linux/fs/ext2/xattr.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * linux/fs/ext2/xattr.c
   4 *
   5 * Copyright (C) 2001-2003 Andreas Gruenbacher <agruen@suse.de>
   6 *
   7 * Fix by Harrison Xing <harrison@mountainviewdata.com>.
   8 * Extended attributes for symlinks and special files added per
   9 *  suggestion of Luka Renko <luka.renko@hermes.si>.
  10 * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
  11 *  Red Hat Inc.
  12 *
  13 */
  14
  15/*
  16 * Extended attributes are stored on disk blocks allocated outside of
  17 * any inode. The i_file_acl field is then made to point to this allocated
  18 * block. If all extended attributes of an inode are identical, these
  19 * inodes may share the same extended attribute block. Such situations
  20 * are automatically detected by keeping a cache of recent attribute block
  21 * numbers and hashes over the block's contents in memory.
  22 *
  23 *
  24 * Extended attribute block layout:
  25 *
  26 *   +------------------+
  27 *   | header           |
  28 *   | entry 1          | |
  29 *   | entry 2          | | growing downwards
  30 *   | entry 3          | v
  31 *   | four null bytes  |
  32 *   | . . .            |
  33 *   | value 1          | ^
  34 *   | value 3          | | growing upwards
  35 *   | value 2          | |
  36 *   +------------------+
  37 *
  38 * The block header is followed by multiple entry descriptors. These entry
  39 * descriptors are variable in size, and aligned to EXT2_XATTR_PAD
  40 * byte boundaries. The entry descriptors are sorted by attribute name,
  41 * so that two extended attribute blocks can be compared efficiently.
  42 *
  43 * Attribute values are aligned to the end of the block, stored in
  44 * no specific order. They are also padded to EXT2_XATTR_PAD byte
  45 * boundaries. No additional gaps are left between them.
  46 *
  47 * Locking strategy
  48 * ----------------
  49 * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
  50 * EA blocks are only changed if they are exclusive to an inode, so
  51 * holding xattr_sem also means that nothing but the EA block's reference
  52 * count will change. Multiple writers to an EA block are synchronized
  53 * by the bh lock. No more than a single bh lock is held at any time
  54 * to avoid deadlocks.
  55 */
  56
  57#include <linux/buffer_head.h>
  58#include <linux/init.h>
  59#include <linux/printk.h>
  60#include <linux/slab.h>
  61#include <linux/mbcache.h>
  62#include <linux/quotaops.h>
  63#include <linux/rwsem.h>
  64#include <linux/security.h>
  65#include "ext2.h"
  66#include "xattr.h"
  67#include "acl.h"
  68
  69#define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  70#define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  71#define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  72#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  73
  74#ifdef EXT2_XATTR_DEBUG
  75# define ea_idebug(inode, f...) do { \
  76                printk(KERN_DEBUG "inode %s:%ld: ", \
  77                        inode->i_sb->s_id, inode->i_ino); \
  78                printk(f); \
  79                printk("\n"); \
  80        } while (0)
  81# define ea_bdebug(bh, f...) do { \
  82                printk(KERN_DEBUG "block %pg:%lu: ", \
  83                        bh->b_bdev, (unsigned long) bh->b_blocknr); \
  84                printk(f); \
  85                printk("\n"); \
  86        } while (0)
  87#else
  88# define ea_idebug(inode, f...) no_printk(f)
  89# define ea_bdebug(bh, f...)    no_printk(f)
  90#endif
  91
  92static int ext2_xattr_set2(struct inode *, struct buffer_head *,
  93                           struct ext2_xattr_header *);
  94
  95static int ext2_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
  96static struct buffer_head *ext2_xattr_cache_find(struct inode *,
  97                                                 struct ext2_xattr_header *);
  98static void ext2_xattr_rehash(struct ext2_xattr_header *,
  99                              struct ext2_xattr_entry *);
 100
 101static const struct xattr_handler *ext2_xattr_handler_map[] = {
 102        [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 103#ifdef CONFIG_EXT2_FS_POSIX_ACL
 104        [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
 105        [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
 106#endif
 107        [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
 108#ifdef CONFIG_EXT2_FS_SECURITY
 109        [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
 110#endif
 111};
 112
 113const struct xattr_handler *ext2_xattr_handlers[] = {
 114        &ext2_xattr_user_handler,
 115        &ext2_xattr_trusted_handler,
 116#ifdef CONFIG_EXT2_FS_POSIX_ACL
 117        &posix_acl_access_xattr_handler,
 118        &posix_acl_default_xattr_handler,
 119#endif
 120#ifdef CONFIG_EXT2_FS_SECURITY
 121        &ext2_xattr_security_handler,
 122#endif
 123        NULL
 124};
 125
 126#define EA_BLOCK_CACHE(inode)   (EXT2_SB(inode->i_sb)->s_ea_block_cache)
 127
 128static inline const struct xattr_handler *
 129ext2_xattr_handler(int name_index)
 130{
 131        const struct xattr_handler *handler = NULL;
 132
 133        if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 134                handler = ext2_xattr_handler_map[name_index];
 135        return handler;
 136}
 137
 138static bool
 139ext2_xattr_header_valid(struct ext2_xattr_header *header)
 140{
 141        if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 142            header->h_blocks != cpu_to_le32(1))
 143                return false;
 144
 145        return true;
 146}
 147
 148static bool
 149ext2_xattr_entry_valid(struct ext2_xattr_entry *entry,
 150                       char *end, size_t end_offs)
 151{
 152        struct ext2_xattr_entry *next;
 153        size_t size;
 154
 155        next = EXT2_XATTR_NEXT(entry);
 156        if ((char *)next >= end)
 157                return false;
 158
 159        if (entry->e_value_block != 0)
 160                return false;
 161
 162        size = le32_to_cpu(entry->e_value_size);
 163        if (size > end_offs ||
 164            le16_to_cpu(entry->e_value_offs) + size > end_offs)
 165                return false;
 166
 167        return true;
 168}
 169
 170static int
 171ext2_xattr_cmp_entry(int name_index, size_t name_len, const char *name,
 172                     struct ext2_xattr_entry *entry)
 173{
 174        int cmp;
 175
 176        cmp = name_index - entry->e_name_index;
 177        if (!cmp)
 178                cmp = name_len - entry->e_name_len;
 179        if (!cmp)
 180                cmp = memcmp(name, entry->e_name, name_len);
 181
 182        return cmp;
 183}
 184
 185/*
 186 * ext2_xattr_get()
 187 *
 188 * Copy an extended attribute into the buffer
 189 * provided, or compute the buffer size required.
 190 * Buffer is NULL to compute the size of the buffer required.
 191 *
 192 * Returns a negative error number on failure, or the number of bytes
 193 * used / required on success.
 194 */
 195int
 196ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 197               void *buffer, size_t buffer_size)
 198{
 199        struct buffer_head *bh = NULL;
 200        struct ext2_xattr_entry *entry;
 201        size_t name_len, size;
 202        char *end;
 203        int error, not_found;
 204        struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 205
 206        ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 207                  name_index, name, buffer, (long)buffer_size);
 208
 209        if (name == NULL)
 210                return -EINVAL;
 211        name_len = strlen(name);
 212        if (name_len > 255)
 213                return -ERANGE;
 214
 215        down_read(&EXT2_I(inode)->xattr_sem);
 216        error = -ENODATA;
 217        if (!EXT2_I(inode)->i_file_acl)
 218                goto cleanup;
 219        ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 220        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 221        error = -EIO;
 222        if (!bh)
 223                goto cleanup;
 224        ea_bdebug(bh, "b_count=%d, refcount=%d",
 225                atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 226        end = bh->b_data + bh->b_size;
 227        if (!ext2_xattr_header_valid(HDR(bh))) {
 228bad_block:
 229                ext2_error(inode->i_sb, "ext2_xattr_get",
 230                        "inode %ld: bad block %d", inode->i_ino,
 231                        EXT2_I(inode)->i_file_acl);
 232                error = -EIO;
 233                goto cleanup;
 234        }
 235
 236        /* find named attribute */
 237        entry = FIRST_ENTRY(bh);
 238        while (!IS_LAST_ENTRY(entry)) {
 239                if (!ext2_xattr_entry_valid(entry, end,
 240                    inode->i_sb->s_blocksize))
 241                        goto bad_block;
 242
 243                not_found = ext2_xattr_cmp_entry(name_index, name_len, name,
 244                                                 entry);
 245                if (!not_found)
 246                        goto found;
 247                if (not_found < 0)
 248                        break;
 249
 250                entry = EXT2_XATTR_NEXT(entry);
 251        }
 252        if (ext2_xattr_cache_insert(ea_block_cache, bh))
 253                ea_idebug(inode, "cache insert failed");
 254        error = -ENODATA;
 255        goto cleanup;
 256found:
 257        size = le32_to_cpu(entry->e_value_size);
 258        if (ext2_xattr_cache_insert(ea_block_cache, bh))
 259                ea_idebug(inode, "cache insert failed");
 260        if (buffer) {
 261                error = -ERANGE;
 262                if (size > buffer_size)
 263                        goto cleanup;
 264                /* return value of attribute */
 265                memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 266                        size);
 267        }
 268        error = size;
 269
 270cleanup:
 271        brelse(bh);
 272        up_read(&EXT2_I(inode)->xattr_sem);
 273
 274        return error;
 275}
 276
 277/*
 278 * ext2_xattr_list()
 279 *
 280 * Copy a list of attribute names into the buffer
 281 * provided, or compute the buffer size required.
 282 * Buffer is NULL to compute the size of the buffer required.
 283 *
 284 * Returns a negative error number on failure, or the number of bytes
 285 * used / required on success.
 286 */
 287static int
 288ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 289{
 290        struct inode *inode = d_inode(dentry);
 291        struct buffer_head *bh = NULL;
 292        struct ext2_xattr_entry *entry;
 293        char *end;
 294        size_t rest = buffer_size;
 295        int error;
 296        struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 297
 298        ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 299                  buffer, (long)buffer_size);
 300
 301        down_read(&EXT2_I(inode)->xattr_sem);
 302        error = 0;
 303        if (!EXT2_I(inode)->i_file_acl)
 304                goto cleanup;
 305        ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 306        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 307        error = -EIO;
 308        if (!bh)
 309                goto cleanup;
 310        ea_bdebug(bh, "b_count=%d, refcount=%d",
 311                atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 312        end = bh->b_data + bh->b_size;
 313        if (!ext2_xattr_header_valid(HDR(bh))) {
 314bad_block:
 315                ext2_error(inode->i_sb, "ext2_xattr_list",
 316                        "inode %ld: bad block %d", inode->i_ino,
 317                        EXT2_I(inode)->i_file_acl);
 318                error = -EIO;
 319                goto cleanup;
 320        }
 321
 322        /* check the on-disk data structure */
 323        entry = FIRST_ENTRY(bh);
 324        while (!IS_LAST_ENTRY(entry)) {
 325                if (!ext2_xattr_entry_valid(entry, end,
 326                    inode->i_sb->s_blocksize))
 327                        goto bad_block;
 328                entry = EXT2_XATTR_NEXT(entry);
 329        }
 330        if (ext2_xattr_cache_insert(ea_block_cache, bh))
 331                ea_idebug(inode, "cache insert failed");
 332
 333        /* list the attribute names */
 334        for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 335             entry = EXT2_XATTR_NEXT(entry)) {
 336                const struct xattr_handler *handler =
 337                        ext2_xattr_handler(entry->e_name_index);
 338
 339                if (handler && (!handler->list || handler->list(dentry))) {
 340                        const char *prefix = handler->prefix ?: handler->name;
 341                        size_t prefix_len = strlen(prefix);
 342                        size_t size = prefix_len + entry->e_name_len + 1;
 343
 344                        if (buffer) {
 345                                if (size > rest) {
 346                                        error = -ERANGE;
 347                                        goto cleanup;
 348                                }
 349                                memcpy(buffer, prefix, prefix_len);
 350                                buffer += prefix_len;
 351                                memcpy(buffer, entry->e_name, entry->e_name_len);
 352                                buffer += entry->e_name_len;
 353                                *buffer++ = 0;
 354                        }
 355                        rest -= size;
 356                }
 357        }
 358        error = buffer_size - rest;  /* total size */
 359
 360cleanup:
 361        brelse(bh);
 362        up_read(&EXT2_I(inode)->xattr_sem);
 363
 364        return error;
 365}
 366
 367/*
 368 * Inode operation listxattr()
 369 *
 370 * d_inode(dentry)->i_mutex: don't care
 371 */
 372ssize_t
 373ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 374{
 375        return ext2_xattr_list(dentry, buffer, size);
 376}
 377
 378/*
 379 * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 380 * not set, set it.
 381 */
 382static void ext2_xattr_update_super_block(struct super_block *sb)
 383{
 384        if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 385                return;
 386
 387        spin_lock(&EXT2_SB(sb)->s_lock);
 388        ext2_update_dynamic_rev(sb);
 389        EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 390        spin_unlock(&EXT2_SB(sb)->s_lock);
 391        mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 392}
 393
 394/*
 395 * ext2_xattr_set()
 396 *
 397 * Create, replace or remove an extended attribute for this inode.  Value
 398 * is NULL to remove an existing extended attribute, and non-NULL to
 399 * either replace an existing extended attribute, or create a new extended
 400 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 401 * specify that an extended attribute must exist and must not exist
 402 * previous to the call, respectively.
 403 *
 404 * Returns 0, or a negative error number on failure.
 405 */
 406int
 407ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 408               const void *value, size_t value_len, int flags)
 409{
 410        struct super_block *sb = inode->i_sb;
 411        struct buffer_head *bh = NULL;
 412        struct ext2_xattr_header *header = NULL;
 413        struct ext2_xattr_entry *here = NULL, *last = NULL;
 414        size_t name_len, free, min_offs = sb->s_blocksize;
 415        int not_found = 1, error;
 416        char *end;
 417        
 418        /*
 419         * header -- Points either into bh, or to a temporarily
 420         *           allocated buffer.
 421         * here -- The named entry found, or the place for inserting, within
 422         *         the block pointed to by header.
 423         * last -- Points right after the last named entry within the block
 424         *         pointed to by header.
 425         * min_offs -- The offset of the first value (values are aligned
 426         *             towards the end of the block).
 427         * end -- Points right after the block pointed to by header.
 428         */
 429        
 430        ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 431                  name_index, name, value, (long)value_len);
 432
 433        if (value == NULL)
 434                value_len = 0;
 435        if (name == NULL)
 436                return -EINVAL;
 437        name_len = strlen(name);
 438        if (name_len > 255 || value_len > sb->s_blocksize)
 439                return -ERANGE;
 440        down_write(&EXT2_I(inode)->xattr_sem);
 441        if (EXT2_I(inode)->i_file_acl) {
 442                /* The inode already has an extended attribute block. */
 443                bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 444                error = -EIO;
 445                if (!bh)
 446                        goto cleanup;
 447                ea_bdebug(bh, "b_count=%d, refcount=%d",
 448                        atomic_read(&(bh->b_count)),
 449                        le32_to_cpu(HDR(bh)->h_refcount));
 450                header = HDR(bh);
 451                end = bh->b_data + bh->b_size;
 452                if (!ext2_xattr_header_valid(header)) {
 453bad_block:
 454                        ext2_error(sb, "ext2_xattr_set",
 455                                "inode %ld: bad block %d", inode->i_ino, 
 456                                   EXT2_I(inode)->i_file_acl);
 457                        error = -EIO;
 458                        goto cleanup;
 459                }
 460                /*
 461                 * Find the named attribute. If not found, 'here' will point
 462                 * to entry where the new attribute should be inserted to
 463                 * maintain sorting.
 464                 */
 465                last = FIRST_ENTRY(bh);
 466                while (!IS_LAST_ENTRY(last)) {
 467                        if (!ext2_xattr_entry_valid(last, end, sb->s_blocksize))
 468                                goto bad_block;
 469                        if (last->e_value_size) {
 470                                size_t offs = le16_to_cpu(last->e_value_offs);
 471                                if (offs < min_offs)
 472                                        min_offs = offs;
 473                        }
 474                        if (not_found > 0) {
 475                                not_found = ext2_xattr_cmp_entry(name_index,
 476                                                                 name_len,
 477                                                                 name, last);
 478                                if (not_found <= 0)
 479                                        here = last;
 480                        }
 481                        last = EXT2_XATTR_NEXT(last);
 482                }
 483                if (not_found > 0)
 484                        here = last;
 485
 486                /* Check whether we have enough space left. */
 487                free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 488        } else {
 489                /* We will use a new extended attribute block. */
 490                free = sb->s_blocksize -
 491                        sizeof(struct ext2_xattr_header) - sizeof(__u32);
 492        }
 493
 494        if (not_found) {
 495                /* Request to remove a nonexistent attribute? */
 496                error = -ENODATA;
 497                if (flags & XATTR_REPLACE)
 498                        goto cleanup;
 499                error = 0;
 500                if (value == NULL)
 501                        goto cleanup;
 502        } else {
 503                /* Request to create an existing attribute? */
 504                error = -EEXIST;
 505                if (flags & XATTR_CREATE)
 506                        goto cleanup;
 507                free += EXT2_XATTR_SIZE(le32_to_cpu(here->e_value_size));
 508                free += EXT2_XATTR_LEN(name_len);
 509        }
 510        error = -ENOSPC;
 511        if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 512                goto cleanup;
 513
 514        /* Here we know that we can set the new attribute. */
 515
 516        if (header) {
 517                /* assert(header == HDR(bh)); */
 518                lock_buffer(bh);
 519                if (header->h_refcount == cpu_to_le32(1)) {
 520                        __u32 hash = le32_to_cpu(header->h_hash);
 521
 522                        ea_bdebug(bh, "modifying in-place");
 523                        /*
 524                         * This must happen under buffer lock for
 525                         * ext2_xattr_set2() to reliably detect modified block
 526                         */
 527                        mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 528                                              bh->b_blocknr);
 529
 530                        /* keep the buffer locked while modifying it. */
 531                } else {
 532                        int offset;
 533
 534                        unlock_buffer(bh);
 535                        ea_bdebug(bh, "cloning");
 536                        header = kmemdup(HDR(bh), bh->b_size, GFP_KERNEL);
 537                        error = -ENOMEM;
 538                        if (header == NULL)
 539                                goto cleanup;
 540                        header->h_refcount = cpu_to_le32(1);
 541
 542                        offset = (char *)here - bh->b_data;
 543                        here = ENTRY((char *)header + offset);
 544                        offset = (char *)last - bh->b_data;
 545                        last = ENTRY((char *)header + offset);
 546                }
 547        } else {
 548                /* Allocate a buffer where we construct the new block. */
 549                header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 550                error = -ENOMEM;
 551                if (header == NULL)
 552                        goto cleanup;
 553                end = (char *)header + sb->s_blocksize;
 554                header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 555                header->h_blocks = header->h_refcount = cpu_to_le32(1);
 556                last = here = ENTRY(header+1);
 557        }
 558
 559        /* Iff we are modifying the block in-place, bh is locked here. */
 560
 561        if (not_found) {
 562                /* Insert the new name. */
 563                size_t size = EXT2_XATTR_LEN(name_len);
 564                size_t rest = (char *)last - (char *)here;
 565                memmove((char *)here + size, here, rest);
 566                memset(here, 0, size);
 567                here->e_name_index = name_index;
 568                here->e_name_len = name_len;
 569                memcpy(here->e_name, name, name_len);
 570        } else {
 571                if (here->e_value_size) {
 572                        char *first_val = (char *)header + min_offs;
 573                        size_t offs = le16_to_cpu(here->e_value_offs);
 574                        char *val = (char *)header + offs;
 575                        size_t size = EXT2_XATTR_SIZE(
 576                                le32_to_cpu(here->e_value_size));
 577
 578                        if (size == EXT2_XATTR_SIZE(value_len)) {
 579                                /* The old and the new value have the same
 580                                   size. Just replace. */
 581                                here->e_value_size = cpu_to_le32(value_len);
 582                                memset(val + size - EXT2_XATTR_PAD, 0,
 583                                       EXT2_XATTR_PAD); /* Clear pad bytes. */
 584                                memcpy(val, value, value_len);
 585                                goto skip_replace;
 586                        }
 587
 588                        /* Remove the old value. */
 589                        memmove(first_val + size, first_val, val - first_val);
 590                        memset(first_val, 0, size);
 591                        here->e_value_offs = 0;
 592                        min_offs += size;
 593
 594                        /* Adjust all value offsets. */
 595                        last = ENTRY(header+1);
 596                        while (!IS_LAST_ENTRY(last)) {
 597                                size_t o = le16_to_cpu(last->e_value_offs);
 598                                if (o < offs)
 599                                        last->e_value_offs =
 600                                                cpu_to_le16(o + size);
 601                                last = EXT2_XATTR_NEXT(last);
 602                        }
 603                }
 604                if (value == NULL) {
 605                        /* Remove the old name. */
 606                        size_t size = EXT2_XATTR_LEN(name_len);
 607                        last = ENTRY((char *)last - size);
 608                        memmove(here, (char*)here + size,
 609                                (char*)last - (char*)here);
 610                        memset(last, 0, size);
 611                }
 612        }
 613
 614        if (value != NULL) {
 615                /* Insert the new value. */
 616                here->e_value_size = cpu_to_le32(value_len);
 617                if (value_len) {
 618                        size_t size = EXT2_XATTR_SIZE(value_len);
 619                        char *val = (char *)header + min_offs - size;
 620                        here->e_value_offs =
 621                                cpu_to_le16((char *)val - (char *)header);
 622                        memset(val + size - EXT2_XATTR_PAD, 0,
 623                               EXT2_XATTR_PAD); /* Clear the pad bytes. */
 624                        memcpy(val, value, value_len);
 625                }
 626        }
 627
 628skip_replace:
 629        if (IS_LAST_ENTRY(ENTRY(header+1))) {
 630                /* This block is now empty. */
 631                if (bh && header == HDR(bh))
 632                        unlock_buffer(bh);  /* we were modifying in-place. */
 633                error = ext2_xattr_set2(inode, bh, NULL);
 634        } else {
 635                ext2_xattr_rehash(header, here);
 636                if (bh && header == HDR(bh))
 637                        unlock_buffer(bh);  /* we were modifying in-place. */
 638                error = ext2_xattr_set2(inode, bh, header);
 639        }
 640
 641cleanup:
 642        if (!(bh && header == HDR(bh)))
 643                kfree(header);
 644        brelse(bh);
 645        up_write(&EXT2_I(inode)->xattr_sem);
 646
 647        return error;
 648}
 649
 650/*
 651 * Second half of ext2_xattr_set(): Update the file system.
 652 */
 653static int
 654ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 655                struct ext2_xattr_header *header)
 656{
 657        struct super_block *sb = inode->i_sb;
 658        struct buffer_head *new_bh = NULL;
 659        int error;
 660        struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 661
 662        if (header) {
 663                new_bh = ext2_xattr_cache_find(inode, header);
 664                if (new_bh) {
 665                        /* We found an identical block in the cache. */
 666                        if (new_bh == old_bh) {
 667                                ea_bdebug(new_bh, "keeping this block");
 668                        } else {
 669                                /* The old block is released after updating
 670                                   the inode.  */
 671                                ea_bdebug(new_bh, "reusing block");
 672
 673                                error = dquot_alloc_block(inode, 1);
 674                                if (error) {
 675                                        unlock_buffer(new_bh);
 676                                        goto cleanup;
 677                                }
 678                                le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 679                                ea_bdebug(new_bh, "refcount now=%d",
 680                                        le32_to_cpu(HDR(new_bh)->h_refcount));
 681                        }
 682                        unlock_buffer(new_bh);
 683                } else if (old_bh && header == HDR(old_bh)) {
 684                        /* Keep this block. No need to lock the block as we
 685                           don't need to change the reference count. */
 686                        new_bh = old_bh;
 687                        get_bh(new_bh);
 688                        ext2_xattr_cache_insert(ea_block_cache, new_bh);
 689                } else {
 690                        /* We need to allocate a new block */
 691                        ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 692                                                EXT2_I(inode)->i_block_group);
 693                        int block = ext2_new_block(inode, goal, &error);
 694                        if (error)
 695                                goto cleanup;
 696                        ea_idebug(inode, "creating block %d", block);
 697
 698                        new_bh = sb_getblk(sb, block);
 699                        if (unlikely(!new_bh)) {
 700                                ext2_free_blocks(inode, block, 1);
 701                                mark_inode_dirty(inode);
 702                                error = -ENOMEM;
 703                                goto cleanup;
 704                        }
 705                        lock_buffer(new_bh);
 706                        memcpy(new_bh->b_data, header, new_bh->b_size);
 707                        set_buffer_uptodate(new_bh);
 708                        unlock_buffer(new_bh);
 709                        ext2_xattr_cache_insert(ea_block_cache, new_bh);
 710                        
 711                        ext2_xattr_update_super_block(sb);
 712                }
 713                mark_buffer_dirty(new_bh);
 714                if (IS_SYNC(inode)) {
 715                        sync_dirty_buffer(new_bh);
 716                        error = -EIO;
 717                        if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 718                                goto cleanup;
 719                }
 720        }
 721
 722        /* Update the inode. */
 723        EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 724        inode->i_ctime = current_time(inode);
 725        if (IS_SYNC(inode)) {
 726                error = sync_inode_metadata(inode, 1);
 727                /* In case sync failed due to ENOSPC the inode was actually
 728                 * written (only some dirty data were not) so we just proceed
 729                 * as if nothing happened and cleanup the unused block */
 730                if (error && error != -ENOSPC) {
 731                        if (new_bh && new_bh != old_bh) {
 732                                dquot_free_block_nodirty(inode, 1);
 733                                mark_inode_dirty(inode);
 734                        }
 735                        goto cleanup;
 736                }
 737        } else
 738                mark_inode_dirty(inode);
 739
 740        error = 0;
 741        if (old_bh && old_bh != new_bh) {
 742                /*
 743                 * If there was an old block and we are no longer using it,
 744                 * release the old block.
 745                 */
 746                lock_buffer(old_bh);
 747                if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 748                        __u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
 749
 750                        /*
 751                         * This must happen under buffer lock for
 752                         * ext2_xattr_set2() to reliably detect freed block
 753                         */
 754                        mb_cache_entry_delete(ea_block_cache, hash,
 755                                              old_bh->b_blocknr);
 756                        /* Free the old block. */
 757                        ea_bdebug(old_bh, "freeing");
 758                        ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 759                        mark_inode_dirty(inode);
 760                        /* We let our caller release old_bh, so we
 761                         * need to duplicate the buffer before. */
 762                        get_bh(old_bh);
 763                        bforget(old_bh);
 764                } else {
 765                        /* Decrement the refcount only. */
 766                        le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 767                        dquot_free_block_nodirty(inode, 1);
 768                        mark_inode_dirty(inode);
 769                        mark_buffer_dirty(old_bh);
 770                        ea_bdebug(old_bh, "refcount now=%d",
 771                                le32_to_cpu(HDR(old_bh)->h_refcount));
 772                }
 773                unlock_buffer(old_bh);
 774        }
 775
 776cleanup:
 777        brelse(new_bh);
 778
 779        return error;
 780}
 781
 782/*
 783 * ext2_xattr_delete_inode()
 784 *
 785 * Free extended attribute resources associated with this inode. This
 786 * is called immediately before an inode is freed.
 787 */
 788void
 789ext2_xattr_delete_inode(struct inode *inode)
 790{
 791        struct buffer_head *bh = NULL;
 792        struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 793
 794        /*
 795         * We are the only ones holding inode reference. The xattr_sem should
 796         * better be unlocked! We could as well just not acquire xattr_sem at
 797         * all but this makes the code more futureproof. OTOH we need trylock
 798         * here to avoid false-positive warning from lockdep about reclaim
 799         * circular dependency.
 800         */
 801        if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
 802                return;
 803        if (!EXT2_I(inode)->i_file_acl)
 804                goto cleanup;
 805
 806        if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 1)) {
 807                ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 808                        "inode %ld: xattr block %d is out of data blocks range",
 809                        inode->i_ino, EXT2_I(inode)->i_file_acl);
 810                goto cleanup;
 811        }
 812
 813        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 814        if (!bh) {
 815                ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 816                        "inode %ld: block %d read error", inode->i_ino,
 817                        EXT2_I(inode)->i_file_acl);
 818                goto cleanup;
 819        }
 820        ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 821        if (!ext2_xattr_header_valid(HDR(bh))) {
 822                ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 823                        "inode %ld: bad block %d", inode->i_ino,
 824                        EXT2_I(inode)->i_file_acl);
 825                goto cleanup;
 826        }
 827        lock_buffer(bh);
 828        if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 829                __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 830
 831                /*
 832                 * This must happen under buffer lock for ext2_xattr_set2() to
 833                 * reliably detect freed block
 834                 */
 835                mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 836                                      bh->b_blocknr);
 837                ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 838                get_bh(bh);
 839                bforget(bh);
 840                unlock_buffer(bh);
 841        } else {
 842                le32_add_cpu(&HDR(bh)->h_refcount, -1);
 843                ea_bdebug(bh, "refcount now=%d",
 844                        le32_to_cpu(HDR(bh)->h_refcount));
 845                unlock_buffer(bh);
 846                mark_buffer_dirty(bh);
 847                if (IS_SYNC(inode))
 848                        sync_dirty_buffer(bh);
 849                dquot_free_block_nodirty(inode, 1);
 850        }
 851        EXT2_I(inode)->i_file_acl = 0;
 852
 853cleanup:
 854        brelse(bh);
 855        up_write(&EXT2_I(inode)->xattr_sem);
 856}
 857
 858/*
 859 * ext2_xattr_cache_insert()
 860 *
 861 * Create a new entry in the extended attribute cache, and insert
 862 * it unless such an entry is already in the cache.
 863 *
 864 * Returns 0, or a negative error number on failure.
 865 */
 866static int
 867ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 868{
 869        __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 870        int error;
 871
 872        error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr,
 873                                      true);
 874        if (error) {
 875                if (error == -EBUSY) {
 876                        ea_bdebug(bh, "already in cache");
 877                        error = 0;
 878                }
 879        } else
 880                ea_bdebug(bh, "inserting [%x]", (int)hash);
 881        return error;
 882}
 883
 884/*
 885 * ext2_xattr_cmp()
 886 *
 887 * Compare two extended attribute blocks for equality.
 888 *
 889 * Returns 0 if the blocks are equal, 1 if they differ, and
 890 * a negative error number on errors.
 891 */
 892static int
 893ext2_xattr_cmp(struct ext2_xattr_header *header1,
 894               struct ext2_xattr_header *header2)
 895{
 896        struct ext2_xattr_entry *entry1, *entry2;
 897
 898        entry1 = ENTRY(header1+1);
 899        entry2 = ENTRY(header2+1);
 900        while (!IS_LAST_ENTRY(entry1)) {
 901                if (IS_LAST_ENTRY(entry2))
 902                        return 1;
 903                if (entry1->e_hash != entry2->e_hash ||
 904                    entry1->e_name_index != entry2->e_name_index ||
 905                    entry1->e_name_len != entry2->e_name_len ||
 906                    entry1->e_value_size != entry2->e_value_size ||
 907                    memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 908                        return 1;
 909                if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 910                        return -EIO;
 911                if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 912                           (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 913                           le32_to_cpu(entry1->e_value_size)))
 914                        return 1;
 915
 916                entry1 = EXT2_XATTR_NEXT(entry1);
 917                entry2 = EXT2_XATTR_NEXT(entry2);
 918        }
 919        if (!IS_LAST_ENTRY(entry2))
 920                return 1;
 921        return 0;
 922}
 923
 924/*
 925 * ext2_xattr_cache_find()
 926 *
 927 * Find an identical extended attribute block.
 928 *
 929 * Returns a locked buffer head to the block found, or NULL if such
 930 * a block was not found or an error occurred.
 931 */
 932static struct buffer_head *
 933ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 934{
 935        __u32 hash = le32_to_cpu(header->h_hash);
 936        struct mb_cache_entry *ce;
 937        struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 938
 939        if (!header->h_hash)
 940                return NULL;  /* never share */
 941        ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 942again:
 943        ce = mb_cache_entry_find_first(ea_block_cache, hash);
 944        while (ce) {
 945                struct buffer_head *bh;
 946
 947                bh = sb_bread(inode->i_sb, ce->e_value);
 948                if (!bh) {
 949                        ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 950                                "inode %ld: block %ld read error",
 951                                inode->i_ino, (unsigned long) ce->e_value);
 952                } else {
 953                        lock_buffer(bh);
 954                        /*
 955                         * We have to be careful about races with freeing or
 956                         * rehashing of xattr block. Once we hold buffer lock
 957                         * xattr block's state is stable so we can check
 958                         * whether the block got freed / rehashed or not.
 959                         * Since we unhash mbcache entry under buffer lock when
 960                         * freeing / rehashing xattr block, checking whether
 961                         * entry is still hashed is reliable.
 962                         */
 963                        if (hlist_bl_unhashed(&ce->e_hash_list)) {
 964                                mb_cache_entry_put(ea_block_cache, ce);
 965                                unlock_buffer(bh);
 966                                brelse(bh);
 967                                goto again;
 968                        } else if (le32_to_cpu(HDR(bh)->h_refcount) >
 969                                   EXT2_XATTR_REFCOUNT_MAX) {
 970                                ea_idebug(inode, "block %ld refcount %d>%d",
 971                                          (unsigned long) ce->e_value,
 972                                          le32_to_cpu(HDR(bh)->h_refcount),
 973                                          EXT2_XATTR_REFCOUNT_MAX);
 974                        } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 975                                ea_bdebug(bh, "b_count=%d",
 976                                          atomic_read(&(bh->b_count)));
 977                                mb_cache_entry_touch(ea_block_cache, ce);
 978                                mb_cache_entry_put(ea_block_cache, ce);
 979                                return bh;
 980                        }
 981                        unlock_buffer(bh);
 982                        brelse(bh);
 983                }
 984                ce = mb_cache_entry_find_next(ea_block_cache, ce);
 985        }
 986        return NULL;
 987}
 988
 989#define NAME_HASH_SHIFT 5
 990#define VALUE_HASH_SHIFT 16
 991
 992/*
 993 * ext2_xattr_hash_entry()
 994 *
 995 * Compute the hash of an extended attribute.
 996 */
 997static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 998                                         struct ext2_xattr_entry *entry)
 999{
1000        __u32 hash = 0;
1001        char *name = entry->e_name;
1002        int n;
1003
1004        for (n=0; n < entry->e_name_len; n++) {
1005                hash = (hash << NAME_HASH_SHIFT) ^
1006                       (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
1007                       *name++;
1008        }
1009
1010        if (entry->e_value_block == 0 && entry->e_value_size != 0) {
1011                __le32 *value = (__le32 *)((char *)header +
1012                        le16_to_cpu(entry->e_value_offs));
1013                for (n = (le32_to_cpu(entry->e_value_size) +
1014                     EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
1015                        hash = (hash << VALUE_HASH_SHIFT) ^
1016                               (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
1017                               le32_to_cpu(*value++);
1018                }
1019        }
1020        entry->e_hash = cpu_to_le32(hash);
1021}
1022
1023#undef NAME_HASH_SHIFT
1024#undef VALUE_HASH_SHIFT
1025
1026#define BLOCK_HASH_SHIFT 16
1027
1028/*
1029 * ext2_xattr_rehash()
1030 *
1031 * Re-compute the extended attribute hash value after an entry has changed.
1032 */
1033static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1034                              struct ext2_xattr_entry *entry)
1035{
1036        struct ext2_xattr_entry *here;
1037        __u32 hash = 0;
1038        
1039        ext2_xattr_hash_entry(header, entry);
1040        here = ENTRY(header+1);
1041        while (!IS_LAST_ENTRY(here)) {
1042                if (!here->e_hash) {
1043                        /* Block is not shared if an entry's hash value == 0 */
1044                        hash = 0;
1045                        break;
1046                }
1047                hash = (hash << BLOCK_HASH_SHIFT) ^
1048                       (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1049                       le32_to_cpu(here->e_hash);
1050                here = EXT2_XATTR_NEXT(here);
1051        }
1052        header->h_hash = cpu_to_le32(hash);
1053}
1054
1055#undef BLOCK_HASH_SHIFT
1056
1057#define HASH_BUCKET_BITS 10
1058
1059struct mb_cache *ext2_xattr_create_cache(void)
1060{
1061        return mb_cache_create(HASH_BUCKET_BITS);
1062}
1063
1064void ext2_xattr_destroy_cache(struct mb_cache *cache)
1065{
1066        if (cache)
1067                mb_cache_destroy(cache);
1068}
1069