The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/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  */
   39 ntfs_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  */
   57 void 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  */
  119 int 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)) {
  208 ir_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;
  215 done:
  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;
  272 descend_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);
  288 fast_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)) {
  378 ia_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);
  440 unm_err_out:
  441         unlock_page(page);
  442         ntfs_unmap_page(page);
  443 err_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;
  451 idx_err_out:
  452         ntfs_error(sb, "Corrupt index.  Aborting lookup.");
  453         goto err_out;
  454 }

Cache object: 639608b28ff6a6996fb84164943df43c


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