xref: /freebsd-11-stable/contrib/subversion/subversion/libsvn_fs_fs/verify.c

/* verify.c --- verification of FSFS filesystems
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */

#include "svn_sorts.h"
#include "svn_checksum.h"
#include "svn_time.h"
#include "private/svn_subr_private.h"

#include "verify.h"
#include "fs_fs.h"

#include "cached_data.h"
#include "rep-cache.h"
#include "revprops.h"
#include "util.h"
#include "index.h"

#include "../libsvn_fs/fs-loader.h"

#include "svn_private_config.h"


/** Verifying. **/

/* Baton type expected by verify_walker().  The purpose is to reuse open
 * rev / pack file handles between calls.  Its contents need to be cleaned
 * periodically to limit resource usage.
 */
typedef struct verify_walker_baton_t
{
  /* number of calls to verify_walker() since the last clean */
  int iteration_count;

  /* number of files opened since the last clean */
  int file_count;

  /* progress notification callback to invoke periodically (may be NULL) */
  svn_fs_progress_notify_func_t notify_func;

  /* baton to use with NOTIFY_FUNC */
  void *notify_baton;

  /* remember the last revision for which we called notify_func */
  svn_revnum_t last_notified_revision;

  /* cached hint for successive calls to svn_fs_fs__check_rep() */
  void *hint;

  /* pool to use for the file handles etc. */
  apr_pool_t *pool;
} verify_walker_baton_t;

/* Used by svn_fs_fs__verify().
   Implements svn_fs_fs__walk_rep_reference().walker.  */
static svn_error_t *
verify_walker(representation_t *rep,
              void *baton,
              svn_fs_t *fs,
              apr_pool_t *scratch_pool)
{
  verify_walker_baton_t *walker_baton = baton;
  void *previous_hint;

  /* notify and free resources periodically */
  if (   walker_baton->iteration_count > 1000
      || walker_baton->file_count > 16)
    {
      if (   walker_baton->notify_func
          && rep->revision != walker_baton->last_notified_revision)
        {
          walker_baton->notify_func(rep->revision,
                                    walker_baton->notify_baton,
                                    scratch_pool);
          walker_baton->last_notified_revision = rep->revision;
        }

      svn_pool_clear(walker_baton->pool);

      walker_baton->iteration_count = 0;
      walker_baton->file_count = 0;
      walker_baton->hint = NULL;
    }

  /* access the repo data */
  previous_hint = walker_baton->hint;
  SVN_ERR(svn_fs_fs__check_rep(rep, fs, &walker_baton->hint,
                               walker_baton->pool));

  /* update resource usage counters */
  walker_baton->iteration_count++;
  if (previous_hint != walker_baton->hint)
    walker_baton->file_count++;

  return SVN_NO_ERROR;
}

/* Verify the rep cache DB's consistency with our rev / pack data.
 * The function signature is similar to svn_fs_fs__verify.
 * The values of START and END have already been auto-selected and
 * verified.
 */
static svn_error_t *
verify_rep_cache(svn_fs_t *fs,
                 svn_revnum_t start,
                 svn_revnum_t end,
                 svn_fs_progress_notify_func_t notify_func,
                 void *notify_baton,
                 svn_cancel_func_t cancel_func,
                 void *cancel_baton,
                 apr_pool_t *pool)
{
  svn_boolean_t exists;

  /* rep-cache verification. */
  SVN_ERR(svn_fs_fs__exists_rep_cache(&exists, fs, pool));
  if (exists)
    {
      /* provide a baton to allow the reuse of open file handles between
         iterations (saves 2/3 of OS level file operations). */
      verify_walker_baton_t *baton = apr_pcalloc(pool, sizeof(*baton));
      baton->pool = svn_pool_create(pool);
      baton->last_notified_revision = SVN_INVALID_REVNUM;
      baton->notify_func = notify_func;
      baton->notify_baton = notify_baton;

      /* tell the user that we are now ready to do *something* */
      if (notify_func)
        notify_func(SVN_INVALID_REVNUM, notify_baton, baton->pool);

      /* Do not attempt to walk the rep-cache database if its file does
         not exist,  since doing so would create it --- which may confuse
         the administrator.   Don't take any lock. */
      SVN_ERR(svn_fs_fs__walk_rep_reference(fs, start, end,
                                            verify_walker, baton,
                                            cancel_func, cancel_baton,
                                            pool));

      /* walker resource cleanup */
      svn_pool_destroy(baton->pool);
    }

  return SVN_NO_ERROR;
}

/* Verify that the MD5 checksum of the data between offsets START and END
 * in FILE matches the EXPECTED checksum.  If there is a mismatch use the
 * indedx NAME in the error message.  Supports cancellation with CANCEL_FUNC
 * and CANCEL_BATON.  SCRATCH_POOL is for temporary allocations. */
static svn_error_t *
verify_index_checksum(apr_file_t *file,
                      const char *name,
                      apr_off_t start,
                      apr_off_t end,
                      svn_checksum_t *expected,
                      svn_cancel_func_t cancel_func,
                      void *cancel_baton,
                      apr_pool_t *scratch_pool)
{
  unsigned char buffer[SVN__STREAM_CHUNK_SIZE];
  apr_off_t size = end - start;
  svn_checksum_t *actual;
  svn_checksum_ctx_t *context
    = svn_checksum_ctx_create(svn_checksum_md5, scratch_pool);

  /* Calculate the index checksum. */
  SVN_ERR(svn_io_file_seek(file, APR_SET, &start, scratch_pool));
  while (size > 0)
    {
      apr_size_t to_read = size > sizeof(buffer)
                         ? sizeof(buffer)
                         : (apr_size_t)size;
      SVN_ERR(svn_io_file_read_full2(file, buffer, to_read, NULL, NULL,
                                     scratch_pool));
      SVN_ERR(svn_checksum_update(context, buffer, to_read));
      size -= to_read;

      if (cancel_func)
        SVN_ERR(cancel_func(cancel_baton));
    }

  SVN_ERR(svn_checksum_final(&actual, context, scratch_pool));

  /* Verify that it matches the expected checksum. */
  if (!svn_checksum_match(expected, actual))
    {
      const char *file_name;

      SVN_ERR(svn_io_file_name_get(&file_name, file, scratch_pool));
      SVN_ERR(svn_checksum_mismatch_err(expected, actual, scratch_pool,
                                        _("%s checksum mismatch in file %s"),
                                        name, file_name));
    }

  return SVN_NO_ERROR;
}

/* Verify the MD5 checksums of the index data in the rev / pack file
 * containing revision START in FS.  If given, invoke CANCEL_FUNC with
 * CANCEL_BATON at regular intervals.  Use SCRATCH_POOL for temporary
 * allocations.
 */
static svn_error_t *
verify_index_checksums(svn_fs_t *fs,
                       svn_revnum_t start,
                       svn_cancel_func_t cancel_func,
                       void *cancel_baton,
                       apr_pool_t *scratch_pool)
{
  svn_fs_fs__revision_file_t *rev_file;

  /* Open the rev / pack file and read the footer */
  SVN_ERR(svn_fs_fs__open_pack_or_rev_file(&rev_file, fs, start,
                                           scratch_pool, scratch_pool));
  SVN_ERR(svn_fs_fs__auto_read_footer(rev_file));

  /* Verify the index contents against the checksum from the footer. */
  SVN_ERR(verify_index_checksum(rev_file->file, "L2P index",
                                rev_file->l2p_offset, rev_file->p2l_offset,
                                rev_file->l2p_checksum,
                                cancel_func, cancel_baton, scratch_pool));
  SVN_ERR(verify_index_checksum(rev_file->file, "P2L index",
                                rev_file->p2l_offset, rev_file->footer_offset,
                                rev_file->p2l_checksum,
                                cancel_func, cancel_baton, scratch_pool));

  /* Done. */
  SVN_ERR(svn_fs_fs__close_revision_file(rev_file));

  return SVN_NO_ERROR;
}

/* Verify that for all log-to-phys index entries for revisions START to
 * START + COUNT-1 in FS there is a consistent entry in the phys-to-log
 * index.  If given, invoke CANCEL_FUNC with CANCEL_BATON at regular
 * intervals. Use POOL for allocations.
 */
static svn_error_t *
compare_l2p_to_p2l_index(svn_fs_t *fs,
                         svn_revnum_t start,
                         svn_revnum_t count,
                         svn_cancel_func_t cancel_func,
                         void *cancel_baton,
                         apr_pool_t *pool)
{
  svn_revnum_t i;
  apr_pool_t *iterpool = svn_pool_create(pool);
  apr_array_header_t *max_ids;

  /* common file access structure */
  svn_fs_fs__revision_file_t *rev_file;
  SVN_ERR(svn_fs_fs__open_pack_or_rev_file(&rev_file, fs, start, pool,
                                           iterpool));

  /* determine the range of items to check for each revision */
  SVN_ERR(svn_fs_fs__l2p_get_max_ids(&max_ids, fs, start, count, pool,
                                     iterpool));

  /* check all items in all revisions if the given range */
  for (i = 0; i < max_ids->nelts; ++i)
    {
      apr_uint64_t k;
      apr_uint64_t max_id = APR_ARRAY_IDX(max_ids, i, apr_uint64_t);
      svn_revnum_t revision = start + i;

      for (k = 0; k < max_id; ++k)
        {
          apr_off_t offset;
          svn_fs_fs__p2l_entry_t *p2l_entry;
          svn_pool_clear(iterpool);

          /* get L2P entry.  Ignore unused entries. */
          SVN_ERR(svn_fs_fs__item_offset(&offset, fs, rev_file, revision,
                                         NULL, k, iterpool));
          if (offset == -1)
            continue;

          /* find the corresponding P2L entry */
          SVN_ERR(svn_fs_fs__p2l_entry_lookup(&p2l_entry, fs, rev_file,
                                              revision, offset, iterpool,
                                              iterpool));

          if (p2l_entry == NULL)
            return svn_error_createf(SVN_ERR_FS_INDEX_INCONSISTENT,
                                     NULL,
                                     _("p2l index entry not found for "
                                       "PHYS %s returned by "
                                       "l2p index for LOG r%ld:i%ld"),
                                     apr_off_t_toa(pool, offset),
                                     revision, (long)k);

          if (   p2l_entry->item.number != k
              || p2l_entry->item.revision != revision)
            return svn_error_createf(SVN_ERR_FS_INDEX_INCONSISTENT,
                                     NULL,
                                     _("p2l index info LOG r%ld:i%ld"
                                       " does not match "
                                       "l2p index for LOG r%ld:i%ld"),
                                     p2l_entry->item.revision,
                                     (long)p2l_entry->item.number,
                                     revision, (long)k);
        }

      if (cancel_func)
        SVN_ERR(cancel_func(cancel_baton));
    }

  svn_pool_destroy(iterpool);

  SVN_ERR(svn_fs_fs__close_revision_file(rev_file));

  return SVN_NO_ERROR;
}

/* Verify that for all phys-to-log index entries for revisions START to
 * START + COUNT-1 in FS there is a consistent entry in the log-to-phys
 * index.  If given, invoke CANCEL_FUNC with CANCEL_BATON at regular
 * intervals. Use POOL for allocations.
 *
 * Please note that we can only check on pack / rev file granularity and
 * must only be called for a single rev / pack file.
 */
static svn_error_t *
compare_p2l_to_l2p_index(svn_fs_t *fs,
                         svn_revnum_t start,
                         svn_revnum_t count,
                         svn_cancel_func_t cancel_func,
                         void *cancel_baton,
                         apr_pool_t *pool)
{
  fs_fs_data_t *ffd = fs->fsap_data;
  apr_pool_t *iterpool = svn_pool_create(pool);
  apr_off_t max_offset;
  apr_off_t offset = 0;

  /* common file access structure */
  svn_fs_fs__revision_file_t *rev_file;
  SVN_ERR(svn_fs_fs__open_pack_or_rev_file(&rev_file, fs, start, pool,
                                           iterpool));

  /* get the size of the rev / pack file as covered by the P2L index */
  SVN_ERR(svn_fs_fs__p2l_get_max_offset(&max_offset, fs, rev_file, start,
                                        pool));

  /* for all offsets in the file, get the P2L index entries and check
     them against the L2P index */
  for (offset = 0; offset < max_offset; )
    {
      apr_array_header_t *entries;
      svn_fs_fs__p2l_entry_t *last_entry;
      int i;

      svn_pool_clear(iterpool);

      /* get all entries for the current block */
      SVN_ERR(svn_fs_fs__p2l_index_lookup(&entries, fs, rev_file, start,
                                          offset, ffd->p2l_page_size,
                                          iterpool, iterpool));
      if (entries->nelts == 0)
        return svn_error_createf(SVN_ERR_FS_INDEX_CORRUPTION,
                                 NULL,
                                 _("p2l does not cover offset %s"
                                   " for revision %ld"),
                                  apr_off_t_toa(pool, offset), start);

      /* process all entries (and later continue with the next block) */
      last_entry
        = &APR_ARRAY_IDX(entries, entries->nelts-1, svn_fs_fs__p2l_entry_t);
      offset = last_entry->offset + last_entry->size;

      for (i = 0; i < entries->nelts; ++i)
        {
          svn_fs_fs__p2l_entry_t *entry
            = &APR_ARRAY_IDX(entries, i, svn_fs_fs__p2l_entry_t);

          /* check all sub-items for consist entries in the L2P index */
          if (entry->type == SVN_FS_FS__ITEM_TYPE_UNUSED)
            {
              /* There is no L2P entry for unused rev file sections.
               * And its P2L index data is hardly ever used.  But we
               * should still check whether someone tempered with it. */
              if (   entry->item.revision != SVN_INVALID_REVNUM
                  && (   entry->item.revision < start
                      || entry->item.revision >= start + count))
                return svn_error_createf(SVN_ERR_FS_INDEX_INCONSISTENT,
                                         NULL,
                                         _("Empty P2L entry for PHYS %s "
                                           "refers to revision %ld outside "
                                           "the rev / pack file (%ld-%ld)"),
                                         apr_off_t_toa(pool, entry->offset),
                                         entry->item.revision,
                                         start, start + count - 1);
            }
          else
            {
              apr_off_t l2p_offset;
              SVN_ERR(svn_fs_fs__item_offset(&l2p_offset, fs, rev_file,
                                             entry->item.revision, NULL,
                                             entry->item.number, iterpool));

              if (l2p_offset != entry->offset)
                return svn_error_createf(SVN_ERR_FS_INDEX_INCONSISTENT,
                                         NULL,
                                         _("l2p index entry PHYS %s"
                                           "does not match p2l index value "
                                           "LOG r%ld:i%ld for PHYS %s"),
                                         apr_off_t_toa(pool, l2p_offset),
                                         entry->item.revision,
                                         (long)entry->item.number,
                                         apr_off_t_toa(pool, entry->offset));
            }
        }

      if (cancel_func)
        SVN_ERR(cancel_func(cancel_baton));
    }

  svn_pool_destroy(iterpool);

  SVN_ERR(svn_fs_fs__close_revision_file(rev_file));

  return SVN_NO_ERROR;
}

/* Items smaller than this can be read at once into a buffer and directly
 * be checksummed.  Larger items require stream processing.
 * Must be a multiple of 8. */
#define STREAM_THRESHOLD 4096

/* Verify that the next SIZE bytes read from FILE are NUL.
 * SIZE must not exceed STREAM_THRESHOLD.  Use POOL for allocations.
 */
static svn_error_t *
expect_buffer_nul(apr_file_t *file,
                  apr_off_t size,
                  apr_pool_t *pool)
{
  union
  {
    unsigned char buffer[STREAM_THRESHOLD];
    apr_uint64_t chunks[STREAM_THRESHOLD / sizeof(apr_uint64_t)];
  } data;

  apr_size_t i;
  SVN_ERR_ASSERT(size <= STREAM_THRESHOLD);

  /* read the whole data block; error out on failure */
  data.chunks[(size - 1)/ sizeof(apr_uint64_t)] = 0;
  SVN_ERR(svn_io_file_read_full2(file, data.buffer, (apr_size_t)size, NULL,
                                 NULL, pool));

  /* chunky check */
  for (i = 0; i < size / sizeof(apr_uint64_t); ++i)
    if (data.chunks[i] != 0)
      break;

  /* byte-wise check upon mismatch or at the end of the block */
  for (i *= sizeof(apr_uint64_t); i < size; ++i)
    if (data.buffer[i] != 0)
      {
        const char *file_name;
        apr_off_t offset;

        SVN_ERR(svn_io_file_name_get(&file_name, file, pool));
        SVN_ERR(svn_io_file_get_offset(&offset, file, pool));
        offset -= size - i;

        return svn_error_createf(SVN_ERR_FS_CORRUPT, NULL,
                                 _("Empty section in file %s contains "
                                   "non-NUL data at offset %s"),
                                 file_name, apr_off_t_toa(pool, offset));
      }

  return SVN_NO_ERROR;
}

/* Verify that the next SIZE bytes read from FILE are NUL.
 * Use POOL for allocations.
 */
static svn_error_t *
read_all_nul(apr_file_t *file,
             apr_off_t size,
             apr_pool_t *pool)
{
  for (; size >= STREAM_THRESHOLD; size -= STREAM_THRESHOLD)
    SVN_ERR(expect_buffer_nul(file, STREAM_THRESHOLD, pool));

  if (size)
    SVN_ERR(expect_buffer_nul(file, size, pool));

  return SVN_NO_ERROR;
}

/* Compare the ACTUAL checksum with the one expected by ENTRY.
 * Return an error in case of mismatch.  Use the name of FILE
 * in error message.  Allocate data in POOL.
 */
static svn_error_t *
expected_checksum(apr_file_t *file,
                  svn_fs_fs__p2l_entry_t *entry,
                  apr_uint32_t actual,
                  apr_pool_t *pool)
{
  if (actual != entry->fnv1_checksum)
    {
      const char *file_name;

      SVN_ERR(svn_io_file_name_get(&file_name, file, pool));
      return svn_error_createf(SVN_ERR_FS_CORRUPT, NULL,
                               _("Checksum mismatch in item at offset %s of "
                                 "length %s bytes in file %s"),
                               apr_off_t_toa(pool, entry->offset),
                               apr_off_t_toa(pool, entry->size), file_name);
    }

  return SVN_NO_ERROR;
}

/* Verify that the FNV checksum over the next ENTRY->SIZE bytes read
 * from FILE will match ENTRY's expected checksum.  SIZE must not
 * exceed STREAM_THRESHOLD.  Use POOL for allocations.
 */
static svn_error_t *
expected_buffered_checksum(apr_file_t *file,
                           svn_fs_fs__p2l_entry_t *entry,
                           apr_pool_t *pool)
{
  unsigned char buffer[STREAM_THRESHOLD];
  SVN_ERR_ASSERT(entry->size <= STREAM_THRESHOLD);

  SVN_ERR(svn_io_file_read_full2(file, buffer, (apr_size_t)entry->size,
                                 NULL, NULL, pool));
  SVN_ERR(expected_checksum(file, entry,
                            svn__fnv1a_32x4(buffer, (apr_size_t)entry->size),
                            pool));

  return SVN_NO_ERROR;
}

/* Verify that the FNV checksum over the next ENTRY->SIZE bytes read from
 * FILE will match ENTRY's expected checksum.  Use POOL for allocations.
 */
static svn_error_t *
expected_streamed_checksum(apr_file_t *file,
                           svn_fs_fs__p2l_entry_t *entry,
                           apr_pool_t *pool)
{
  unsigned char buffer[STREAM_THRESHOLD];
  svn_checksum_t *checksum;
  svn_checksum_ctx_t *context
    = svn_checksum_ctx_create(svn_checksum_fnv1a_32x4, pool);
  apr_off_t size = entry->size;

  while (size > 0)
    {
      apr_size_t to_read = size > sizeof(buffer)
                         ? sizeof(buffer)
                         : (apr_size_t)size;
      SVN_ERR(svn_io_file_read_full2(file, buffer, to_read, NULL, NULL,
                                     pool));
      SVN_ERR(svn_checksum_update(context, buffer, to_read));
      size -= to_read;
    }

  SVN_ERR(svn_checksum_final(&checksum, context, pool));
  SVN_ERR(expected_checksum(file, entry,
                            ntohl(*(const apr_uint32_t *)checksum->digest),
                            pool));

  return SVN_NO_ERROR;
}

/* Verify that for all phys-to-log index entries for revisions START to
 * START + COUNT-1 in FS match the actual pack / rev file contents.
 * If given, invoke CANCEL_FUNC with CANCEL_BATON at regular intervals.
 * Use POOL for allocations.
 *
 * Please note that we can only check on pack / rev file granularity and
 * must only be called for a single rev / pack file.
 */
static svn_error_t *
compare_p2l_to_rev(svn_fs_t *fs,
                   svn_revnum_t start,
                   svn_revnum_t count,
                   svn_cancel_func_t cancel_func,
                   void *cancel_baton,
                   apr_pool_t *pool)
{
  fs_fs_data_t *ffd = fs->fsap_data;
  apr_pool_t *iterpool = svn_pool_create(pool);
  apr_off_t max_offset;
  apr_off_t offset = 0;
  svn_fs_fs__revision_file_t *rev_file;

  /* open the pack / rev file that is covered by the p2l index */
  SVN_ERR(svn_fs_fs__open_pack_or_rev_file(&rev_file, fs, start, pool,
                                           iterpool));

  /* check file size vs. range covered by index */
  SVN_ERR(svn_fs_fs__auto_read_footer(rev_file));
  SVN_ERR(svn_fs_fs__p2l_get_max_offset(&max_offset, fs, rev_file, start,
                                        pool));

  if (rev_file->l2p_offset != max_offset)
    return svn_error_createf(SVN_ERR_FS_INDEX_INCONSISTENT, NULL,
                             _("File size of %s for revision r%ld does "
                               "not match p2l index size of %s"),
                             apr_off_t_toa(pool, rev_file->l2p_offset), start,
                             apr_off_t_toa(pool, max_offset));

  SVN_ERR(svn_io_file_aligned_seek(rev_file->file, ffd->block_size, NULL, 0,
                                   pool));

  /* for all offsets in the file, get the P2L index entries and check
     them against the L2P index */
  for (offset = 0; offset < max_offset; )
    {
      apr_array_header_t *entries;
      int i;

      svn_pool_clear(iterpool);

      /* get all entries for the current block */
      SVN_ERR(svn_fs_fs__p2l_index_lookup(&entries, fs, rev_file, start,
                                          offset, ffd->p2l_page_size,
                                          iterpool, iterpool));

      /* The above might have moved the file pointer.
       * Ensure we actually start reading at OFFSET.  */
      SVN_ERR(svn_io_file_aligned_seek(rev_file->file, ffd->block_size,
                                       NULL, offset, iterpool));

      /* process all entries (and later continue with the next block) */
      for (i = 0; i < entries->nelts; ++i)
        {
          svn_fs_fs__p2l_entry_t *entry
            = &APR_ARRAY_IDX(entries, i, svn_fs_fs__p2l_entry_t);

          /* skip bits we previously checked */
          if (i == 0 && entry->offset < offset)
            continue;

          /* skip zero-sized entries */
          if (entry->size == 0)
            continue;

          /* p2l index must cover all rev / pack file offsets exactly once */
          if (entry->offset != offset)
            return svn_error_createf(SVN_ERR_FS_INDEX_INCONSISTENT,
                                     NULL,
                                     _("p2l index entry for revision r%ld"
                                       " is non-contiguous between offsets "
                                       " %s and %s"),
                                     start,
                                     apr_off_t_toa(pool, offset),
                                     apr_off_t_toa(pool, entry->offset));

          /* Check type <-> item dependencies. */

          /* Entry types must be within the valid range. */
          if (entry->type >= SVN_FS_FS__ITEM_TYPE_ANY_REP)
            return svn_error_createf(SVN_ERR_FS_INDEX_CORRUPTION,
                                     NULL,
                                     _("p2l index entry for revision r%ld"
                                       " at offset %s contains invalid item"
                                       " type %u"),
                                     start,
                                     apr_off_t_toa(pool, offset),
                                     (unsigned int)entry->type);

          /* There can be only one changes entry and that has a fixed type
           * and item number.  Its presence and parse-ability will be checked
           * during later stages of the verification process. */
          if (   (entry->type == SVN_FS_FS__ITEM_TYPE_CHANGES)
              != (entry->item.number == SVN_FS_FS__ITEM_INDEX_CHANGES))
            return svn_error_createf(SVN_ERR_FS_INDEX_CORRUPTION,
                                     NULL,
                                     _("p2l index entry for changes in"
                                       " revision r%ld is item"
                                       " %"APR_UINT64_T_FMT
                                       " of type %u at offset %s"),
                                     entry->item.revision,
                                     entry->item.number,
                                     (unsigned int)entry->type,
                                     apr_off_t_toa(pool, offset));

          /* Check contents. */
          if (entry->type == SVN_FS_FS__ITEM_TYPE_UNUSED)
            {
              /* Empty sections must contain NUL bytes only.
               * Beware of the filler at the end of the p2l index. */
              if (entry->offset != max_offset)
                SVN_ERR(read_all_nul(rev_file->file, entry->size, pool));
            }
          else
            {
              /* Generic contents check against checksum. */
              if (entry->size < STREAM_THRESHOLD)
                SVN_ERR(expected_buffered_checksum(rev_file->file, entry,
                                                   pool));
              else
                SVN_ERR(expected_streamed_checksum(rev_file->file, entry,
                                                   pool));
            }

          /* advance offset */
          offset += entry->size;
        }

      if (cancel_func)
        SVN_ERR(cancel_func(cancel_baton));
    }

  svn_pool_destroy(iterpool);

  SVN_ERR(svn_fs_fs__close_revision_file(rev_file));

  return SVN_NO_ERROR;
}

/* Verify that the revprops of the revisions START to END in FS can be
 * accessed.  Invoke CANCEL_FUNC with CANCEL_BATON at regular intervals.
 *
 * The values of START and END have already been auto-selected and
 * verified.
 */
static svn_error_t *
verify_revprops(svn_fs_t *fs,
                svn_revnum_t start,
                svn_revnum_t end,
                svn_cancel_func_t cancel_func,
                void *cancel_baton,
                apr_pool_t *pool)
{
  svn_revnum_t revision;
  apr_pool_t *iterpool = svn_pool_create(pool);

  /* Invalidate the revprop cache once.
   * Use the cache inside the loop to speed up packed revprop access. */
  svn_fs_fs__reset_revprop_cache(fs);

  for (revision = start; revision < end; ++revision)
    {
      svn_string_t *date;
      apr_time_t timetemp;

      svn_pool_clear(iterpool);

      /* Access the svn:date revprop.
       * This implies parsing all revprops for that revision. */
      SVN_ERR(svn_fs_fs__revision_prop(&date, fs, revision,
                                       SVN_PROP_REVISION_DATE, FALSE,
                                       iterpool, iterpool));

      /* The time stamp is the only revprop that, if given, needs to
       * have a valid content. */
      if (date)
        SVN_ERR(svn_time_from_cstring(&timetemp, date->data, iterpool));

      if (cancel_func)
        SVN_ERR(cancel_func(cancel_baton));
    }

  svn_pool_destroy(iterpool);

  return SVN_NO_ERROR;
}

static svn_revnum_t
pack_size(svn_fs_t *fs, svn_revnum_t rev)
{
  fs_fs_data_t *ffd = fs->fsap_data;

  return rev < ffd->min_unpacked_rev ? ffd->max_files_per_dir : 1;
}

/* Verify that on-disk representation has not been tempered with (in a way
 * that leaves the repository in a corrupted state).  This compares log-to-
 * phys with phys-to-log indexes, verifies the low-level checksums and
 * checks that all revprops are available.  The function signature is
 * similar to svn_fs_fs__verify.
 *
 * The values of START and END have already been auto-selected and
 * verified.  You may call this for format7 or higher repos.
 */
static svn_error_t *
verify_f7_metadata_consistency(svn_fs_t *fs,
                               svn_revnum_t start,
                               svn_revnum_t end,
                               svn_fs_progress_notify_func_t notify_func,
                               void *notify_baton,
                               svn_cancel_func_t cancel_func,
                               void *cancel_baton,
                               apr_pool_t *pool)
{
  fs_fs_data_t *ffd = fs->fsap_data;
  svn_revnum_t revision, next_revision;
  apr_pool_t *iterpool = svn_pool_create(pool);

  for (revision = start; revision <= end; revision = next_revision)
    {
      svn_error_t *err = SVN_NO_ERROR;

      svn_revnum_t count = pack_size(fs, revision);
      svn_revnum_t pack_start = svn_fs_fs__packed_base_rev(fs, revision);
      svn_revnum_t pack_end = pack_start + count;

      svn_pool_clear(iterpool);

      if (notify_func && (pack_start % ffd->max_files_per_dir == 0))
        notify_func(pack_start, notify_baton, iterpool);

      /* Check for external corruption to the indexes. */
      err = verify_index_checksums(fs, pack_start, cancel_func,
                                   cancel_baton, iterpool);

      /* two-way index check */
      if (!err)
        err = compare_l2p_to_p2l_index(fs, pack_start, pack_end - pack_start,
                                       cancel_func, cancel_baton, iterpool);
      if (!err)
        err = compare_p2l_to_l2p_index(fs, pack_start, pack_end - pack_start,
                                       cancel_func, cancel_baton, iterpool);

      /* verify in-index checksums and types vs. actual rev / pack files */
      if (!err)
        err = compare_p2l_to_rev(fs, pack_start, pack_end - pack_start,
                                 cancel_func, cancel_baton, iterpool);

      /* ensure that revprops are available and accessible */
      if (!err)
        err = verify_revprops(fs, pack_start, pack_end,
                              cancel_func, cancel_baton, iterpool);

      /* concurrent packing is one of the reasons why verification may fail.
         Make sure, we operate on up-to-date information. */
      if (err)
        {
          svn_error_t *err2
            = svn_fs_fs__read_min_unpacked_rev(&ffd->min_unpacked_rev,
                                               fs, pool);

          /* Be careful to not leak ERR. */
          if (err2)
            return svn_error_trace(svn_error_compose_create(err, err2));
        }

      /* retry the whole shard if it got packed in the meantime */
      if (err && count != pack_size(fs, revision))
        {
          svn_error_clear(err);

          /* We could simply assign revision here but the code below is
             more intuitive to maintainers. */
          next_revision = svn_fs_fs__packed_base_rev(fs, revision);
        }
      else
        {
          SVN_ERR(err);
          next_revision = pack_end;
        }
    }

  svn_pool_destroy(iterpool);

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_fs__verify(svn_fs_t *fs,
                  svn_revnum_t start,
                  svn_revnum_t end,
                  svn_fs_progress_notify_func_t notify_func,
                  void *notify_baton,
                  svn_cancel_func_t cancel_func,
                  void *cancel_baton,
                  apr_pool_t *pool)
{
  fs_fs_data_t *ffd = fs->fsap_data;

  /* Input validation. */
  if (! SVN_IS_VALID_REVNUM(start))
    start = 0;
  if (! SVN_IS_VALID_REVNUM(end))
    {
      SVN_ERR(svn_fs_fs__youngest_rev(&end, fs, pool));
    }

  SVN_ERR(svn_fs_fs__ensure_revision_exists(start, fs, pool));
  SVN_ERR(svn_fs_fs__ensure_revision_exists(end, fs, pool));

  /* log/phys index consistency.  We need to check them first to make
     sure we can access the rev / pack files in format7. */
  if (svn_fs_fs__use_log_addressing(fs))
    SVN_ERR(verify_f7_metadata_consistency(fs, start, end,
                                           notify_func, notify_baton,
                                           cancel_func, cancel_baton, pool));

  /* rep cache consistency */
  if (ffd->format >= SVN_FS_FS__MIN_REP_SHARING_FORMAT)
    SVN_ERR(verify_rep_cache(fs, start, end, notify_func, notify_baton,
                             cancel_func, cancel_baton, pool));

  return SVN_NO_ERROR;
}