linux/fs/ext2/xattr.c
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   1/*
   2 * linux/fs/ext2/xattr.c
   3 *
   4 * Copyright (C) 2001-2003 Andreas Gruenbacher <agruen@suse.de>
   5 *
   6 * Fix by Harrison Xing <harrison@mountainviewdata.com>.
   7 * Extended attributes for symlinks and special files added per
   8 *  suggestion of Luka Renko <luka.renko@hermes.si>.
   9 * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
  10 *  Red Hat Inc.
  11 *
  12 */
  13
  14/*
  15 * Extended attributes are stored on disk blocks allocated outside of
  16 * any inode. The i_file_acl field is then made to point to this allocated
  17 * block. If all extended attributes of an inode are identical, these
  18 * inodes may share the same extended attribute block. Such situations
  19 * are automatically detected by keeping a cache of recent attribute block
  20 * numbers and hashes over the block's contents in memory.
  21 *
  22 *
  23 * Extended attribute block layout:
  24 *
  25 *   +------------------+
  26 *   | header           |
  27 *   | entry 1          | |
  28 *   | entry 2          | | growing downwards
  29 *   | entry 3          | v
  30 *   | four null bytes  |
  31 *   | . . .            |
  32 *   | value 1          | ^
  33 *   | value 3          | | growing upwards
  34 *   | value 2          | |
  35 *   +------------------+
  36 *
  37 * The block header is followed by multiple entry descriptors. These entry
  38 * descriptors are variable in size, and aligned to EXT2_XATTR_PAD
  39 * byte boundaries. The entry descriptors are sorted by attribute name,
  40 * so that two extended attribute blocks can be compared efficiently.
  41 *
  42 * Attribute values are aligned to the end of the block, stored in
  43 * no specific order. They are also padded to EXT2_XATTR_PAD byte
  44 * boundaries. No additional gaps are left between them.
  45 *
  46 * Locking strategy
  47 * ----------------
  48 * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
  49 * EA blocks are only changed if they are exclusive to an inode, so
  50 * holding xattr_sem also means that nothing but the EA block's reference
  51 * count will change. Multiple writers to an EA block are synchronized
  52 * by the bh lock. No more than a single bh lock is held at any time
  53 * to avoid deadlocks.
  54 */
  55
  56#include <linux/buffer_head.h>
  57#include <linux/init.h>
  58#include <linux/slab.h>
  59#include <linux/mbcache.h>
  60#include <linux/quotaops.h>
  61#include <linux/rwsem.h>
  62#include <linux/security.h>
  63#include "ext2.h"
  64#include "xattr.h"
  65#include "acl.h"
  66
  67#define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  68#define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  69#define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  70#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  71
  72#ifdef EXT2_XATTR_DEBUG
  73# define ea_idebug(inode, f...) do { \
  74                printk(KERN_DEBUG "inode %s:%ld: ", \
  75                        inode->i_sb->s_id, inode->i_ino); \
  76                printk(f); \
  77                printk("\n"); \
  78        } while (0)
  79# define ea_bdebug(bh, f...) do { \
  80                char b[BDEVNAME_SIZE]; \
  81                printk(KERN_DEBUG "block %s:%lu: ", \
  82                        bdevname(bh->b_bdev, b), \
  83                        (unsigned long) bh->b_blocknr); \
  84                printk(f); \
  85                printk("\n"); \
  86        } while (0)
  87#else
  88# define ea_idebug(f...)
  89# define ea_bdebug(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 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 struct mb_cache *ext2_xattr_cache;
 102
 103static const struct xattr_handler *ext2_xattr_handler_map[] = {
 104        [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 105#ifdef CONFIG_EXT2_FS_POSIX_ACL
 106        [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext2_xattr_acl_access_handler,
 107        [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext2_xattr_acl_default_handler,
 108#endif
 109        [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
 110#ifdef CONFIG_EXT2_FS_SECURITY
 111        [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
 112#endif
 113};
 114
 115const struct xattr_handler *ext2_xattr_handlers[] = {
 116        &ext2_xattr_user_handler,
 117        &ext2_xattr_trusted_handler,
 118#ifdef CONFIG_EXT2_FS_POSIX_ACL
 119        &ext2_xattr_acl_access_handler,
 120        &ext2_xattr_acl_default_handler,
 121#endif
 122#ifdef CONFIG_EXT2_FS_SECURITY
 123        &ext2_xattr_security_handler,
 124#endif
 125        NULL
 126};
 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
 138/*
 139 * ext2_xattr_get()
 140 *
 141 * Copy an extended attribute into the buffer
 142 * provided, or compute the buffer size required.
 143 * Buffer is NULL to compute the size of the buffer required.
 144 *
 145 * Returns a negative error number on failure, or the number of bytes
 146 * used / required on success.
 147 */
 148int
 149ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 150               void *buffer, size_t buffer_size)
 151{
 152        struct buffer_head *bh = NULL;
 153        struct ext2_xattr_entry *entry;
 154        size_t name_len, size;
 155        char *end;
 156        int error;
 157
 158        ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 159                  name_index, name, buffer, (long)buffer_size);
 160
 161        if (name == NULL)
 162                return -EINVAL;
 163        name_len = strlen(name);
 164        if (name_len > 255)
 165                return -ERANGE;
 166
 167        down_read(&EXT2_I(inode)->xattr_sem);
 168        error = -ENODATA;
 169        if (!EXT2_I(inode)->i_file_acl)
 170                goto cleanup;
 171        ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 172        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 173        error = -EIO;
 174        if (!bh)
 175                goto cleanup;
 176        ea_bdebug(bh, "b_count=%d, refcount=%d",
 177                atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 178        end = bh->b_data + bh->b_size;
 179        if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 180            HDR(bh)->h_blocks != cpu_to_le32(1)) {
 181bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
 182                        "inode %ld: bad block %d", inode->i_ino,
 183                        EXT2_I(inode)->i_file_acl);
 184                error = -EIO;
 185                goto cleanup;
 186        }
 187
 188        /* find named attribute */
 189        entry = FIRST_ENTRY(bh);
 190        while (!IS_LAST_ENTRY(entry)) {
 191                struct ext2_xattr_entry *next =
 192                        EXT2_XATTR_NEXT(entry);
 193                if ((char *)next >= end)
 194                        goto bad_block;
 195                if (name_index == entry->e_name_index &&
 196                    name_len == entry->e_name_len &&
 197                    memcmp(name, entry->e_name, name_len) == 0)
 198                        goto found;
 199                entry = next;
 200        }
 201        if (ext2_xattr_cache_insert(bh))
 202                ea_idebug(inode, "cache insert failed");
 203        error = -ENODATA;
 204        goto cleanup;
 205found:
 206        /* check the buffer size */
 207        if (entry->e_value_block != 0)
 208                goto bad_block;
 209        size = le32_to_cpu(entry->e_value_size);
 210        if (size > inode->i_sb->s_blocksize ||
 211            le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
 212                goto bad_block;
 213
 214        if (ext2_xattr_cache_insert(bh))
 215                ea_idebug(inode, "cache insert failed");
 216        if (buffer) {
 217                error = -ERANGE;
 218                if (size > buffer_size)
 219                        goto cleanup;
 220                /* return value of attribute */
 221                memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 222                        size);
 223        }
 224        error = size;
 225
 226cleanup:
 227        brelse(bh);
 228        up_read(&EXT2_I(inode)->xattr_sem);
 229
 230        return error;
 231}
 232
 233/*
 234 * ext2_xattr_list()
 235 *
 236 * Copy a list of attribute names into the buffer
 237 * provided, or compute the buffer size required.
 238 * Buffer is NULL to compute the size of the buffer required.
 239 *
 240 * Returns a negative error number on failure, or the number of bytes
 241 * used / required on success.
 242 */
 243static int
 244ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 245{
 246        struct inode *inode = dentry->d_inode;
 247        struct buffer_head *bh = NULL;
 248        struct ext2_xattr_entry *entry;
 249        char *end;
 250        size_t rest = buffer_size;
 251        int error;
 252
 253        ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 254                  buffer, (long)buffer_size);
 255
 256        down_read(&EXT2_I(inode)->xattr_sem);
 257        error = 0;
 258        if (!EXT2_I(inode)->i_file_acl)
 259                goto cleanup;
 260        ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 261        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 262        error = -EIO;
 263        if (!bh)
 264                goto cleanup;
 265        ea_bdebug(bh, "b_count=%d, refcount=%d",
 266                atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 267        end = bh->b_data + bh->b_size;
 268        if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 269            HDR(bh)->h_blocks != cpu_to_le32(1)) {
 270bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
 271                        "inode %ld: bad block %d", inode->i_ino,
 272                        EXT2_I(inode)->i_file_acl);
 273                error = -EIO;
 274                goto cleanup;
 275        }
 276
 277        /* check the on-disk data structure */
 278        entry = FIRST_ENTRY(bh);
 279        while (!IS_LAST_ENTRY(entry)) {
 280                struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
 281
 282                if ((char *)next >= end)
 283                        goto bad_block;
 284                entry = next;
 285        }
 286        if (ext2_xattr_cache_insert(bh))
 287                ea_idebug(inode, "cache insert failed");
 288
 289        /* list the attribute names */
 290        for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 291             entry = EXT2_XATTR_NEXT(entry)) {
 292                const struct xattr_handler *handler =
 293                        ext2_xattr_handler(entry->e_name_index);
 294
 295                if (handler) {
 296                        size_t size = handler->list(dentry, buffer, rest,
 297                                                    entry->e_name,
 298                                                    entry->e_name_len,
 299                                                    handler->flags);
 300                        if (buffer) {
 301                                if (size > rest) {
 302                                        error = -ERANGE;
 303                                        goto cleanup;
 304                                }
 305                                buffer += size;
 306                        }
 307                        rest -= size;
 308                }
 309        }
 310        error = buffer_size - rest;  /* total size */
 311
 312cleanup:
 313        brelse(bh);
 314        up_read(&EXT2_I(inode)->xattr_sem);
 315
 316        return error;
 317}
 318
 319/*
 320 * Inode operation listxattr()
 321 *
 322 * dentry->d_inode->i_mutex: don't care
 323 */
 324ssize_t
 325ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 326{
 327        return ext2_xattr_list(dentry, buffer, size);
 328}
 329
 330/*
 331 * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 332 * not set, set it.
 333 */
 334static void ext2_xattr_update_super_block(struct super_block *sb)
 335{
 336        if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 337                return;
 338
 339        spin_lock(&EXT2_SB(sb)->s_lock);
 340        EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 341        spin_unlock(&EXT2_SB(sb)->s_lock);
 342        mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 343}
 344
 345/*
 346 * ext2_xattr_set()
 347 *
 348 * Create, replace or remove an extended attribute for this inode.  Value
 349 * is NULL to remove an existing extended attribute, and non-NULL to
 350 * either replace an existing extended attribute, or create a new extended
 351 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 352 * specify that an extended attribute must exist and must not exist
 353 * previous to the call, respectively.
 354 *
 355 * Returns 0, or a negative error number on failure.
 356 */
 357int
 358ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 359               const void *value, size_t value_len, int flags)
 360{
 361        struct super_block *sb = inode->i_sb;
 362        struct buffer_head *bh = NULL;
 363        struct ext2_xattr_header *header = NULL;
 364        struct ext2_xattr_entry *here, *last;
 365        size_t name_len, free, min_offs = sb->s_blocksize;
 366        int not_found = 1, error;
 367        char *end;
 368        
 369        /*
 370         * header -- Points either into bh, or to a temporarily
 371         *           allocated buffer.
 372         * here -- The named entry found, or the place for inserting, within
 373         *         the block pointed to by header.
 374         * last -- Points right after the last named entry within the block
 375         *         pointed to by header.
 376         * min_offs -- The offset of the first value (values are aligned
 377         *             towards the end of the block).
 378         * end -- Points right after the block pointed to by header.
 379         */
 380        
 381        ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 382                  name_index, name, value, (long)value_len);
 383
 384        if (value == NULL)
 385                value_len = 0;
 386        if (name == NULL)
 387                return -EINVAL;
 388        name_len = strlen(name);
 389        if (name_len > 255 || value_len > sb->s_blocksize)
 390                return -ERANGE;
 391        down_write(&EXT2_I(inode)->xattr_sem);
 392        if (EXT2_I(inode)->i_file_acl) {
 393                /* The inode already has an extended attribute block. */
 394                bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 395                error = -EIO;
 396                if (!bh)
 397                        goto cleanup;
 398                ea_bdebug(bh, "b_count=%d, refcount=%d",
 399                        atomic_read(&(bh->b_count)),
 400                        le32_to_cpu(HDR(bh)->h_refcount));
 401                header = HDR(bh);
 402                end = bh->b_data + bh->b_size;
 403                if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 404                    header->h_blocks != cpu_to_le32(1)) {
 405bad_block:              ext2_error(sb, "ext2_xattr_set",
 406                                "inode %ld: bad block %d", inode->i_ino, 
 407                                   EXT2_I(inode)->i_file_acl);
 408                        error = -EIO;
 409                        goto cleanup;
 410                }
 411                /* Find the named attribute. */
 412                here = FIRST_ENTRY(bh);
 413                while (!IS_LAST_ENTRY(here)) {
 414                        struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 415                        if ((char *)next >= end)
 416                                goto bad_block;
 417                        if (!here->e_value_block && here->e_value_size) {
 418                                size_t offs = le16_to_cpu(here->e_value_offs);
 419                                if (offs < min_offs)
 420                                        min_offs = offs;
 421                        }
 422                        not_found = name_index - here->e_name_index;
 423                        if (!not_found)
 424                                not_found = name_len - here->e_name_len;
 425                        if (!not_found)
 426                                not_found = memcmp(name, here->e_name,name_len);
 427                        if (not_found <= 0)
 428                                break;
 429                        here = next;
 430                }
 431                last = here;
 432                /* We still need to compute min_offs and last. */
 433                while (!IS_LAST_ENTRY(last)) {
 434                        struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 435                        if ((char *)next >= end)
 436                                goto bad_block;
 437                        if (!last->e_value_block && last->e_value_size) {
 438                                size_t offs = le16_to_cpu(last->e_value_offs);
 439                                if (offs < min_offs)
 440                                        min_offs = offs;
 441                        }
 442                        last = next;
 443                }
 444
 445                /* Check whether we have enough space left. */
 446                free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 447        } else {
 448                /* We will use a new extended attribute block. */
 449                free = sb->s_blocksize -
 450                        sizeof(struct ext2_xattr_header) - sizeof(__u32);
 451                here = last = NULL;  /* avoid gcc uninitialized warning. */
 452        }
 453
 454        if (not_found) {
 455                /* Request to remove a nonexistent attribute? */
 456                error = -ENODATA;
 457                if (flags & XATTR_REPLACE)
 458                        goto cleanup;
 459                error = 0;
 460                if (value == NULL)
 461                        goto cleanup;
 462        } else {
 463                /* Request to create an existing attribute? */
 464                error = -EEXIST;
 465                if (flags & XATTR_CREATE)
 466                        goto cleanup;
 467                if (!here->e_value_block && here->e_value_size) {
 468                        size_t size = le32_to_cpu(here->e_value_size);
 469
 470                        if (le16_to_cpu(here->e_value_offs) + size > 
 471                            sb->s_blocksize || size > sb->s_blocksize)
 472                                goto bad_block;
 473                        free += EXT2_XATTR_SIZE(size);
 474                }
 475                free += EXT2_XATTR_LEN(name_len);
 476        }
 477        error = -ENOSPC;
 478        if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 479                goto cleanup;
 480
 481        /* Here we know that we can set the new attribute. */
 482
 483        if (header) {
 484                struct mb_cache_entry *ce;
 485
 486                /* assert(header == HDR(bh)); */
 487                ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
 488                                        bh->b_blocknr);
 489                lock_buffer(bh);
 490                if (header->h_refcount == cpu_to_le32(1)) {
 491                        ea_bdebug(bh, "modifying in-place");
 492                        if (ce)
 493                                mb_cache_entry_free(ce);
 494                        /* keep the buffer locked while modifying it. */
 495                } else {
 496                        int offset;
 497
 498                        if (ce)
 499                                mb_cache_entry_release(ce);
 500                        unlock_buffer(bh);
 501                        ea_bdebug(bh, "cloning");
 502                        header = kmalloc(bh->b_size, GFP_KERNEL);
 503                        error = -ENOMEM;
 504                        if (header == NULL)
 505                                goto cleanup;
 506                        memcpy(header, HDR(bh), bh->b_size);
 507                        header->h_refcount = cpu_to_le32(1);
 508
 509                        offset = (char *)here - bh->b_data;
 510                        here = ENTRY((char *)header + offset);
 511                        offset = (char *)last - bh->b_data;
 512                        last = ENTRY((char *)header + offset);
 513                }
 514        } else {
 515                /* Allocate a buffer where we construct the new block. */
 516                header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 517                error = -ENOMEM;
 518                if (header == NULL)
 519                        goto cleanup;
 520                end = (char *)header + sb->s_blocksize;
 521                header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 522                header->h_blocks = header->h_refcount = cpu_to_le32(1);
 523                last = here = ENTRY(header+1);
 524        }
 525
 526        /* Iff we are modifying the block in-place, bh is locked here. */
 527
 528        if (not_found) {
 529                /* Insert the new name. */
 530                size_t size = EXT2_XATTR_LEN(name_len);
 531                size_t rest = (char *)last - (char *)here;
 532                memmove((char *)here + size, here, rest);
 533                memset(here, 0, size);
 534                here->e_name_index = name_index;
 535                here->e_name_len = name_len;
 536                memcpy(here->e_name, name, name_len);
 537        } else {
 538                if (!here->e_value_block && here->e_value_size) {
 539                        char *first_val = (char *)header + min_offs;
 540                        size_t offs = le16_to_cpu(here->e_value_offs);
 541                        char *val = (char *)header + offs;
 542                        size_t size = EXT2_XATTR_SIZE(
 543                                le32_to_cpu(here->e_value_size));
 544
 545                        if (size == EXT2_XATTR_SIZE(value_len)) {
 546                                /* The old and the new value have the same
 547                                   size. Just replace. */
 548                                here->e_value_size = cpu_to_le32(value_len);
 549                                memset(val + size - EXT2_XATTR_PAD, 0,
 550                                       EXT2_XATTR_PAD); /* Clear pad bytes. */
 551                                memcpy(val, value, value_len);
 552                                goto skip_replace;
 553                        }
 554
 555                        /* Remove the old value. */
 556                        memmove(first_val + size, first_val, val - first_val);
 557                        memset(first_val, 0, size);
 558                        here->e_value_offs = 0;
 559                        min_offs += size;
 560
 561                        /* Adjust all value offsets. */
 562                        last = ENTRY(header+1);
 563                        while (!IS_LAST_ENTRY(last)) {
 564                                size_t o = le16_to_cpu(last->e_value_offs);
 565                                if (!last->e_value_block && o < offs)
 566                                        last->e_value_offs =
 567                                                cpu_to_le16(o + size);
 568                                last = EXT2_XATTR_NEXT(last);
 569                        }
 570                }
 571                if (value == NULL) {
 572                        /* Remove the old name. */
 573                        size_t size = EXT2_XATTR_LEN(name_len);
 574                        last = ENTRY((char *)last - size);
 575                        memmove(here, (char*)here + size,
 576                                (char*)last - (char*)here);
 577                        memset(last, 0, size);
 578                }
 579        }
 580
 581        if (value != NULL) {
 582                /* Insert the new value. */
 583                here->e_value_size = cpu_to_le32(value_len);
 584                if (value_len) {
 585                        size_t size = EXT2_XATTR_SIZE(value_len);
 586                        char *val = (char *)header + min_offs - size;
 587                        here->e_value_offs =
 588                                cpu_to_le16((char *)val - (char *)header);
 589                        memset(val + size - EXT2_XATTR_PAD, 0,
 590                               EXT2_XATTR_PAD); /* Clear the pad bytes. */
 591                        memcpy(val, value, value_len);
 592                }
 593        }
 594
 595skip_replace:
 596        if (IS_LAST_ENTRY(ENTRY(header+1))) {
 597                /* This block is now empty. */
 598                if (bh && header == HDR(bh))
 599                        unlock_buffer(bh);  /* we were modifying in-place. */
 600                error = ext2_xattr_set2(inode, bh, NULL);
 601        } else {
 602                ext2_xattr_rehash(header, here);
 603                if (bh && header == HDR(bh))
 604                        unlock_buffer(bh);  /* we were modifying in-place. */
 605                error = ext2_xattr_set2(inode, bh, header);
 606        }
 607
 608cleanup:
 609        brelse(bh);
 610        if (!(bh && header == HDR(bh)))
 611                kfree(header);
 612        up_write(&EXT2_I(inode)->xattr_sem);
 613
 614        return error;
 615}
 616
 617/*
 618 * Second half of ext2_xattr_set(): Update the file system.
 619 */
 620static int
 621ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 622                struct ext2_xattr_header *header)
 623{
 624        struct super_block *sb = inode->i_sb;
 625        struct buffer_head *new_bh = NULL;
 626        int error;
 627
 628        if (header) {
 629                new_bh = ext2_xattr_cache_find(inode, header);
 630                if (new_bh) {
 631                        /* We found an identical block in the cache. */
 632                        if (new_bh == old_bh) {
 633                                ea_bdebug(new_bh, "keeping this block");
 634                        } else {
 635                                /* The old block is released after updating
 636                                   the inode.  */
 637                                ea_bdebug(new_bh, "reusing block");
 638
 639                                error = dquot_alloc_block(inode, 1);
 640                                if (error) {
 641                                        unlock_buffer(new_bh);
 642                                        goto cleanup;
 643                                }
 644                                le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 645                                ea_bdebug(new_bh, "refcount now=%d",
 646                                        le32_to_cpu(HDR(new_bh)->h_refcount));
 647                        }
 648                        unlock_buffer(new_bh);
 649                } else if (old_bh && header == HDR(old_bh)) {
 650                        /* Keep this block. No need to lock the block as we
 651                           don't need to change the reference count. */
 652                        new_bh = old_bh;
 653                        get_bh(new_bh);
 654                        ext2_xattr_cache_insert(new_bh);
 655                } else {
 656                        /* We need to allocate a new block */
 657                        ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 658                                                EXT2_I(inode)->i_block_group);
 659                        int block = ext2_new_block(inode, goal, &error);
 660                        if (error)
 661                                goto cleanup;
 662                        ea_idebug(inode, "creating block %d", block);
 663
 664                        new_bh = sb_getblk(sb, block);
 665                        if (!new_bh) {
 666                                ext2_free_blocks(inode, block, 1);
 667                                mark_inode_dirty(inode);
 668                                error = -EIO;
 669                                goto cleanup;
 670                        }
 671                        lock_buffer(new_bh);
 672                        memcpy(new_bh->b_data, header, new_bh->b_size);
 673                        set_buffer_uptodate(new_bh);
 674                        unlock_buffer(new_bh);
 675                        ext2_xattr_cache_insert(new_bh);
 676                        
 677                        ext2_xattr_update_super_block(sb);
 678                }
 679                mark_buffer_dirty(new_bh);
 680                if (IS_SYNC(inode)) {
 681                        sync_dirty_buffer(new_bh);
 682                        error = -EIO;
 683                        if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 684                                goto cleanup;
 685                }
 686        }
 687
 688        /* Update the inode. */
 689        EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 690        inode->i_ctime = CURRENT_TIME_SEC;
 691        if (IS_SYNC(inode)) {
 692                error = sync_inode_metadata(inode, 1);
 693                /* In case sync failed due to ENOSPC the inode was actually
 694                 * written (only some dirty data were not) so we just proceed
 695                 * as if nothing happened and cleanup the unused block */
 696                if (error && error != -ENOSPC) {
 697                        if (new_bh && new_bh != old_bh) {
 698                                dquot_free_block_nodirty(inode, 1);
 699                                mark_inode_dirty(inode);
 700                        }
 701                        goto cleanup;
 702                }
 703        } else
 704                mark_inode_dirty(inode);
 705
 706        error = 0;
 707        if (old_bh && old_bh != new_bh) {
 708                struct mb_cache_entry *ce;
 709
 710                /*
 711                 * If there was an old block and we are no longer using it,
 712                 * release the old block.
 713                 */
 714                ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
 715                                        old_bh->b_blocknr);
 716                lock_buffer(old_bh);
 717                if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 718                        /* Free the old block. */
 719                        if (ce)
 720                                mb_cache_entry_free(ce);
 721                        ea_bdebug(old_bh, "freeing");
 722                        ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 723                        mark_inode_dirty(inode);
 724                        /* We let our caller release old_bh, so we
 725                         * need to duplicate the buffer before. */
 726                        get_bh(old_bh);
 727                        bforget(old_bh);
 728                } else {
 729                        /* Decrement the refcount only. */
 730                        le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 731                        if (ce)
 732                                mb_cache_entry_release(ce);
 733                        dquot_free_block_nodirty(inode, 1);
 734                        mark_inode_dirty(inode);
 735                        mark_buffer_dirty(old_bh);
 736                        ea_bdebug(old_bh, "refcount now=%d",
 737                                le32_to_cpu(HDR(old_bh)->h_refcount));
 738                }
 739                unlock_buffer(old_bh);
 740        }
 741
 742cleanup:
 743        brelse(new_bh);
 744
 745        return error;
 746}
 747
 748/*
 749 * ext2_xattr_delete_inode()
 750 *
 751 * Free extended attribute resources associated with this inode. This
 752 * is called immediately before an inode is freed.
 753 */
 754void
 755ext2_xattr_delete_inode(struct inode *inode)
 756{
 757        struct buffer_head *bh = NULL;
 758        struct mb_cache_entry *ce;
 759
 760        down_write(&EXT2_I(inode)->xattr_sem);
 761        if (!EXT2_I(inode)->i_file_acl)
 762                goto cleanup;
 763        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 764        if (!bh) {
 765                ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 766                        "inode %ld: block %d read error", inode->i_ino,
 767                        EXT2_I(inode)->i_file_acl);
 768                goto cleanup;
 769        }
 770        ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 771        if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 772            HDR(bh)->h_blocks != cpu_to_le32(1)) {
 773                ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 774                        "inode %ld: bad block %d", inode->i_ino,
 775                        EXT2_I(inode)->i_file_acl);
 776                goto cleanup;
 777        }
 778        ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
 779        lock_buffer(bh);
 780        if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 781                if (ce)
 782                        mb_cache_entry_free(ce);
 783                ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 784                get_bh(bh);
 785                bforget(bh);
 786                unlock_buffer(bh);
 787        } else {
 788                le32_add_cpu(&HDR(bh)->h_refcount, -1);
 789                if (ce)
 790                        mb_cache_entry_release(ce);
 791                ea_bdebug(bh, "refcount now=%d",
 792                        le32_to_cpu(HDR(bh)->h_refcount));
 793                unlock_buffer(bh);
 794                mark_buffer_dirty(bh);
 795                if (IS_SYNC(inode))
 796                        sync_dirty_buffer(bh);
 797                dquot_free_block_nodirty(inode, 1);
 798        }
 799        EXT2_I(inode)->i_file_acl = 0;
 800
 801cleanup:
 802        brelse(bh);
 803        up_write(&EXT2_I(inode)->xattr_sem);
 804}
 805
 806/*
 807 * ext2_xattr_put_super()
 808 *
 809 * This is called when a file system is unmounted.
 810 */
 811void
 812ext2_xattr_put_super(struct super_block *sb)
 813{
 814        mb_cache_shrink(sb->s_bdev);
 815}
 816
 817
 818/*
 819 * ext2_xattr_cache_insert()
 820 *
 821 * Create a new entry in the extended attribute cache, and insert
 822 * it unless such an entry is already in the cache.
 823 *
 824 * Returns 0, or a negative error number on failure.
 825 */
 826static int
 827ext2_xattr_cache_insert(struct buffer_head *bh)
 828{
 829        __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 830        struct mb_cache_entry *ce;
 831        int error;
 832
 833        ce = mb_cache_entry_alloc(ext2_xattr_cache, GFP_NOFS);
 834        if (!ce)
 835                return -ENOMEM;
 836        error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, hash);
 837        if (error) {
 838                mb_cache_entry_free(ce);
 839                if (error == -EBUSY) {
 840                        ea_bdebug(bh, "already in cache (%d cache entries)",
 841                                atomic_read(&ext2_xattr_cache->c_entry_count));
 842                        error = 0;
 843                }
 844        } else {
 845                ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
 846                          atomic_read(&ext2_xattr_cache->c_entry_count));
 847                mb_cache_entry_release(ce);
 848        }
 849        return error;
 850}
 851
 852/*
 853 * ext2_xattr_cmp()
 854 *
 855 * Compare two extended attribute blocks for equality.
 856 *
 857 * Returns 0 if the blocks are equal, 1 if they differ, and
 858 * a negative error number on errors.
 859 */
 860static int
 861ext2_xattr_cmp(struct ext2_xattr_header *header1,
 862               struct ext2_xattr_header *header2)
 863{
 864        struct ext2_xattr_entry *entry1, *entry2;
 865
 866        entry1 = ENTRY(header1+1);
 867        entry2 = ENTRY(header2+1);
 868        while (!IS_LAST_ENTRY(entry1)) {
 869                if (IS_LAST_ENTRY(entry2))
 870                        return 1;
 871                if (entry1->e_hash != entry2->e_hash ||
 872                    entry1->e_name_index != entry2->e_name_index ||
 873                    entry1->e_name_len != entry2->e_name_len ||
 874                    entry1->e_value_size != entry2->e_value_size ||
 875                    memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 876                        return 1;
 877                if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 878                        return -EIO;
 879                if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 880                           (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 881                           le32_to_cpu(entry1->e_value_size)))
 882                        return 1;
 883
 884                entry1 = EXT2_XATTR_NEXT(entry1);
 885                entry2 = EXT2_XATTR_NEXT(entry2);
 886        }
 887        if (!IS_LAST_ENTRY(entry2))
 888                return 1;
 889        return 0;
 890}
 891
 892/*
 893 * ext2_xattr_cache_find()
 894 *
 895 * Find an identical extended attribute block.
 896 *
 897 * Returns a locked buffer head to the block found, or NULL if such
 898 * a block was not found or an error occurred.
 899 */
 900static struct buffer_head *
 901ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 902{
 903        __u32 hash = le32_to_cpu(header->h_hash);
 904        struct mb_cache_entry *ce;
 905
 906        if (!header->h_hash)
 907                return NULL;  /* never share */
 908        ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 909again:
 910        ce = mb_cache_entry_find_first(ext2_xattr_cache, inode->i_sb->s_bdev,
 911                                       hash);
 912        while (ce) {
 913                struct buffer_head *bh;
 914
 915                if (IS_ERR(ce)) {
 916                        if (PTR_ERR(ce) == -EAGAIN)
 917                                goto again;
 918                        break;
 919                }
 920
 921                bh = sb_bread(inode->i_sb, ce->e_block);
 922                if (!bh) {
 923                        ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 924                                "inode %ld: block %ld read error",
 925                                inode->i_ino, (unsigned long) ce->e_block);
 926                } else {
 927                        lock_buffer(bh);
 928                        if (le32_to_cpu(HDR(bh)->h_refcount) >
 929                                   EXT2_XATTR_REFCOUNT_MAX) {
 930                                ea_idebug(inode, "block %ld refcount %d>%d",
 931                                          (unsigned long) ce->e_block,
 932                                          le32_to_cpu(HDR(bh)->h_refcount),
 933                                          EXT2_XATTR_REFCOUNT_MAX);
 934                        } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 935                                ea_bdebug(bh, "b_count=%d",
 936                                          atomic_read(&(bh->b_count)));
 937                                mb_cache_entry_release(ce);
 938                                return bh;
 939                        }
 940                        unlock_buffer(bh);
 941                        brelse(bh);
 942                }
 943                ce = mb_cache_entry_find_next(ce, inode->i_sb->s_bdev, hash);
 944        }
 945        return NULL;
 946}
 947
 948#define NAME_HASH_SHIFT 5
 949#define VALUE_HASH_SHIFT 16
 950
 951/*
 952 * ext2_xattr_hash_entry()
 953 *
 954 * Compute the hash of an extended attribute.
 955 */
 956static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 957                                         struct ext2_xattr_entry *entry)
 958{
 959        __u32 hash = 0;
 960        char *name = entry->e_name;
 961        int n;
 962
 963        for (n=0; n < entry->e_name_len; n++) {
 964                hash = (hash << NAME_HASH_SHIFT) ^
 965                       (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 966                       *name++;
 967        }
 968
 969        if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 970                __le32 *value = (__le32 *)((char *)header +
 971                        le16_to_cpu(entry->e_value_offs));
 972                for (n = (le32_to_cpu(entry->e_value_size) +
 973                     EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
 974                        hash = (hash << VALUE_HASH_SHIFT) ^
 975                               (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 976                               le32_to_cpu(*value++);
 977                }
 978        }
 979        entry->e_hash = cpu_to_le32(hash);
 980}
 981
 982#undef NAME_HASH_SHIFT
 983#undef VALUE_HASH_SHIFT
 984
 985#define BLOCK_HASH_SHIFT 16
 986
 987/*
 988 * ext2_xattr_rehash()
 989 *
 990 * Re-compute the extended attribute hash value after an entry has changed.
 991 */
 992static void ext2_xattr_rehash(struct ext2_xattr_header *header,
 993                              struct ext2_xattr_entry *entry)
 994{
 995        struct ext2_xattr_entry *here;
 996        __u32 hash = 0;
 997        
 998        ext2_xattr_hash_entry(header, entry);
 999        here = ENTRY(header+1);
1000        while (!IS_LAST_ENTRY(here)) {
1001                if (!here->e_hash) {
1002                        /* Block is not shared if an entry's hash value == 0 */
1003                        hash = 0;
1004                        break;
1005                }
1006                hash = (hash << BLOCK_HASH_SHIFT) ^
1007                       (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1008                       le32_to_cpu(here->e_hash);
1009                here = EXT2_XATTR_NEXT(here);
1010        }
1011        header->h_hash = cpu_to_le32(hash);
1012}
1013
1014#undef BLOCK_HASH_SHIFT
1015
1016int __init
1017init_ext2_xattr(void)
1018{
1019        ext2_xattr_cache = mb_cache_create("ext2_xattr", 6);
1020        if (!ext2_xattr_cache)
1021                return -ENOMEM;
1022        return 0;
1023}
1024
1025void
1026exit_ext2_xattr(void)
1027{
1028        mb_cache_destroy(ext2_xattr_cache);
1029}
1030
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