linux/fs/ntfs/index.c
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   1/*
   2 * index.c - NTFS kernel index handling.  Part of the Linux-NTFS project.
   3 *
   4 * Copyright (c) 2004-2005 Anton Altaparmakov
   5 *
   6 * This program/include file is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License as published
   8 * by the Free Software Foundation; either version 2 of the License, or
   9 * (at your option) any later version.
  10 *
  11 * This program/include file is distributed in the hope that it will be
  12 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program (in the main directory of the Linux-NTFS
  18 * distribution in the file COPYING); if not, write to the Free Software
  19 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20 */
  21
  22#include <linux/slab.h>
  23
  24#include "aops.h"
  25#include "collate.h"
  26#include "debug.h"
  27#include "index.h"
  28#include "ntfs.h"
  29
  30/**
  31 * ntfs_index_ctx_get - allocate and initialize a new index context
  32 * @idx_ni:     ntfs index inode with which to initialize the context
  33 *
  34 * Allocate a new index context, initialize it with @idx_ni and return it.
  35 * Return NULL if allocation failed.
  36 *
  37 * Locking:  Caller must hold i_mutex on the index inode.
  38 */
  39ntfs_index_context *ntfs_index_ctx_get(ntfs_inode *idx_ni)
  40{
  41        ntfs_index_context *ictx;
  42
  43        ictx = kmem_cache_alloc(ntfs_index_ctx_cache, GFP_NOFS);
  44        if (ictx)
  45                *ictx = (ntfs_index_context){ .idx_ni = idx_ni };
  46        return ictx;
  47}
  48
  49/**
  50 * ntfs_index_ctx_put - release an index context
  51 * @ictx:       index context to free
  52 *
  53 * Release the index context @ictx, releasing all associated resources.
  54 *
  55 * Locking:  Caller must hold i_mutex on the index inode.
  56 */
  57void ntfs_index_ctx_put(ntfs_index_context *ictx)
  58{
  59        if (ictx->entry) {
  60                if (ictx->is_in_root) {
  61                        if (ictx->actx)
  62                                ntfs_attr_put_search_ctx(ictx->actx);
  63                        if (ictx->base_ni)
  64                                unmap_mft_record(ictx->base_ni);
  65                } else {
  66                        struct page *page = ictx->page;
  67                        if (page) {
  68                                BUG_ON(!PageLocked(page));
  69                                unlock_page(page);
  70                                ntfs_unmap_page(page);
  71                        }
  72                }
  73        }
  74        kmem_cache_free(ntfs_index_ctx_cache, ictx);
  75        return;
  76}
  77
  78/**
  79 * ntfs_index_lookup - find a key in an index and return its index entry
  80 * @key:        [IN] key for which to search in the index
  81 * @key_len:    [IN] length of @key in bytes
  82 * @ictx:       [IN/OUT] context describing the index and the returned entry
  83 *
  84 * Before calling ntfs_index_lookup(), @ictx must have been obtained from a
  85 * call to ntfs_index_ctx_get().
  86 *
  87 * Look for the @key in the index specified by the index lookup context @ictx.
  88 * ntfs_index_lookup() walks the contents of the index looking for the @key.
  89 *
  90 * If the @key is found in the index, 0 is returned and @ictx is setup to
  91 * describe the index entry containing the matching @key.  @ictx->entry is the
  92 * index entry and @ictx->data and @ictx->data_len are the index entry data and
  93 * its length in bytes, respectively.
  94 *
  95 * If the @key is not found in the index, -ENOENT is returned and @ictx is
  96 * setup to describe the index entry whose key collates immediately after the
  97 * search @key, i.e. this is the position in the index at which an index entry
  98 * with a key of @key would need to be inserted.
  99 *
 100 * If an error occurs return the negative error code and @ictx is left
 101 * untouched.
 102 *
 103 * When finished with the entry and its data, call ntfs_index_ctx_put() to free
 104 * the context and other associated resources.
 105 *
 106 * If the index entry was modified, call flush_dcache_index_entry_page()
 107 * immediately after the modification and either ntfs_index_entry_mark_dirty()
 108 * or ntfs_index_entry_write() before the call to ntfs_index_ctx_put() to
 109 * ensure that the changes are written to disk.
 110 *
 111 * Locking:  - Caller must hold i_mutex on the index inode.
 112 *           - Each page cache page in the index allocation mapping must be
 113 *             locked whilst being accessed otherwise we may find a corrupt
 114 *             page due to it being under ->writepage at the moment which
 115 *             applies the mst protection fixups before writing out and then
 116 *             removes them again after the write is complete after which it 
 117 *             unlocks the page.
 118 */
 119int ntfs_index_lookup(const void *key, const int key_len,
 120                ntfs_index_context *ictx)
 121{
 122        VCN vcn, old_vcn;
 123        ntfs_inode *idx_ni = ictx->idx_ni;
 124        ntfs_volume *vol = idx_ni->vol;
 125        struct super_block *sb = vol->sb;
 126        ntfs_inode *base_ni = idx_ni->ext.base_ntfs_ino;
 127        MFT_RECORD *m;
 128        INDEX_ROOT *ir;
 129        INDEX_ENTRY *ie;
 130        INDEX_ALLOCATION *ia;
 131        u8 *index_end, *kaddr;
 132        ntfs_attr_search_ctx *actx;
 133        struct address_space *ia_mapping;
 134        struct page *page;
 135        int rc, err = 0;
 136
 137        ntfs_debug("Entering.");
 138        BUG_ON(!NInoAttr(idx_ni));
 139        BUG_ON(idx_ni->type != AT_INDEX_ALLOCATION);
 140        BUG_ON(idx_ni->nr_extents != -1);
 141        BUG_ON(!base_ni);
 142        BUG_ON(!key);
 143        BUG_ON(key_len <= 0);
 144        if (!ntfs_is_collation_rule_supported(
 145                        idx_ni->itype.index.collation_rule)) {
 146                ntfs_error(sb, "Index uses unsupported collation rule 0x%x.  "
 147                                "Aborting lookup.", le32_to_cpu(
 148                                idx_ni->itype.index.collation_rule));
 149                return -EOPNOTSUPP;
 150        }
 151        /* Get hold of the mft record for the index inode. */
 152        m = map_mft_record(base_ni);
 153        if (IS_ERR(m)) {
 154                ntfs_error(sb, "map_mft_record() failed with error code %ld.",
 155                                -PTR_ERR(m));
 156                return PTR_ERR(m);
 157        }
 158        actx = ntfs_attr_get_search_ctx(base_ni, m);
 159        if (unlikely(!actx)) {
 160                err = -ENOMEM;
 161                goto err_out;
 162        }
 163        /* Find the index root attribute in the mft record. */
 164        err = ntfs_attr_lookup(AT_INDEX_ROOT, idx_ni->name, idx_ni->name_len,
 165                        CASE_SENSITIVE, 0, NULL, 0, actx);
 166        if (unlikely(err)) {
 167                if (err == -ENOENT) {
 168                        ntfs_error(sb, "Index root attribute missing in inode "
 169                                        "0x%lx.", idx_ni->mft_no);
 170                        err = -EIO;
 171                }
 172                goto err_out;
 173        }
 174        /* Get to the index root value (it has been verified in read_inode). */
 175        ir = (INDEX_ROOT*)((u8*)actx->attr +
 176                        le16_to_cpu(actx->attr->data.resident.value_offset));
 177        index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
 178        /* The first index entry. */
 179        ie = (INDEX_ENTRY*)((u8*)&ir->index +
 180                        le32_to_cpu(ir->index.entries_offset));
 181        /*
 182         * Loop until we exceed valid memory (corruption case) or until we
 183         * reach the last entry.
 184         */
 185        for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
 186                /* Bounds checks. */
 187                if ((u8*)ie < (u8*)actx->mrec || (u8*)ie +
 188                                sizeof(INDEX_ENTRY_HEADER) > index_end ||
 189                                (u8*)ie + le16_to_cpu(ie->length) > index_end)
 190                        goto idx_err_out;
 191                /*
 192                 * The last entry cannot contain a key.  It can however contain
 193                 * a pointer to a child node in the B+tree so we just break out.
 194                 */
 195                if (ie->flags & INDEX_ENTRY_END)
 196                        break;
 197                /* Further bounds checks. */
 198                if ((u32)sizeof(INDEX_ENTRY_HEADER) +
 199                                le16_to_cpu(ie->key_length) >
 200                                le16_to_cpu(ie->data.vi.data_offset) ||
 201                                (u32)le16_to_cpu(ie->data.vi.data_offset) +
 202                                le16_to_cpu(ie->data.vi.data_length) >
 203                                le16_to_cpu(ie->length))
 204                        goto idx_err_out;
 205                /* If the keys match perfectly, we setup @ictx and return 0. */
 206                if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
 207                                &ie->key, key_len)) {
 208ir_done:
 209                        ictx->is_in_root = true;
 210                        ictx->ir = ir;
 211                        ictx->actx = actx;
 212                        ictx->base_ni = base_ni;
 213                        ictx->ia = NULL;
 214                        ictx->page = NULL;
 215done:
 216                        ictx->entry = ie;
 217                        ictx->data = (u8*)ie +
 218                                        le16_to_cpu(ie->data.vi.data_offset);
 219                        ictx->data_len = le16_to_cpu(ie->data.vi.data_length);
 220                        ntfs_debug("Done.");
 221                        return err;
 222                }
 223                /*
 224                 * Not a perfect match, need to do full blown collation so we
 225                 * know which way in the B+tree we have to go.
 226                 */
 227                rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
 228                                key_len, &ie->key, le16_to_cpu(ie->key_length));
 229                /*
 230                 * If @key collates before the key of the current entry, there
 231                 * is definitely no such key in this index but we might need to
 232                 * descend into the B+tree so we just break out of the loop.
 233                 */
 234                if (rc == -1)
 235                        break;
 236                /*
 237                 * A match should never happen as the memcmp() call should have
 238                 * cought it, but we still treat it correctly.
 239                 */
 240                if (!rc)
 241                        goto ir_done;
 242                /* The keys are not equal, continue the search. */
 243        }
 244        /*
 245         * We have finished with this index without success.  Check for the
 246         * presence of a child node and if not present setup @ictx and return
 247         * -ENOENT.
 248         */
 249        if (!(ie->flags & INDEX_ENTRY_NODE)) {
 250                ntfs_debug("Entry not found.");
 251                err = -ENOENT;
 252                goto ir_done;
 253        } /* Child node present, descend into it. */
 254        /* Consistency check: Verify that an index allocation exists. */
 255        if (!NInoIndexAllocPresent(idx_ni)) {
 256                ntfs_error(sb, "No index allocation attribute but index entry "
 257                                "requires one.  Inode 0x%lx is corrupt or "
 258                                "driver bug.", idx_ni->mft_no);
 259                goto err_out;
 260        }
 261        /* Get the starting vcn of the index_block holding the child node. */
 262        vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
 263        ia_mapping = VFS_I(idx_ni)->i_mapping;
 264        /*
 265         * We are done with the index root and the mft record.  Release them,
 266         * otherwise we deadlock with ntfs_map_page().
 267         */
 268        ntfs_attr_put_search_ctx(actx);
 269        unmap_mft_record(base_ni);
 270        m = NULL;
 271        actx = NULL;
 272descend_into_child_node:
 273        /*
 274         * Convert vcn to index into the index allocation attribute in units
 275         * of PAGE_CACHE_SIZE and map the page cache page, reading it from
 276         * disk if necessary.
 277         */
 278        page = ntfs_map_page(ia_mapping, vcn <<
 279                        idx_ni->itype.index.vcn_size_bits >> PAGE_CACHE_SHIFT);
 280        if (IS_ERR(page)) {
 281                ntfs_error(sb, "Failed to map index page, error %ld.",
 282                                -PTR_ERR(page));
 283                err = PTR_ERR(page);
 284                goto err_out;
 285        }
 286        lock_page(page);
 287        kaddr = (u8*)page_address(page);
 288fast_descend_into_child_node:
 289        /* Get to the index allocation block. */
 290        ia = (INDEX_ALLOCATION*)(kaddr + ((vcn <<
 291                        idx_ni->itype.index.vcn_size_bits) & ~PAGE_CACHE_MASK));
 292        /* Bounds checks. */
 293        if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_SIZE) {
 294                ntfs_error(sb, "Out of bounds check failed.  Corrupt inode "
 295                                "0x%lx or driver bug.", idx_ni->mft_no);
 296                goto unm_err_out;
 297        }
 298        /* Catch multi sector transfer fixup errors. */
 299        if (unlikely(!ntfs_is_indx_record(ia->magic))) {
 300                ntfs_error(sb, "Index record with vcn 0x%llx is corrupt.  "
 301                                "Corrupt inode 0x%lx.  Run chkdsk.",
 302                                (long long)vcn, idx_ni->mft_no);
 303                goto unm_err_out;
 304        }
 305        if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
 306                ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
 307                                "different from expected VCN (0x%llx).  Inode "
 308                                "0x%lx is corrupt or driver bug.",
 309                                (unsigned long long)
 310                                sle64_to_cpu(ia->index_block_vcn),
 311                                (unsigned long long)vcn, idx_ni->mft_no);
 312                goto unm_err_out;
 313        }
 314        if (le32_to_cpu(ia->index.allocated_size) + 0x18 !=
 315                        idx_ni->itype.index.block_size) {
 316                ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx has "
 317                                "a size (%u) differing from the index "
 318                                "specified size (%u).  Inode is corrupt or "
 319                                "driver bug.", (unsigned long long)vcn,
 320                                idx_ni->mft_no,
 321                                le32_to_cpu(ia->index.allocated_size) + 0x18,
 322                                idx_ni->itype.index.block_size);
 323                goto unm_err_out;
 324        }
 325        index_end = (u8*)ia + idx_ni->itype.index.block_size;
 326        if (index_end > kaddr + PAGE_CACHE_SIZE) {
 327                ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx "
 328                                "crosses page boundary.  Impossible!  Cannot "
 329                                "access!  This is probably a bug in the "
 330                                "driver.", (unsigned long long)vcn,
 331                                idx_ni->mft_no);
 332                goto unm_err_out;
 333        }
 334        index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
 335        if (index_end > (u8*)ia + idx_ni->itype.index.block_size) {
 336                ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of inode "
 337                                "0x%lx exceeds maximum size.",
 338                                (unsigned long long)vcn, idx_ni->mft_no);
 339                goto unm_err_out;
 340        }
 341        /* The first index entry. */
 342        ie = (INDEX_ENTRY*)((u8*)&ia->index +
 343                        le32_to_cpu(ia->index.entries_offset));
 344        /*
 345         * Iterate similar to above big loop but applied to index buffer, thus
 346         * loop until we exceed valid memory (corruption case) or until we
 347         * reach the last entry.
 348         */
 349        for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
 350                /* Bounds checks. */
 351                if ((u8*)ie < (u8*)ia || (u8*)ie +
 352                                sizeof(INDEX_ENTRY_HEADER) > index_end ||
 353                                (u8*)ie + le16_to_cpu(ie->length) > index_end) {
 354                        ntfs_error(sb, "Index entry out of bounds in inode "
 355                                        "0x%lx.", idx_ni->mft_no);
 356                        goto unm_err_out;
 357                }
 358                /*
 359                 * The last entry cannot contain a key.  It can however contain
 360                 * a pointer to a child node in the B+tree so we just break out.
 361                 */
 362                if (ie->flags & INDEX_ENTRY_END)
 363                        break;
 364                /* Further bounds checks. */
 365                if ((u32)sizeof(INDEX_ENTRY_HEADER) +
 366                                le16_to_cpu(ie->key_length) >
 367                                le16_to_cpu(ie->data.vi.data_offset) ||
 368                                (u32)le16_to_cpu(ie->data.vi.data_offset) +
 369                                le16_to_cpu(ie->data.vi.data_length) >
 370                                le16_to_cpu(ie->length)) {
 371                        ntfs_error(sb, "Index entry out of bounds in inode "
 372                                        "0x%lx.", idx_ni->mft_no);
 373                        goto unm_err_out;
 374                }
 375                /* If the keys match perfectly, we setup @ictx and return 0. */
 376                if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
 377                                &ie->key, key_len)) {
 378ia_done:
 379                        ictx->is_in_root = false;
 380                        ictx->actx = NULL;
 381                        ictx->base_ni = NULL;
 382                        ictx->ia = ia;
 383                        ictx->page = page;
 384                        goto done;
 385                }
 386                /*
 387                 * Not a perfect match, need to do full blown collation so we
 388                 * know which way in the B+tree we have to go.
 389                 */
 390                rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
 391                                key_len, &ie->key, le16_to_cpu(ie->key_length));
 392                /*
 393                 * If @key collates before the key of the current entry, there
 394                 * is definitely no such key in this index but we might need to
 395                 * descend into the B+tree so we just break out of the loop.
 396                 */
 397                if (rc == -1)
 398                        break;
 399                /*
 400                 * A match should never happen as the memcmp() call should have
 401                 * cought it, but we still treat it correctly.
 402                 */
 403                if (!rc)
 404                        goto ia_done;
 405                /* The keys are not equal, continue the search. */
 406        }
 407        /*
 408         * We have finished with this index buffer without success.  Check for
 409         * the presence of a child node and if not present return -ENOENT.
 410         */
 411        if (!(ie->flags & INDEX_ENTRY_NODE)) {
 412                ntfs_debug("Entry not found.");
 413                err = -ENOENT;
 414                goto ia_done;
 415        }
 416        if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
 417                ntfs_error(sb, "Index entry with child node found in a leaf "
 418                                "node in inode 0x%lx.", idx_ni->mft_no);
 419                goto unm_err_out;
 420        }
 421        /* Child node present, descend into it. */
 422        old_vcn = vcn;
 423        vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
 424        if (vcn >= 0) {
 425                /*
 426                 * If vcn is in the same page cache page as old_vcn we recycle
 427                 * the mapped page.
 428                 */
 429                if (old_vcn << vol->cluster_size_bits >>
 430                                PAGE_CACHE_SHIFT == vcn <<
 431                                vol->cluster_size_bits >>
 432                                PAGE_CACHE_SHIFT)
 433                        goto fast_descend_into_child_node;
 434                unlock_page(page);
 435                ntfs_unmap_page(page);
 436                goto descend_into_child_node;
 437        }
 438        ntfs_error(sb, "Negative child node vcn in inode 0x%lx.",
 439                        idx_ni->mft_no);
 440unm_err_out:
 441        unlock_page(page);
 442        ntfs_unmap_page(page);
 443err_out:
 444        if (!err)
 445                err = -EIO;
 446        if (actx)
 447                ntfs_attr_put_search_ctx(actx);
 448        if (m)
 449                unmap_mft_record(base_ni);
 450        return err;
 451idx_err_out:
 452        ntfs_error(sb, "Corrupt index.  Aborting lookup.");
 453        goto err_out;
 454}
 455
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