path: root/src/third_party/wiredtiger/src/block/block_vrfy.c

/*-
 * Copyright (c) 2014-2020 MongoDB, Inc.
 * Copyright (c) 2008-2014 WiredTiger, Inc.
 *	All rights reserved.
 *
 * See the file LICENSE for redistribution information.
 */

#include "wt_internal.h"

static int __verify_ckptfrag_add(WT_SESSION_IMPL *, WT_BLOCK *, wt_off_t, wt_off_t);
static int __verify_ckptfrag_chk(WT_SESSION_IMPL *, WT_BLOCK *);
static int __verify_filefrag_add(
  WT_SESSION_IMPL *, WT_BLOCK *, const char *, wt_off_t, wt_off_t, bool);
static int __verify_filefrag_chk(WT_SESSION_IMPL *, WT_BLOCK *);
static int __verify_last_avail(WT_SESSION_IMPL *, WT_BLOCK *, WT_CKPT *);
static int __verify_set_file_size(WT_SESSION_IMPL *, WT_BLOCK *, WT_CKPT *);

/* The bit list ignores the first block: convert to/from a frag/offset. */
#define WT_wt_off_TO_FRAG(block, off) ((off) / (block)->allocsize - 1)
#define WT_FRAG_TO_OFF(block, frag) (((wt_off_t)((frag) + 1)) * (block)->allocsize)

/*
 * __wt_block_verify_start --
 *     Start file verification.
 */
int
__wt_block_verify_start(
  WT_SESSION_IMPL *session, WT_BLOCK *block, WT_CKPT *ckptbase, const char *cfg[])
{
    WT_CKPT *ckpt, *t;
    WT_CONFIG_ITEM cval;
    wt_off_t size;

    /* Configuration: strict behavior on any error. */
    WT_RET(__wt_config_gets(session, cfg, "strict", &cval));
    block->verify_strict = cval.val != 0;

    /* Configuration: dump the file's layout. */
    WT_RET(__wt_config_gets(session, cfg, "dump_layout", &cval));
    block->verify_layout = cval.val != 0;

    /*
     * Find the last checkpoint in the list: if there are none, or the only checkpoint we have is
     * fake, there's no work to do. Don't complain, that's not our problem to solve.
     */
    ckpt = NULL;
    WT_CKPT_FOREACH (ckptbase, t)
        if (t->name != NULL && !F_ISSET(t, WT_CKPT_FAKE))
            ckpt = t;
    if (ckpt == NULL)
        return (0);

    /* Set the size of the file to the size of the last checkpoint. */
    WT_RET(__verify_set_file_size(session, block, ckpt));

    /*
     * We're done if the file has no data pages (this happens if we verify a file immediately after
     * creation or the checkpoint doesn't reflect any of the data pages).
     */
    size = block->size;
    if (size <= block->allocsize)
        return (0);

    /* The file size should be a multiple of the allocation size. */
    if (size % block->allocsize != 0)
        WT_RET_MSG(session, WT_ERROR, "the file size is not a multiple of the allocation size");

    /*
     * Allocate a bit array, where each bit represents a single allocation
     * size piece of the file (this is how we track the parts of the file
     * we've verified, and check for multiply referenced or unreferenced
     * blocks).  Storing this on the heap seems reasonable, verifying a 1TB
     * file with an 512B allocation size would require a 256MB bit array:
     *
     *	(((1 * 2^40) / 512) / 8) = 256 * 2^20
     *
     * To verify larger files than we can handle in this way, we'd have to
     * write parts of the bit array into a disk file.
     *
     * Alternatively, we could switch to maintaining ranges of the file as
     * we do with the extents, but that has its own failure mode, where we
     * verify many non-contiguous blocks creating too many entries on the
     * list to fit into memory.
     */
    block->frags = (uint64_t)WT_wt_off_TO_FRAG(block, size);
    WT_RET(__bit_alloc(session, block->frags, &block->fragfile));

    /*
     * Set this before reading any extent lists: don't panic if we see corruption.
     */
    block->verify = true;

    /*
     * We maintain an allocation list that is rolled forward through the set of checkpoints.
     */
    WT_RET(__wt_block_extlist_init(session, &block->verify_alloc, "verify", "alloc", false));

    /*
     * The only checkpoint avail list we care about is the last one written; get it now and
     * initialize the list of file fragments.
     */
    WT_RET(__verify_last_avail(session, block, ckpt));

    return (0);
}

/*
 * __verify_last_avail --
 *     Get the last checkpoint's avail list and load it into the list of file fragments.
 */
static int
__verify_last_avail(WT_SESSION_IMPL *session, WT_BLOCK *block, WT_CKPT *ckpt)
{
    WT_BLOCK_CKPT *ci, _ci;
    WT_DECL_RET;
    WT_EXT *ext;
    WT_EXTLIST *el;

    ci = &_ci;
    WT_RET(__wt_block_ckpt_init(session, ci, ckpt->name));
    WT_ERR(__wt_block_buffer_to_ckpt(session, block, ckpt->raw.data, ci));

    el = &ci->avail;
    if (el->offset != WT_BLOCK_INVALID_OFFSET) {
        WT_ERR(__wt_block_extlist_read_avail(session, block, el, ci->file_size));
        WT_EXT_FOREACH (ext, el->off)
            if ((ret = __verify_filefrag_add(
                   session, block, "avail-list chunk", ext->off, ext->size, true)) != 0)
                break;
    }

err:
    __wt_block_ckpt_destroy(session, ci);
    return (ret);
}

/*
 * __verify_set_file_size --
 *     Set the file size to the last checkpoint's size.
 */
static int
__verify_set_file_size(WT_SESSION_IMPL *session, WT_BLOCK *block, WT_CKPT *ckpt)
{
    WT_BLOCK_CKPT *ci, _ci;
    WT_DECL_ITEM(tmp);
    WT_DECL_RET;

    ci = &_ci;
    WT_RET(__wt_block_ckpt_init(session, ci, ckpt->name));
    WT_ERR(__wt_block_buffer_to_ckpt(session, block, ckpt->raw.data, ci));

    if (block->verify_layout) {
        WT_ERR(__wt_scr_alloc(session, 0, &tmp));
        WT_ERR(__wt_msg(session, "%s: physical size %s", block->name,
          __wt_buf_set_size(session, (uint64_t)block->size, true, tmp)));
        WT_ERR(__wt_msg(session, "%s: correcting to %s checkpoint size %s", block->name, ckpt->name,
          __wt_buf_set_size(session, (uint64_t)ci->file_size, true, tmp)));
    }

    /*
     * Verify is read-only. Set the block's file size information as if we truncated the file during
     * checkpoint load, so references to blocks after last checkpoint's file size fail.
     */
    block->size = block->extend_size = ci->file_size;

err:
    __wt_block_ckpt_destroy(session, ci);
    __wt_scr_free(session, &tmp);
    return (ret);
}

/*
 * __wt_block_verify_end --
 *     End file verification.
 */
int
__wt_block_verify_end(WT_SESSION_IMPL *session, WT_BLOCK *block)
{
    WT_DECL_RET;

    /* Confirm we verified every file block. */
    ret = __verify_filefrag_chk(session, block);

    block->verify = false;
    block->verify_strict = false;
    block->verify_size = 0;

    /* Discard the accumulated allocation list. */
    __wt_block_extlist_free(session, &block->verify_alloc);

    /* Discard the fragment tracking lists. */
    block->frags = 0;
    __wt_free(session, block->fragfile);
    __wt_free(session, block->fragckpt);

    return (ret);
}

/*
 * __wt_verify_ckpt_load --
 *     Verify work done when a checkpoint is loaded.
 */
int
__wt_verify_ckpt_load(WT_SESSION_IMPL *session, WT_BLOCK *block, WT_BLOCK_CKPT *ci)
{
    WT_EXT *ext;
    WT_EXTLIST *el;
    uint64_t frag, frags;

    /* Set the maximum file size for this checkpoint. */
    block->verify_size = ci->file_size;

    /*
     * Add the root page and disk blocks used to store the extent lists to the list of blocks we've
     * "seen" from the file.
     */
    if (ci->root_offset != WT_BLOCK_INVALID_OFFSET)
        WT_RET(__verify_filefrag_add(
          session, block, "checkpoint", ci->root_offset, (wt_off_t)ci->root_size, true));
    if (ci->alloc.offset != WT_BLOCK_INVALID_OFFSET)
        WT_RET(__verify_filefrag_add(
          session, block, "alloc list", ci->alloc.offset, (wt_off_t)ci->alloc.size, true));
    if (ci->avail.offset != WT_BLOCK_INVALID_OFFSET)
        WT_RET(__verify_filefrag_add(
          session, block, "avail list", ci->avail.offset, (wt_off_t)ci->avail.size, true));
    if (ci->discard.offset != WT_BLOCK_INVALID_OFFSET)
        WT_RET(__verify_filefrag_add(
          session, block, "discard list", ci->discard.offset, (wt_off_t)ci->discard.size, true));

    /*
     * Checkpoint verification is similar to deleting checkpoints. As we read each new checkpoint,
     * we merge the allocation lists (accumulating all allocated pages as we move through the
     * system), and then remove any pages found in the discard list. The result should be a
     * one-to-one mapping to the pages we find in this specific checkpoint.
     */
    el = &ci->alloc;
    if (el->offset != WT_BLOCK_INVALID_OFFSET) {
        WT_RET(__wt_block_extlist_read(session, block, el, ci->file_size));
        WT_RET(__wt_block_extlist_merge(session, block, el, &block->verify_alloc));
        __wt_block_extlist_free(session, el);
    }
    el = &ci->discard;
    if (el->offset != WT_BLOCK_INVALID_OFFSET) {
        WT_RET(__wt_block_extlist_read(session, block, el, ci->file_size));
        WT_EXT_FOREACH (ext, el->off)
            WT_RET(__wt_block_off_remove_overlap(
              session, block, &block->verify_alloc, ext->off, ext->size));
        __wt_block_extlist_free(session, el);
    }

    /*
     * We don't need the blocks on a checkpoint's avail list, but we read it to ensure it wasn't
     * corrupted. We could confirm correctness of the intermediate avail lists (that is, if they're
     * logically the result of the allocations and discards to this point). We don't because the
     * only avail list ever used is the one for the last checkpoint, which is separately verified by
     * checking it against all of the blocks found in the file.
     */
    el = &ci->avail;
    if (el->offset != WT_BLOCK_INVALID_OFFSET) {
        WT_RET(__wt_block_extlist_read(session, block, el, ci->file_size));
        __wt_block_extlist_free(session, el);
    }

    /*
     * The root page of the checkpoint appears on the alloc list, but not, at least until the
     * checkpoint is deleted, on a discard list. To handle this case, remove the root page from the
     * accumulated list of checkpoint pages, so it doesn't add a new requirement for subsequent
     * checkpoints.
     */
    if (ci->root_offset != WT_BLOCK_INVALID_OFFSET)
        WT_RET(__wt_block_off_remove_overlap(
          session, block, &block->verify_alloc, ci->root_offset, ci->root_size));

    /*
     * Allocate the per-checkpoint bit map. The per-checkpoint bit map is the opposite of the
     * per-file bit map, that is, we set all the bits that we expect to be set based on the
     * checkpoint's allocation and discard lists, then clear bits as we verify blocks. When finished
     * verifying the checkpoint, the bit list should be empty.
     */
    WT_RET(__bit_alloc(session, block->frags, &block->fragckpt));
    el = &block->verify_alloc;
    WT_EXT_FOREACH (ext, el->off) {
        frag = (uint64_t)WT_wt_off_TO_FRAG(block, ext->off);
        frags = (uint64_t)(ext->size / block->allocsize);
        __bit_nset(block->fragckpt, frag, frag + (frags - 1));
    }

    return (0);
}

/*
 * __wt_verify_ckpt_unload --
 *     Verify work done when a checkpoint is unloaded.
 */
int
__wt_verify_ckpt_unload(WT_SESSION_IMPL *session, WT_BLOCK *block)
{
    WT_DECL_RET;

    /* Confirm we verified every checkpoint block. */
    ret = __verify_ckptfrag_chk(session, block);

    /* Discard the per-checkpoint fragment list. */
    __wt_free(session, block->fragckpt);

    return (ret);
}

/*
 * __wt_block_verify_addr --
 *     Update an address in a checkpoint as verified.
 */
int
__wt_block_verify_addr(
  WT_SESSION_IMPL *session, WT_BLOCK *block, const uint8_t *addr, size_t addr_size)
{
    wt_off_t offset;
    uint32_t checksum, size;

    WT_UNUSED(addr_size);

    /* Crack the cookie. */
    WT_RET(__wt_block_buffer_to_addr(block, addr, &offset, &size, &checksum));

    /* Add to the per-file list. */
    WT_RET(__verify_filefrag_add(session, block, NULL, offset, size, false));

    /*
     * It's tempting to try and flag a page as "verified" when we read it. That doesn't work because
     * we may visit a page multiple times when verifying a single checkpoint (for example, when
     * verifying the physical image of a row-store leaf page with overflow keys, the overflow keys
     * are read when checking for key sort issues, and read again when more general overflow item
     * checking is done). This function is called by the btree verification code, once per logical
     * visit in a checkpoint, so we can detect if a page is referenced multiple times within a
     * single checkpoint. This doesn't apply to the per-file list, because it is expected for the
     * same btree blocks to appear in multiple checkpoints.
     *
     * Add the block to the per-checkpoint list.
     */
    WT_RET(__verify_ckptfrag_add(session, block, offset, size));

    return (0);
}

/*
 * __verify_filefrag_add --
 *     Add the fragments to the per-file fragment list, optionally complain if we've already
 *     verified this chunk of the file.
 */
static int
__verify_filefrag_add(WT_SESSION_IMPL *session, WT_BLOCK *block, const char *type, wt_off_t offset,
  wt_off_t size, bool nodup)
{
    uint64_t f, frag, frags, i;

    __wt_verbose(session, WT_VERB_VERIFY,
      "add file block%s%s%s at %" PRIuMAX "-%" PRIuMAX " (%" PRIuMAX ")", type == NULL ? "" : " (",
      type == NULL ? "" : type, type == NULL ? "" : ")", (uintmax_t)offset,
      (uintmax_t)(offset + size), (uintmax_t)size);

    /* Check each chunk against the total file size. */
    if (offset + size > block->size)
        WT_RET_MSG(session, WT_ERROR,
          "fragment %" PRIuMAX "-%" PRIuMAX " references non-existent file blocks",
          (uintmax_t)offset, (uintmax_t)(offset + size));

    frag = (uint64_t)WT_wt_off_TO_FRAG(block, offset);
    frags = (uint64_t)(size / block->allocsize);

    /* It may be illegal to reference a particular chunk more than once. */
    if (nodup)
        for (f = frag, i = 0; i < frags; ++f, ++i)
            if (__bit_test(block->fragfile, f))
                WT_RET_MSG(session, WT_ERROR,
                  "file fragment at %" PRIuMAX " referenced multiple times", (uintmax_t)offset);

    /* Add fragments to the file's fragment list. */
    __bit_nset(block->fragfile, frag, frag + (frags - 1));

    return (0);
}

/*
 * __verify_filefrag_chk --
 *     Verify we've checked all the fragments in the file.
 */
static int
__verify_filefrag_chk(WT_SESSION_IMPL *session, WT_BLOCK *block)
{
    uint64_t count, first, last;

    /* If there's nothing to verify, it was a fast run. */
    if (block->frags == 0)
        return (0);

    /*
     * It's OK if we have not verified blocks at the end of the file: that happens if the file is
     * truncated during a checkpoint or load or was extended after writing a checkpoint. We should
     * never see unverified blocks anywhere else, though.
     *
     * I'm deliberately testing for a last fragment of 0, it makes no sense there would be no
     * fragments verified, complain if the first fragment in the file wasn't verified.
     */
    for (last = block->frags - 1; last != 0; --last) {
        if (__bit_test(block->fragfile, last))
            break;
        __bit_set(block->fragfile, last);
    }

    /*
     * Check for any other file fragments we haven't verified -- every time we find a bit that's
     * clear, complain. We re-start the search each time after setting the clear bit(s) we found:
     * it's simpler and this isn't supposed to happen a lot.
     */
    for (count = 0;; ++count) {
        if (__bit_ffc(block->fragfile, block->frags, &first) != 0)
            break;
        __bit_set(block->fragfile, first);
        for (last = first + 1; last < block->frags; ++last) {
            if (__bit_test(block->fragfile, last))
                break;
            __bit_set(block->fragfile, last);
        }

        if (!WT_VERBOSE_ISSET(session, WT_VERB_VERIFY))
            continue;

        __wt_errx(session, "file range %" PRIuMAX "-%" PRIuMAX " never verified",
          (uintmax_t)WT_FRAG_TO_OFF(block, first), (uintmax_t)WT_FRAG_TO_OFF(block, last));
    }
    if (count == 0)
        return (0);

    __wt_errx(session, "file ranges never verified: %" PRIu64, count);
    return (block->verify_strict ? WT_ERROR : 0);
}

/*
 * __verify_ckptfrag_add --
 *     Clear the fragments in the per-checkpoint fragment list, and complain if we've already
 *     verified this chunk of the checkpoint.
 */
static int
__verify_ckptfrag_add(WT_SESSION_IMPL *session, WT_BLOCK *block, wt_off_t offset, wt_off_t size)
{
    uint64_t f, frag, frags, i;

    __wt_verbose(session, WT_VERB_VERIFY,
      "add checkpoint block at %" PRIuMAX "-%" PRIuMAX " (%" PRIuMAX ")", (uintmax_t)offset,
      (uintmax_t)(offset + size), (uintmax_t)size);

    /*
     * Check each chunk against the checkpoint's size, a checkpoint should never reference a block
     * outside of the checkpoint's stored size.
     */
    if (offset + size > block->verify_size)
        WT_RET_MSG(session, WT_ERROR,
          "fragment %" PRIuMAX "-%" PRIuMAX " references file blocks outside the checkpoint",
          (uintmax_t)offset, (uintmax_t)(offset + size));

    frag = (uint64_t)WT_wt_off_TO_FRAG(block, offset);
    frags = (uint64_t)(size / block->allocsize);

    /* It is illegal to reference a particular chunk more than once. */
    for (f = frag, i = 0; i < frags; ++f, ++i)
        if (!__bit_test(block->fragckpt, f))
            WT_RET_MSG(session, WT_ERROR,
              "fragment at %" PRIuMAX
              " referenced multiple times in a single checkpoint or found in the checkpoint but "
              "not listed in the checkpoint's allocation list",
              (uintmax_t)offset);

    /* Remove fragments from the checkpoint's allocation list. */
    __bit_nclr(block->fragckpt, frag, frag + (frags - 1));

    return (0);
}

/*
 * __verify_ckptfrag_chk --
 *     Verify we've checked all the fragments in the checkpoint.
 */
static int
__verify_ckptfrag_chk(WT_SESSION_IMPL *session, WT_BLOCK *block)
{
    uint64_t count, first, last;

    /*
     * The checkpoint fragment memory is only allocated as a checkpoint is successfully loaded;
     * don't check if there's nothing there.
     */
    if (block->fragckpt == NULL)
        return (0);

    /*
     * Check for checkpoint fragments we haven't verified -- every time we find a bit that's set,
     * complain. We re-start the search each time after clearing the set bit(s) we found: it's
     * simpler and this isn't supposed to happen a lot.
     */
    for (count = 0;; ++count) {
        if (__bit_ffs(block->fragckpt, block->frags, &first) != 0)
            break;
        __bit_clear(block->fragckpt, first);
        for (last = first + 1; last < block->frags; ++last) {
            if (!__bit_test(block->fragckpt, last))
                break;
            __bit_clear(block->fragckpt, last);
        }

        if (!WT_VERBOSE_ISSET(session, WT_VERB_VERIFY))
            continue;

        __wt_errx(session, "checkpoint range %" PRIuMAX "-%" PRIuMAX " never verified",
          (uintmax_t)WT_FRAG_TO_OFF(block, first), (uintmax_t)WT_FRAG_TO_OFF(block, last));
    }

    if (count == 0)
        return (0);

    __wt_errx(session, "checkpoint ranges never verified: %" PRIu64, count);
    return (block->verify_strict ? WT_ERROR : 0);
}