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 mb_cache *, 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 const struct xattr_handler *ext2_xattr_handler_map[] = {
 100         [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 101 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 102         [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
 103         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
 104 #endif
 105         [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
 106 #ifdef CONFIG_EXT2_FS_SECURITY
 107         [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
 108 #endif
 109 };
 110
 111 const struct xattr_handler *ext2_xattr_handlers[] = {
 112         &ext2_xattr_user_handler,
 113         &ext2_xattr_trusted_handler,
 114 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 115         &posix_acl_access_xattr_handler,
 116         &posix_acl_default_xattr_handler,
 117 #endif
 118 #ifdef CONFIG_EXT2_FS_SECURITY
 119         &ext2_xattr_security_handler,
 120 #endif
 121         NULL
 122 };
 123
 124 static inline const struct xattr_handler *
 125 ext2_xattr_handler(int name_index)
 126 {
 127         const struct xattr_handler *handler = NULL;
 128
 129         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 130                 handler = ext2_xattr_handler_map[name_index];
 131         return handler;
 132 }
 133
 134 /*
 135  * ext2_xattr_get()
 136  *
 137  * Copy an extended attribute into the buffer
 138  * provided, or compute the buffer size required.
 139  * Buffer is NULL to compute the size of the buffer required.
 140  *
 141  * Returns a negative error number on failure, or the number of bytes
 142  * used / required on success.
 143  */
 144 int
 145 ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 146                void *buffer, size_t buffer_size)
 147 {
 148         struct buffer_head *bh = NULL;
 149         struct ext2_xattr_entry *entry;
 150         size_t name_len, size;
 151         char *end;
 152         int error;
 153         struct mb_cache *ext2_mb_cache = EXT2_SB(inode->i_sb)->s_mb_cache;
 154
 155         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 156                   name_index, name, buffer, (long)buffer_size);
 157
 158         if (name == NULL)
 159                 return -EINVAL;
 160         name_len = strlen(name);
 161         if (name_len > 255)
 162                 return -ERANGE;
 163
 164         down_read(&EXT2_I(inode)->xattr_sem);
 165         error = -ENODATA;
 166         if (!EXT2_I(inode)->i_file_acl)
 167                 goto cleanup;
 168         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 169         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 170         error = -EIO;
 171         if (!bh)
 172                 goto cleanup;
 173         ea_bdebug(bh, "b_count=%d, refcount=%d",
 174                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 175         end = bh->b_data + bh->b_size;
 176         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 177             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 178 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
 179                         "inode %ld: bad block %d", inode->i_ino,
 180                         EXT2_I(inode)->i_file_acl);
 181                 error = -EIO;
 182                 goto cleanup;
 183         }
 184
 185         /* find named attribute */
 186         entry = FIRST_ENTRY(bh);
 187         while (!IS_LAST_ENTRY(entry)) {
 188                 struct ext2_xattr_entry *next =
 189                         EXT2_XATTR_NEXT(entry);
 190                 if ((char *)next >= end)
 191                         goto bad_block;
 192                 if (name_index == entry->e_name_index &&
 193                     name_len == entry->e_name_len &&
 194                     memcmp(name, entry->e_name, name_len) == 0)
 195                         goto found;
 196                 entry = next;
 197         }
 198         if (ext2_xattr_cache_insert(ext2_mb_cache, bh))
 199                 ea_idebug(inode, "cache insert failed");
 200         error = -ENODATA;
 201         goto cleanup;
 202 found:
 203         /* check the buffer size */
 204         if (entry->e_value_block != 0)
 205                 goto bad_block;
 206         size = le32_to_cpu(entry->e_value_size);
 207         if (size > inode->i_sb->s_blocksize ||
 208             le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
 209                 goto bad_block;
 210
 211         if (ext2_xattr_cache_insert(ext2_mb_cache, bh))
 212                 ea_idebug(inode, "cache insert failed");
 213         if (buffer) {
 214                 error = -ERANGE;
 215                 if (size > buffer_size)
 216                         goto cleanup;
 217                 /* return value of attribute */
 218                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 219                         size);
 220         }
 221         error = size;
 222
 223 cleanup:
 224         brelse(bh);
 225         up_read(&EXT2_I(inode)->xattr_sem);
 226
 227         return error;
 228 }
 229
 230 /*
 231  * ext2_xattr_list()
 232  *
 233  * Copy a list of attribute names into the buffer
 234  * provided, or compute the buffer size required.
 235  * Buffer is NULL to compute the size of the buffer required.
 236  *
 237  * Returns a negative error number on failure, or the number of bytes
 238  * used / required on success.
 239  */
 240 static int
 241 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 242 {
 243         struct inode *inode = d_inode(dentry);
 244         struct buffer_head *bh = NULL;
 245         struct ext2_xattr_entry *entry;
 246         char *end;
 247         size_t rest = buffer_size;
 248         int error;
 249         struct mb_cache *ext2_mb_cache = EXT2_SB(inode->i_sb)->s_mb_cache;
 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(ext2_mb_cache, 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 && (!handler->list || handler->list(dentry))) {
 294                         const char *prefix = handler->prefix ?: handler->name;
 295                         size_t prefix_len = strlen(prefix);
 296                         size_t size = prefix_len + entry->e_name_len + 1;
 297
 298                         if (buffer) {
 299                                 if (size > rest) {
 300                                         error = -ERANGE;
 301                                         goto cleanup;
 302                                 }
 303                                 memcpy(buffer, prefix, prefix_len);
 304                                 buffer += prefix_len;
 305                                 memcpy(buffer, entry->e_name, entry->e_name_len);
 306                                 buffer += entry->e_name_len;
 307                                 *buffer++ = 0;
 308                         }
 309                         rest -= size;
 310                 }
 311         }
 312         error = buffer_size - rest;  /* total size */
 313
 314 cleanup:
 315         brelse(bh);
 316         up_read(&EXT2_I(inode)->xattr_sem);
 317
 318         return error;
 319 }
 320
 321 /*
 322  * Inode operation listxattr()
 323  *
 324  * d_inode(dentry)->i_mutex: don't care
 325  */
 326 ssize_t
 327 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 328 {
 329         return ext2_xattr_list(dentry, buffer, size);
 330 }
 331
 332 /*
 333  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 334  * not set, set it.
 335  */
 336 static void ext2_xattr_update_super_block(struct super_block *sb)
 337 {
 338         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 339                 return;
 340
 341         spin_lock(&EXT2_SB(sb)->s_lock);
 342         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 343         spin_unlock(&EXT2_SB(sb)->s_lock);
 344         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 345 }
 346
 347 /*
 348  * ext2_xattr_set()
 349  *
 350  * Create, replace or remove an extended attribute for this inode.  Value
 351  * is NULL to remove an existing extended attribute, and non-NULL to
 352  * either replace an existing extended attribute, or create a new extended
 353  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 354  * specify that an extended attribute must exist and must not exist
 355  * previous to the call, respectively.
 356  *
 357  * Returns 0, or a negative error number on failure.
 358  */
 359 int
 360 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 361                const void *value, size_t value_len, int flags)
 362 {
 363         struct super_block *sb = inode->i_sb;
 364         struct buffer_head *bh = NULL;
 365         struct ext2_xattr_header *header = NULL;
 366         struct ext2_xattr_entry *here, *last;
 367         size_t name_len, free, min_offs = sb->s_blocksize;
 368         int not_found = 1, error;
 369         char *end;
 370
 371         /*
 372          * header -- Points either into bh, or to a temporarily
 373          *           allocated buffer.
 374          * here -- The named entry found, or the place for inserting, within
 375          *         the block pointed to by header.
 376          * last -- Points right after the last named entry within the block
 377          *         pointed to by header.
 378          * min_offs -- The offset of the first value (values are aligned
 379          *             towards the end of the block).
 380          * end -- Points right after the block pointed to by header.
 381          */
 382
 383         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 384                   name_index, name, value, (long)value_len);
 385
 386         if (value == NULL)
 387                 value_len = 0;
 388         if (name == NULL)
 389                 return -EINVAL;
 390         name_len = strlen(name);
 391         if (name_len > 255 || value_len > sb->s_blocksize)
 392                 return -ERANGE;
 393         down_write(&EXT2_I(inode)->xattr_sem);
 394         if (EXT2_I(inode)->i_file_acl) {
 395                 /* The inode already has an extended attribute block. */
 396                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 397                 error = -EIO;
 398                 if (!bh)
 399                         goto cleanup;
 400                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 401                         atomic_read(&(bh->b_count)),
 402                         le32_to_cpu(HDR(bh)->h_refcount));
 403                 header = HDR(bh);
 404                 end = bh->b_data + bh->b_size;
 405                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 406                     header->h_blocks != cpu_to_le32(1)) {
 407 bad_block:              ext2_error(sb, "ext2_xattr_set",
 408                                 "inode %ld: bad block %d", inode->i_ino,
 409                                    EXT2_I(inode)->i_file_acl);
 410                         error = -EIO;
 411                         goto cleanup;
 412                 }
 413                 /* Find the named attribute. */
 414                 here = FIRST_ENTRY(bh);
 415                 while (!IS_LAST_ENTRY(here)) {
 416                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 417                         if ((char *)next >= end)
 418                                 goto bad_block;
 419                         if (!here->e_value_block && here->e_value_size) {
 420                                 size_t offs = le16_to_cpu(here->e_value_offs);
 421                                 if (offs < min_offs)
 422                                         min_offs = offs;
 423                         }
 424                         not_found = name_index - here->e_name_index;
 425                         if (!not_found)
 426                                 not_found = name_len - here->e_name_len;
 427                         if (!not_found)
 428                                 not_found = memcmp(name, here->e_name,name_len);
 429                         if (not_found <= 0)
 430                                 break;
 431                         here = next;
 432                 }
 433                 last = here;
 434                 /* We still need to compute min_offs and last. */
 435                 while (!IS_LAST_ENTRY(last)) {
 436                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 437                         if ((char *)next >= end)
 438                                 goto bad_block;
 439                         if (!last->e_value_block && last->e_value_size) {
 440                                 size_t offs = le16_to_cpu(last->e_value_offs);
 441                                 if (offs < min_offs)
 442                                         min_offs = offs;
 443                         }
 444                         last = next;
 445                 }
 446
 447                 /* Check whether we have enough space left. */
 448                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 449         } else {
 450                 /* We will use a new extended attribute block. */
 451                 free = sb->s_blocksize -
 452                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 453                 here = last = NULL;  /* avoid gcc uninitialized warning. */
 454         }
 455
 456         if (not_found) {
 457                 /* Request to remove a nonexistent attribute? */
 458                 error = -ENODATA;
 459                 if (flags & XATTR_REPLACE)
 460                         goto cleanup;
 461                 error = 0;
 462                 if (value == NULL)
 463                         goto cleanup;
 464         } else {
 465                 /* Request to create an existing attribute? */
 466                 error = -EEXIST;
 467                 if (flags & XATTR_CREATE)
 468                         goto cleanup;
 469                 if (!here->e_value_block && here->e_value_size) {
 470                         size_t size = le32_to_cpu(here->e_value_size);
 471
 472                         if (le16_to_cpu(here->e_value_offs) + size >
 473                             sb->s_blocksize || size > sb->s_blocksize)
 474                                 goto bad_block;
 475                         free += EXT2_XATTR_SIZE(size);
 476                 }
 477                 free += EXT2_XATTR_LEN(name_len);
 478         }
 479         error = -ENOSPC;
 480         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 481                 goto cleanup;
 482
 483         /* Here we know that we can set the new attribute. */
 484
 485         if (header) {
 486                 /* assert(header == HDR(bh)); */
 487                 lock_buffer(bh);
 488                 if (header->h_refcount == cpu_to_le32(1)) {
 489                         __u32 hash = le32_to_cpu(header->h_hash);
 490
 491                         ea_bdebug(bh, "modifying in-place");
 492                         /*
 493                          * This must happen under buffer lock for
 494                          * ext2_xattr_set2() to reliably detect modified block
 495                          */
 496                         mb_cache_entry_delete_block(EXT2_SB(sb)->s_mb_cache,
 497                                                     hash, bh->b_blocknr);
 498
 499                         /* keep the buffer locked while modifying it. */
 500                 } else {
 501                         int offset;
 502
 503                         unlock_buffer(bh);
 504                         ea_bdebug(bh, "cloning");
 505                         header = kmalloc(bh->b_size, GFP_KERNEL);
 506                         error = -ENOMEM;
 507                         if (header == NULL)
 508                                 goto cleanup;
 509                         memcpy(header, HDR(bh), bh->b_size);
 510                         header->h_refcount = cpu_to_le32(1);
 511
 512                         offset = (char *)here - bh->b_data;
 513                         here = ENTRY((char *)header + offset);
 514                         offset = (char *)last - bh->b_data;
 515                         last = ENTRY((char *)header + offset);
 516                 }
 517         } else {
 518                 /* Allocate a buffer where we construct the new block. */
 519                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 520                 error = -ENOMEM;
 521                 if (header == NULL)
 522                         goto cleanup;
 523                 end = (char *)header + sb->s_blocksize;
 524                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 525                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 526                 last = here = ENTRY(header+1);
 527         }
 528
 529         /* Iff we are modifying the block in-place, bh is locked here. */
 530
 531         if (not_found) {
 532                 /* Insert the new name. */
 533                 size_t size = EXT2_XATTR_LEN(name_len);
 534                 size_t rest = (char *)last - (char *)here;
 535                 memmove((char *)here + size, here, rest);
 536                 memset(here, 0, size);
 537                 here->e_name_index = name_index;
 538                 here->e_name_len = name_len;
 539                 memcpy(here->e_name, name, name_len);
 540         } else {
 541                 if (!here->e_value_block && here->e_value_size) {
 542                         char *first_val = (char *)header + min_offs;
 543                         size_t offs = le16_to_cpu(here->e_value_offs);
 544                         char *val = (char *)header + offs;
 545                         size_t size = EXT2_XATTR_SIZE(
 546                                 le32_to_cpu(here->e_value_size));
 547
 548                         if (size == EXT2_XATTR_SIZE(value_len)) {
 549                                 /* The old and the new value have the same
 550                                    size. Just replace. */
 551                                 here->e_value_size = cpu_to_le32(value_len);
 552                                 memset(val + size - EXT2_XATTR_PAD, 0,
 553                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 554                                 memcpy(val, value, value_len);
 555                                 goto skip_replace;
 556                         }
 557
 558                         /* Remove the old value. */
 559                         memmove(first_val + size, first_val, val - first_val);
 560                         memset(first_val, 0, size);
 561                         here->e_value_offs = 0;
 562                         min_offs += size;
 563
 564                         /* Adjust all value offsets. */
 565                         last = ENTRY(header+1);
 566                         while (!IS_LAST_ENTRY(last)) {
 567                                 size_t o = le16_to_cpu(last->e_value_offs);
 568                                 if (!last->e_value_block && o < offs)
 569                                         last->e_value_offs =
 570                                                 cpu_to_le16(o + size);
 571                                 last = EXT2_XATTR_NEXT(last);
 572                         }
 573                 }
 574                 if (value == NULL) {
 575                         /* Remove the old name. */
 576                         size_t size = EXT2_XATTR_LEN(name_len);
 577                         last = ENTRY((char *)last - size);
 578                         memmove(here, (char*)here + size,
 579                                 (char*)last - (char*)here);
 580                         memset(last, 0, size);
 581                 }
 582         }
 583
 584         if (value != NULL) {
 585                 /* Insert the new value. */
 586                 here->e_value_size = cpu_to_le32(value_len);
 587                 if (value_len) {
 588                         size_t size = EXT2_XATTR_SIZE(value_len);
 589                         char *val = (char *)header + min_offs - size;
 590                         here->e_value_offs =
 591                                 cpu_to_le16((char *)val - (char *)header);
 592                         memset(val + size - EXT2_XATTR_PAD, 0,
 593                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 594                         memcpy(val, value, value_len);
 595                 }
 596         }
 597
 598 skip_replace:
 599         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 600                 /* This block is now empty. */
 601                 if (bh && header == HDR(bh))
 602                         unlock_buffer(bh);  /* we were modifying in-place. */
 603                 error = ext2_xattr_set2(inode, bh, NULL);
 604         } else {
 605                 ext2_xattr_rehash(header, here);
 606                 if (bh && header == HDR(bh))
 607                         unlock_buffer(bh);  /* we were modifying in-place. */
 608                 error = ext2_xattr_set2(inode, bh, header);
 609         }
 610
 611 cleanup:
 612         brelse(bh);
 613         if (!(bh && header == HDR(bh)))
 614                 kfree(header);
 615         up_write(&EXT2_I(inode)->xattr_sem);
 616
 617         return error;
 618 }
 619
 620 /*
 621  * Second half of ext2_xattr_set(): Update the file system.
 622  */
 623 static int
 624 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 625                 struct ext2_xattr_header *header)
 626 {
 627         struct super_block *sb = inode->i_sb;
 628         struct buffer_head *new_bh = NULL;
 629         int error;
 630         struct mb_cache *ext2_mb_cache = EXT2_SB(sb)->s_mb_cache;
 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(ext2_mb_cache, 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(ext2_mb_cache, 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                 /*
 713                  * If there was an old block and we are no longer using it,
 714                  * release the old block.
 715                  */
 716                 lock_buffer(old_bh);
 717                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 718                         __u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
 719
 720                         /*
 721                          * This must happen under buffer lock for
 722                          * ext2_xattr_set2() to reliably detect freed block
 723                          */
 724                         mb_cache_entry_delete_block(ext2_mb_cache,
 725                                                     hash, old_bh->b_blocknr);
 726                         /* Free the old block. */
 727                         ea_bdebug(old_bh, "freeing");
 728                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 729                         mark_inode_dirty(inode);
 730                         /* We let our caller release old_bh, so we
 731                          * need to duplicate the buffer before. */
 732                         get_bh(old_bh);
 733                         bforget(old_bh);
 734                 } else {
 735                         /* Decrement the refcount only. */
 736                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 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 ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 763
 764         down_write(&EXT2_I(inode)->xattr_sem);
 765         if (!EXT2_I(inode)->i_file_acl)
 766                 goto cleanup;
 767
 768         if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 0)) {
 769                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 770                         "inode %ld: xattr block %d is out of data blocks range",
 771                         inode->i_ino, EXT2_I(inode)->i_file_acl);
 772                 goto cleanup;
 773         }
 774
 775         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 776         if (!bh) {
 777                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 778                         "inode %ld: block %d read error", inode->i_ino,
 779                         EXT2_I(inode)->i_file_acl);
 780                 goto cleanup;
 781         }
 782         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 783         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 784             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 785                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 786                         "inode %ld: bad block %d", inode->i_ino,
 787                         EXT2_I(inode)->i_file_acl);
 788                 goto cleanup;
 789         }
 790         lock_buffer(bh);
 791         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 792                 __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 793
 794                 /*
 795                  * This must happen under buffer lock for ext2_xattr_set2() to
 796                  * reliably detect freed block
 797                  */
 798                 mb_cache_entry_delete_block(EXT2_SB(inode->i_sb)->s_mb_cache,
 799                                             hash, bh->b_blocknr);
 800                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 801                 get_bh(bh);
 802                 bforget(bh);
 803                 unlock_buffer(bh);
 804         } else {
 805                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 806                 ea_bdebug(bh, "refcount now=%d",
 807                         le32_to_cpu(HDR(bh)->h_refcount));
 808                 unlock_buffer(bh);
 809                 mark_buffer_dirty(bh);
 810                 if (IS_SYNC(inode))
 811                         sync_dirty_buffer(bh);
 812                 dquot_free_block_nodirty(inode, 1);
 813         }
 814         EXT2_I(inode)->i_file_acl = 0;
 815
 816 cleanup:
 817         brelse(bh);
 818         up_write(&EXT2_I(inode)->xattr_sem);
 819 }
 820
 821 /*
 822  * ext2_xattr_cache_insert()
 823  *
 824  * Create a new entry in the extended attribute cache, and insert
 825  * it unless such an entry is already in the cache.
 826  *
 827  * Returns 0, or a negative error number on failure.
 828  */
 829 static int
 830 ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 831 {
 832         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 833         int error;
 834
 835         error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr, 1);
 836         if (error) {
 837                 if (error == -EBUSY) {
 838                         ea_bdebug(bh, "already in cache (%d cache entries)",
 839                                 atomic_read(&ext2_xattr_cache->c_entry_count));
 840                         error = 0;
 841                 }
 842         } else
 843                 ea_bdebug(bh, "inserting [%x]", (int)hash);
 844         return error;
 845 }
 846
 847 /*
 848  * ext2_xattr_cmp()
 849  *
 850  * Compare two extended attribute blocks for equality.
 851  *
 852  * Returns 0 if the blocks are equal, 1 if they differ, and
 853  * a negative error number on errors.
 854  */
 855 static int
 856 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 857                struct ext2_xattr_header *header2)
 858 {
 859         struct ext2_xattr_entry *entry1, *entry2;
 860
 861         entry1 = ENTRY(header1+1);
 862         entry2 = ENTRY(header2+1);
 863         while (!IS_LAST_ENTRY(entry1)) {
 864                 if (IS_LAST_ENTRY(entry2))
 865                         return 1;
 866                 if (entry1->e_hash != entry2->e_hash ||
 867                     entry1->e_name_index != entry2->e_name_index ||
 868                     entry1->e_name_len != entry2->e_name_len ||
 869                     entry1->e_value_size != entry2->e_value_size ||
 870                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 871                         return 1;
 872                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 873                         return -EIO;
 874                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 875                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 876                            le32_to_cpu(entry1->e_value_size)))
 877                         return 1;
 878
 879                 entry1 = EXT2_XATTR_NEXT(entry1);
 880                 entry2 = EXT2_XATTR_NEXT(entry2);
 881         }
 882         if (!IS_LAST_ENTRY(entry2))
 883                 return 1;
 884         return 0;
 885 }
 886
 887 /*
 888  * ext2_xattr_cache_find()
 889  *
 890  * Find an identical extended attribute block.
 891  *
 892  * Returns a locked buffer head to the block found, or NULL if such
 893  * a block was not found or an error occurred.
 894  */
 895 static struct buffer_head *
 896 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 897 {
 898         __u32 hash = le32_to_cpu(header->h_hash);
 899         struct mb_cache_entry *ce;
 900         struct mb_cache *ext2_mb_cache = EXT2_SB(inode->i_sb)->s_mb_cache;
 901
 902         if (!header->h_hash)
 903                 return NULL;  /* never share */
 904         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 905 again:
 906         ce = mb_cache_entry_find_first(ext2_mb_cache, hash);
 907         while (ce) {
 908                 struct buffer_head *bh;
 909
 910                 bh = sb_bread(inode->i_sb, ce->e_block);
 911                 if (!bh) {
 912                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 913                                 "inode %ld: block %ld read error",
 914                                 inode->i_ino, (unsigned long) ce->e_block);
 915                 } else {
 916                         lock_buffer(bh);
 917                         /*
 918                          * We have to be careful about races with freeing or
 919                          * rehashing of xattr block. Once we hold buffer lock
 920                          * xattr block's state is stable so we can check
 921                          * whether the block got freed / rehashed or not.
 922                          * Since we unhash mbcache entry under buffer lock when
 923                          * freeing / rehashing xattr block, checking whether
 924                          * entry is still hashed is reliable.
 925                          */
 926                         if (hlist_bl_unhashed(&ce->e_hash_list)) {
 927                                 mb_cache_entry_put(ext2_mb_cache, ce);
 928                                 unlock_buffer(bh);
 929                                 brelse(bh);
 930                                 goto again;
 931                         } else if (le32_to_cpu(HDR(bh)->h_refcount) >
 932                                    EXT2_XATTR_REFCOUNT_MAX) {
 933                                 ea_idebug(inode, "block %ld refcount %d>%d",
 934                                           (unsigned long) ce->e_block,
 935                                           le32_to_cpu(HDR(bh)->h_refcount),
 936                                           EXT2_XATTR_REFCOUNT_MAX);
 937                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 938                                 ea_bdebug(bh, "b_count=%d",
 939                                           atomic_read(&(bh->b_count)));
 940                                 mb_cache_entry_touch(ext2_mb_cache, ce);
 941                                 mb_cache_entry_put(ext2_mb_cache, ce);
 942                                 return bh;
 943                         }
 944                         unlock_buffer(bh);
 945                         brelse(bh);
 946                 }
 947                 ce = mb_cache_entry_find_next(ext2_mb_cache, ce);
 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 #define HASH_BUCKET_BITS 10
1021
1022 struct mb_cache *ext2_xattr_create_cache(void)
1023 {
1024         return mb_cache_create(HASH_BUCKET_BITS);
1025 }
1026
1027 void ext2_xattr_destroy_cache(struct mb_cache *cache)
1028 {
1029         if (cache)
1030                 mb_cache_destroy(cache);
1031 }