fs/ext2/xattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/fs/ext2/xattr.c
   4  *
   5  * Copyright (C) 2001-2003 Andreas Gruenbacher <agruen@suse.de>
   6  *
   7  * Fix by Harrison Xing <harrison@mountainviewdata.com>.
   8  * Extended attributes for symlinks and special files added per
   9  *  suggestion of Luka Renko <luka.renko@hermes.si>.
  10  * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
  11  *  Red Hat Inc.
  12  *
  13  */
  14
  15 /*
  16  * Extended attributes are stored on disk blocks allocated outside of
  17  * any inode. The i_file_acl field is then made to point to this allocated
  18  * block. If all extended attributes of an inode are identical, these
  19  * inodes may share the same extended attribute block. Such situations
  20  * are automatically detected by keeping a cache of recent attribute block
  21  * numbers and hashes over the block's contents in memory.
  22  *
  23  *
  24  * Extended attribute block layout:
  25  *
  26  *   +------------------+
  27  *   | header           |
  28  *   | entry 1          | |
  29  *   | entry 2          | | growing downwards
  30  *   | entry 3          | v
  31  *   | four null bytes  |
  32  *   | . . .            |
  33  *   | value 1          | ^
  34  *   | value 3          | | growing upwards
  35  *   | value 2          | |
  36  *   +------------------+
  37  *
  38  * The block header is followed by multiple entry descriptors. These entry
  39  * descriptors are variable in size, and aligned to EXT2_XATTR_PAD
  40  * byte boundaries. The entry descriptors are sorted by attribute name,
  41  * so that two extended attribute blocks can be compared efficiently.
  42  *
  43  * Attribute values are aligned to the end of the block, stored in
  44  * no specific order. They are also padded to EXT2_XATTR_PAD byte
  45  * boundaries. No additional gaps are left between them.
  46  *
  47  * Locking strategy
  48  * ----------------
  49  * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
  50  * EA blocks are only changed if they are exclusive to an inode, so
  51  * holding xattr_sem also means that nothing but the EA block's reference
  52  * count will change. Multiple writers to an EA block are synchronized
  53  * by the bh lock. No more than a single bh lock is held at any time
  54  * to avoid deadlocks.
  55  */
  56
  57 #include <linux/buffer_head.h>
  58 #include <linux/init.h>
  59 #include <linux/printk.h>
  60 #include <linux/slab.h>
  61 #include <linux/mbcache.h>
  62 #include <linux/quotaops.h>
  63 #include <linux/rwsem.h>
  64 #include <linux/security.h>
  65 #include "ext2.h"
  66 #include "xattr.h"
  67 #include "acl.h"
  68
  69 #define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  70 #define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  71 #define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  72 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  73
  74 #ifdef EXT2_XATTR_DEBUG
  75 # define ea_idebug(inode, f...) do { \
  76                 printk(KERN_DEBUG "inode %s:%ld: ", \
  77                         inode->i_sb->s_id, inode->i_ino); \
  78                 printk(f); \
  79                 printk("\n"); \
  80         } while (0)
  81 # define ea_bdebug(bh, f...) do { \
  82                 printk(KERN_DEBUG "block %pg:%lu: ", \
  83                         bh->b_bdev, (unsigned long) bh->b_blocknr); \
  84                 printk(f); \
  85                 printk("\n"); \
  86         } while (0)
  87 #else
  88 # define ea_idebug(inode, f...) no_printk(f)
  89 # define ea_bdebug(bh, f...)    no_printk(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 mb_cache *, 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 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 #define EA_BLOCK_CACHE(inode)   (EXT2_SB(inode->i_sb)->s_ea_block_cache)
 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         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 158
 159         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 160                   name_index, name, buffer, (long)buffer_size);
 161
 162         if (name == NULL)
 163                 return -EINVAL;
 164         name_len = strlen(name);
 165         if (name_len > 255)
 166                 return -ERANGE;
 167
 168         down_read(&EXT2_I(inode)->xattr_sem);
 169         error = -ENODATA;
 170         if (!EXT2_I(inode)->i_file_acl)
 171                 goto cleanup;
 172         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 173         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 174         error = -EIO;
 175         if (!bh)
 176                 goto cleanup;
 177         ea_bdebug(bh, "b_count=%d, refcount=%d",
 178                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 179         end = bh->b_data + bh->b_size;
 180         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 181             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 182 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
 183                         "inode %ld: bad block %d", inode->i_ino,
 184                         EXT2_I(inode)->i_file_acl);
 185                 error = -EIO;
 186                 goto cleanup;
 187         }
 188
 189         /* find named attribute */
 190         entry = FIRST_ENTRY(bh);
 191         while (!IS_LAST_ENTRY(entry)) {
 192                 struct ext2_xattr_entry *next =
 193                         EXT2_XATTR_NEXT(entry);
 194                 if ((char *)next >= end)
 195                         goto bad_block;
 196                 if (name_index == entry->e_name_index &&
 197                     name_len == entry->e_name_len &&
 198                     memcmp(name, entry->e_name, name_len) == 0)
 199                         goto found;
 200                 entry = next;
 201         }
 202         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 203                 ea_idebug(inode, "cache insert failed");
 204         error = -ENODATA;
 205         goto cleanup;
 206 found:
 207         /* check the buffer size */
 208         if (entry->e_value_block != 0)
 209                 goto bad_block;
 210         size = le32_to_cpu(entry->e_value_size);
 211         if (size > inode->i_sb->s_blocksize ||
 212             le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
 213                 goto bad_block;
 214
 215         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 216                 ea_idebug(inode, "cache insert failed");
 217         if (buffer) {
 218                 error = -ERANGE;
 219                 if (size > buffer_size)
 220                         goto cleanup;
 221                 /* return value of attribute */
 222                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 223                         size);
 224         }
 225         error = size;
 226
 227 cleanup:
 228         brelse(bh);
 229         up_read(&EXT2_I(inode)->xattr_sem);
 230
 231         return error;
 232 }
 233
 234 /*
 235  * ext2_xattr_list()
 236  *
 237  * Copy a list of attribute names into the buffer
 238  * provided, or compute the buffer size required.
 239  * Buffer is NULL to compute the size of the buffer required.
 240  *
 241  * Returns a negative error number on failure, or the number of bytes
 242  * used / required on success.
 243  */
 244 static int
 245 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 246 {
 247         struct inode *inode = d_inode(dentry);
 248         struct buffer_head *bh = NULL;
 249         struct ext2_xattr_entry *entry;
 250         char *end;
 251         size_t rest = buffer_size;
 252         int error;
 253         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 254
 255         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 256                   buffer, (long)buffer_size);
 257
 258         down_read(&EXT2_I(inode)->xattr_sem);
 259         error = 0;
 260         if (!EXT2_I(inode)->i_file_acl)
 261                 goto cleanup;
 262         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 263         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 264         error = -EIO;
 265         if (!bh)
 266                 goto cleanup;
 267         ea_bdebug(bh, "b_count=%d, refcount=%d",
 268                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 269         end = bh->b_data + bh->b_size;
 270         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 271             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 272 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
 273                         "inode %ld: bad block %d", inode->i_ino,
 274                         EXT2_I(inode)->i_file_acl);
 275                 error = -EIO;
 276                 goto cleanup;
 277         }
 278
 279         /* check the on-disk data structure */
 280         entry = FIRST_ENTRY(bh);
 281         while (!IS_LAST_ENTRY(entry)) {
 282                 struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
 283
 284                 if ((char *)next >= end)
 285                         goto bad_block;
 286                 entry = next;
 287         }
 288         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 289                 ea_idebug(inode, "cache insert failed");
 290
 291         /* list the attribute names */
 292         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 293              entry = EXT2_XATTR_NEXT(entry)) {
 294                 const struct xattr_handler *handler =
 295                         ext2_xattr_handler(entry->e_name_index);
 296
 297                 if (handler && (!handler->list || handler->list(dentry))) {
 298                         const char *prefix = handler->prefix ?: handler->name;
 299                         size_t prefix_len = strlen(prefix);
 300                         size_t size = prefix_len + entry->e_name_len + 1;
 301
 302                         if (buffer) {
 303                                 if (size > rest) {
 304                                         error = -ERANGE;
 305                                         goto cleanup;
 306                                 }
 307                                 memcpy(buffer, prefix, prefix_len);
 308                                 buffer += prefix_len;
 309                                 memcpy(buffer, entry->e_name, entry->e_name_len);
 310                                 buffer += entry->e_name_len;
 311                                 *buffer++ = 0;
 312                         }
 313                         rest -= size;
 314                 }
 315         }
 316         error = buffer_size - rest;  /* total size */
 317
 318 cleanup:
 319         brelse(bh);
 320         up_read(&EXT2_I(inode)->xattr_sem);
 321
 322         return error;
 323 }
 324
 325 /*
 326  * Inode operation listxattr()
 327  *
 328  * d_inode(dentry)->i_mutex: don't care
 329  */
 330 ssize_t
 331 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 332 {
 333         return ext2_xattr_list(dentry, buffer, size);
 334 }
 335
 336 /*
 337  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 338  * not set, set it.
 339  */
 340 static void ext2_xattr_update_super_block(struct super_block *sb)
 341 {
 342         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 343                 return;
 344
 345         spin_lock(&EXT2_SB(sb)->s_lock);
 346         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 347         spin_unlock(&EXT2_SB(sb)->s_lock);
 348         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 349 }
 350
 351 /*
 352  * ext2_xattr_set()
 353  *
 354  * Create, replace or remove an extended attribute for this inode.  Value
 355  * is NULL to remove an existing extended attribute, and non-NULL to
 356  * either replace an existing extended attribute, or create a new extended
 357  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 358  * specify that an extended attribute must exist and must not exist
 359  * previous to the call, respectively.
 360  *
 361  * Returns 0, or a negative error number on failure.
 362  */
 363 int
 364 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 365                const void *value, size_t value_len, int flags)
 366 {
 367         struct super_block *sb = inode->i_sb;
 368         struct buffer_head *bh = NULL;
 369         struct ext2_xattr_header *header = NULL;
 370         struct ext2_xattr_entry *here, *last;
 371         size_t name_len, free, min_offs = sb->s_blocksize;
 372         int not_found = 1, error;
 373         char *end;
 374
 375         /*
 376          * header -- Points either into bh, or to a temporarily
 377          *           allocated buffer.
 378          * here -- The named entry found, or the place for inserting, within
 379          *         the block pointed to by header.
 380          * last -- Points right after the last named entry within the block
 381          *         pointed to by header.
 382          * min_offs -- The offset of the first value (values are aligned
 383          *             towards the end of the block).
 384          * end -- Points right after the block pointed to by header.
 385          */
 386
 387         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 388                   name_index, name, value, (long)value_len);
 389
 390         if (value == NULL)
 391                 value_len = 0;
 392         if (name == NULL)
 393                 return -EINVAL;
 394         name_len = strlen(name);
 395         if (name_len > 255 || value_len > sb->s_blocksize)
 396                 return -ERANGE;
 397         down_write(&EXT2_I(inode)->xattr_sem);
 398         if (EXT2_I(inode)->i_file_acl) {
 399                 /* The inode already has an extended attribute block. */
 400                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 401                 error = -EIO;
 402                 if (!bh)
 403                         goto cleanup;
 404                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 405                         atomic_read(&(bh->b_count)),
 406                         le32_to_cpu(HDR(bh)->h_refcount));
 407                 header = HDR(bh);
 408                 end = bh->b_data + bh->b_size;
 409                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 410                     header->h_blocks != cpu_to_le32(1)) {
 411 bad_block:              ext2_error(sb, "ext2_xattr_set",
 412                                 "inode %ld: bad block %d", inode->i_ino,
 413                                    EXT2_I(inode)->i_file_acl);
 414                         error = -EIO;
 415                         goto cleanup;
 416                 }
 417                 /* Find the named attribute. */
 418                 here = FIRST_ENTRY(bh);
 419                 while (!IS_LAST_ENTRY(here)) {
 420                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
 421                         if ((char *)next >= end)
 422                                 goto bad_block;
 423                         if (!here->e_value_block && here->e_value_size) {
 424                                 size_t offs = le16_to_cpu(here->e_value_offs);
 425                                 if (offs < min_offs)
 426                                         min_offs = offs;
 427                         }
 428                         not_found = name_index - here->e_name_index;
 429                         if (!not_found)
 430                                 not_found = name_len - here->e_name_len;
 431                         if (!not_found)
 432                                 not_found = memcmp(name, here->e_name,name_len);
 433                         if (not_found <= 0)
 434                                 break;
 435                         here = next;
 436                 }
 437                 last = here;
 438                 /* We still need to compute min_offs and last. */
 439                 while (!IS_LAST_ENTRY(last)) {
 440                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
 441                         if ((char *)next >= end)
 442                                 goto bad_block;
 443                         if (!last->e_value_block && last->e_value_size) {
 444                                 size_t offs = le16_to_cpu(last->e_value_offs);
 445                                 if (offs < min_offs)
 446                                         min_offs = offs;
 447                         }
 448                         last = next;
 449                 }
 450
 451                 /* Check whether we have enough space left. */
 452                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 453         } else {
 454                 /* We will use a new extended attribute block. */
 455                 free = sb->s_blocksize -
 456                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 457                 here = last = NULL;  /* avoid gcc uninitialized warning. */
 458         }
 459
 460         if (not_found) {
 461                 /* Request to remove a nonexistent attribute? */
 462                 error = -ENODATA;
 463                 if (flags & XATTR_REPLACE)
 464                         goto cleanup;
 465                 error = 0;
 466                 if (value == NULL)
 467                         goto cleanup;
 468         } else {
 469                 /* Request to create an existing attribute? */
 470                 error = -EEXIST;
 471                 if (flags & XATTR_CREATE)
 472                         goto cleanup;
 473                 if (!here->e_value_block && here->e_value_size) {
 474                         size_t size = le32_to_cpu(here->e_value_size);
 475
 476                         if (le16_to_cpu(here->e_value_offs) + size >
 477                             sb->s_blocksize || size > sb->s_blocksize)
 478                                 goto bad_block;
 479                         free += EXT2_XATTR_SIZE(size);
 480                 }
 481                 free += EXT2_XATTR_LEN(name_len);
 482         }
 483         error = -ENOSPC;
 484         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 485                 goto cleanup;
 486
 487         /* Here we know that we can set the new attribute. */
 488
 489         if (header) {
 490                 /* assert(header == HDR(bh)); */
 491                 lock_buffer(bh);
 492                 if (header->h_refcount == cpu_to_le32(1)) {
 493                         __u32 hash = le32_to_cpu(header->h_hash);
 494
 495                         ea_bdebug(bh, "modifying in-place");
 496                         /*
 497                          * This must happen under buffer lock for
 498                          * ext2_xattr_set2() to reliably detect modified block
 499                          */
 500                         mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 501                                               bh->b_blocknr);
 502
 503                         /* keep the buffer locked while modifying it. */
 504                 } else {
 505                         int offset;
 506
 507                         unlock_buffer(bh);
 508                         ea_bdebug(bh, "cloning");
 509                         header = kmalloc(bh->b_size, GFP_KERNEL);
 510                         error = -ENOMEM;
 511                         if (header == NULL)
 512                                 goto cleanup;
 513                         memcpy(header, HDR(bh), bh->b_size);
 514                         header->h_refcount = cpu_to_le32(1);
 515
 516                         offset = (char *)here - bh->b_data;
 517                         here = ENTRY((char *)header + offset);
 518                         offset = (char *)last - bh->b_data;
 519                         last = ENTRY((char *)header + offset);
 520                 }
 521         } else {
 522                 /* Allocate a buffer where we construct the new block. */
 523                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 524                 error = -ENOMEM;
 525                 if (header == NULL)
 526                         goto cleanup;
 527                 end = (char *)header + sb->s_blocksize;
 528                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 529                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 530                 last = here = ENTRY(header+1);
 531         }
 532
 533         /* Iff we are modifying the block in-place, bh is locked here. */
 534
 535         if (not_found) {
 536                 /* Insert the new name. */
 537                 size_t size = EXT2_XATTR_LEN(name_len);
 538                 size_t rest = (char *)last - (char *)here;
 539                 memmove((char *)here + size, here, rest);
 540                 memset(here, 0, size);
 541                 here->e_name_index = name_index;
 542                 here->e_name_len = name_len;
 543                 memcpy(here->e_name, name, name_len);
 544         } else {
 545                 if (!here->e_value_block && here->e_value_size) {
 546                         char *first_val = (char *)header + min_offs;
 547                         size_t offs = le16_to_cpu(here->e_value_offs);
 548                         char *val = (char *)header + offs;
 549                         size_t size = EXT2_XATTR_SIZE(
 550                                 le32_to_cpu(here->e_value_size));
 551
 552                         if (size == EXT2_XATTR_SIZE(value_len)) {
 553                                 /* The old and the new value have the same
 554                                    size. Just replace. */
 555                                 here->e_value_size = cpu_to_le32(value_len);
 556                                 memset(val + size - EXT2_XATTR_PAD, 0,
 557                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 558                                 memcpy(val, value, value_len);
 559                                 goto skip_replace;
 560                         }
 561
 562                         /* Remove the old value. */
 563                         memmove(first_val + size, first_val, val - first_val);
 564                         memset(first_val, 0, size);
 565                         here->e_value_offs = 0;
 566                         min_offs += size;
 567
 568                         /* Adjust all value offsets. */
 569                         last = ENTRY(header+1);
 570                         while (!IS_LAST_ENTRY(last)) {
 571                                 size_t o = le16_to_cpu(last->e_value_offs);
 572                                 if (!last->e_value_block && o < offs)
 573                                         last->e_value_offs =
 574                                                 cpu_to_le16(o + size);
 575                                 last = EXT2_XATTR_NEXT(last);
 576                         }
 577                 }
 578                 if (value == NULL) {
 579                         /* Remove the old name. */
 580                         size_t size = EXT2_XATTR_LEN(name_len);
 581                         last = ENTRY((char *)last - size);
 582                         memmove(here, (char*)here + size,
 583                                 (char*)last - (char*)here);
 584                         memset(last, 0, size);
 585                 }
 586         }
 587
 588         if (value != NULL) {
 589                 /* Insert the new value. */
 590                 here->e_value_size = cpu_to_le32(value_len);
 591                 if (value_len) {
 592                         size_t size = EXT2_XATTR_SIZE(value_len);
 593                         char *val = (char *)header + min_offs - size;
 594                         here->e_value_offs =
 595                                 cpu_to_le16((char *)val - (char *)header);
 596                         memset(val + size - EXT2_XATTR_PAD, 0,
 597                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 598                         memcpy(val, value, value_len);
 599                 }
 600         }
 601
 602 skip_replace:
 603         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 604                 /* This block is now empty. */
 605                 if (bh && header == HDR(bh))
 606                         unlock_buffer(bh);  /* we were modifying in-place. */
 607                 error = ext2_xattr_set2(inode, bh, NULL);
 608         } else {
 609                 ext2_xattr_rehash(header, here);
 610                 if (bh && header == HDR(bh))
 611                         unlock_buffer(bh);  /* we were modifying in-place. */
 612                 error = ext2_xattr_set2(inode, bh, header);
 613         }
 614
 615 cleanup:
 616         if (!(bh && header == HDR(bh)))
 617                 kfree(header);
 618         brelse(bh);
 619         up_write(&EXT2_I(inode)->xattr_sem);
 620
 621         return error;
 622 }
 623
 624 /*
 625  * Second half of ext2_xattr_set(): Update the file system.
 626  */
 627 static int
 628 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 629                 struct ext2_xattr_header *header)
 630 {
 631         struct super_block *sb = inode->i_sb;
 632         struct buffer_head *new_bh = NULL;
 633         int error;
 634         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 635
 636         if (header) {
 637                 new_bh = ext2_xattr_cache_find(inode, header);
 638                 if (new_bh) {
 639                         /* We found an identical block in the cache. */
 640                         if (new_bh == old_bh) {
 641                                 ea_bdebug(new_bh, "keeping this block");
 642                         } else {
 643                                 /* The old block is released after updating
 644                                    the inode.  */
 645                                 ea_bdebug(new_bh, "reusing block");
 646
 647                                 error = dquot_alloc_block(inode, 1);
 648                                 if (error) {
 649                                         unlock_buffer(new_bh);
 650                                         goto cleanup;
 651                                 }
 652                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 653                                 ea_bdebug(new_bh, "refcount now=%d",
 654                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 655                         }
 656                         unlock_buffer(new_bh);
 657                 } else if (old_bh && header == HDR(old_bh)) {
 658                         /* Keep this block. No need to lock the block as we
 659                            don't need to change the reference count. */
 660                         new_bh = old_bh;
 661                         get_bh(new_bh);
 662                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 663                 } else {
 664                         /* We need to allocate a new block */
 665                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 666                                                 EXT2_I(inode)->i_block_group);
 667                         int block = ext2_new_block(inode, goal, &error);
 668                         if (error)
 669                                 goto cleanup;
 670                         ea_idebug(inode, "creating block %d", block);
 671
 672                         new_bh = sb_getblk(sb, block);
 673                         if (unlikely(!new_bh)) {
 674                                 ext2_free_blocks(inode, block, 1);
 675                                 mark_inode_dirty(inode);
 676                                 error = -ENOMEM;
 677                                 goto cleanup;
 678                         }
 679                         lock_buffer(new_bh);
 680                         memcpy(new_bh->b_data, header, new_bh->b_size);
 681                         set_buffer_uptodate(new_bh);
 682                         unlock_buffer(new_bh);
 683                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 684
 685                         ext2_xattr_update_super_block(sb);
 686                 }
 687                 mark_buffer_dirty(new_bh);
 688                 if (IS_SYNC(inode)) {
 689                         sync_dirty_buffer(new_bh);
 690                         error = -EIO;
 691                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 692                                 goto cleanup;
 693                 }
 694         }
 695
 696         /* Update the inode. */
 697         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 698         inode->i_ctime = current_time(inode);
 699         if (IS_SYNC(inode)) {
 700                 error = sync_inode_metadata(inode, 1);
 701                 /* In case sync failed due to ENOSPC the inode was actually
 702                  * written (only some dirty data were not) so we just proceed
 703                  * as if nothing happened and cleanup the unused block */
 704                 if (error && error != -ENOSPC) {
 705                         if (new_bh && new_bh != old_bh) {
 706                                 dquot_free_block_nodirty(inode, 1);
 707                                 mark_inode_dirty(inode);
 708                         }
 709                         goto cleanup;
 710                 }
 711         } else
 712                 mark_inode_dirty(inode);
 713
 714         error = 0;
 715         if (old_bh && old_bh != new_bh) {
 716                 /*
 717                  * If there was an old block and we are no longer using it,
 718                  * release the old block.
 719                  */
 720                 lock_buffer(old_bh);
 721                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 722                         __u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
 723
 724                         /*
 725                          * This must happen under buffer lock for
 726                          * ext2_xattr_set2() to reliably detect freed block
 727                          */
 728                         mb_cache_entry_delete(ea_block_cache, hash,
 729                                               old_bh->b_blocknr);
 730                         /* Free the old block. */
 731                         ea_bdebug(old_bh, "freeing");
 732                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 733                         mark_inode_dirty(inode);
 734                         /* We let our caller release old_bh, so we
 735                          * need to duplicate the buffer before. */
 736                         get_bh(old_bh);
 737                         bforget(old_bh);
 738                 } else {
 739                         /* Decrement the refcount only. */
 740                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 741                         dquot_free_block_nodirty(inode, 1);
 742                         mark_inode_dirty(inode);
 743                         mark_buffer_dirty(old_bh);
 744                         ea_bdebug(old_bh, "refcount now=%d",
 745                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 746                 }
 747                 unlock_buffer(old_bh);
 748         }
 749
 750 cleanup:
 751         brelse(new_bh);
 752
 753         return error;
 754 }
 755
 756 /*
 757  * ext2_xattr_delete_inode()
 758  *
 759  * Free extended attribute resources associated with this inode. This
 760  * is called immediately before an inode is freed.
 761  */
 762 void
 763 ext2_xattr_delete_inode(struct inode *inode)
 764 {
 765         struct buffer_head *bh = NULL;
 766         struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 767
 768         down_write(&EXT2_I(inode)->xattr_sem);
 769         if (!EXT2_I(inode)->i_file_acl)
 770                 goto cleanup;
 771
 772         if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 0)) {
 773                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 774                         "inode %ld: xattr block %d is out of data blocks range",
 775                         inode->i_ino, EXT2_I(inode)->i_file_acl);
 776                 goto cleanup;
 777         }
 778
 779         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 780         if (!bh) {
 781                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 782                         "inode %ld: block %d read error", inode->i_ino,
 783                         EXT2_I(inode)->i_file_acl);
 784                 goto cleanup;
 785         }
 786         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 787         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 788             HDR(bh)->h_blocks != cpu_to_le32(1)) {
 789                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 790                         "inode %ld: bad block %d", inode->i_ino,
 791                         EXT2_I(inode)->i_file_acl);
 792                 goto cleanup;
 793         }
 794         lock_buffer(bh);
 795         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 796                 __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 797
 798                 /*
 799                  * This must happen under buffer lock for ext2_xattr_set2() to
 800                  * reliably detect freed block
 801                  */
 802                 mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 803                                       bh->b_blocknr);
 804                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 805                 get_bh(bh);
 806                 bforget(bh);
 807                 unlock_buffer(bh);
 808         } else {
 809                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 810                 ea_bdebug(bh, "refcount now=%d",
 811                         le32_to_cpu(HDR(bh)->h_refcount));
 812                 unlock_buffer(bh);
 813                 mark_buffer_dirty(bh);
 814                 if (IS_SYNC(inode))
 815                         sync_dirty_buffer(bh);
 816                 dquot_free_block_nodirty(inode, 1);
 817         }
 818         EXT2_I(inode)->i_file_acl = 0;
 819
 820 cleanup:
 821         brelse(bh);
 822         up_write(&EXT2_I(inode)->xattr_sem);
 823 }
 824
 825 /*
 826  * ext2_xattr_cache_insert()
 827  *
 828  * Create a new entry in the extended attribute cache, and insert
 829  * it unless such an entry is already in the cache.
 830  *
 831  * Returns 0, or a negative error number on failure.
 832  */
 833 static int
 834 ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 835 {
 836         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 837         int error;
 838
 839         error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr, 1);
 840         if (error) {
 841                 if (error == -EBUSY) {
 842                         ea_bdebug(bh, "already in cache");
 843                         error = 0;
 844                 }
 845         } else
 846                 ea_bdebug(bh, "inserting [%x]", (int)hash);
 847         return error;
 848 }
 849
 850 /*
 851  * ext2_xattr_cmp()
 852  *
 853  * Compare two extended attribute blocks for equality.
 854  *
 855  * Returns 0 if the blocks are equal, 1 if they differ, and
 856  * a negative error number on errors.
 857  */
 858 static int
 859 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 860                struct ext2_xattr_header *header2)
 861 {
 862         struct ext2_xattr_entry *entry1, *entry2;
 863
 864         entry1 = ENTRY(header1+1);
 865         entry2 = ENTRY(header2+1);
 866         while (!IS_LAST_ENTRY(entry1)) {
 867                 if (IS_LAST_ENTRY(entry2))
 868                         return 1;
 869                 if (entry1->e_hash != entry2->e_hash ||
 870                     entry1->e_name_index != entry2->e_name_index ||
 871                     entry1->e_name_len != entry2->e_name_len ||
 872                     entry1->e_value_size != entry2->e_value_size ||
 873                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 874                         return 1;
 875                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 876                         return -EIO;
 877                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 878                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 879                            le32_to_cpu(entry1->e_value_size)))
 880                         return 1;
 881
 882                 entry1 = EXT2_XATTR_NEXT(entry1);
 883                 entry2 = EXT2_XATTR_NEXT(entry2);
 884         }
 885         if (!IS_LAST_ENTRY(entry2))
 886                 return 1;
 887         return 0;
 888 }
 889
 890 /*
 891  * ext2_xattr_cache_find()
 892  *
 893  * Find an identical extended attribute block.
 894  *
 895  * Returns a locked buffer head to the block found, or NULL if such
 896  * a block was not found or an error occurred.
 897  */
 898 static struct buffer_head *
 899 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 900 {
 901         __u32 hash = le32_to_cpu(header->h_hash);
 902         struct mb_cache_entry *ce;
 903         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 904
 905         if (!header->h_hash)
 906                 return NULL;  /* never share */
 907         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 908 again:
 909         ce = mb_cache_entry_find_first(ea_block_cache, hash);
 910         while (ce) {
 911                 struct buffer_head *bh;
 912
 913                 bh = sb_bread(inode->i_sb, ce->e_value);
 914                 if (!bh) {
 915                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 916                                 "inode %ld: block %ld read error",
 917                                 inode->i_ino, (unsigned long) ce->e_value);
 918                 } else {
 919                         lock_buffer(bh);
 920                         /*
 921                          * We have to be careful about races with freeing or
 922                          * rehashing of xattr block. Once we hold buffer lock
 923                          * xattr block's state is stable so we can check
 924                          * whether the block got freed / rehashed or not.
 925                          * Since we unhash mbcache entry under buffer lock when
 926                          * freeing / rehashing xattr block, checking whether
 927                          * entry is still hashed is reliable.
 928                          */
 929                         if (hlist_bl_unhashed(&ce->e_hash_list)) {
 930                                 mb_cache_entry_put(ea_block_cache, ce);
 931                                 unlock_buffer(bh);
 932                                 brelse(bh);
 933                                 goto again;
 934                         } else if (le32_to_cpu(HDR(bh)->h_refcount) >
 935                                    EXT2_XATTR_REFCOUNT_MAX) {
 936                                 ea_idebug(inode, "block %ld refcount %d>%d",
 937                                           (unsigned long) ce->e_value,
 938                                           le32_to_cpu(HDR(bh)->h_refcount),
 939                                           EXT2_XATTR_REFCOUNT_MAX);
 940                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 941                                 ea_bdebug(bh, "b_count=%d",
 942                                           atomic_read(&(bh->b_count)));
 943                                 mb_cache_entry_touch(ea_block_cache, ce);
 944                                 mb_cache_entry_put(ea_block_cache, ce);
 945                                 return bh;
 946                         }
 947                         unlock_buffer(bh);
 948                         brelse(bh);
 949                 }
 950                 ce = mb_cache_entry_find_next(ea_block_cache, ce);
 951         }
 952         return NULL;
 953 }
 954
 955 #define NAME_HASH_SHIFT 5
 956 #define VALUE_HASH_SHIFT 16
 957
 958 /*
 959  * ext2_xattr_hash_entry()
 960  *
 961  * Compute the hash of an extended attribute.
 962  */
 963 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 964                                          struct ext2_xattr_entry *entry)
 965 {
 966         __u32 hash = 0;
 967         char *name = entry->e_name;
 968         int n;
 969
 970         for (n=0; n < entry->e_name_len; n++) {
 971                 hash = (hash << NAME_HASH_SHIFT) ^
 972                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 973                        *name++;
 974         }
 975
 976         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 977                 __le32 *value = (__le32 *)((char *)header +
 978                         le16_to_cpu(entry->e_value_offs));
 979                 for (n = (le32_to_cpu(entry->e_value_size) +
 980                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
 981                         hash = (hash << VALUE_HASH_SHIFT) ^
 982                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 983                                le32_to_cpu(*value++);
 984                 }
 985         }
 986         entry->e_hash = cpu_to_le32(hash);
 987 }
 988
 989 #undef NAME_HASH_SHIFT
 990 #undef VALUE_HASH_SHIFT
 991
 992 #define BLOCK_HASH_SHIFT 16
 993
 994 /*
 995  * ext2_xattr_rehash()
 996  *
 997  * Re-compute the extended attribute hash value after an entry has changed.
 998  */
 999 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1000                               struct ext2_xattr_entry *entry)
1001 {
1002         struct ext2_xattr_entry *here;
1003         __u32 hash = 0;
1004
1005         ext2_xattr_hash_entry(header, entry);
1006         here = ENTRY(header+1);
1007         while (!IS_LAST_ENTRY(here)) {
1008                 if (!here->e_hash) {
1009                         /* Block is not shared if an entry's hash value == 0 */
1010                         hash = 0;
1011                         break;
1012                 }
1013                 hash = (hash << BLOCK_HASH_SHIFT) ^
1014                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1015                        le32_to_cpu(here->e_hash);
1016                 here = EXT2_XATTR_NEXT(here);
1017         }
1018         header->h_hash = cpu_to_le32(hash);
1019 }
1020
1021 #undef BLOCK_HASH_SHIFT
1022
1023 #define HASH_BUCKET_BITS 10
1024
1025 struct mb_cache *ext2_xattr_create_cache(void)
1026 {
1027         return mb_cache_create(HASH_BUCKET_BITS);
1028 }
1029
1030 void ext2_xattr_destroy_cache(struct mb_cache *cache)
1031 {
1032         if (cache)
1033                 mb_cache_destroy(cache);
1034 }