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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
  92 static int ext2_xattr_set2(struct inode *, struct buffer_head *,
  93                            struct ext2_xattr_header *);
  94
  95 static int ext2_xattr_cache_insert(struct buffer_head *);
  96 static struct buffer_head *ext2_xattr_cache_find(struct inode *,
  97                                                  struct ext2_xattr_header *);
  98 static void ext2_xattr_rehash(struct ext2_xattr_header *,
  99                               struct ext2_xattr_entry *);
 100
 101 static struct mb_cache *ext2_xattr_cache;
 102
 103 static 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
 115 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
 128 static inline struct xattr_handler *
 129 ext2_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  */
 148 int
 149 ext2_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)) {
 177 bad_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;
 213 found:
 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
 234 cleanup:
 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  */
 251 static int
 252 ext2_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)) {
 277 bad_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
 318 cleanup:
 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  */
 330 ssize_t
 331 ext2_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  */
 340 static 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         lock_super(sb);
 346         EXT2_SB(sb)->s_es->s_feature_compat |=
 347                 cpu_to_le32(EXT2_FEATURE_COMPAT_EXT_ATTR);
 348         sb->s_dirt = 1;
 349         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 350         unlock_super(sb);
 351 }
 352
 353 /*
 354  * ext2_xattr_set()
 355  *
 356  * Create, replace or remove an extended attribute for this inode. Buffer
 357  * is NULL to remove an existing extended attribute, and non-NULL to
 358  * either replace an existing extended attribute, or create a new extended
 359  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 360  * specify that an extended attribute must exist and must not exist
 361  * previous to the call, respectively.
 362  *
 363  * Returns 0, or a negative error number on failure.
 364  */
 365 int
 366 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 367                const void *value, size_t value_len, int flags)
 368 {
 369         struct super_block *sb = inode->i_sb;
 370         struct buffer_head *bh = NULL;
 371         struct ext2_xattr_header *header = NULL;
 372         struct ext2_xattr_entry *here, *last;
 373         size_t name_len, free, min_offs = sb->s_blocksize;
 374         int not_found = 1, error;
 375         char *end;
 376
 377         /*
 378          * header -- Points either into bh, or to a temporarily
 379          *           allocated buffer.
 380          * here -- The named entry found, or the place for inserting, within
 381          *         the block pointed to by header.
 382          * last -- Points right after the last named entry within the block
 383          *         pointed to by header.
 384          * min_offs -- The offset of the first value (values are aligned
 385          *             towards the end of the block).
 386          * end -- Points right after the block pointed to by header.
 387          */
 388
 389         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 390                   name_index, name, value, (long)value_len);
 391
 392         if (value == NULL)
 393                 value_len = 0;
 394         if (name == NULL)
 395                 return -EINVAL;
 396         name_len = strlen(name);
 397         if (name_len > 255 || value_len > sb->s_blocksize)
 398                 return -ERANGE;
 399         down_write(&EXT2_I(inode)->xattr_sem);
 400         if (EXT2_I(inode)->i_file_acl) {
 401                 /* The inode already has an extended attribute block. */
 402                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 403                 error = -EIO;
 404                 if (!bh)
 405                         goto cleanup;
 406                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 407                         atomic_read(&(bh->b_count)),
 408                         le32_to_cpu(HDR(bh)->h_refcount));
 409                 header = HDR(bh);
 410                 end = bh->b_data + bh->b_size;
 411                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 412                     header->h_blocks != cpu_to_le32(1)) {
 413 bad_block:              ext2_error(sb, "ext2_xattr_set",
 414                                 "inode %ld: bad block %d", inode->i_ino,
 415                                    EXT2_I(inode)->i_file_acl);
 416                         error = -EIO;
 417                         goto cleanup;
 418                 }
 419                 /* Find the named attribute. */
 420                 here = FIRST_ENTRY(bh);
 421                 while (!IS_LAST_ENTRY(here)) {
 422                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 423                         if ((char *)next >= end)
 424                                 goto bad_block;
 425                         if (!here->e_value_block && here->e_value_size) {
 426                                 size_t offs = le16_to_cpu(here->e_value_offs);
 427                                 if (offs < min_offs)
 428                                         min_offs = offs;
 429                         }
 430                         not_found = name_index - here->e_name_index;
 431                         if (!not_found)
 432                                 not_found = name_len - here->e_name_len;
 433                         if (!not_found)
 434                                 not_found = memcmp(name, here->e_name,name_len);
 435                         if (not_found <= 0)
 436                                 break;
 437                         here = next;
 438                 }
 439                 last = here;
 440                 /* We still need to compute min_offs and last. */
 441                 while (!IS_LAST_ENTRY(last)) {
 442                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 443                         if ((char *)next >= end)
 444                                 goto bad_block;
 445                         if (!last->e_value_block && last->e_value_size) {
 446                                 size_t offs = le16_to_cpu(last->e_value_offs);
 447                                 if (offs < min_offs)
 448                                         min_offs = offs;
 449                         }
 450                         last = next;
 451                 }
 452
 453                 /* Check whether we have enough space left. */
 454                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 455         } else {
 456                 /* We will use a new extended attribute block. */
 457                 free = sb->s_blocksize -
 458                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 459                 here = last = NULL;  /* avoid gcc uninitialized warning. */
 460         }
 461
 462         if (not_found) {
 463                 /* Request to remove a nonexistent attribute? */
 464                 error = -ENODATA;
 465                 if (flags & XATTR_REPLACE)
 466                         goto cleanup;
 467                 error = 0;
 468                 if (value == NULL)
 469                         goto cleanup;
 470         } else {
 471                 /* Request to create an existing attribute? */
 472                 error = -EEXIST;
 473                 if (flags & XATTR_CREATE)
 474                         goto cleanup;
 475                 if (!here->e_value_block && here->e_value_size) {
 476                         size_t size = le32_to_cpu(here->e_value_size);
 477
 478                         if (le16_to_cpu(here->e_value_offs) + size >
 479                             sb->s_blocksize || size > sb->s_blocksize)
 480                                 goto bad_block;
 481                         free += EXT2_XATTR_SIZE(size);
 482                 }
 483                 free += EXT2_XATTR_LEN(name_len);
 484         }
 485         error = -ENOSPC;
 486         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 487                 goto cleanup;
 488
 489         /* Here we know that we can set the new attribute. */
 490
 491         if (header) {
 492                 struct mb_cache_entry *ce;
 493
 494                 /* assert(header == HDR(bh)); */
 495                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
 496                                         bh->b_blocknr);
 497                 lock_buffer(bh);
 498                 if (header->h_refcount == cpu_to_le32(1)) {
 499                         ea_bdebug(bh, "modifying in-place");
 500                         if (ce)
 501                                 mb_cache_entry_free(ce);
 502                         /* keep the buffer locked while modifying it. */
 503                 } else {
 504                         int offset;
 505
 506                         if (ce)
 507                                 mb_cache_entry_release(ce);
 508                         unlock_buffer(bh);
 509                         ea_bdebug(bh, "cloning");
 510                         header = kmalloc(bh->b_size, GFP_KERNEL);
 511                         error = -ENOMEM;
 512                         if (header == NULL)
 513                                 goto cleanup;
 514                         memcpy(header, HDR(bh), bh->b_size);
 515                         header->h_refcount = cpu_to_le32(1);
 516
 517                         offset = (char *)here - bh->b_data;
 518                         here = ENTRY((char *)header + offset);
 519                         offset = (char *)last - bh->b_data;
 520                         last = ENTRY((char *)header + offset);
 521                 }
 522         } else {
 523                 /* Allocate a buffer where we construct the new block. */
 524                 header = kmalloc(sb->s_blocksize, GFP_KERNEL);
 525                 error = -ENOMEM;
 526                 if (header == NULL)
 527                         goto cleanup;
 528                 memset(header, 0, sb->s_blocksize);
 529                 end = (char *)header + sb->s_blocksize;
 530                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 531                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 532                 last = here = ENTRY(header+1);
 533         }
 534
 535         /* Iff we are modifying the block in-place, bh is locked here. */
 536
 537         if (not_found) {
 538                 /* Insert the new name. */
 539                 size_t size = EXT2_XATTR_LEN(name_len);
 540                 size_t rest = (char *)last - (char *)here;
 541                 memmove((char *)here + size, here, rest);
 542                 memset(here, 0, size);
 543                 here->e_name_index = name_index;
 544                 here->e_name_len = name_len;
 545                 memcpy(here->e_name, name, name_len);
 546         } else {
 547                 if (!here->e_value_block && here->e_value_size) {
 548                         char *first_val = (char *)header + min_offs;
 549                         size_t offs = le16_to_cpu(here->e_value_offs);
 550                         char *val = (char *)header + offs;
 551                         size_t size = EXT2_XATTR_SIZE(
 552                                 le32_to_cpu(here->e_value_size));
 553
 554                         if (size == EXT2_XATTR_SIZE(value_len)) {
 555                                 /* The old and the new value have the same
 556                                    size. Just replace. */
 557                                 here->e_value_size = cpu_to_le32(value_len);
 558                                 memset(val + size - EXT2_XATTR_PAD, 0,
 559                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 560                                 memcpy(val, value, value_len);
 561                                 goto skip_replace;
 562                         }
 563
 564                         /* Remove the old value. */
 565                         memmove(first_val + size, first_val, val - first_val);
 566                         memset(first_val, 0, size);
 567                         here->e_value_offs = 0;
 568                         min_offs += size;
 569
 570                         /* Adjust all value offsets. */
 571                         last = ENTRY(header+1);
 572                         while (!IS_LAST_ENTRY(last)) {
 573                                 size_t o = le16_to_cpu(last->e_value_offs);
 574                                 if (!last->e_value_block && o < offs)
 575                                         last->e_value_offs =
 576                                                 cpu_to_le16(o + size);
 577                                 last = EXT2_XATTR_NEXT(last);
 578                         }
 579                 }
 580                 if (value == NULL) {
 581                         /* Remove the old name. */
 582                         size_t size = EXT2_XATTR_LEN(name_len);
 583                         last = ENTRY((char *)last - size);
 584                         memmove(here, (char*)here + size,
 585                                 (char*)last - (char*)here);
 586                         memset(last, 0, size);
 587                 }
 588         }
 589
 590         if (value != NULL) {
 591                 /* Insert the new value. */
 592                 here->e_value_size = cpu_to_le32(value_len);
 593                 if (value_len) {
 594                         size_t size = EXT2_XATTR_SIZE(value_len);
 595                         char *val = (char *)header + min_offs - size;
 596                         here->e_value_offs =
 597                                 cpu_to_le16((char *)val - (char *)header);
 598                         memset(val + size - EXT2_XATTR_PAD, 0,
 599                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 600                         memcpy(val, value, value_len);
 601                 }
 602         }
 603
 604 skip_replace:
 605         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 606                 /* This block is now empty. */
 607                 if (bh && header == HDR(bh))
 608                         unlock_buffer(bh);  /* we were modifying in-place. */
 609                 error = ext2_xattr_set2(inode, bh, NULL);
 610         } else {
 611                 ext2_xattr_rehash(header, here);
 612                 if (bh && header == HDR(bh))
 613                         unlock_buffer(bh);  /* we were modifying in-place. */
 614                 error = ext2_xattr_set2(inode, bh, header);
 615         }
 616
 617 cleanup:
 618         brelse(bh);
 619         if (!(bh && header == HDR(bh)))
 620                 kfree(header);
 621         up_write(&EXT2_I(inode)->xattr_sem);
 622
 623         return error;
 624 }
 625
 626 /*
 627  * Second half of ext2_xattr_set(): Update the file system.
 628  */
 629 static int
 630 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 631                 struct ext2_xattr_header *header)
 632 {
 633         struct super_block *sb = inode->i_sb;
 634         struct buffer_head *new_bh = NULL;
 635         int error;
 636
 637         if (header) {
 638                 new_bh = ext2_xattr_cache_find(inode, header);
 639                 if (new_bh) {
 640                         /* We found an identical block in the cache. */
 641                         if (new_bh == old_bh) {
 642                                 ea_bdebug(new_bh, "keeping this block");
 643                         } else {
 644                                 /* The old block is released after updating
 645                                    the inode.  */
 646                                 ea_bdebug(new_bh, "reusing block");
 647
 648                                 error = -EDQUOT;
 649                                 if (DQUOT_ALLOC_BLOCK(inode, 1)) {
 650                                         unlock_buffer(new_bh);
 651                                         goto cleanup;
 652                                 }
 653                                 HDR(new_bh)->h_refcount = cpu_to_le32(1 +
 654                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 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                         int goal = le32_to_cpu(EXT2_SB(sb)->s_es->
 668                                                            s_first_data_block) +
 669                                    EXT2_I(inode)->i_block_group *
 670                                    EXT2_BLOCKS_PER_GROUP(sb);
 671                         int block = ext2_new_block(inode, goal,
 672                                                    NULL, NULL, &error);
 673                         if (error)
 674                                 goto cleanup;
 675                         ea_idebug(inode, "creating block %d", block);
 676
 677                         new_bh = sb_getblk(sb, block);
 678                         if (!new_bh) {
 679                                 ext2_free_blocks(inode, block, 1);
 680                                 error = -EIO;
 681                                 goto cleanup;
 682                         }
 683                         lock_buffer(new_bh);
 684                         memcpy(new_bh->b_data, header, new_bh->b_size);
 685                         set_buffer_uptodate(new_bh);
 686                         unlock_buffer(new_bh);
 687                         ext2_xattr_cache_insert(new_bh);
 688
 689                         ext2_xattr_update_super_block(sb);
 690                 }
 691                 mark_buffer_dirty(new_bh);
 692                 if (IS_SYNC(inode)) {
 693                         sync_dirty_buffer(new_bh);
 694                         error = -EIO;
 695                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 696                                 goto cleanup;
 697                 }
 698         }
 699
 700         /* Update the inode. */
 701         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 702         inode->i_ctime = CURRENT_TIME_SEC;
 703         if (IS_SYNC(inode)) {
 704                 error = ext2_sync_inode (inode);
 705                 /* In case sync failed due to ENOSPC the inode was actually
 706                  * written (only some dirty data were not) so we just proceed
 707                  * as if nothing happened and cleanup the unused block */
 708                 if (error && error != -ENOSPC) {
 709                         if (new_bh && new_bh != old_bh)
 710                                 DQUOT_FREE_BLOCK(inode, 1);
 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                         /* We let our caller release old_bh, so we
 734                          * need to duplicate the buffer before. */
 735                         get_bh(old_bh);
 736                         bforget(old_bh);
 737                 } else {
 738                         /* Decrement the refcount only. */
 739                         HDR(old_bh)->h_refcount = cpu_to_le32(
 740                                 le32_to_cpu(HDR(old_bh)->h_refcount) - 1);
 741                         if (ce)
 742                                 mb_cache_entry_release(ce);
 743                         DQUOT_FREE_BLOCK(inode, 1);
 744                         mark_buffer_dirty(old_bh);
 745                         ea_bdebug(old_bh, "refcount now=%d",
 746                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 747                 }
 748                 unlock_buffer(old_bh);
 749         }
 750
 751 cleanup:
 752         brelse(new_bh);
 753
 754         return error;
 755 }
 756
 757 /*
 758  * ext2_xattr_delete_inode()
 759  *
 760  * Free extended attribute resources associated with this inode. This
 761  * is called immediately before an inode is freed.
 762  */
 763 void
 764 ext2_xattr_delete_inode(struct inode *inode)
 765 {
 766         struct buffer_head *bh = NULL;
 767         struct mb_cache_entry *ce;
 768
 769         down_write(&EXT2_I(inode)->xattr_sem);
 770         if (!EXT2_I(inode)->i_file_acl)
 771                 goto cleanup;
 772         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 773         if (!bh) {
 774                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 775                         "inode %ld: block %d read error", inode->i_ino,
 776                         EXT2_I(inode)->i_file_acl);
 777                 goto cleanup;
 778         }
 779         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 780         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 781             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 782                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 783                         "inode %ld: bad block %d", inode->i_ino,
 784                         EXT2_I(inode)->i_file_acl);
 785                 goto cleanup;
 786         }
 787         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
 788         lock_buffer(bh);
 789         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 790                 if (ce)
 791                         mb_cache_entry_free(ce);
 792                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 793                 get_bh(bh);
 794                 bforget(bh);
 795                 unlock_buffer(bh);
 796         } else {
 797                 HDR(bh)->h_refcount = cpu_to_le32(
 798                         le32_to_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(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);
 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, 0,
 921                                        inode->i_sb->s_bdev, 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, 0, 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", NULL,
1030                 sizeof(struct mb_cache_entry) +
1031                 sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
1032         if (!ext2_xattr_cache)
1033                 return -ENOMEM;
1034         return 0;
1035 }
1036
1037 void
1038 exit_ext2_xattr(void)
1039 {
1040         mb_cache_destroy(ext2_xattr_cache);
1041 }