release/src-rt-6.x.4708/linux/linux-2.6.36/fs/ext2/xattr.c

   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 <linux/security.h>
  64 #include "ext2.h"
  65 #include "xattr.h"
  66 #include "acl.h"
  67
  68 #define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  69 #define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  70 #define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  71 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  72
  73 #ifdef EXT2_XATTR_DEBUG
  74 # define ea_idebug(inode, f...) do { \
  75                 printk(KERN_DEBUG "inode %s:%ld: ", \
  76                         inode->i_sb->s_id, inode->i_ino); \
  77                 printk(f); \
  78                 printk("\n"); \
  79         } while (0)
  80 # define ea_bdebug(bh, f...) do { \
  81                 char b[BDEVNAME_SIZE]; \
  82                 printk(KERN_DEBUG "block %s:%lu: ", \
  83                         bdevname(bh->b_bdev, b), \
  84                         (unsigned long) bh->b_blocknr); \
  85                 printk(f); \
  86                 printk("\n"); \
  87         } while (0)
  88 #else
  89 # define ea_idebug(f...)
  90 # define ea_bdebug(f...)
  91 #endif
  92
  93 static int ext2_xattr_set2(struct inode *, struct buffer_head *,
  94                            struct ext2_xattr_header *);
  95
  96 static int ext2_xattr_cache_insert(struct buffer_head *);
  97 static struct buffer_head *ext2_xattr_cache_find(struct inode *,
  98                                                  struct ext2_xattr_header *);
  99 static void ext2_xattr_rehash(struct ext2_xattr_header *,
 100                               struct ext2_xattr_entry *);
 101
 102 static struct mb_cache *ext2_xattr_cache;
 103
 104 static const struct xattr_handler *ext2_xattr_handler_map[] = {
 105         [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 106 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 107         [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext2_xattr_acl_access_handler,
 108         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext2_xattr_acl_default_handler,
 109 #endif
 110         [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
 111 #ifdef CONFIG_EXT2_FS_SECURITY
 112         [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
 113 #endif
 114 };
 115
 116 const struct xattr_handler *ext2_xattr_handlers[] = {
 117         &ext2_xattr_user_handler,
 118         &ext2_xattr_trusted_handler,
 119 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 120         &ext2_xattr_acl_access_handler,
 121         &ext2_xattr_acl_default_handler,
 122 #endif
 123 #ifdef CONFIG_EXT2_FS_SECURITY
 124         &ext2_xattr_security_handler,
 125 #endif
 126         NULL
 127 };
 128
 129 static inline const struct xattr_handler *
 130 ext2_xattr_handler(int name_index)
 131 {
 132         const struct xattr_handler *handler = NULL;
 133
 134         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 135                 handler = ext2_xattr_handler_map[name_index];
 136         return handler;
 137 }
 138
 139 /*
 140  * ext2_xattr_get()
 141  *
 142  * Copy an extended attribute into the buffer
 143  * provided, or compute the buffer size required.
 144  * Buffer is NULL to compute the size of the buffer required.
 145  *
 146  * Returns a negative error number on failure, or the number of bytes
 147  * used / required on success.
 148  */
 149 int
 150 ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 151                void *buffer, size_t buffer_size)
 152 {
 153         struct buffer_head *bh = NULL;
 154         struct ext2_xattr_entry *entry;
 155         size_t name_len, size;
 156         char *end;
 157         int error;
 158
 159         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 160                   name_index, name, buffer, (long)buffer_size);
 161
 162         if (name == NULL)
 163                 return -EINVAL;
 164         down_read(&EXT2_I(inode)->xattr_sem);
 165         error = -ENODATA;
 166         if (!EXT2_I(inode)->i_file_acl)
 167                 goto cleanup;
 168         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 169         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 170         error = -EIO;
 171         if (!bh)
 172                 goto cleanup;
 173         ea_bdebug(bh, "b_count=%d, refcount=%d",
 174                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 175         end = bh->b_data + bh->b_size;
 176         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 177             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 178 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
 179                         "inode %ld: bad block %d", inode->i_ino,
 180                         EXT2_I(inode)->i_file_acl);
 181                 error = -EIO;
 182                 goto cleanup;
 183         }
 184         /* find named attribute */
 185         name_len = strlen(name);
 186
 187         error = -ERANGE;
 188         if (name_len > 255)
 189                 goto cleanup;
 190         entry = FIRST_ENTRY(bh);
 191         while (!IS_LAST_ENTRY(entry)) {
 192                 struct ext2_xattr_entry *next =
 193                         EXT2_XATTR_NEXT(entry);
 194                 if ((char *)next >= end)
 195                         goto bad_block;
 196                 if (name_index == entry->e_name_index &&
 197                     name_len == entry->e_name_len &&
 198                     memcmp(name, entry->e_name, name_len) == 0)
 199                         goto found;
 200                 entry = next;
 201         }
 202         /* Check the remaining name entries */
 203         while (!IS_LAST_ENTRY(entry)) {
 204                 struct ext2_xattr_entry *next =
 205                         EXT2_XATTR_NEXT(entry);
 206                 if ((char *)next >= end)
 207                         goto bad_block;
 208                 entry = next;
 209         }
 210         if (ext2_xattr_cache_insert(bh))
 211                 ea_idebug(inode, "cache insert failed");
 212         error = -ENODATA;
 213         goto cleanup;
 214 found:
 215         /* check the buffer size */
 216         if (entry->e_value_block != 0)
 217                 goto bad_block;
 218         size = le32_to_cpu(entry->e_value_size);
 219         if (size > inode->i_sb->s_blocksize ||
 220             le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
 221                 goto bad_block;
 222
 223         if (ext2_xattr_cache_insert(bh))
 224                 ea_idebug(inode, "cache insert failed");
 225         if (buffer) {
 226                 error = -ERANGE;
 227                 if (size > buffer_size)
 228                         goto cleanup;
 229                 /* return value of attribute */
 230                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 231                         size);
 232         }
 233         error = size;
 234
 235 cleanup:
 236         brelse(bh);
 237         up_read(&EXT2_I(inode)->xattr_sem);
 238
 239         return error;
 240 }
 241
 242 /*
 243  * ext2_xattr_list()
 244  *
 245  * Copy a list of attribute names into the buffer
 246  * provided, or compute the buffer size required.
 247  * Buffer is NULL to compute the size of the buffer required.
 248  *
 249  * Returns a negative error number on failure, or the number of bytes
 250  * used / required on success.
 251  */
 252 static int
 253 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 254 {
 255         struct inode *inode = dentry->d_inode;
 256         struct buffer_head *bh = NULL;
 257         struct ext2_xattr_entry *entry;
 258         char *end;
 259         size_t rest = buffer_size;
 260         int error;
 261
 262         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 263                   buffer, (long)buffer_size);
 264
 265         down_read(&EXT2_I(inode)->xattr_sem);
 266         error = 0;
 267         if (!EXT2_I(inode)->i_file_acl)
 268                 goto cleanup;
 269         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 270         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 271         error = -EIO;
 272         if (!bh)
 273                 goto cleanup;
 274         ea_bdebug(bh, "b_count=%d, refcount=%d",
 275                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 276         end = bh->b_data + bh->b_size;
 277         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 278             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 279 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
 280                         "inode %ld: bad block %d", inode->i_ino,
 281                         EXT2_I(inode)->i_file_acl);
 282                 error = -EIO;
 283                 goto cleanup;
 284         }
 285
 286         /* check the on-disk data structure */
 287         entry = FIRST_ENTRY(bh);
 288         while (!IS_LAST_ENTRY(entry)) {
 289                 struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
 290
 291                 if ((char *)next >= end)
 292                         goto bad_block;
 293                 entry = next;
 294         }
 295         if (ext2_xattr_cache_insert(bh))
 296                 ea_idebug(inode, "cache insert failed");
 297
 298         /* list the attribute names */
 299         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 300              entry = EXT2_XATTR_NEXT(entry)) {
 301                 const struct xattr_handler *handler =
 302                         ext2_xattr_handler(entry->e_name_index);
 303
 304                 if (handler) {
 305                         size_t size = handler->list(dentry, buffer, rest,
 306                                                     entry->e_name,
 307                                                     entry->e_name_len,
 308                                                     handler->flags);
 309                         if (buffer) {
 310                                 if (size > rest) {
 311                                         error = -ERANGE;
 312                                         goto cleanup;
 313                                 }
 314                                 buffer += size;
 315                         }
 316                         rest -= size;
 317                 }
 318         }
 319         error = buffer_size - rest;  /* total size */
 320
 321 cleanup:
 322         brelse(bh);
 323         up_read(&EXT2_I(inode)->xattr_sem);
 324
 325         return error;
 326 }
 327
 328 /*
 329  * Inode operation listxattr()
 330  *
 331  * dentry->d_inode->i_mutex: don't care
 332  */
 333 ssize_t
 334 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 335 {
 336         return ext2_xattr_list(dentry, buffer, size);
 337 }
 338
 339 /*
 340  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 341  * not set, set it.
 342  */
 343 static void ext2_xattr_update_super_block(struct super_block *sb)
 344 {
 345         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 346                 return;
 347
 348         spin_lock(&EXT2_SB(sb)->s_lock);
 349         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 350         spin_unlock(&EXT2_SB(sb)->s_lock);
 351         sb->s_dirt = 1;
 352         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 353 }
 354
 355 /*
 356  * ext2_xattr_set()
 357  *
 358  * Create, replace or remove an extended attribute for this inode. Buffer
 359  * is NULL to remove an existing extended attribute, and non-NULL to
 360  * either replace an existing extended attribute, or create a new extended
 361  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 362  * specify that an extended attribute must exist and must not exist
 363  * previous to the call, respectively.
 364  *
 365  * Returns 0, or a negative error number on failure.
 366  */
 367 int
 368 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 369                const void *value, size_t value_len, int flags)
 370 {
 371         struct super_block *sb = inode->i_sb;
 372         struct buffer_head *bh = NULL;
 373         struct ext2_xattr_header *header = NULL;
 374         struct ext2_xattr_entry *here, *last;
 375         size_t name_len, free, min_offs = sb->s_blocksize;
 376         int not_found = 1, error;
 377         char *end;
 378
 379         /*
 380          * header -- Points either into bh, or to a temporarily
 381          *           allocated buffer.
 382          * here -- The named entry found, or the place for inserting, within
 383          *         the block pointed to by header.
 384          * last -- Points right after the last named entry within the block
 385          *         pointed to by header.
 386          * min_offs -- The offset of the first value (values are aligned
 387          *             towards the end of the block).
 388          * end -- Points right after the block pointed to by header.
 389          */
 390
 391         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 392                   name_index, name, value, (long)value_len);
 393
 394         if (value == NULL)
 395                 value_len = 0;
 396         if (name == NULL)
 397                 return -EINVAL;
 398         name_len = strlen(name);
 399         if (name_len > 255 || value_len > sb->s_blocksize)
 400                 return -ERANGE;
 401         down_write(&EXT2_I(inode)->xattr_sem);
 402         if (EXT2_I(inode)->i_file_acl) {
 403                 /* The inode already has an extended attribute block. */
 404                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 405                 error = -EIO;
 406                 if (!bh)
 407                         goto cleanup;
 408                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 409                         atomic_read(&(bh->b_count)),
 410                         le32_to_cpu(HDR(bh)->h_refcount));
 411                 header = HDR(bh);
 412                 end = bh->b_data + bh->b_size;
 413                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 414                     header->h_blocks != cpu_to_le32(1)) {
 415 bad_block:              ext2_error(sb, "ext2_xattr_set",
 416                                 "inode %ld: bad block %d", inode->i_ino,
 417                                    EXT2_I(inode)->i_file_acl);
 418                         error = -EIO;
 419                         goto cleanup;
 420                 }
 421                 /* Find the named attribute. */
 422                 here = FIRST_ENTRY(bh);
 423                 while (!IS_LAST_ENTRY(here)) {
 424                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 425                         if ((char *)next >= end)
 426                                 goto bad_block;
 427                         if (!here->e_value_block && here->e_value_size) {
 428                                 size_t offs = le16_to_cpu(here->e_value_offs);
 429                                 if (offs < min_offs)
 430                                         min_offs = offs;
 431                         }
 432                         not_found = name_index - here->e_name_index;
 433                         if (!not_found)
 434                                 not_found = name_len - here->e_name_len;
 435                         if (!not_found)
 436                                 not_found = memcmp(name, here->e_name,name_len);
 437                         if (not_found <= 0)
 438                                 break;
 439                         here = next;
 440                 }
 441                 last = here;
 442                 /* We still need to compute min_offs and last. */
 443                 while (!IS_LAST_ENTRY(last)) {
 444                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 445                         if ((char *)next >= end)
 446                                 goto bad_block;
 447                         if (!last->e_value_block && last->e_value_size) {
 448                                 size_t offs = le16_to_cpu(last->e_value_offs);
 449                                 if (offs < min_offs)
 450                                         min_offs = offs;
 451                         }
 452                         last = next;
 453                 }
 454
 455                 /* Check whether we have enough space left. */
 456                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 457         } else {
 458                 /* We will use a new extended attribute block. */
 459                 free = sb->s_blocksize -
 460                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 461                 here = last = NULL;  /* avoid gcc uninitialized warning. */
 462         }
 463
 464         if (not_found) {
 465                 /* Request to remove a nonexistent attribute? */
 466                 error = -ENODATA;
 467                 if (flags & XATTR_REPLACE)
 468                         goto cleanup;
 469                 error = 0;
 470                 if (value == NULL)
 471                         goto cleanup;
 472         } else {
 473                 /* Request to create an existing attribute? */
 474                 error = -EEXIST;
 475                 if (flags & XATTR_CREATE)
 476                         goto cleanup;
 477                 if (!here->e_value_block && here->e_value_size) {
 478                         size_t size = le32_to_cpu(here->e_value_size);
 479
 480                         if (le16_to_cpu(here->e_value_offs) + size >
 481                             sb->s_blocksize || size > sb->s_blocksize)
 482                                 goto bad_block;
 483                         free += EXT2_XATTR_SIZE(size);
 484                 }
 485                 free += EXT2_XATTR_LEN(name_len);
 486         }
 487         error = -ENOSPC;
 488         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 489                 goto cleanup;
 490
 491         /* Here we know that we can set the new attribute. */
 492
 493         if (header) {
 494                 struct mb_cache_entry *ce;
 495
 496                 /* assert(header == HDR(bh)); */
 497                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
 498                                         bh->b_blocknr);
 499                 lock_buffer(bh);
 500                 if (header->h_refcount == cpu_to_le32(1)) {
 501                         ea_bdebug(bh, "modifying in-place");
 502                         if (ce)
 503                                 mb_cache_entry_free(ce);
 504                         /* keep the buffer locked while modifying it. */
 505                 } else {
 506                         int offset;
 507
 508                         if (ce)
 509                                 mb_cache_entry_release(ce);
 510                         unlock_buffer(bh);
 511                         ea_bdebug(bh, "cloning");
 512                         header = kmalloc(bh->b_size, GFP_KERNEL);
 513                         error = -ENOMEM;
 514                         if (header == NULL)
 515                                 goto cleanup;
 516                         memcpy(header, HDR(bh), bh->b_size);
 517                         header->h_refcount = cpu_to_le32(1);
 518
 519                         offset = (char *)here - bh->b_data;
 520                         here = ENTRY((char *)header + offset);
 521                         offset = (char *)last - bh->b_data;
 522                         last = ENTRY((char *)header + offset);
 523                 }
 524         } else {
 525                 /* Allocate a buffer where we construct the new block. */
 526                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 527                 error = -ENOMEM;
 528                 if (header == NULL)
 529                         goto cleanup;
 530                 end = (char *)header + sb->s_blocksize;
 531                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 532                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 533                 last = here = ENTRY(header+1);
 534         }
 535
 536         /* Iff we are modifying the block in-place, bh is locked here. */
 537
 538         if (not_found) {
 539                 /* Insert the new name. */
 540                 size_t size = EXT2_XATTR_LEN(name_len);
 541                 size_t rest = (char *)last - (char *)here;
 542                 memmove((char *)here + size, here, rest);
 543                 memset(here, 0, size);
 544                 here->e_name_index = name_index;
 545                 here->e_name_len = name_len;
 546                 memcpy(here->e_name, name, name_len);
 547         } else {
 548                 if (!here->e_value_block && here->e_value_size) {
 549                         char *first_val = (char *)header + min_offs;
 550                         size_t offs = le16_to_cpu(here->e_value_offs);
 551                         char *val = (char *)header + offs;
 552                         size_t size = EXT2_XATTR_SIZE(
 553                                 le32_to_cpu(here->e_value_size));
 554
 555                         if (size == EXT2_XATTR_SIZE(value_len)) {
 556                                 /* The old and the new value have the same
 557                                    size. Just replace. */
 558                                 here->e_value_size = cpu_to_le32(value_len);
 559                                 memset(val + size - EXT2_XATTR_PAD, 0,
 560                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 561                                 memcpy(val, value, value_len);
 562                                 goto skip_replace;
 563                         }
 564
 565                         /* Remove the old value. */
 566                         memmove(first_val + size, first_val, val - first_val);
 567                         memset(first_val, 0, size);
 568                         here->e_value_offs = 0;
 569                         min_offs += size;
 570
 571                         /* Adjust all value offsets. */
 572                         last = ENTRY(header+1);
 573                         while (!IS_LAST_ENTRY(last)) {
 574                                 size_t o = le16_to_cpu(last->e_value_offs);
 575                                 if (!last->e_value_block && o < offs)
 576                                         last->e_value_offs =
 577                                                 cpu_to_le16(o + size);
 578                                 last = EXT2_XATTR_NEXT(last);
 579                         }
 580                 }
 581                 if (value == NULL) {
 582                         /* Remove the old name. */
 583                         size_t size = EXT2_XATTR_LEN(name_len);
 584                         last = ENTRY((char *)last - size);
 585                         memmove(here, (char*)here + size,
 586                                 (char*)last - (char*)here);
 587                         memset(last, 0, size);
 588                 }
 589         }
 590
 591         if (value != NULL) {
 592                 /* Insert the new value. */
 593                 here->e_value_size = cpu_to_le32(value_len);
 594                 if (value_len) {
 595                         size_t size = EXT2_XATTR_SIZE(value_len);
 596                         char *val = (char *)header + min_offs - size;
 597                         here->e_value_offs =
 598                                 cpu_to_le16((char *)val - (char *)header);
 599                         memset(val + size - EXT2_XATTR_PAD, 0,
 600                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 601                         memcpy(val, value, value_len);
 602                 }
 603         }
 604
 605 skip_replace:
 606         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 607                 /* This block is now empty. */
 608                 if (bh && header == HDR(bh))
 609                         unlock_buffer(bh);  /* we were modifying in-place. */
 610                 error = ext2_xattr_set2(inode, bh, NULL);
 611         } else {
 612                 ext2_xattr_rehash(header, here);
 613                 if (bh && header == HDR(bh))
 614                         unlock_buffer(bh);  /* we were modifying in-place. */
 615                 error = ext2_xattr_set2(inode, bh, header);
 616         }
 617
 618 cleanup:
 619         brelse(bh);
 620         if (!(bh && header == HDR(bh)))
 621                 kfree(header);
 622         up_write(&EXT2_I(inode)->xattr_sem);
 623
 624         return error;
 625 }
 626
 627 /*
 628  * Second half of ext2_xattr_set(): Update the file system.
 629  */
 630 static int
 631 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 632                 struct ext2_xattr_header *header)
 633 {
 634         struct super_block *sb = inode->i_sb;
 635         struct buffer_head *new_bh = NULL;
 636         int error;
 637
 638         if (header) {
 639                 new_bh = ext2_xattr_cache_find(inode, header);
 640                 if (new_bh) {
 641                         /* We found an identical block in the cache. */
 642                         if (new_bh == old_bh) {
 643                                 ea_bdebug(new_bh, "keeping this block");
 644                         } else {
 645                                 /* The old block is released after updating
 646                                    the inode.  */
 647                                 ea_bdebug(new_bh, "reusing block");
 648
 649                                 error = dquot_alloc_block(inode, 1);
 650                                 if (error) {
 651                                         unlock_buffer(new_bh);
 652                                         goto cleanup;
 653                                 }
 654                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 655                                 ea_bdebug(new_bh, "refcount now=%d",
 656                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 657                         }
 658                         unlock_buffer(new_bh);
 659                 } else if (old_bh && header == HDR(old_bh)) {
 660                         /* Keep this block. No need to lock the block as we
 661                            don't need to change the reference count. */
 662                         new_bh = old_bh;
 663                         get_bh(new_bh);
 664                         ext2_xattr_cache_insert(new_bh);
 665                 } else {
 666                         /* We need to allocate a new block */
 667                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 668                                                 EXT2_I(inode)->i_block_group);
 669                         int block = ext2_new_block(inode, goal, &error);
 670                         if (error)
 671                                 goto cleanup;
 672                         ea_idebug(inode, "creating block %d", block);
 673
 674                         new_bh = sb_getblk(sb, block);
 675                         if (!new_bh) {
 676                                 ext2_free_blocks(inode, block, 1);
 677                                 mark_inode_dirty(inode);
 678                                 error = -EIO;
 679                                 goto cleanup;
 680                         }
 681                         lock_buffer(new_bh);
 682                         memcpy(new_bh->b_data, header, new_bh->b_size);
 683                         set_buffer_uptodate(new_bh);
 684                         unlock_buffer(new_bh);
 685                         ext2_xattr_cache_insert(new_bh);
 686
 687                         ext2_xattr_update_super_block(sb);
 688                 }
 689                 mark_buffer_dirty(new_bh);
 690                 if (IS_SYNC(inode)) {
 691                         sync_dirty_buffer(new_bh);
 692                         error = -EIO;
 693                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 694                                 goto cleanup;
 695                 }
 696         }
 697
 698         /* Update the inode. */
 699         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 700         inode->i_ctime = CURRENT_TIME_SEC;
 701         if (IS_SYNC(inode)) {
 702                 error = ext2_sync_inode (inode);
 703                 /* In case sync failed due to ENOSPC the inode was actually
 704                  * written (only some dirty data were not) so we just proceed
 705                  * as if nothing happened and cleanup the unused block */
 706                 if (error && error != -ENOSPC) {
 707                         if (new_bh && new_bh != old_bh) {
 708                                 dquot_free_block_nodirty(inode, 1);
 709                                 mark_inode_dirty(inode);
 710                         }
 711                         goto cleanup;
 712                 }
 713         } else
 714                 mark_inode_dirty(inode);
 715
 716         error = 0;
 717         if (old_bh && old_bh != new_bh) {
 718                 struct mb_cache_entry *ce;
 719
 720                 /*
 721                  * If there was an old block and we are no longer using it,
 722                  * release the old block.
 723                  */
 724                 ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
 725                                         old_bh->b_blocknr);
 726                 lock_buffer(old_bh);
 727                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 728                         /* Free the old block. */
 729                         if (ce)
 730                                 mb_cache_entry_free(ce);
 731                         ea_bdebug(old_bh, "freeing");
 732                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 733                         mark_inode_dirty(inode);
 734                         /* We let our caller release old_bh, so we
 735                          * need to duplicate the buffer before. */
 736                         get_bh(old_bh);
 737                         bforget(old_bh);
 738                 } else {
 739                         /* Decrement the refcount only. */
 740                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 741                         if (ce)
 742                                 mb_cache_entry_release(ce);
 743                         dquot_free_block_nodirty(inode, 1);
 744                         mark_inode_dirty(inode);
 745                         mark_buffer_dirty(old_bh);
 746                         ea_bdebug(old_bh, "refcount now=%d",
 747                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 748                 }
 749                 unlock_buffer(old_bh);
 750         }
 751
 752 cleanup:
 753         brelse(new_bh);
 754
 755         return error;
 756 }
 757
 758 /*
 759  * ext2_xattr_delete_inode()
 760  *
 761  * Free extended attribute resources associated with this inode. This
 762  * is called immediately before an inode is freed.
 763  */
 764 void
 765 ext2_xattr_delete_inode(struct inode *inode)
 766 {
 767         struct buffer_head *bh = NULL;
 768         struct mb_cache_entry *ce;
 769
 770         down_write(&EXT2_I(inode)->xattr_sem);
 771         if (!EXT2_I(inode)->i_file_acl)
 772                 goto cleanup;
 773         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 774         if (!bh) {
 775                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 776                         "inode %ld: block %d read error", inode->i_ino,
 777                         EXT2_I(inode)->i_file_acl);
 778                 goto cleanup;
 779         }
 780         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 781         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 782             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 783                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 784                         "inode %ld: bad block %d", inode->i_ino,
 785                         EXT2_I(inode)->i_file_acl);
 786                 goto cleanup;
 787         }
 788         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
 789         lock_buffer(bh);
 790         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 791                 if (ce)
 792                         mb_cache_entry_free(ce);
 793                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 794                 get_bh(bh);
 795                 bforget(bh);
 796                 unlock_buffer(bh);
 797         } else {
 798                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 799                 if (ce)
 800                         mb_cache_entry_release(ce);
 801                 ea_bdebug(bh, "refcount now=%d",
 802                         le32_to_cpu(HDR(bh)->h_refcount));
 803                 unlock_buffer(bh);
 804                 mark_buffer_dirty(bh);
 805                 if (IS_SYNC(inode))
 806                         sync_dirty_buffer(bh);
 807                 dquot_free_block_nodirty(inode, 1);
 808         }
 809         EXT2_I(inode)->i_file_acl = 0;
 810
 811 cleanup:
 812         brelse(bh);
 813         up_write(&EXT2_I(inode)->xattr_sem);
 814 }
 815
 816 /*
 817  * ext2_xattr_put_super()
 818  *
 819  * This is called when a file system is unmounted.
 820  */
 821 void
 822 ext2_xattr_put_super(struct super_block *sb)
 823 {
 824         mb_cache_shrink(sb->s_bdev);
 825 }
 826
 827
 828 /*
 829  * ext2_xattr_cache_insert()
 830  *
 831  * Create a new entry in the extended attribute cache, and insert
 832  * it unless such an entry is already in the cache.
 833  *
 834  * Returns 0, or a negative error number on failure.
 835  */
 836 static int
 837 ext2_xattr_cache_insert(struct buffer_head *bh)
 838 {
 839         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 840         struct mb_cache_entry *ce;
 841         int error;
 842
 843         ce = mb_cache_entry_alloc(ext2_xattr_cache, GFP_NOFS);
 844         if (!ce)
 845                 return -ENOMEM;
 846         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, hash);
 847         if (error) {
 848                 mb_cache_entry_free(ce);
 849                 if (error == -EBUSY) {
 850                         ea_bdebug(bh, "already in cache (%d cache entries)",
 851                                 atomic_read(&ext2_xattr_cache->c_entry_count));
 852                         error = 0;
 853                 }
 854         } else {
 855                 ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
 856                           atomic_read(&ext2_xattr_cache->c_entry_count));
 857                 mb_cache_entry_release(ce);
 858         }
 859         return error;
 860 }
 861
 862 /*
 863  * ext2_xattr_cmp()
 864  *
 865  * Compare two extended attribute blocks for equality.
 866  *
 867  * Returns 0 if the blocks are equal, 1 if they differ, and
 868  * a negative error number on errors.
 869  */
 870 static int
 871 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 872                struct ext2_xattr_header *header2)
 873 {
 874         struct ext2_xattr_entry *entry1, *entry2;
 875
 876         entry1 = ENTRY(header1+1);
 877         entry2 = ENTRY(header2+1);
 878         while (!IS_LAST_ENTRY(entry1)) {
 879                 if (IS_LAST_ENTRY(entry2))
 880                         return 1;
 881                 if (entry1->e_hash != entry2->e_hash ||
 882                     entry1->e_name_index != entry2->e_name_index ||
 883                     entry1->e_name_len != entry2->e_name_len ||
 884                     entry1->e_value_size != entry2->e_value_size ||
 885                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 886                         return 1;
 887                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 888                         return -EIO;
 889                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 890                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 891                            le32_to_cpu(entry1->e_value_size)))
 892                         return 1;
 893
 894                 entry1 = EXT2_XATTR_NEXT(entry1);
 895                 entry2 = EXT2_XATTR_NEXT(entry2);
 896         }
 897         if (!IS_LAST_ENTRY(entry2))
 898                 return 1;
 899         return 0;
 900 }
 901
 902 /*
 903  * ext2_xattr_cache_find()
 904  *
 905  * Find an identical extended attribute block.
 906  *
 907  * Returns a locked buffer head to the block found, or NULL if such
 908  * a block was not found or an error occurred.
 909  */
 910 static struct buffer_head *
 911 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 912 {
 913         __u32 hash = le32_to_cpu(header->h_hash);
 914         struct mb_cache_entry *ce;
 915
 916         if (!header->h_hash)
 917                 return NULL;  /* never share */
 918         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 919 again:
 920         ce = mb_cache_entry_find_first(ext2_xattr_cache, inode->i_sb->s_bdev,
 921                                        hash);
 922         while (ce) {
 923                 struct buffer_head *bh;
 924
 925                 if (IS_ERR(ce)) {
 926                         if (PTR_ERR(ce) == -EAGAIN)
 927                                 goto again;
 928                         break;
 929                 }
 930
 931                 bh = sb_bread(inode->i_sb, ce->e_block);
 932                 if (!bh) {
 933                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 934                                 "inode %ld: block %ld read error",
 935                                 inode->i_ino, (unsigned long) ce->e_block);
 936                 } else {
 937                         lock_buffer(bh);
 938                         if (le32_to_cpu(HDR(bh)->h_refcount) >
 939                                    EXT2_XATTR_REFCOUNT_MAX) {
 940                                 ea_idebug(inode, "block %ld refcount %d>%d",
 941                                           (unsigned long) ce->e_block,
 942                                           le32_to_cpu(HDR(bh)->h_refcount),
 943                                           EXT2_XATTR_REFCOUNT_MAX);
 944                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 945                                 ea_bdebug(bh, "b_count=%d",
 946                                           atomic_read(&(bh->b_count)));
 947                                 mb_cache_entry_release(ce);
 948                                 return bh;
 949                         }
 950                         unlock_buffer(bh);
 951                         brelse(bh);
 952                 }
 953                 ce = mb_cache_entry_find_next(ce, inode->i_sb->s_bdev, hash);
 954         }
 955         return NULL;
 956 }
 957
 958 #define NAME_HASH_SHIFT 5
 959 #define VALUE_HASH_SHIFT 16
 960
 961 /*
 962  * ext2_xattr_hash_entry()
 963  *
 964  * Compute the hash of an extended attribute.
 965  */
 966 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 967                                          struct ext2_xattr_entry *entry)
 968 {
 969         __u32 hash = 0;
 970         char *name = entry->e_name;
 971         int n;
 972
 973         for (n=0; n < entry->e_name_len; n++) {
 974                 hash = (hash << NAME_HASH_SHIFT) ^
 975                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 976                        *name++;
 977         }
 978
 979         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 980                 __le32 *value = (__le32 *)((char *)header +
 981                         le16_to_cpu(entry->e_value_offs));
 982                 for (n = (le32_to_cpu(entry->e_value_size) +
 983                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
 984                         hash = (hash << VALUE_HASH_SHIFT) ^
 985                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 986                                le32_to_cpu(*value++);
 987                 }
 988         }
 989         entry->e_hash = cpu_to_le32(hash);
 990 }
 991
 992 #undef NAME_HASH_SHIFT
 993 #undef VALUE_HASH_SHIFT
 994
 995 #define BLOCK_HASH_SHIFT 16
 996
 997 /*
 998  * ext2_xattr_rehash()
 999  *
1000  * Re-compute the extended attribute hash value after an entry has changed.
1001  */
1002 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1003                               struct ext2_xattr_entry *entry)
1004 {
1005         struct ext2_xattr_entry *here;
1006         __u32 hash = 0;
1007
1008         ext2_xattr_hash_entry(header, entry);
1009         here = ENTRY(header+1);
1010         while (!IS_LAST_ENTRY(here)) {
1011                 if (!here->e_hash) {
1012                         /* Block is not shared if an entry's hash value == 0 */
1013                         hash = 0;
1014                         break;
1015                 }
1016                 hash = (hash << BLOCK_HASH_SHIFT) ^
1017                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1018                        le32_to_cpu(here->e_hash);
1019                 here = EXT2_XATTR_NEXT(here);
1020         }
1021         header->h_hash = cpu_to_le32(hash);
1022 }
1023
1024 #undef BLOCK_HASH_SHIFT
1025
1026 int __init
1027 init_ext2_xattr(void)
1028 {
1029         ext2_xattr_cache = mb_cache_create("ext2_xattr", 6);
1030         if (!ext2_xattr_cache)
1031                 return -ENOMEM;
1032         return 0;
1033 }
1034
1035 void
1036 exit_ext2_xattr(void)
1037 {
1038         mb_cache_destroy(ext2_xattr_cache);
1039 }