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