode operation getxattr()
 */
ssize_t
reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
		  size_t size)
{
	const struct xattr_handler *handler;

	handler = find_xattr_handler_prefix(dentry->d_sb->s_xattr, name);

	if (!handler || get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	return handler->get(dentry, name, buffer, size, handler->flags);
}

/*
 * Inode operation setxattr()
 *
 * dentry->d_inode->i_mutex down
 */
int
reiserfs_setxattr(struct dentry *dentry, const char *name, const void *value,
		  size_t size, int flags)
{
	const struct xattr_handler *handler;

	handler = find_xattr_handler_prefix(dentry->d_sb->s_xattr, name);

	if (!handler || get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	return handler->set(dentry, name, value, size, flags, handler->flags);
}

/*
 * Inode operation removexattr()
 *
 * dentry->d_inode->i_mutex down
 */
int reiserfs_removexattr(struct dentry *dentry, const char *name)
{
	const struct xattr_handler *handler;
	handler = find_xattr_handler_prefix(dentry->d_sb->s_xattr, name);

	if (!handler || get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	return handler->set(dentry, name, NULL, 0, XATTR_REPLACE, handler->flags);
}

struct listxattr_buf {
	struct dir_context ctx;
	size_t size;
	size_t pos;
	char *buf;
	struct dentry *dentry;
};

static int listxattr_filler(void *buf, const char *name, int namelen,
			    loff_t offset, u64 ino, unsigned int d_type)
{
	struct listxattr_buf *b = (struct listxattr_buf *)buf;
	size_t size;
	if (name[0] != '.' ||
	    (namelen != 1 && (name[1] != '.' || namelen != 2))) {
		const struct xattr_handler *handler;
		handler = find_xattr_handler_prefix(b->dentry->d_sb->s_xattr,
						    name);
		if (!handler)	/* Unsupported xattr name */
			return 0;
		if (b->buf) {
			size = handler->list(b->dentry, b->buf + b->pos,
					 b->size, name, namelen,
					 handler->flags);
			if (size > b->size)
				return -ERANGE;
		} else {
			size = handler->list(b->dentry, NULL, 0, name,
					     namelen, handler->flags);
		}

		b->pos += size;
	}
	return 0;
}

/*
 * Inode operation listxattr()
 *
 * We totally ignore the generic listxattr here because it would be stupid
 * not to. Since the xattrs are organized in a directory, we can just
 * readdir to find them.
 */
ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
{
	struct dentry *dir;
	int err = 0;
	struct listxattr_buf buf = {
		.ctx.actor = listxattr_filler,
		.dentry = dentry,
		.buf = buffer,
		.size = buffer ? size : 0,
	};

	if (!dentry->d_inode)
		return -EINVAL;

	if (!dentry->d_sb->s_xattr ||
	    get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
		return -EOPNOTSUPP;

	dir = open_xa_dir(dentry->d_inode, XATTR_REPLACE);
	if (IS_ERR(dir)) {
		err = PTR_ERR(dir);
		if (err == -ENODATA)
			err = 0;  /* Not an error if there aren't any xattrs */
		goto out;
	}

	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_XATTR);
	err = reiserfs_readdir_inode(dir->d_inode, &buf.ctx);
	mutex_unlock(&dir->d_inode->i_mutex);

	if (!err)
		err = buf.pos;

	dput(dir);
out:
	return err;
}

static int create_privroot(struct dentry *dentry)
{
	int err;
	struct inode *inode = dentry->d_parent->d_inode;
	WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));

	err = xattr_mkdir(inode, dentry, 0700);
	if (err || !dentry->d_inode) {
		reiserfs_warning(dentry->d_sb, "jdm-20006",
				 "xattrs/ACLs enabled and couldn't "
				 "find/create .reiserfs_priv. "
				 "Failing mount.");
		return -EOPNOTSUPP;
	}

	dentry->d_inode->i_flags |= S_PRIVATE;
	reiserfs_info(dentry->d_sb, "Created %s - reserved for xattr "
		      "storage.\n", PRIVROOT_NAME);

	return 0;
}

#else
int __init reiserfs_xattr_register_handlers(void) { return 0; }
void reiserfs_xattr_unregister_handlers(void) {}
static int create_privroot(struct dentry *dentry) { return 0; }
#endif

/* Actual operations that are exported to VFS-land */
static const struct xattr_handler *reiserfs_xattr_handlers[] = {
#ifdef CONFIG_REISERFS_FS_XATTR
	&reiserfs_xattr_user_handler,
	&reiserfs_xattr_trusted_handler,
#endif
#ifdef CONFIG_REISERFS_FS_SECURITY
	&reiserfs_xattr_security_handler,
#endif
#ifdef CONFIG_REISERFS_FS_POSIX_ACL
	&posix_acl_access_xattr_handler,
	&posix_acl_default_xattr_handler,
#endif
	NULL
};

static int xattr_mount_check(struct super_block *s)
{
	/* We need generation numbers to ensure that the oid mapping is correct
	 * v3.5 filesystems don't have them. */
	if (old_format_only(s)) {
		if (reiserfs_xattrs_optional(s)) {
			/* Old format filesystem, but optional xattrs have
			 * been enabled. Error out. */
			reiserfs_warning(s, "jdm-2005",
					 "xattrs/ACLs not supported "
					 "on pre-v3.6 format filesystems. "
					 "Failing mount.");
			return -EOPNOTSUPP;
		}
	}

	return 0;
}

int reiserfs_permission(struct inode *inode, int mask)
{
	/*
	 * We don't do permission checks on the internal objects.
	 * Permissions are determined by the "owning" object.
	 */
	if (IS_PRIVATE(inode))
		return 0;

	return generic_permission(inode, mask);
}

static int xattr_hide_revalidate(struct dentry *dentry, unsigned int flags)
{
	return -EPERM;
}

static const struct dentry_operations xattr_lookup_poison_ops = {
	.d_revalidate = xattr_hide_revalidate,
};

int reiserfs_lookup_privroot(struct super_block *s)
{
	struct dentry *dentry;
	int err = 0;

	/* If we don't have the privroot located yet - go find it */
	mutex_lock(&s->s_root->d_inode->i_mutex);
	dentry = lookup_one_len(PRIVROOT_NAME, s->s_root,
				strlen(PRIVROOT_NAME));
	if (!IS_ERR(dentry)) {
		REISERFS_SB(s)->priv_root = dentry;
		d_set_d_op(dentry, &xattr_lookup_poison_ops);
		if (dentry->d_inode)
			dentry->d_inode->i_flags |= S_PRIVATE;
	} else
		err = PTR_ERR(dentry);
	mutex_unlock(&s->s_root->d_inode->i_mutex);

	return err;
}

/* We need to take a copy of the mount flags since things like
 * MS_RDONLY don't get set until *after* we're called.
 * mount_flags != mount_options */
int reiserfs_xattr_init(struct super_block *s, int mount_flags)
{
	int err = 0;
	struct dentry *privroot = REISERFS_SB(s)->priv_root;

	err = xattr_mount_check(s);
	if (err)
		goto error;

	if (!privroot->d_inode && !(mount_flags & MS_RDONLY)) {
		mutex_lock(&s->s_root->d_inode->i_mutex);
		err = create_privroot(REISERFS_SB(s)->priv_root);
		mutex_unlock(&s->s_root->d_inode->i_mutex);
	}

	if (privroot->d_inode) {
		s->s_xattr = reiserfs_xattr_handlers;
		mutex_lock(&privroot->d_inode->i_mutex);
		if (!REISERFS_SB(s)->xattr_root) {
			struct dentry *dentry;
			dentry = lookup_one_len(XAROOT_NAME, privroot,
						strlen(XAROOT_NAME));
			if (!IS_ERR(dentry))
				REISERFS_SB(s)->xattr_root = dentry;
			else
				err = PTR_ERR(dentry);
		}
		mutex_unlock(&privroot->d_inode->i_mutex);
	}

error:
	if (err) {
		clear_bit(REISERFS_XATTRS_USER, &(REISERFS_SB(s)->s_mount_opt));
		clear_bit(REISERFS_POSIXACL, &(REISERFS_SB(s)->s_mount_opt));
	}

	/* The super_block MS_POSIXACL must mirror the (no)acl mount option. */
	if (reiserfs_posixacl(s))
		s->s_flags |= MS_POSIXACL;
	else
		s->s_flags &= ~MS_POSIXACL;

	return err;
}