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 aligned to EXT2_XATTR_PAD
  39  * byte boundaries. The entry descriptors are sorted by attribute name,
  40  * so that two extended attribute blocks can be compared efficiently.
  41  *
  42  * Attribute values are aligned to the end of the block, stored in
  43  * no specific order. They are also padded to EXT2_XATTR_PAD byte
  44  * boundaries. No additional gaps are left between them.
  45  *
  46  * Locking strategy
  47  * ----------------
  48  * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
  49  * EA blocks are only changed if they are exclusive to an inode, so
  50  * holding xattr_sem also means that nothing but the EA block's reference
  51  * count will change. Multiple writers to an EA block are synchronized
  52  * by the bh lock. No more than a single bh lock is held at any time
  53  * to avoid deadlocks.
  54  */
  55
  56 #include <linux/buffer_head.h>
  57 #include <linux/init.h>
  58 #include <linux/slab.h>
  59 #include <linux/mbcache.h>
  60 #include <linux/quotaops.h>
  61 #include <linux/rwsem.h>
  62 #include <linux/security.h>
  63 #include "ext2.h"
  64 #include "xattr.h"
  65 #include "acl.h"
  66
  67 #define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  68 #define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  69 #define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  70 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  71
  72 #ifdef EXT2_XATTR_DEBUG
  73 # define ea_idebug(inode, f...) do { \
  74                 printk(KERN_DEBUG "inode %s:%ld: ", \
  75                         inode->i_sb->s_id, inode->i_ino); \
  76                 printk(f); \
  77                 printk("\n"); \
  78         } while (0)
  79 # define ea_bdebug(bh, f...) do { \
  80                 char b[BDEVNAME_SIZE]; \
  81                 printk(KERN_DEBUG "block %s:%lu: ", \
  82                         bdevname(bh->b_bdev, b), \
  83                         (unsigned long) bh->b_blocknr); \
  84                 printk(f); \
  85                 printk("\n"); \
  86         } while (0)
  87 #else
  88 # define ea_idebug(f...)
  89 # define ea_bdebug(f...)
  90 #endif
  91
  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 const struct xattr_handler *ext2_xattr_handler_map[] = {
 104         [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 105 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 106         [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
 107         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_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 const struct xattr_handler *ext2_xattr_handlers[] = {
 116         &ext2_xattr_user_handler,
 117         &ext2_xattr_trusted_handler,
 118 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 119         &posix_acl_access_xattr_handler,
 120         &posix_acl_default_xattr_handler,
 121 #endif
 122 #ifdef CONFIG_EXT2_FS_SECURITY
 123         &ext2_xattr_security_handler,
 124 #endif
 125         NULL
 126 };
 127
 128 static inline const struct xattr_handler *
 129 ext2_xattr_handler(int name_index)
 130 {
 131         const struct xattr_handler *handler = NULL;
 132
 133         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 134                 handler = ext2_xattr_handler_map[name_index];
 135         return handler;
 136 }
 137
 138 /*
 139  * ext2_xattr_get()
 140  *
 141  * Copy an extended attribute into the buffer
 142  * provided, or compute the buffer size required.
 143  * Buffer is NULL to compute the size of the buffer required.
 144  *
 145  * Returns a negative error number on failure, or the number of bytes
 146  * used / required on success.
 147  */
 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         name_len = strlen(name);
 164         if (name_len > 255)
 165                 return -ERANGE;
 166
 167         down_read(&EXT2_I(inode)->xattr_sem);
 168         error = -ENODATA;
 169         if (!EXT2_I(inode)->i_file_acl)
 170                 goto cleanup;
 171         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 172         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 173         error = -EIO;
 174         if (!bh)
 175                 goto cleanup;
 176         ea_bdebug(bh, "b_count=%d, refcount=%d",
 177                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 178         end = bh->b_data + bh->b_size;
 179         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 180             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 181 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
 182                         "inode %ld: bad block %d", inode->i_ino,
 183                         EXT2_I(inode)->i_file_acl);
 184                 error = -EIO;
 185                 goto cleanup;
 186         }
 187
 188         /* find named attribute */
 189         entry = FIRST_ENTRY(bh);
 190         while (!IS_LAST_ENTRY(entry)) {
 191                 struct ext2_xattr_entry *next =
 192                         EXT2_XATTR_NEXT(entry);
 193                 if ((char *)next >= end)
 194                         goto bad_block;
 195                 if (name_index == entry->e_name_index &&
 196                     name_len == entry->e_name_len &&
 197                     memcmp(name, entry->e_name, name_len) == 0)
 198                         goto found;
 199                 entry = next;
 200         }
 201         if (ext2_xattr_cache_insert(bh))
 202                 ea_idebug(inode, "cache insert failed");
 203         error = -ENODATA;
 204         goto cleanup;
 205 found:
 206         /* check the buffer size */
 207         if (entry->e_value_block != 0)
 208                 goto bad_block;
 209         size = le32_to_cpu(entry->e_value_size);
 210         if (size > inode->i_sb->s_blocksize ||
 211             le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
 212                 goto bad_block;
 213
 214         if (ext2_xattr_cache_insert(bh))
 215                 ea_idebug(inode, "cache insert failed");
 216         if (buffer) {
 217                 error = -ERANGE;
 218                 if (size > buffer_size)
 219                         goto cleanup;
 220                 /* return value of attribute */
 221                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 222                         size);
 223         }
 224         error = size;
 225
 226 cleanup:
 227         brelse(bh);
 228         up_read(&EXT2_I(inode)->xattr_sem);
 229
 230         return error;
 231 }
 232
 233 /*
 234  * ext2_xattr_list()
 235  *
 236  * Copy a list of attribute names into the buffer
 237  * provided, or compute the buffer size required.
 238  * Buffer is NULL to compute the size of the buffer required.
 239  *
 240  * Returns a negative error number on failure, or the number of bytes
 241  * used / required on success.
 242  */
 243 static int
 244 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 245 {
 246         struct inode *inode = d_inode(dentry);
 247         struct buffer_head *bh = NULL;
 248         struct ext2_xattr_entry *entry;
 249         char *end;
 250         size_t rest = buffer_size;
 251         int error;
 252
 253         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 254                   buffer, (long)buffer_size);
 255
 256         down_read(&EXT2_I(inode)->xattr_sem);
 257         error = 0;
 258         if (!EXT2_I(inode)->i_file_acl)
 259                 goto cleanup;
 260         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 261         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 262         error = -EIO;
 263         if (!bh)
 264                 goto cleanup;
 265         ea_bdebug(bh, "b_count=%d, refcount=%d",
 266                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 267         end = bh->b_data + bh->b_size;
 268         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 269             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 270 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
 271                         "inode %ld: bad block %d", inode->i_ino,
 272                         EXT2_I(inode)->i_file_acl);
 273                 error = -EIO;
 274                 goto cleanup;
 275         }
 276
 277         /* check the on-disk data structure */
 278         entry = FIRST_ENTRY(bh);
 279         while (!IS_LAST_ENTRY(entry)) {
 280                 struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
 281
 282                 if ((char *)next >= end)
 283                         goto bad_block;
 284                 entry = next;
 285         }
 286         if (ext2_xattr_cache_insert(bh))
 287                 ea_idebug(inode, "cache insert failed");
 288
 289         /* list the attribute names */
 290         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 291              entry = EXT2_XATTR_NEXT(entry)) {
 292                 const struct xattr_handler *handler =
 293                         ext2_xattr_handler(entry->e_name_index);
 294
 295                 if (handler && (!handler->list || handler->list(dentry))) {
 296                         const char *prefix = handler->prefix ?: handler->name;
 297                         size_t prefix_len = strlen(prefix);
 298                         size_t size = prefix_len + entry->e_name_len + 1;
 299
 300                         if (buffer) {
 301                                 if (size > rest) {
 302                                         error = -ERANGE;
 303                                         goto cleanup;
 304                                 }
 305                                 memcpy(buffer, prefix, prefix_len);
 306                                 buffer += prefix_len;
 307                                 memcpy(buffer, entry->e_name, entry->e_name_len);
 308                                 buffer += entry->e_name_len;
 309                                 *buffer++ = 0;
 310                         }
 311                         rest -= size;
 312                 }
 313         }
 314         error = buffer_size - rest;  /* total size */
 315
 316 cleanup:
 317         brelse(bh);
 318         up_read(&EXT2_I(inode)->xattr_sem);
 319
 320         return error;
 321 }
 322
 323 /*
 324  * Inode operation listxattr()
 325  *
 326  * d_inode(dentry)->i_mutex: don't care
 327  */
 328 ssize_t
 329 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 330 {
 331         return ext2_xattr_list(dentry, buffer, size);
 332 }
 333
 334 /*
 335  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 336  * not set, set it.
 337  */
 338 static void ext2_xattr_update_super_block(struct super_block *sb)
 339 {
 340         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 341                 return;
 342
 343         spin_lock(&EXT2_SB(sb)->s_lock);
 344         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 345         spin_unlock(&EXT2_SB(sb)->s_lock);
 346         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 347 }
 348
 349 /*
 350  * ext2_xattr_set()
 351  *
 352  * Create, replace or remove an extended attribute for this inode.  Value
 353  * is NULL to remove an existing extended attribute, and non-NULL to
 354  * either replace an existing extended attribute, or create a new extended
 355  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 356  * specify that an extended attribute must exist and must not exist
 357  * previous to the call, respectively.
 358  *
 359  * Returns 0, or a negative error number on failure.
 360  */
 361 int
 362 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 363                const void *value, size_t value_len, int flags)
 364 {
 365         struct super_block *sb = inode->i_sb;
 366         struct buffer_head *bh = NULL;
 367         struct ext2_xattr_header *header = NULL;
 368         struct ext2_xattr_entry *here, *last;
 369         size_t name_len, free, min_offs = sb->s_blocksize;
 370         int not_found = 1, error;
 371         char *end;
 372
 373         /*
 374          * header -- Points either into bh, or to a temporarily
 375          *           allocated buffer.
 376          * here -- The named entry found, or the place for inserting, within
 377          *         the block pointed to by header.
 378          * last -- Points right after the last named entry within the block
 379          *         pointed to by header.
 380          * min_offs -- The offset of the first value (values are aligned
 381          *             towards the end of the block).
 382          * end -- Points right after the block pointed to by header.
 383          */
 384
 385         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 386                   name_index, name, value, (long)value_len);
 387
 388         if (value == NULL)
 389                 value_len = 0;
 390         if (name == NULL)
 391                 return -EINVAL;
 392         name_len = strlen(name);
 393         if (name_len > 255 || value_len > sb->s_blocksize)
 394                 return -ERANGE;
 395         down_write(&EXT2_I(inode)->xattr_sem);
 396         if (EXT2_I(inode)->i_file_acl) {
 397                 /* The inode already has an extended attribute block. */
 398                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 399                 error = -EIO;
 400                 if (!bh)
 401                         goto cleanup;
 402                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 403                         atomic_read(&(bh->b_count)),
 404                         le32_to_cpu(HDR(bh)->h_refcount));
 405                 header = HDR(bh);
 406                 end = bh->b_data + bh->b_size;
 407                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 408                     header->h_blocks != cpu_to_le32(1)) {
 409 bad_block:              ext2_error(sb, "ext2_xattr_set",
 410                                 "inode %ld: bad block %d", inode->i_ino,
 411                                    EXT2_I(inode)->i_file_acl);
 412                         error = -EIO;
 413                         goto cleanup;
 414                 }
 415                 /* Find the named attribute. */
 416                 here = FIRST_ENTRY(bh);
 417                 while (!IS_LAST_ENTRY(here)) {
 418                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 419                         if ((char *)next >= end)
 420                                 goto bad_block;
 421                         if (!here->e_value_block && here->e_value_size) {
 422                                 size_t offs = le16_to_cpu(here->e_value_offs);
 423                                 if (offs < min_offs)
 424                                         min_offs = offs;
 425                         }
 426                         not_found = name_index - here->e_name_index;
 427                         if (!not_found)
 428                                 not_found = name_len - here->e_name_len;
 429                         if (!not_found)
 430                                 not_found = memcmp(name, here->e_name,name_len);
 431                         if (not_found <= 0)
 432                                 break;
 433                         here = next;
 434                 }
 435                 last = here;
 436                 /* We still need to compute min_offs and last. */
 437                 while (!IS_LAST_ENTRY(last)) {
 438                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 439                         if ((char *)next >= end)
 440                                 goto bad_block;
 441                         if (!last->e_value_block && last->e_value_size) {
 442                                 size_t offs = le16_to_cpu(last->e_value_offs);
 443                                 if (offs < min_offs)
 444                                         min_offs = offs;
 445                         }
 446                         last = next;
 447                 }
 448
 449                 /* Check whether we have enough space left. */
 450                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 451         } else {
 452                 /* We will use a new extended attribute block. */
 453                 free = sb->s_blocksize -
 454                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 455                 here = last = NULL;  /* avoid gcc uninitialized warning. */
 456         }
 457
 458         if (not_found) {
 459                 /* Request to remove a nonexistent attribute? */
 460                 error = -ENODATA;
 461                 if (flags & XATTR_REPLACE)
 462                         goto cleanup;
 463                 error = 0;
 464                 if (value == NULL)
 465                         goto cleanup;
 466         } else {
 467                 /* Request to create an existing attribute? */
 468                 error = -EEXIST;
 469                 if (flags & XATTR_CREATE)
 470                         goto cleanup;
 471                 if (!here->e_value_block && here->e_value_size) {
 472                         size_t size = le32_to_cpu(here->e_value_size);
 473
 474                         if (le16_to_cpu(here->e_value_offs) + size >
 475                             sb->s_blocksize || size > sb->s_blocksize)
 476                                 goto bad_block;
 477                         free += EXT2_XATTR_SIZE(size);
 478                 }
 479                 free += EXT2_XATTR_LEN(name_len);
 480         }
 481         error = -ENOSPC;
 482         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 483                 goto cleanup;
 484
 485         /* Here we know that we can set the new attribute. */
 486
 487         if (header) {
 488                 struct mb_cache_entry *ce;
 489
 490                 /* assert(header == HDR(bh)); */
 491                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
 492                                         bh->b_blocknr);
 493                 lock_buffer(bh);
 494                 if (header->h_refcount == cpu_to_le32(1)) {
 495                         ea_bdebug(bh, "modifying in-place");
 496                         if (ce)
 497                                 mb_cache_entry_free(ce);
 498                         /* keep the buffer locked while modifying it. */
 499                 } else {
 500                         int offset;
 501
 502                         if (ce)
 503                                 mb_cache_entry_release(ce);
 504                         unlock_buffer(bh);
 505                         ea_bdebug(bh, "cloning");
 506                         header = kmalloc(bh->b_size, GFP_KERNEL);
 507                         error = -ENOMEM;
 508                         if (header == NULL)
 509                                 goto cleanup;
 510                         memcpy(header, HDR(bh), bh->b_size);
 511                         header->h_refcount = cpu_to_le32(1);
 512
 513                         offset = (char *)here - bh->b_data;
 514                         here = ENTRY((char *)header + offset);
 515                         offset = (char *)last - bh->b_data;
 516                         last = ENTRY((char *)header + offset);
 517                 }
 518         } else {
 519                 /* Allocate a buffer where we construct the new block. */
 520                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 521                 error = -ENOMEM;
 522                 if (header == NULL)
 523                         goto cleanup;
 524                 end = (char *)header + sb->s_blocksize;
 525                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 526                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 527                 last = here = ENTRY(header+1);
 528         }
 529
 530         /* Iff we are modifying the block in-place, bh is locked here. */
 531
 532         if (not_found) {
 533                 /* Insert the new name. */
 534                 size_t size = EXT2_XATTR_LEN(name_len);
 535                 size_t rest = (char *)last - (char *)here;
 536                 memmove((char *)here + size, here, rest);
 537                 memset(here, 0, size);
 538                 here->e_name_index = name_index;
 539                 here->e_name_len = name_len;
 540                 memcpy(here->e_name, name, name_len);
 541         } else {
 542                 if (!here->e_value_block && here->e_value_size) {
 543                         char *first_val = (char *)header + min_offs;
 544                         size_t offs = le16_to_cpu(here->e_value_offs);
 545                         char *val = (char *)header + offs;
 546                         size_t size = EXT2_XATTR_SIZE(
 547                                 le32_to_cpu(here->e_value_size));
 548
 549                         if (size == EXT2_XATTR_SIZE(value_len)) {
 550                                 /* The old and the new value have the same
 551                                    size. Just replace. */
 552                                 here->e_value_size = cpu_to_le32(value_len);
 553                                 memset(val + size - EXT2_XATTR_PAD, 0,
 554                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 555                                 memcpy(val, value, value_len);
 556                                 goto skip_replace;
 557                         }
 558
 559                         /* Remove the old value. */
 560                         memmove(first_val + size, first_val, val - first_val);
 561                         memset(first_val, 0, size);
 562                         here->e_value_offs = 0;
 563                         min_offs += size;
 564
 565                         /* Adjust all value offsets. */
 566                         last = ENTRY(header+1);
 567                         while (!IS_LAST_ENTRY(last)) {
 568                                 size_t o = le16_to_cpu(last->e_value_offs);
 569                                 if (!last->e_value_block && o < offs)
 570                                         last->e_value_offs =
 571                                                 cpu_to_le16(o + size);
 572                                 last = EXT2_XATTR_NEXT(last);
 573                         }
 574                 }
 575                 if (value == NULL) {
 576                         /* Remove the old name. */
 577                         size_t size = EXT2_XATTR_LEN(name_len);
 578                         last = ENTRY((char *)last - size);
 579                         memmove(here, (char*)here + size,
 580                                 (char*)last - (char*)here);
 581                         memset(last, 0, size);
 582                 }
 583         }
 584
 585         if (value != NULL) {
 586                 /* Insert the new value. */
 587                 here->e_value_size = cpu_to_le32(value_len);
 588                 if (value_len) {
 589                         size_t size = EXT2_XATTR_SIZE(value_len);
 590                         char *val = (char *)header + min_offs - size;
 591                         here->e_value_offs =
 592                                 cpu_to_le16((char *)val - (char *)header);
 593                         memset(val + size - EXT2_XATTR_PAD, 0,
 594                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 595                         memcpy(val, value, value_len);
 596                 }
 597         }
 598
 599 skip_replace:
 600         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 601                 /* This block is now empty. */
 602                 if (bh && header == HDR(bh))
 603                         unlock_buffer(bh);  /* we were modifying in-place. */
 604                 error = ext2_xattr_set2(inode, bh, NULL);
 605         } else {
 606                 ext2_xattr_rehash(header, here);
 607                 if (bh && header == HDR(bh))
 608                         unlock_buffer(bh);  /* we were modifying in-place. */
 609                 error = ext2_xattr_set2(inode, bh, header);
 610         }
 611
 612 cleanup:
 613         brelse(bh);
 614         if (!(bh && header == HDR(bh)))
 615                 kfree(header);
 616         up_write(&EXT2_I(inode)->xattr_sem);
 617
 618         return error;
 619 }
 620
 621 /*
 622  * Second half of ext2_xattr_set(): Update the file system.
 623  */
 624 static int
 625 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 626                 struct ext2_xattr_header *header)
 627 {
 628         struct super_block *sb = inode->i_sb;
 629         struct buffer_head *new_bh = NULL;
 630         int error;
 631
 632         if (header) {
 633                 new_bh = ext2_xattr_cache_find(inode, header);
 634                 if (new_bh) {
 635                         /* We found an identical block in the cache. */
 636                         if (new_bh == old_bh) {
 637                                 ea_bdebug(new_bh, "keeping this block");
 638                         } else {
 639                                 /* The old block is released after updating
 640                                    the inode.  */
 641                                 ea_bdebug(new_bh, "reusing block");
 642
 643                                 error = dquot_alloc_block(inode, 1);
 644                                 if (error) {
 645                                         unlock_buffer(new_bh);
 646                                         goto cleanup;
 647                                 }
 648                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 649                                 ea_bdebug(new_bh, "refcount now=%d",
 650                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 651                         }
 652                         unlock_buffer(new_bh);
 653                 } else if (old_bh && header == HDR(old_bh)) {
 654                         /* Keep this block. No need to lock the block as we
 655                            don't need to change the reference count. */
 656                         new_bh = old_bh;
 657                         get_bh(new_bh);
 658                         ext2_xattr_cache_insert(new_bh);
 659                 } else {
 660                         /* We need to allocate a new block */
 661                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 662                                                 EXT2_I(inode)->i_block_group);
 663                         int block = ext2_new_block(inode, goal, &error);
 664                         if (error)
 665                                 goto cleanup;
 666                         ea_idebug(inode, "creating block %d", block);
 667
 668                         new_bh = sb_getblk(sb, block);
 669                         if (unlikely(!new_bh)) {
 670                                 ext2_free_blocks(inode, block, 1);
 671                                 mark_inode_dirty(inode);
 672                                 error = -ENOMEM;
 673                                 goto cleanup;
 674                         }
 675                         lock_buffer(new_bh);
 676                         memcpy(new_bh->b_data, header, new_bh->b_size);
 677                         set_buffer_uptodate(new_bh);
 678                         unlock_buffer(new_bh);
 679                         ext2_xattr_cache_insert(new_bh);
 680
 681                         ext2_xattr_update_super_block(sb);
 682                 }
 683                 mark_buffer_dirty(new_bh);
 684                 if (IS_SYNC(inode)) {
 685                         sync_dirty_buffer(new_bh);
 686                         error = -EIO;
 687                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 688                                 goto cleanup;
 689                 }
 690         }
 691
 692         /* Update the inode. */
 693         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 694         inode->i_ctime = CURRENT_TIME_SEC;
 695         if (IS_SYNC(inode)) {
 696                 error = sync_inode_metadata(inode, 1);
 697                 /* In case sync failed due to ENOSPC the inode was actually
 698                  * written (only some dirty data were not) so we just proceed
 699                  * as if nothing happened and cleanup the unused block */
 700                 if (error && error != -ENOSPC) {
 701                         if (new_bh && new_bh != old_bh) {
 702                                 dquot_free_block_nodirty(inode, 1);
 703                                 mark_inode_dirty(inode);
 704                         }
 705                         goto cleanup;
 706                 }
 707         } else
 708                 mark_inode_dirty(inode);
 709
 710         error = 0;
 711         if (old_bh && old_bh != new_bh) {
 712                 struct mb_cache_entry *ce;
 713
 714                 /*
 715                  * If there was an old block and we are no longer using it,
 716                  * release the old block.
 717                  */
 718                 ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
 719                                         old_bh->b_blocknr);
 720                 lock_buffer(old_bh);
 721                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 722                         /* Free the old block. */
 723                         if (ce)
 724                                 mb_cache_entry_free(ce);
 725                         ea_bdebug(old_bh, "freeing");
 726                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 727                         mark_inode_dirty(inode);
 728                         /* We let our caller release old_bh, so we
 729                          * need to duplicate the buffer before. */
 730                         get_bh(old_bh);
 731                         bforget(old_bh);
 732                 } else {
 733                         /* Decrement the refcount only. */
 734                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 735                         if (ce)
 736                                 mb_cache_entry_release(ce);
 737                         dquot_free_block_nodirty(inode, 1);
 738                         mark_inode_dirty(inode);
 739                         mark_buffer_dirty(old_bh);
 740                         ea_bdebug(old_bh, "refcount now=%d",
 741                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 742                 }
 743                 unlock_buffer(old_bh);
 744         }
 745
 746 cleanup:
 747         brelse(new_bh);
 748
 749         return error;
 750 }
 751
 752 /*
 753  * ext2_xattr_delete_inode()
 754  *
 755  * Free extended attribute resources associated with this inode. This
 756  * is called immediately before an inode is freed.
 757  */
 758 void
 759 ext2_xattr_delete_inode(struct inode *inode)
 760 {
 761         struct buffer_head *bh = NULL;
 762         struct mb_cache_entry *ce;
 763
 764         down_write(&EXT2_I(inode)->xattr_sem);
 765         if (!EXT2_I(inode)->i_file_acl)
 766                 goto cleanup;
 767         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 768         if (!bh) {
 769                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 770                         "inode %ld: block %d read error", inode->i_ino,
 771                         EXT2_I(inode)->i_file_acl);
 772                 goto cleanup;
 773         }
 774         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 775         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 776             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 777                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 778                         "inode %ld: bad block %d", inode->i_ino,
 779                         EXT2_I(inode)->i_file_acl);
 780                 goto cleanup;
 781         }
 782         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
 783         lock_buffer(bh);
 784         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 785                 if (ce)
 786                         mb_cache_entry_free(ce);
 787                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 788                 get_bh(bh);
 789                 bforget(bh);
 790                 unlock_buffer(bh);
 791         } else {
 792                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 793                 if (ce)
 794                         mb_cache_entry_release(ce);
 795                 ea_bdebug(bh, "refcount now=%d",
 796                         le32_to_cpu(HDR(bh)->h_refcount));
 797                 unlock_buffer(bh);
 798                 mark_buffer_dirty(bh);
 799                 if (IS_SYNC(inode))
 800                         sync_dirty_buffer(bh);
 801                 dquot_free_block_nodirty(inode, 1);
 802         }
 803         EXT2_I(inode)->i_file_acl = 0;
 804
 805 cleanup:
 806         brelse(bh);
 807         up_write(&EXT2_I(inode)->xattr_sem);
 808 }
 809
 810 /*
 811  * ext2_xattr_put_super()
 812  *
 813  * This is called when a file system is unmounted.
 814  */
 815 void
 816 ext2_xattr_put_super(struct super_block *sb)
 817 {
 818         mb_cache_shrink(sb->s_bdev);
 819 }
 820
 821
 822 /*
 823  * ext2_xattr_cache_insert()
 824  *
 825  * Create a new entry in the extended attribute cache, and insert
 826  * it unless such an entry is already in the cache.
 827  *
 828  * Returns 0, or a negative error number on failure.
 829  */
 830 static int
 831 ext2_xattr_cache_insert(struct buffer_head *bh)
 832 {
 833         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 834         struct mb_cache_entry *ce;
 835         int error;
 836
 837         ce = mb_cache_entry_alloc(ext2_xattr_cache, GFP_NOFS);
 838         if (!ce)
 839                 return -ENOMEM;
 840         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, hash);
 841         if (error) {
 842                 mb_cache_entry_free(ce);
 843                 if (error == -EBUSY) {
 844                         ea_bdebug(bh, "already in cache (%d cache entries)",
 845                                 atomic_read(&ext2_xattr_cache->c_entry_count));
 846                         error = 0;
 847                 }
 848         } else {
 849                 ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
 850                           atomic_read(&ext2_xattr_cache->c_entry_count));
 851                 mb_cache_entry_release(ce);
 852         }
 853         return error;
 854 }
 855
 856 /*
 857  * ext2_xattr_cmp()
 858  *
 859  * Compare two extended attribute blocks for equality.
 860  *
 861  * Returns 0 if the blocks are equal, 1 if they differ, and
 862  * a negative error number on errors.
 863  */
 864 static int
 865 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 866                struct ext2_xattr_header *header2)
 867 {
 868         struct ext2_xattr_entry *entry1, *entry2;
 869
 870         entry1 = ENTRY(header1+1);
 871         entry2 = ENTRY(header2+1);
 872         while (!IS_LAST_ENTRY(entry1)) {
 873                 if (IS_LAST_ENTRY(entry2))
 874                         return 1;
 875                 if (entry1->e_hash != entry2->e_hash ||
 876                     entry1->e_name_index != entry2->e_name_index ||
 877                     entry1->e_name_len != entry2->e_name_len ||
 878                     entry1->e_value_size != entry2->e_value_size ||
 879                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 880                         return 1;
 881                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 882                         return -EIO;
 883                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 884                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 885                            le32_to_cpu(entry1->e_value_size)))
 886                         return 1;
 887
 888                 entry1 = EXT2_XATTR_NEXT(entry1);
 889                 entry2 = EXT2_XATTR_NEXT(entry2);
 890         }
 891         if (!IS_LAST_ENTRY(entry2))
 892                 return 1;
 893         return 0;
 894 }
 895
 896 /*
 897  * ext2_xattr_cache_find()
 898  *
 899  * Find an identical extended attribute block.
 900  *
 901  * Returns a locked buffer head to the block found, or NULL if such
 902  * a block was not found or an error occurred.
 903  */
 904 static struct buffer_head *
 905 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 906 {
 907         __u32 hash = le32_to_cpu(header->h_hash);
 908         struct mb_cache_entry *ce;
 909
 910         if (!header->h_hash)
 911                 return NULL;  /* never share */
 912         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 913 again:
 914         ce = mb_cache_entry_find_first(ext2_xattr_cache, inode->i_sb->s_bdev,
 915                                        hash);
 916         while (ce) {
 917                 struct buffer_head *bh;
 918
 919                 if (IS_ERR(ce)) {
 920                         if (PTR_ERR(ce) == -EAGAIN)
 921                                 goto again;
 922                         break;
 923                 }
 924
 925                 bh = sb_bread(inode->i_sb, ce->e_block);
 926                 if (!bh) {
 927                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 928                                 "inode %ld: block %ld read error",
 929                                 inode->i_ino, (unsigned long) ce->e_block);
 930                 } else {
 931                         lock_buffer(bh);
 932                         if (le32_to_cpu(HDR(bh)->h_refcount) >
 933                                    EXT2_XATTR_REFCOUNT_MAX) {
 934                                 ea_idebug(inode, "block %ld refcount %d>%d",
 935                                           (unsigned long) ce->e_block,
 936                                           le32_to_cpu(HDR(bh)->h_refcount),
 937                                           EXT2_XATTR_REFCOUNT_MAX);
 938                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 939                                 ea_bdebug(bh, "b_count=%d",
 940                                           atomic_read(&(bh->b_count)));
 941                                 mb_cache_entry_release(ce);
 942                                 return bh;
 943                         }
 944                         unlock_buffer(bh);
 945                         brelse(bh);
 946                 }
 947                 ce = mb_cache_entry_find_next(ce, inode->i_sb->s_bdev, hash);
 948         }
 949         return NULL;
 950 }
 951
 952 #define NAME_HASH_SHIFT 5
 953 #define VALUE_HASH_SHIFT 16
 954
 955 /*
 956  * ext2_xattr_hash_entry()
 957  *
 958  * Compute the hash of an extended attribute.
 959  */
 960 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 961                                          struct ext2_xattr_entry *entry)
 962 {
 963         __u32 hash = 0;
 964         char *name = entry->e_name;
 965         int n;
 966
 967         for (n=0; n < entry->e_name_len; n++) {
 968                 hash = (hash << NAME_HASH_SHIFT) ^
 969                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 970                        *name++;
 971         }
 972
 973         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 974                 __le32 *value = (__le32 *)((char *)header +
 975                         le16_to_cpu(entry->e_value_offs));
 976                 for (n = (le32_to_cpu(entry->e_value_size) +
 977                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
 978                         hash = (hash << VALUE_HASH_SHIFT) ^
 979                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 980                                le32_to_cpu(*value++);
 981                 }
 982         }
 983         entry->e_hash = cpu_to_le32(hash);
 984 }
 985
 986 #undef NAME_HASH_SHIFT
 987 #undef VALUE_HASH_SHIFT
 988
 989 #define BLOCK_HASH_SHIFT 16
 990
 991 /*
 992  * ext2_xattr_rehash()
 993  *
 994  * Re-compute the extended attribute hash value after an entry has changed.
 995  */
 996 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
 997                               struct ext2_xattr_entry *entry)
 998 {
 999         struct ext2_xattr_entry *here;
1000         __u32 hash = 0;
1001
1002         ext2_xattr_hash_entry(header, entry);
1003         here = ENTRY(header+1);
1004         while (!IS_LAST_ENTRY(here)) {
1005                 if (!here->e_hash) {
1006                         /* Block is not shared if an entry's hash value == 0 */
1007                         hash = 0;
1008                         break;
1009                 }
1010                 hash = (hash << BLOCK_HASH_SHIFT) ^
1011                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1012                        le32_to_cpu(here->e_hash);
1013                 here = EXT2_XATTR_NEXT(here);
1014         }
1015         header->h_hash = cpu_to_le32(hash);
1016 }
1017
1018 #undef BLOCK_HASH_SHIFT
1019
1020 int __init
1021 init_ext2_xattr(void)
1022 {
1023         ext2_xattr_cache = mb_cache_create("ext2_xattr", 6);
1024         if (!ext2_xattr_cache)
1025                 return -ENOMEM;
1026         return 0;
1027 }
1028
1029 void
1030 exit_ext2_xattr(void)
1031 {
1032         mb_cache_destroy(ext2_xattr_cache);
1033 }