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 "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_sem: 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 (IS_RDONLY(inode))
 393                 return -EROFS;
 394         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 395                 return -EPERM;
 396         if (value == NULL)
 397                 value_len = 0;
 398         if (name == NULL)
 399                 return -EINVAL;
 400         name_len = strlen(name);
 401         if (name_len > 255 || value_len > sb->s_blocksize)
 402                 return -ERANGE;
 403         down_write(&EXT2_I(inode)->xattr_sem);
 404         if (EXT2_I(inode)->i_file_acl) {
 405                 /* The inode already has an extended attribute block. */
 406                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 407                 error = -EIO;
 408                 if (!bh)
 409                         goto cleanup;
 410                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 411                         atomic_read(&(bh->b_count)),
 412                         le32_to_cpu(HDR(bh)->h_refcount));
 413                 header = HDR(bh);
 414                 end = bh->b_data + bh->b_size;
 415                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 416                     header->h_blocks != cpu_to_le32(1)) {
 417 bad_block:              ext2_error(sb, "ext2_xattr_set",
 418                                 "inode %ld: bad block %d", inode->i_ino,
 419                                    EXT2_I(inode)->i_file_acl);
 420                         error = -EIO;
 421                         goto cleanup;
 422                 }
 423                 /* Find the named attribute. */
 424                 here = FIRST_ENTRY(bh);
 425                 while (!IS_LAST_ENTRY(here)) {
 426                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 427                         if ((char *)next >= end)
 428                                 goto bad_block;
 429                         if (!here->e_value_block && here->e_value_size) {
 430                                 size_t offs = le16_to_cpu(here->e_value_offs);
 431                                 if (offs < min_offs)
 432                                         min_offs = offs;
 433                         }
 434                         not_found = name_index - here->e_name_index;
 435                         if (!not_found)
 436                                 not_found = name_len - here->e_name_len;
 437                         if (!not_found)
 438                                 not_found = memcmp(name, here->e_name,name_len);
 439                         if (not_found <= 0)
 440                                 break;
 441                         here = next;
 442                 }
 443                 last = here;
 444                 /* We still need to compute min_offs and last. */
 445                 while (!IS_LAST_ENTRY(last)) {
 446                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 447                         if ((char *)next >= end)
 448                                 goto bad_block;
 449                         if (!last->e_value_block && last->e_value_size) {
 450                                 size_t offs = le16_to_cpu(last->e_value_offs);
 451                                 if (offs < min_offs)
 452                                         min_offs = offs;
 453                         }
 454                         last = next;
 455                 }
 456
 457                 /* Check whether we have enough space left. */
 458                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 459         } else {
 460                 /* We will use a new extended attribute block. */
 461                 free = sb->s_blocksize -
 462                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 463                 here = last = NULL;  /* avoid gcc uninitialized warning. */
 464         }
 465
 466         if (not_found) {
 467                 /* Request to remove a nonexistent attribute? */
 468                 error = -ENODATA;
 469                 if (flags & XATTR_REPLACE)
 470                         goto cleanup;
 471                 error = 0;
 472                 if (value == NULL)
 473                         goto cleanup;
 474         } else {
 475                 /* Request to create an existing attribute? */
 476                 error = -EEXIST;
 477                 if (flags & XATTR_CREATE)
 478                         goto cleanup;
 479                 if (!here->e_value_block && here->e_value_size) {
 480                         size_t size = le32_to_cpu(here->e_value_size);
 481
 482                         if (le16_to_cpu(here->e_value_offs) + size >
 483                             sb->s_blocksize || size > sb->s_blocksize)
 484                                 goto bad_block;
 485                         free += EXT2_XATTR_SIZE(size);
 486                 }
 487                 free += EXT2_XATTR_LEN(name_len);
 488         }
 489         error = -ENOSPC;
 490         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 491                 goto cleanup;
 492
 493         /* Here we know that we can set the new attribute. */
 494
 495         if (header) {
 496                 struct mb_cache_entry *ce;
 497
 498                 /* assert(header == HDR(bh)); */
 499                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
 500                                         bh->b_blocknr);
 501                 lock_buffer(bh);
 502                 if (header->h_refcount == cpu_to_le32(1)) {
 503                         ea_bdebug(bh, "modifying in-place");
 504                         if (ce)
 505                                 mb_cache_entry_free(ce);
 506                         /* keep the buffer locked while modifying it. */
 507                 } else {
 508                         int offset;
 509
 510                         if (ce)
 511                                 mb_cache_entry_release(ce);
 512                         unlock_buffer(bh);
 513                         ea_bdebug(bh, "cloning");
 514                         header = kmalloc(bh->b_size, GFP_KERNEL);
 515                         error = -ENOMEM;
 516                         if (header == NULL)
 517                                 goto cleanup;
 518                         memcpy(header, HDR(bh), bh->b_size);
 519                         header->h_refcount = cpu_to_le32(1);
 520
 521                         offset = (char *)here - bh->b_data;
 522                         here = ENTRY((char *)header + offset);
 523                         offset = (char *)last - bh->b_data;
 524                         last = ENTRY((char *)header + offset);
 525                 }
 526         } else {
 527                 /* Allocate a buffer where we construct the new block. */
 528                 header = kmalloc(sb->s_blocksize, GFP_KERNEL);
 529                 error = -ENOMEM;
 530                 if (header == NULL)
 531                         goto cleanup;
 532                 memset(header, 0, sb->s_blocksize);
 533                 end = (char *)header + sb->s_blocksize;
 534                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 535                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 536                 last = here = ENTRY(header+1);
 537         }
 538
 539         /* Iff we are modifying the block in-place, bh is locked here. */
 540
 541         if (not_found) {
 542                 /* Insert the new name. */
 543                 size_t size = EXT2_XATTR_LEN(name_len);
 544                 size_t rest = (char *)last - (char *)here;
 545                 memmove((char *)here + size, here, rest);
 546                 memset(here, 0, size);
 547                 here->e_name_index = name_index;
 548                 here->e_name_len = name_len;
 549                 memcpy(here->e_name, name, name_len);
 550         } else {
 551                 if (!here->e_value_block && here->e_value_size) {
 552                         char *first_val = (char *)header + min_offs;
 553                         size_t offs = le16_to_cpu(here->e_value_offs);
 554                         char *val = (char *)header + offs;
 555                         size_t size = EXT2_XATTR_SIZE(
 556                                 le32_to_cpu(here->e_value_size));
 557
 558                         if (size == EXT2_XATTR_SIZE(value_len)) {
 559                                 /* The old and the new value have the same
 560                                    size. Just replace. */
 561                                 here->e_value_size = cpu_to_le32(value_len);
 562                                 memset(val + size - EXT2_XATTR_PAD, 0,
 563                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 564                                 memcpy(val, value, value_len);
 565                                 goto skip_replace;
 566                         }
 567
 568                         /* Remove the old value. */
 569                         memmove(first_val + size, first_val, val - first_val);
 570                         memset(first_val, 0, size);
 571                         here->e_value_offs = 0;
 572                         min_offs += size;
 573
 574                         /* Adjust all value offsets. */
 575                         last = ENTRY(header+1);
 576                         while (!IS_LAST_ENTRY(last)) {
 577                                 size_t o = le16_to_cpu(last->e_value_offs);
 578                                 if (!last->e_value_block && o < offs)
 579                                         last->e_value_offs =
 580                                                 cpu_to_le16(o + size);
 581                                 last = EXT2_XATTR_NEXT(last);
 582                         }
 583                 }
 584                 if (value == NULL) {
 585                         /* Remove the old name. */
 586                         size_t size = EXT2_XATTR_LEN(name_len);
 587                         last = ENTRY((char *)last - size);
 588                         memmove(here, (char*)here + size,
 589                                 (char*)last - (char*)here);
 590                         memset(last, 0, size);
 591                 }
 592         }
 593
 594         if (value != NULL) {
 595                 /* Insert the new value. */
 596                 here->e_value_size = cpu_to_le32(value_len);
 597                 if (value_len) {
 598                         size_t size = EXT2_XATTR_SIZE(value_len);
 599                         char *val = (char *)header + min_offs - size;
 600                         here->e_value_offs =
 601                                 cpu_to_le16((char *)val - (char *)header);
 602                         memset(val + size - EXT2_XATTR_PAD, 0,
 603                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 604                         memcpy(val, value, value_len);
 605                 }
 606         }
 607
 608 skip_replace:
 609         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 610                 /* This block is now empty. */
 611                 if (bh && header == HDR(bh))
 612                         unlock_buffer(bh);  /* we were modifying in-place. */
 613                 error = ext2_xattr_set2(inode, bh, NULL);
 614         } else {
 615                 ext2_xattr_rehash(header, here);
 616                 if (bh && header == HDR(bh))
 617                         unlock_buffer(bh);  /* we were modifying in-place. */
 618                 error = ext2_xattr_set2(inode, bh, header);
 619         }
 620
 621 cleanup:
 622         brelse(bh);
 623         if (!(bh && header == HDR(bh)))
 624                 kfree(header);
 625         up_write(&EXT2_I(inode)->xattr_sem);
 626
 627         return error;
 628 }
 629
 630 /*
 631  * Second half of ext2_xattr_set(): Update the file system.
 632  */
 633 static int
 634 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 635                 struct ext2_xattr_header *header)
 636 {
 637         struct super_block *sb = inode->i_sb;
 638         struct buffer_head *new_bh = NULL;
 639         int error;
 640
 641         if (header) {
 642                 new_bh = ext2_xattr_cache_find(inode, header);
 643                 if (new_bh) {
 644                         /* We found an identical block in the cache. */
 645                         if (new_bh == old_bh) {
 646                                 ea_bdebug(new_bh, "keeping this block");
 647                         } else {
 648                                 /* The old block is released after updating
 649                                    the inode.  */
 650                                 ea_bdebug(new_bh, "reusing block");
 651
 652                                 error = -EDQUOT;
 653                                 if (DQUOT_ALLOC_BLOCK(inode, 1)) {
 654                                         unlock_buffer(new_bh);
 655                                         goto cleanup;
 656                                 }
 657                                 HDR(new_bh)->h_refcount = cpu_to_le32(1 +
 658                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 659                                 ea_bdebug(new_bh, "refcount now=%d",
 660                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 661                         }
 662                         unlock_buffer(new_bh);
 663                 } else if (old_bh && header == HDR(old_bh)) {
 664                         /* Keep this block. No need to lock the block as we
 665                            don't need to change the reference count. */
 666                         new_bh = old_bh;
 667                         get_bh(new_bh);
 668                         ext2_xattr_cache_insert(new_bh);
 669                 } else {
 670                         /* We need to allocate a new block */
 671                         int goal = le32_to_cpu(EXT2_SB(sb)->s_es->
 672                                                            s_first_data_block) +
 673                                    EXT2_I(inode)->i_block_group *
 674                                    EXT2_BLOCKS_PER_GROUP(sb);
 675                         int block = ext2_new_block(inode, goal,
 676                                                    NULL, NULL, &error);
 677                         if (error)
 678                                 goto cleanup;
 679                         ea_idebug(inode, "creating block %d", block);
 680
 681                         new_bh = sb_getblk(sb, block);
 682                         if (!new_bh) {
 683                                 ext2_free_blocks(inode, block, 1);
 684                                 error = -EIO;
 685                                 goto cleanup;
 686                         }
 687                         lock_buffer(new_bh);
 688                         memcpy(new_bh->b_data, header, new_bh->b_size);
 689                         set_buffer_uptodate(new_bh);
 690                         unlock_buffer(new_bh);
 691                         ext2_xattr_cache_insert(new_bh);
 692
 693                         ext2_xattr_update_super_block(sb);
 694                 }
 695                 mark_buffer_dirty(new_bh);
 696                 if (IS_SYNC(inode)) {
 697                         sync_dirty_buffer(new_bh);
 698                         error = -EIO;
 699                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 700                                 goto cleanup;
 701                 }
 702         }
 703
 704         /* Update the inode. */
 705         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 706         inode->i_ctime = CURRENT_TIME_SEC;
 707         if (IS_SYNC(inode)) {
 708                 error = ext2_sync_inode (inode);
 709                 /* In case sync failed due to ENOSPC the inode was actually
 710                  * written (only some dirty data were not) so we just proceed
 711                  * as if nothing happened and cleanup the unused block */
 712                 if (error && error != -ENOSPC) {
 713                         if (new_bh && new_bh != old_bh)
 714                                 DQUOT_FREE_BLOCK(inode, 1);
 715                         goto cleanup;
 716                 }
 717         } else
 718                 mark_inode_dirty(inode);
 719
 720         error = 0;
 721         if (old_bh && old_bh != new_bh) {
 722                 struct mb_cache_entry *ce;
 723
 724                 /*
 725                  * If there was an old block and we are no longer using it,
 726                  * release the old block.
 727                  */
 728                 ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
 729                                         old_bh->b_blocknr);
 730                 lock_buffer(old_bh);
 731                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 732                         /* Free the old block. */
 733                         if (ce)
 734                                 mb_cache_entry_free(ce);
 735                         ea_bdebug(old_bh, "freeing");
 736                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 737                         /* We let our caller release old_bh, so we
 738                          * need to duplicate the buffer before. */
 739                         get_bh(old_bh);
 740                         bforget(old_bh);
 741                 } else {
 742                         /* Decrement the refcount only. */
 743                         HDR(old_bh)->h_refcount = cpu_to_le32(
 744                                 le32_to_cpu(HDR(old_bh)->h_refcount) - 1);
 745                         if (ce)
 746                                 mb_cache_entry_release(ce);
 747                         DQUOT_FREE_BLOCK(inode, 1);
 748                         mark_buffer_dirty(old_bh);
 749                         ea_bdebug(old_bh, "refcount now=%d",
 750                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 751                 }
 752                 unlock_buffer(old_bh);
 753         }
 754
 755 cleanup:
 756         brelse(new_bh);
 757
 758         return error;
 759 }
 760
 761 /*
 762  * ext2_xattr_delete_inode()
 763  *
 764  * Free extended attribute resources associated with this inode. This
 765  * is called immediately before an inode is freed.
 766  */
 767 void
 768 ext2_xattr_delete_inode(struct inode *inode)
 769 {
 770         struct buffer_head *bh = NULL;
 771         struct mb_cache_entry *ce;
 772
 773         down_write(&EXT2_I(inode)->xattr_sem);
 774         if (!EXT2_I(inode)->i_file_acl)
 775                 goto cleanup;
 776         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 777         if (!bh) {
 778                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 779                         "inode %ld: block %d read error", inode->i_ino,
 780                         EXT2_I(inode)->i_file_acl);
 781                 goto cleanup;
 782         }
 783         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 784         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 785             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 786                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 787                         "inode %ld: bad block %d", inode->i_ino,
 788                         EXT2_I(inode)->i_file_acl);
 789                 goto cleanup;
 790         }
 791         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
 792         lock_buffer(bh);
 793         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 794                 if (ce)
 795                         mb_cache_entry_free(ce);
 796                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 797                 get_bh(bh);
 798                 bforget(bh);
 799         } else {
 800                 HDR(bh)->h_refcount = cpu_to_le32(
 801                         le32_to_cpu(HDR(bh)->h_refcount) - 1);
 802                 if (ce)
 803                         mb_cache_entry_release(ce);
 804                 mark_buffer_dirty(bh);
 805                 if (IS_SYNC(inode))
 806                         sync_dirty_buffer(bh);
 807                 DQUOT_FREE_BLOCK(inode, 1);
 808         }
 809         ea_bdebug(bh, "refcount now=%d", le32_to_cpu(HDR(bh)->h_refcount) - 1);
 810         unlock_buffer(bh);
 811         EXT2_I(inode)->i_file_acl = 0;
 812
 813 cleanup:
 814         brelse(bh);
 815         up_write(&EXT2_I(inode)->xattr_sem);
 816 }
 817
 818 /*
 819  * ext2_xattr_put_super()
 820  *
 821  * This is called when a file system is unmounted.
 822  */
 823 void
 824 ext2_xattr_put_super(struct super_block *sb)
 825 {
 826         mb_cache_shrink(ext2_xattr_cache, sb->s_bdev);
 827 }
 828
 829
 830 /*
 831  * ext2_xattr_cache_insert()
 832  *
 833  * Create a new entry in the extended attribute cache, and insert
 834  * it unless such an entry is already in the cache.
 835  *
 836  * Returns 0, or a negative error number on failure.
 837  */
 838 static int
 839 ext2_xattr_cache_insert(struct buffer_head *bh)
 840 {
 841         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 842         struct mb_cache_entry *ce;
 843         int error;
 844
 845         ce = mb_cache_entry_alloc(ext2_xattr_cache);
 846         if (!ce)
 847                 return -ENOMEM;
 848         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
 849         if (error) {
 850                 mb_cache_entry_free(ce);
 851                 if (error == -EBUSY) {
 852                         ea_bdebug(bh, "already in cache (%d cache entries)",
 853                                 atomic_read(&ext2_xattr_cache->c_entry_count));
 854                         error = 0;
 855                 }
 856         } else {
 857                 ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
 858                           atomic_read(&ext2_xattr_cache->c_entry_count));
 859                 mb_cache_entry_release(ce);
 860         }
 861         return error;
 862 }
 863
 864 /*
 865  * ext2_xattr_cmp()
 866  *
 867  * Compare two extended attribute blocks for equality.
 868  *
 869  * Returns 0 if the blocks are equal, 1 if they differ, and
 870  * a negative error number on errors.
 871  */
 872 static int
 873 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 874                struct ext2_xattr_header *header2)
 875 {
 876         struct ext2_xattr_entry *entry1, *entry2;
 877
 878         entry1 = ENTRY(header1+1);
 879         entry2 = ENTRY(header2+1);
 880         while (!IS_LAST_ENTRY(entry1)) {
 881                 if (IS_LAST_ENTRY(entry2))
 882                         return 1;
 883                 if (entry1->e_hash != entry2->e_hash ||
 884                     entry1->e_name_index != entry2->e_name_index ||
 885                     entry1->e_name_len != entry2->e_name_len ||
 886                     entry1->e_value_size != entry2->e_value_size ||
 887                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 888                         return 1;
 889                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 890                         return -EIO;
 891                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 892                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 893                            le32_to_cpu(entry1->e_value_size)))
 894                         return 1;
 895
 896                 entry1 = EXT2_XATTR_NEXT(entry1);
 897                 entry2 = EXT2_XATTR_NEXT(entry2);
 898         }
 899         if (!IS_LAST_ENTRY(entry2))
 900                 return 1;
 901         return 0;
 902 }
 903
 904 /*
 905  * ext2_xattr_cache_find()
 906  *
 907  * Find an identical extended attribute block.
 908  *
 909  * Returns a locked buffer head to the block found, or NULL if such
 910  * a block was not found or an error occurred.
 911  */
 912 static struct buffer_head *
 913 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 914 {
 915         __u32 hash = le32_to_cpu(header->h_hash);
 916         struct mb_cache_entry *ce;
 917
 918         if (!header->h_hash)
 919                 return NULL;  /* never share */
 920         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 921 again:
 922         ce = mb_cache_entry_find_first(ext2_xattr_cache, 0,
 923                                        inode->i_sb->s_bdev, hash);
 924         while (ce) {
 925                 struct buffer_head *bh;
 926
 927                 if (IS_ERR(ce)) {
 928                         if (PTR_ERR(ce) == -EAGAIN)
 929                                 goto again;
 930                         break;
 931                 }
 932
 933                 bh = sb_bread(inode->i_sb, ce->e_block);
 934                 if (!bh) {
 935                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 936                                 "inode %ld: block %ld read error",
 937                                 inode->i_ino, (unsigned long) ce->e_block);
 938                 } else {
 939                         lock_buffer(bh);
 940                         if (le32_to_cpu(HDR(bh)->h_refcount) >
 941                                    EXT2_XATTR_REFCOUNT_MAX) {
 942                                 ea_idebug(inode, "block %ld refcount %d>%d",
 943                                           (unsigned long) ce->e_block,
 944                                           le32_to_cpu(HDR(bh)->h_refcount),
 945                                           EXT2_XATTR_REFCOUNT_MAX);
 946                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 947                                 ea_bdebug(bh, "b_count=%d",
 948                                           atomic_read(&(bh->b_count)));
 949                                 mb_cache_entry_release(ce);
 950                                 return bh;
 951                         }
 952                         unlock_buffer(bh);
 953                         brelse(bh);
 954                 }
 955                 ce = mb_cache_entry_find_next(ce, 0, inode->i_sb->s_bdev, hash);
 956         }
 957         return NULL;
 958 }
 959
 960 #define NAME_HASH_SHIFT 5
 961 #define VALUE_HASH_SHIFT 16
 962
 963 /*
 964  * ext2_xattr_hash_entry()
 965  *
 966  * Compute the hash of an extended attribute.
 967  */
 968 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 969                                          struct ext2_xattr_entry *entry)
 970 {
 971         __u32 hash = 0;
 972         char *name = entry->e_name;
 973         int n;
 974
 975         for (n=0; n < entry->e_name_len; n++) {
 976                 hash = (hash << NAME_HASH_SHIFT) ^
 977                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 978                        *name++;
 979         }
 980
 981         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 982                 __le32 *value = (__le32 *)((char *)header +
 983                         le16_to_cpu(entry->e_value_offs));
 984                 for (n = (le32_to_cpu(entry->e_value_size) +
 985                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
 986                         hash = (hash << VALUE_HASH_SHIFT) ^
 987                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 988                                le32_to_cpu(*value++);
 989                 }
 990         }
 991         entry->e_hash = cpu_to_le32(hash);
 992 }
 993
 994 #undef NAME_HASH_SHIFT
 995 #undef VALUE_HASH_SHIFT
 996
 997 #define BLOCK_HASH_SHIFT 16
 998
 999 /*
1000  * ext2_xattr_rehash()
1001  *
1002  * Re-compute the extended attribute hash value after an entry has changed.
1003  */
1004 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1005                               struct ext2_xattr_entry *entry)
1006 {
1007         struct ext2_xattr_entry *here;
1008         __u32 hash = 0;
1009
1010         ext2_xattr_hash_entry(header, entry);
1011         here = ENTRY(header+1);
1012         while (!IS_LAST_ENTRY(here)) {
1013                 if (!here->e_hash) {
1014                         /* Block is not shared if an entry's hash value == 0 */
1015                         hash = 0;
1016                         break;
1017                 }
1018                 hash = (hash << BLOCK_HASH_SHIFT) ^
1019                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1020                        le32_to_cpu(here->e_hash);
1021                 here = EXT2_XATTR_NEXT(here);
1022         }
1023         header->h_hash = cpu_to_le32(hash);
1024 }
1025
1026 #undef BLOCK_HASH_SHIFT
1027
1028 int __init
1029 init_ext2_xattr(void)
1030 {
1031         ext2_xattr_cache = mb_cache_create("ext2_xattr", NULL,
1032                 sizeof(struct mb_cache_entry) +
1033                 sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
1034         if (!ext2_xattr_cache)
1035                 return -ENOMEM;
1036         return 0;
1037 }
1038
1039 void
1040 exit_ext2_xattr(void)
1041 {
1042         mb_cache_destroy(ext2_xattr_cache);
1043 }