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 alligned 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/module.h>
  58#include <linux/init.h>
  59#include <linux/slab.h>
  60#include <linux/mbcache.h>
  61#include <linux/quotaops.h>
  62#include <linux/rwsem.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 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
 115struct 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 struct xattr_handler *
 129ext2_xattr_handler(int name_index)
 130{
 131        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        down_read(&EXT2_I(inode)->xattr_sem);
 164        error = -ENODATA;
 165        if (!EXT2_I(inode)->i_file_acl)
 166                goto cleanup;
 167        ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 168        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 169        error = -EIO;
 170        if (!bh)
 171                goto cleanup;
 172        ea_bdebug(bh, "b_count=%d, refcount=%d",
 173                atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 174        end = bh->b_data + bh->b_size;
 175        if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 176            HDR(bh)->h_blocks != cpu_to_le32(1)) {
 177bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
 178                        "inode %ld: bad block %d", inode->i_ino,
 179                        EXT2_I(inode)->i_file_acl);
 180                error = -EIO;
 181                goto cleanup;
 182        }
 183        /* find named attribute */
 184        name_len = strlen(name);
 185
 186        error = -ERANGE;
 187        if (name_len > 255)
 188                goto cleanup;
 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        /* Check the remaining name entries */
 202        while (!IS_LAST_ENTRY(entry)) {
 203                struct ext2_xattr_entry *next =
 204                        EXT2_XATTR_NEXT(entry);
 205                if ((char *)next >= end)
 206                        goto bad_block;
 207                entry = next;
 208        }
 209        if (ext2_xattr_cache_insert(bh))
 210                ea_idebug(inode, "cache insert failed");
 211        error = -ENODATA;
 212        goto cleanup;
 213found:
 214        /* check the buffer size */
 215        if (entry->e_value_block != 0)
 216                goto bad_block;
 217        size = le32_to_cpu(entry->e_value_size);
 218        if (size > inode->i_sb->s_blocksize ||
 219            le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
 220                goto bad_block;
 221
 222        if (ext2_xattr_cache_insert(bh))
 223                ea_idebug(inode, "cache insert failed");
 224        if (buffer) {
 225                error = -ERANGE;
 226                if (size > buffer_size)
 227                        goto cleanup;
 228                /* return value of attribute */
 229                memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 230                        size);
 231        }
 232        error = size;
 233
 234cleanup:
 235        brelse(bh);
 236        up_read(&EXT2_I(inode)->xattr_sem);
 237
 238        return error;
 239}
 240
 241/*
 242 * ext2_xattr_list()
 243 *
 244 * Copy a list of attribute names into the buffer
 245 * provided, or compute the buffer size required.
 246 * Buffer is NULL to compute the size of the buffer required.
 247 *
 248 * Returns a negative error number on failure, or the number of bytes
 249 * used / required on success.
 250 */
 251static int
 252ext2_xattr_list(struct inode *inode, char *buffer, size_t buffer_size)
 253{
 254        struct buffer_head *bh = NULL;
 255        struct ext2_xattr_entry *entry;
 256        char *end;
 257        size_t rest = buffer_size;
 258        int error;
 259
 260        ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 261                  buffer, (long)buffer_size);
 262
 263        down_read(&EXT2_I(inode)->xattr_sem);
 264        error = 0;
 265        if (!EXT2_I(inode)->i_file_acl)
 266                goto cleanup;
 267        ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 268        bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 269        error = -EIO;
 270        if (!bh)
 271                goto cleanup;
 272        ea_bdebug(bh, "b_count=%d, refcount=%d",
 273                atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 274        end = bh->b_data + bh->b_size;
 275        if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 276            HDR(bh)->h_blocks != cpu_to_le32(1)) {
 277bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
 278                        "inode %ld: bad block %d", inode->i_ino,
 279                        EXT2_I(inode)->i_file_acl);
 280                error = -EIO;
 281                goto cleanup;
 282        }
 283
 284        /* check the on-disk data structure */
 285        entry = FIRST_ENTRY(bh);
 286        while (!IS_LAST_ENTRY(entry)) {
 287                struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
 288
 289                if ((char *)next >= end)
 290                        goto bad_block;
 291                entry = next;
 292        }
 293        if (ext2_xattr_cache_insert(bh))
 294                ea_idebug(inode, "cache insert failed");
 295
 296        /* list the attribute names */
 297        for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 298             entry = EXT2_XATTR_NEXT(entry)) {
 299                struct xattr_handler *handler =
 300                        ext2_xattr_handler(entry->e_name_index);
 301
 302                if (handler) {
 303                        size_t size = handler->list(inode, buffer, rest,
 304                                                    entry->e_name,
 305                                                    entry->e_name_len);
 306                        if (buffer) {
 307                                if (size > rest) {
 308                                        error = -ERANGE;
 309                                        goto cleanup;
 310                                }
 311                                buffer += size;
 312                        }
 313                        rest -= size;
 314                }
 315        }
 316        error = buffer_size - rest;  /* total size */
 317
 318cleanup:
 319        brelse(bh);
 320        up_read(&EXT2_I(inode)->xattr_sem);
 321
 322        return error;
 323}
 324
 325/*
 326 * Inode operation listxattr()
 327 *
 328 * dentry->d_inode->i_mutex: don't care
 329 */
 330ssize_t
 331ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 332{
 333        return ext2_xattr_list(dentry->d_inode, buffer, size);
 334}
 335
 336/*
 337 * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 338 * not set, set it.
 339 */
 340static void ext2_xattr_update_super_block(struct super_block *sb)
 341{
 342        if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 343                return;
 344
 345        EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 346        sb->s_dirt = 1;
 347        mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 348}
 349
 350/*
 351 * ext2_xattr_set()
 352 *
 353 * Create, replace or remove an extended attribute for this inode. Buffer
 354 * is NULL to remove an existing extended attribute, and non-NULL to
 355 * either replace an existing extended attribute, or create a new extended
 356 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 357 * specify that an extended attribute must exist and must not exist
 358 * previous to the call, respectively.
 359 *
 360 * Returns 0, or a negative error number on failure.
 361 */
 362int
 363ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 364               const void *value, size_t value_len, int flags)
 365{
 366        struct super_block *sb = inode->i_sb;
 367        struct buffer_head *bh = NULL;
 368        struct ext2_xattr_header *header = NULL;
 369        struct ext2_xattr_entry *here, *last;
 370        size_t name_len, free, min_offs = sb->s_blocksize;
 371        int not_found = 1, error;
 372        char *end;
 373        
 374        /*
 375         * header -- Points either into bh, or to a temporarily
 376         *           allocated buffer.
 377         * here -- The named entry found, or the place for inserting, within
 378         *         the block pointed to by header.
 379         * last -- Points right after the last named entry within the block
 380         *         pointed to by header.
 381         * min_offs -- The offset of the first value (values are aligned
 382         *             towards the end of the block).
 383         * end -- Points right after the block pointed to by header.
 384         */
 385        
 386        ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 387                  name_index, name, value, (long)value_len);
 388
 389        if (value == NULL)
 390                value_len = 0;
 391        if (name == NULL)
 392                return -EINVAL;
 393        name_len = strlen(name);
 394        if (name_len > 255 || value_len > sb->s_blocksize)
 395                return -ERANGE;
 396        down_write(&EXT2_I(inode)->xattr_sem);
 397        if (EXT2_I(inode)->i_file_acl) {
 398                /* The inode already has an extended attribute block. */
 399                bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 400                error = -EIO;
 401                if (!bh)
 402                        goto cleanup;
 403                ea_bdebug(bh, "b_count=%d, refcount=%d",
 404                        atomic_read(&(bh->b_count)),
 405                        le32_to_cpu(HDR(bh)->h_refcount));
 406                header = HDR(bh);
 407                end = bh->b_data + bh->b_size;
 408                if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 409                    header->h_blocks != cpu_to_le32(1)) {
 410bad_block:              ext2_error(sb, "ext2_xattr_set",
 411                                "inode %ld: bad block %d", inode->i_ino, 
 412                                   EXT2_I(inode)->i_file_acl);
 413                        error = -EIO;
 414                        goto cleanup;
 415                }
 416                /* Find the named attribute. */
 417                here = FIRST_ENTRY(bh);
 418                while (!IS_LAST_ENTRY(here)) {
 419                        struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 420                        if ((char *)next >= end)
 421                                goto bad_block;
 422                        if (!here->e_value_block && here->e_value_size) {
 423                                size_t offs = le16_to_cpu(here->e_value_offs);
 424                                if (offs < min_offs)
 425                                        min_offs = offs;
 426                        }
 427                        not_found = name_index - here->e_name_index;
 428                        if (!not_found)
 429                                not_found = name_len - here->e_name_len;
 430                        if (!not_found)
 431                                not_found = memcmp(name, here->e_name,name_len);
 432                        if (not_found <= 0)
 433                                break;
 434                        here = next;
 435                }
 436                last = here;
 437                /* We still need to compute min_offs and last. */
 438                while (!IS_LAST_ENTRY(last)) {
 439                        struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 440                        if ((char *)next >= end)
 441                                goto bad_block;
 442                        if (!last->e_value_block && last->e_value_size) {
 443                                size_t offs = le16_to_cpu(last->e_value_offs);
 444                                if (offs < min_offs)
 445                                        min_offs = offs;
 446                        }
 447                        last = next;
 448                }
 449
 450                /* Check whether we have enough space left. */
 451                free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 452        } else {
 453                /* We will use a new extended attribute block. */
 454                free = sb->s_blocksize -
 455                        sizeof(struct ext2_xattr_header) - sizeof(__u32);
 456                here = last = NULL;  /* avoid gcc uninitialized warning. */
 457        }
 458
 459        if (not_found) {
 460                /* Request to remove a nonexistent attribute? */
 461                error = -ENODATA;
 462                if (flags & XATTR_REPLACE)
 463                        goto cleanup;
 464                error = 0;
 465                if (value == NULL)
 466                        goto cleanup;
 467        } else {
 468                /* Request to create an existing attribute? */
 469                error = -EEXIST;
 470                if (flags & XATTR_CREATE)
 471                        goto cleanup;
 472                if (!here->e_value_block && here->e_value_size) {
 473                        size_t size = le32_to_cpu(here->e_value_size);
 474
 475                        if (le16_to_cpu(here->e_value_offs) + size > 
 476                            sb->s_blocksize || size > sb->s_blocksize)
 477                                goto bad_block;
 478                        free += EXT2_XATTR_SIZE(size);
 479                }
 480                free += EXT2_XATTR_LEN(name_len);
 481        }
 482        error = -ENOSPC;
 483        if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 484                goto cleanup;
 485
 486        /* Here we know that we can set the new attribute. */
 487
 488        if (header) {
 489                struct mb_cache_entry *ce;
 490
 491                /* assert(header == HDR(bh)); */
 492                ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
 493                                        bh->b_blocknr);
 494                lock_buffer(bh);
 495                if (header->h_refcount == cpu_to_le32(1)) {
 496                        ea_bdebug(bh, "modifying in-place");
 497                        if (ce)
 498                                mb_cache_entry_free(ce);
 499                        /* keep the buffer locked while modifying it. */
 500                } else {
 501                        int offset;
 502
 503                        if (ce)
 504                                mb_cache_entry_release(ce);
 505                        unlock_buffer(bh);
 506                        ea_bdebug(bh, "cloning");
 507                        header = kmalloc(bh->b_size, GFP_KERNEL);
 508                        error = -ENOMEM;
 509                        if (header == NULL)
 510                                goto cleanup;
 511                        memcpy(header, HDR(bh), bh->b_size);
 512                        header->h_refcount = cpu_to_le32(1);
 513
 514                        offset = (char *)here - bh->b_data;
 515                        here = ENTRY((char *)header + offset);
 516                        offset = (char *)last - bh->b_data;
 517                        last = ENTRY((char *)header + offset);
 518                }
 519        } else {
 520                /* Allocate a buffer where we construct the new block. */
 521                header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 522                error = -ENOMEM;
 523                if (header == NULL)
 524                        goto cleanup;
 525                end = (char *)header + sb->s_blocksize;
 526                header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 527                header->h_blocks = header->h_refcount = cpu_to_le32(1);
 528                last = here = ENTRY(header+1);
 529        }
 530
 531        /* Iff we are modifying the block in-place, bh is locked here. */
 532
 533        if (not_found) {
 534                /* Insert the new name. */
 535                size_t size = EXT2_XATTR_LEN(name_len);
 536                size_t rest = (char *)last - (char *)here;
 537                memmove((char *)here + size, here, rest);
 538                memset(here, 0, size);
 539                here->e_name_index = name_index;
 540                here->e_name_len = name_len;
 541                memcpy(here->e_name, name, name_len);
 542        } else {
 543                if (!here->e_value_block && here->e_value_size) {
 544                        char *first_val = (char *)header + min_offs;
 545                        size_t offs = le16_to_cpu(here->e_value_offs);
 546                        char *val = (char *)header + offs;
 547                        size_t size = EXT2_XATTR_SIZE(
 548                                le32_to_cpu(here->e_value_size));
 549
 550                        if (size == EXT2_XATTR_SIZE(value_len)) {
 551                                /* The old and the new value have the same
 552                                   size. Just replace. */
 553                                here->e_value_size = cpu_to_le32(value_len);
 554                                memset(val + size - EXT2_XATTR_PAD, 0,
 555                                       EXT2_XATTR_PAD); /* Clear pad bytes. */
 556                                memcpy(val, value, value_len);
 557                                goto skip_replace;
 558                        }
 559
 560                        /* Remove the old value. */
 561                        memmove(first_val + size, first_val, val - first_val);
 562                        memset(first_val, 0, size);
 563                        here->e_value_offs = 0;
 564                        min_offs += size;
 565
 566                        /* Adjust all value offsets. */
 567                        last = ENTRY(header+1);
 568                        while (!IS_LAST_ENTRY(last)) {
 569                                size_t o = le16_to_cpu(last->e_value_offs);
 570                                if (!last->e_value_block && o < offs)
 571                                        last->e_value_offs =
 572                                                cpu_to_le16(o + size);
 573                                last = EXT2_XATTR_NEXT(last);
 574                        }
 575                }
 576                if (value == NULL) {
 577                        /* Remove the old name. */
 578                        size_t size = EXT2_XATTR_LEN(name_len);
 579                        last = ENTRY((char *)last - size);
 580                        memmove(here, (char*)here + size,
 581                                (char*)last - (char*)here);
 582                        memset(last, 0, size);
 583                }
 584        }
 585
 586        if (value != NULL) {
 587                /* Insert the new value. */
 588                here->e_value_size = cpu_to_le32(value_len);
 589                if (value_len) {
 590                        size_t size = EXT2_XATTR_SIZE(value_len);
 591                        char *val = (char *)header + min_offs - size;
 592                        here->e_value_offs =
 593                                cpu_to_le16((char *)val - (char *)header);
 594                        memset(val + size - EXT2_XATTR_PAD, 0,
 595                               EXT2_XATTR_PAD); /* Clear the pad bytes. */
 596                        memcpy(val, value, value_len);
 597                }
 598        }
 599
 600skip_replace:
 601        if (IS_LAST_ENTRY(ENTRY(header+1))) {
 602                /* This block is now empty. */
 603                if (bh && header == HDR(bh))
 604                        unlock_buffer(bh);  /* we were modifying in-place. */
 605                error = ext2_xattr_set2(inode, bh, NULL);
 606        } else {
 607                ext2_xattr_rehash(header, here);
 608                if (bh && header == HDR(bh))
 609                        unlock_buffer(bh);  /* we were modifying in-place. */
 610                error = ext2_xattr_set2(inode, bh, header);
 611        }
 612
 613cleanup:
 614        brelse(bh);
 615        if (!(bh && header == HDR(bh)))
 616                kfree(header);
 617        up_write(&EXT2_I(inode)->xattr_sem);
 618
 619        return error;
 620}
 621
 622/*
 623 * Second half of ext2_xattr_set(): Update the file system.
 624 */
 625static int
 626ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 627                struct ext2_xattr_header *header)
 628{
 629        struct super_block *sb = inode->i_sb;
 630        struct buffer_head *new_bh = NULL;
 631        int error;
 632
 633        if (header) {
 634                new_bh = ext2_xattr_cache_find(inode, header);
 635                if (new_bh) {
 636                        /* We found an identical block in the cache. */
 637                        if (new_bh == old_bh) {
 638                                ea_bdebug(new_bh, "keeping this block");
 639                        } else {
 640                                /* The old block is released after updating
 641                                   the inode.  */
 642                                ea_bdebug(new_bh, "reusing block");
 643
 644                                error = -EDQUOT;
 645                                if (DQUOT_ALLOC_BLOCK(inode, 1)) {
 646                                        unlock_buffer(new_bh);
 647                                        goto cleanup;
 648                                }
 649                                le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 650                                ea_bdebug(new_bh, "refcount now=%d",
 651                                        le32_to_cpu(HDR(new_bh)->h_refcount));
 652                        }
 653                        unlock_buffer(new_bh);
 654                } else if (old_bh && header == HDR(old_bh)) {
 655                        /* Keep this block. No need to lock the block as we
 656                           don't need to change the reference count. */
 657                        new_bh = old_bh;
 658                        get_bh(new_bh);
 659                        ext2_xattr_cache_insert(new_bh);
 660                } else {
 661                        /* We need to allocate a new block */
 662                        ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 663                                                EXT2_I(inode)->i_block_group);
 664                        int block = ext2_new_block(inode, goal, &error);
 665                        if (error)
 666                                goto cleanup;
 667                        ea_idebug(inode, "creating block %d", block);
 668
 669                        new_bh = sb_getblk(sb, block);
 670                        if (!new_bh) {
 671                                ext2_free_blocks(inode, block, 1);
 672                                error = -EIO;
 673                                goto cleanup;
 674                        }
 675                        lock_buffer(new_bh);
 676                        memcpy(new_bh->b_data, header, new_bh->b_size);
 677                        set_buffer_uptodate(new_bh);
 678                        unlock_buffer(new_bh);
 679                        ext2_xattr_cache_insert(new_bh);
 680                        
 681                        ext2_xattr_update_super_block(sb);
 682                }
 683                mark_buffer_dirty(new_bh);
 684                if (IS_SYNC(inode)) {
 685                        sync_dirty_buffer(new_bh);
 686                        error = -EIO;
 687                        if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 688                                goto cleanup;
 689                }
 690        }
 691
 692        /* Update the inode. */
 693        EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 694        inode->i_ctime = CURRENT_TIME_SEC;
 695        if (IS_SYNC(inode)) {
 696                error = ext2_sync_inode (inode);
 697                /* In case sync failed due to ENOSPC the inode was actually
 698                 * written (only some dirty data were not) so we just proceed
 699                 * as if nothing happened and cleanup the unused block */
 700                if (error && error != -ENOSPC) {
 701                        if (new_bh && new_bh != old_bh)
 702                                DQUOT_FREE_BLOCK(inode, 1);
 703                        goto cleanup;
 704                }
 705        } else
 706                mark_inode_dirty(inode);
 707
 708        error = 0;
 709        if (old_bh && old_bh != new_bh) {
 710                struct mb_cache_entry *ce;
 711
 712                /*
 713                 * If there was an old block and we are no longer using it,
 714                 * release the old block.
 715                 */
 716                ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
 717                                        old_bh->b_blocknr);
 718                lock_buffer(old_bh);
 719                if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 720                        /* Free the old block. */
 721                        if (ce)
 722                                mb_cache_entry_free(ce);
 723                        ea_bdebug(old_bh, "freeing");
 724                        ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 725                        /* We let our caller release old_bh, so we
 726                         * need to duplicate the buffer before. */
 727                        get_bh(old_bh);
 728                        bforget(old_bh);
 729                } else {
 730                        /* Decrement the refcount only. */
 731                        le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 732                        if (ce)
 733                                mb_cache_entry_release(ce);
 734                        DQUOT_FREE_BLOCK(inode, 1);
 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(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, 0,
 911                                       inode->i_sb->s_bdev, 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, 0, 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", NULL,
1020                sizeof(struct mb_cache_entry) +
1021                sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
1022        if (!ext2_xattr_cache)
1023                return -ENOMEM;
1024        return 0;
1025}
1026
1027void
1028exit_ext2_xattr(void)
1029{
1030        mb_cache_destroy(ext2_xattr_cache);
1031}
1032
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