/*****************************************************************************

Copyright (c) 1997, 2017, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2013, 2022, MariaDB Corporation.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file log/log0recv.cc
Recovery

Created 9/20/1997 Heikki Tuuri
*******************************************************/

#include "univ.i"

#include <map>
#include <string>
#include <my_service_manager.h>

#include "log0recv.h"

#ifdef HAVE_MY_AES_H
#include <my_aes.h>
#endif

#include "log0crypt.h"
#include "mem0mem.h"
#include "buf0buf.h"
#include "buf0dblwr.h"
#include "buf0flu.h"
#include "mtr0mtr.h"
#include "mtr0log.h"
#include "page0page.h"
#include "page0cur.h"
#include "trx0undo.h"
#include "ibuf0ibuf.h"
#include "trx0undo.h"
#include "trx0rec.h"
#include "fil0fil.h"
#include "buf0rea.h"
#include "srv0srv.h"
#include "srv0start.h"
#include "fil0pagecompress.h"
#include "log.h"

/** The recovery system */
recv_sys_t	recv_sys;
/** TRUE when recv_init_crash_recovery() has been called. */
bool	recv_needed_recovery;
#ifdef UNIV_DEBUG
/** TRUE if writing to the redo log (mtr_commit) is forbidden.
Protected by log_sys.latch. */
bool	recv_no_log_write = false;
#endif /* UNIV_DEBUG */

/** If the following is TRUE, the buffer pool file pages must be invalidated
after recovery and no ibuf operations are allowed; this becomes TRUE if
the log record hash table becomes too full, and log records must be merged
to file pages already before the recovery is finished: in this case no
ibuf operations are allowed, as they could modify the pages read in the
buffer pool before the pages have been recovered to the up-to-date state.

true means that recovery is running and no operations on the log file
are allowed yet: the variable name is misleading. */
bool	recv_no_ibuf_operations;

/** Stored physical log record */
struct log_phys_t : public log_rec_t
{
  /** start LSN of the mini-transaction (not necessarily of this record) */
  const lsn_t start_lsn;
private:
  /** @return the start of length and data */
  const byte *start() const
  {
    return my_assume_aligned<sizeof(size_t)>
      (reinterpret_cast<const byte*>(&start_lsn + 1));
  }
  /** @return the start of length and data */
  byte *start()
  { return const_cast<byte*>(const_cast<const log_phys_t*>(this)->start()); }
  /** @return the length of the following record */
  uint16_t len() const { uint16_t i; memcpy(&i, start(), 2); return i; }

  /** @return start of the log records */
  byte *begin() { return start() + 2; }
  /** @return end of the log records */
  byte *end() { byte *e= begin() + len(); ut_ad(!*e); return e; }
public:
  /** @return start of the log records */
  const byte *begin() const { return const_cast<log_phys_t*>(this)->begin(); }
  /** @return end of the log records */
  const byte *end() const { return const_cast<log_phys_t*>(this)->end(); }

  /** Determine the allocated size of the object.
  @param len  length of recs, excluding terminating NUL byte
  @return the total allocation size */
  static inline size_t alloc_size(size_t len);

  /** Constructor.
  @param start_lsn start LSN of the mini-transaction
  @param lsn  mtr_t::commit_lsn() of the mini-transaction
  @param recs the first log record for the page in the mini-transaction
  @param size length of recs, in bytes, excluding terminating NUL byte */
  log_phys_t(lsn_t start_lsn, lsn_t lsn, const byte *recs, size_t size) :
    log_rec_t(lsn), start_lsn(start_lsn)
  {
    ut_ad(start_lsn);
    ut_ad(start_lsn < lsn);
    const uint16_t len= static_cast<uint16_t>(size);
    ut_ad(len == size);
    memcpy(start(), &len, 2);
    reinterpret_cast<byte*>(memcpy(begin(), recs, size))[size]= 0;
  }

  /** Append a record to the log.
  @param recs  log to append
  @param size  size of the log, in bytes */
  void append(const byte *recs, size_t size)
  {
    ut_ad(start_lsn < lsn);
    uint16_t l= len();
    reinterpret_cast<byte*>(memcpy(end(), recs, size))[size]= 0;
    l= static_cast<uint16_t>(l + size);
    memcpy(start(), &l, 2);
  }

  /** Apply an UNDO_APPEND record.
  @see mtr_t::undo_append()
  @param block   undo log page
  @param data    undo log record
  @param len     length of the undo log record
  @return whether the operation failed (inconcistency was noticed) */
  static bool undo_append(const buf_block_t &block, const byte *data,
                          size_t len)
  {
    ut_ad(len > 2);
    byte *free_p= my_assume_aligned<2>
      (TRX_UNDO_PAGE_HDR + TRX_UNDO_PAGE_FREE + block.page.frame);
    const uint16_t free= mach_read_from_2(free_p);
    if (UNIV_UNLIKELY(free < TRX_UNDO_PAGE_HDR + TRX_UNDO_PAGE_HDR_SIZE ||
                      free + len + 6 >= srv_page_size - FIL_PAGE_DATA_END))
    {
      ib::error() << "Not applying UNDO_APPEND due to corruption on "
                  << block.page.id();
      return true;
    }

    byte *p= block.page.frame + free;
    mach_write_to_2(free_p, free + 4 + len);
    memcpy(p, free_p, 2);
    p+= 2;
    memcpy(p, data, len);
    p+= len;
    mach_write_to_2(p, free);
    return false;
  }

  /** Check an OPT_PAGE_CHECKSUM record.
  @see mtr_t::page_checksum()
  @param block   buffer page
  @param l       pointer to checksum
  @return whether an unrecoverable mismatch was found */
  static bool page_checksum(const buf_block_t &block, const byte *l)
  {
    size_t size;
    const byte *page= block.page.zip.data;
    if (UNIV_LIKELY_NULL(page))
      size= (UNIV_ZIP_SIZE_MIN >> 1) << block.page.zip.ssize;
    else
    {
      page= block.page.frame;
      size= srv_page_size;
    }
    if (UNIV_LIKELY(my_crc32c(my_crc32c(my_crc32c(0, page + FIL_PAGE_OFFSET,
                                                  FIL_PAGE_LSN -
                                                  FIL_PAGE_OFFSET),
                                        page + FIL_PAGE_TYPE, 2),
                              page + FIL_PAGE_SPACE_ID,
                              size - (FIL_PAGE_SPACE_ID + 8)) ==
                    mach_read_from_4(l)))
      return false;

    ib::error() << "OPT_PAGE_CHECKSUM mismatch on " << block.page.id();
    return !srv_force_recovery;
  }

  /** The status of apply() */
  enum apply_status {
    /** The page was not affected */
    APPLIED_NO= 0,
    /** The page was modified */
    APPLIED_YES,
    /** The page was modified, affecting the encryption parameters */
    APPLIED_TO_ENCRYPTION,
    /** The page was modified, affecting the tablespace header */
    APPLIED_TO_FSP_HEADER,
    /** The page was found to be corrupted */
    APPLIED_CORRUPTED,
  };

  /** Apply log to a page frame.
  @param[in,out] block         buffer block
  @param[in,out] last_offset   last byte offset, for same_page records
  @return whether any log was applied to the page */
  apply_status apply(const buf_block_t &block, uint16_t &last_offset) const
  {
    const byte * const recs= begin();
    byte *const frame= block.page.zip.data
      ? block.page.zip.data : block.page.frame;
    const size_t size= block.physical_size();
    apply_status applied= APPLIED_NO;

    for (const byte *l= recs;;)
    {
      const byte b= *l++;
      if (!b)
        return applied;
      ut_ad((b & 0x70) != RESERVED);
      size_t rlen= b & 0xf;
      if (!rlen)
      {
        const size_t lenlen= mlog_decode_varint_length(*l);
        const uint32_t addlen= mlog_decode_varint(l);
        ut_ad(addlen != MLOG_DECODE_ERROR);
        rlen= addlen + 15 - lenlen;
        l+= lenlen;
      }
      if (!(b & 0x80))
      {
        /* Skip the page identifier. It has already been validated. */
        size_t idlen= mlog_decode_varint_length(*l);
        ut_ad(idlen <= 5);
        ut_ad(idlen < rlen);
        ut_ad(mlog_decode_varint(l) == block.page.id().space());
        l+= idlen;
        rlen-= idlen;
        idlen= mlog_decode_varint_length(*l);
        ut_ad(idlen <= 5);
        ut_ad(idlen <= rlen);
        ut_ad(mlog_decode_varint(l) == block.page.id().page_no());
        l+= idlen;
        rlen-= idlen;
        last_offset= 0;
      }

      switch (b & 0x70) {
      case FREE_PAGE:
        ut_ad(last_offset == 0);
        goto next_not_same_page;
      case INIT_PAGE:
        if (UNIV_LIKELY(rlen == 0))
        {
          memset_aligned<UNIV_ZIP_SIZE_MIN>(frame, 0, size);
          mach_write_to_4(frame + FIL_PAGE_OFFSET, block.page.id().page_no());
          memset_aligned<8>(FIL_PAGE_PREV + frame, 0xff, 8);
          mach_write_to_4(frame + FIL_PAGE_SPACE_ID, block.page.id().space());
          last_offset= FIL_PAGE_TYPE;
        next_after_applying:
          if (applied == APPLIED_NO)
            applied= APPLIED_YES;
        }
        else
        {
        record_corrupted:
          if (!srv_force_recovery)
          {
            recv_sys.set_corrupt_log();
            return applied;
          }
        next_not_same_page:
          last_offset= 1; /* the next record must not be same_page  */
        }
        l+= rlen;
        continue;
      case OPTION:
        ut_ad(rlen == 5);
        ut_ad(*l == OPT_PAGE_CHECKSUM);
        if (page_checksum(block, l + 1))
        {
page_corrupted:
          sql_print_error("InnoDB: Set innodb_force_recovery=1"
                          " to ignore corruption.");
          return APPLIED_CORRUPTED;
        }
        goto next_after_applying;
      }

      ut_ad(mach_read_from_4(frame + FIL_PAGE_OFFSET) ==
            block.page.id().page_no());
      ut_ad(mach_read_from_4(frame + FIL_PAGE_SPACE_ID) ==
            block.page.id().space());
      ut_ad(last_offset <= 1 || last_offset > 8);
      ut_ad(last_offset <= size);

      switch (b & 0x70) {
      case EXTENDED:
        if (UNIV_UNLIKELY(block.page.id().page_no() < 3 ||
                          block.page.zip.ssize))
          goto record_corrupted;
        static_assert(INIT_ROW_FORMAT_REDUNDANT == 0, "compatiblity");
        static_assert(INIT_ROW_FORMAT_DYNAMIC == 1, "compatibility");
        if (UNIV_UNLIKELY(!rlen))
          goto record_corrupted;
        switch (const byte subtype= *l) {
          uint8_t ll;
          size_t prev_rec, hdr_size;
        default:
          goto record_corrupted;
        case INIT_ROW_FORMAT_REDUNDANT:
        case INIT_ROW_FORMAT_DYNAMIC:
          if (UNIV_UNLIKELY(rlen != 1))
            goto record_corrupted;
          page_create_low(&block, *l != INIT_ROW_FORMAT_REDUNDANT);
          break;
        case UNDO_INIT:
          if (UNIV_UNLIKELY(rlen != 1))
            goto record_corrupted;
          trx_undo_page_init(block);
          break;
        case UNDO_APPEND:
          if (UNIV_UNLIKELY(rlen <= 3))
            goto record_corrupted;
          if (undo_append(block, ++l, --rlen) && !srv_force_recovery)
            goto page_corrupted;
          break;
        case INSERT_HEAP_REDUNDANT:
        case INSERT_REUSE_REDUNDANT:
        case INSERT_HEAP_DYNAMIC:
        case INSERT_REUSE_DYNAMIC:
          if (UNIV_UNLIKELY(rlen < 2))
            goto record_corrupted;
          rlen--;
          ll= mlog_decode_varint_length(*++l);
          if (UNIV_UNLIKELY(ll > 3 || ll >= rlen))
            goto record_corrupted;
          prev_rec= mlog_decode_varint(l);
          ut_ad(prev_rec != MLOG_DECODE_ERROR);
          rlen-= ll;
          l+= ll;
          ll= mlog_decode_varint_length(*l);
          static_assert(INSERT_HEAP_REDUNDANT == 4, "compatibility");
          static_assert(INSERT_REUSE_REDUNDANT == 5, "compatibility");
          static_assert(INSERT_HEAP_DYNAMIC == 6, "compatibility");
          static_assert(INSERT_REUSE_DYNAMIC == 7, "compatibility");
          if (subtype & 2)
          {
            size_t shift= 0;
            if (subtype & 1)
            {
              if (UNIV_UNLIKELY(ll > 3 || ll >= rlen))
                goto record_corrupted;
              shift= mlog_decode_varint(l);
              ut_ad(shift != MLOG_DECODE_ERROR);
              rlen-= ll;
              l+= ll;
              ll= mlog_decode_varint_length(*l);
            }
            if (UNIV_UNLIKELY(ll > 3 || ll >= rlen))
              goto record_corrupted;
            size_t enc_hdr_l= mlog_decode_varint(l);
            ut_ad(enc_hdr_l != MLOG_DECODE_ERROR);
            rlen-= ll;
            l+= ll;
            ll= mlog_decode_varint_length(*l);
            if (UNIV_UNLIKELY(ll > 2 || ll >= rlen))
              goto record_corrupted;
            size_t hdr_c= mlog_decode_varint(l);
            ut_ad(hdr_c != MLOG_DECODE_ERROR);
            rlen-= ll;
            l+= ll;
            ll= mlog_decode_varint_length(*l);
            if (UNIV_UNLIKELY(ll > 3 || ll > rlen))
              goto record_corrupted;
            size_t data_c= mlog_decode_varint(l);
            ut_ad(data_c != MLOG_DECODE_ERROR);
            rlen-= ll;
            l+= ll;
            if (page_apply_insert_dynamic(block, subtype & 1, prev_rec,
                                          shift, enc_hdr_l, hdr_c, data_c,
                                          l, rlen) && !srv_force_recovery)
              goto page_corrupted;
          }
          else
          {
            if (UNIV_UNLIKELY(ll > 2 || ll >= rlen))
              goto record_corrupted;
            size_t header= mlog_decode_varint(l);
            ut_ad(header != MLOG_DECODE_ERROR);
            rlen-= ll;
            l+= ll;
            ll= mlog_decode_varint_length(*l);
            if (UNIV_UNLIKELY(ll > 2 || ll >= rlen))
              goto record_corrupted;
            size_t hdr_c= mlog_decode_varint(l);
            ut_ad(hdr_c != MLOG_DECODE_ERROR);
            rlen-= ll;
            l+= ll;
            ll= mlog_decode_varint_length(*l);
            if (UNIV_UNLIKELY(ll > 2 || ll > rlen))
              goto record_corrupted;
            size_t data_c= mlog_decode_varint(l);
            rlen-= ll;
            l+= ll;
            if (page_apply_insert_redundant(block, subtype & 1, prev_rec,
                                            header, hdr_c, data_c,
                                            l, rlen) && !srv_force_recovery)
              goto page_corrupted;
          }
          break;
        case DELETE_ROW_FORMAT_REDUNDANT:
          if (UNIV_UNLIKELY(rlen < 2 || rlen > 4))
            goto record_corrupted;
          rlen--;
          ll= mlog_decode_varint_length(*++l);
          if (UNIV_UNLIKELY(ll != rlen))
            goto record_corrupted;
          if (page_apply_delete_redundant(block, mlog_decode_varint(l)) &&
              !srv_force_recovery)
            goto page_corrupted;
          break;
        case DELETE_ROW_FORMAT_DYNAMIC:
          if (UNIV_UNLIKELY(rlen < 2))
            goto record_corrupted;
          rlen--;
          ll= mlog_decode_varint_length(*++l);
          if (UNIV_UNLIKELY(ll > 3 || ll >= rlen))
            goto record_corrupted;
          prev_rec= mlog_decode_varint(l);
          ut_ad(prev_rec != MLOG_DECODE_ERROR);
          rlen-= ll;
          l+= ll;
          ll= mlog_decode_varint_length(*l);
          if (UNIV_UNLIKELY(ll > 2 || ll >= rlen))
            goto record_corrupted;
          hdr_size= mlog_decode_varint(l);
          ut_ad(hdr_size != MLOG_DECODE_ERROR);
          rlen-= ll;
          l+= ll;
          ll= mlog_decode_varint_length(*l);
          if (UNIV_UNLIKELY(ll > 3 || ll != rlen))
            goto record_corrupted;
          if (page_apply_delete_dynamic(block, prev_rec, hdr_size,
                                        mlog_decode_varint(l)) &&
              !srv_force_recovery)
            goto page_corrupted;
          break;
        }
        last_offset= FIL_PAGE_TYPE;
        goto next_after_applying;
      case WRITE:
      case MEMSET:
      case MEMMOVE:
        if (UNIV_UNLIKELY(last_offset == 1))
          goto record_corrupted;
        const size_t olen= mlog_decode_varint_length(*l);
        if (UNIV_UNLIKELY(olen >= rlen) || UNIV_UNLIKELY(olen > 3))
          goto record_corrupted;
        const uint32_t offset= mlog_decode_varint(l);
        ut_ad(offset != MLOG_DECODE_ERROR);
        static_assert(FIL_PAGE_OFFSET == 4, "compatibility");
        if (UNIV_UNLIKELY(offset >= size))
          goto record_corrupted;
        if (UNIV_UNLIKELY(offset + last_offset < 8 ||
                          offset + last_offset >= size))
          goto record_corrupted;
        last_offset= static_cast<uint16_t>(last_offset + offset);
        l+= olen;
        rlen-= olen;
        size_t llen= rlen;
        if ((b & 0x70) == WRITE)
        {
          if (UNIV_UNLIKELY(rlen + last_offset > size))
            goto record_corrupted;
          memcpy(frame + last_offset, l, llen);
          if (UNIV_LIKELY(block.page.id().page_no()));
          else if (llen == 11 + MY_AES_BLOCK_SIZE &&
                   last_offset == FSP_HEADER_OFFSET + MAGIC_SZ +
                   fsp_header_get_encryption_offset(block.zip_size()))
            applied= APPLIED_TO_ENCRYPTION;
          else if (last_offset < FSP_HEADER_OFFSET + FSP_FREE + FLST_LEN + 4 &&
                   last_offset + llen >= FSP_HEADER_OFFSET + FSP_SIZE)
            applied= APPLIED_TO_FSP_HEADER;
        next_after_applying_write:
          ut_ad(llen + last_offset <= size);
          last_offset= static_cast<uint16_t>(last_offset + llen);
          goto next_after_applying;
        }
        llen= mlog_decode_varint_length(*l);
        if (UNIV_UNLIKELY(llen > rlen || llen > 3))
          goto record_corrupted;
        const uint32_t len= mlog_decode_varint(l);
        ut_ad(len != MLOG_DECODE_ERROR);
        if (UNIV_UNLIKELY(len + last_offset > size))
          goto record_corrupted;
        l+= llen;
        rlen-= llen;
        llen= len;
        if ((b & 0x70) == MEMSET)
        {
          ut_ad(rlen <= llen);
          if (UNIV_UNLIKELY(rlen != 1))
          {
            size_t s;
            for (s= 0; s < llen; s+= rlen)
              memcpy(frame + last_offset + s, l, rlen);
            memcpy(frame + last_offset + s, l, llen - s);
          }
          else
            memset(frame + last_offset, *l, llen);
          goto next_after_applying_write;
        }
        const size_t slen= mlog_decode_varint_length(*l);
        if (UNIV_UNLIKELY(slen != rlen || slen > 3))
          goto record_corrupted;
        uint32_t s= mlog_decode_varint(l);
        ut_ad(slen != MLOG_DECODE_ERROR);
        if (s & 1)
          s= last_offset - (s >> 1) - 1;
        else
          s= last_offset + (s >> 1) + 1;
        if (UNIV_LIKELY(s >= 8 && s + llen <= size))
        {
          memmove(frame + last_offset, frame + s, llen);
          goto next_after_applying_write;
        }
      }
      goto record_corrupted;
    }
  }
};


inline size_t log_phys_t::alloc_size(size_t len)
{
  return len + (1 + 2 + sizeof(log_phys_t));
}


/** Tablespace item during recovery */
struct file_name_t {
	/** Tablespace file name (FILE_MODIFY) */
	std::string	name;
	/** Tablespace object (NULL if not valid or not found) */
	fil_space_t*	space = nullptr;

	/** Tablespace status. */
	enum fil_status {
		/** Normal tablespace */
		NORMAL,
		/** Deleted tablespace */
		DELETED,
		/** Missing tablespace */
		MISSING
	};

	/** Status of the tablespace */
	fil_status	status;

	/** FSP_SIZE of tablespace */
	uint32_t	size = 0;

	/** Freed pages of tablespace */
	range_set	freed_ranges;

	/** Dummy flags before they have been read from the .ibd file */
	static constexpr uint32_t initial_flags = FSP_FLAGS_FCRC32_MASK_MARKER;
	/** FSP_SPACE_FLAGS of tablespace */
	uint32_t	flags = initial_flags;

	/** Constructor */
	file_name_t(std::string name_, bool deleted)
		: name(std::move(name_)), status(deleted ? DELETED: NORMAL) {}

  /** Add the freed pages */
  void add_freed_page(uint32_t page_no) { freed_ranges.add_value(page_no); }

  /** Remove the freed pages */
  void remove_freed_page(uint32_t page_no)
  {
    if (freed_ranges.empty()) return;
    freed_ranges.remove_value(page_no);
  }
};

/** Map of dirty tablespaces during recovery */
typedef std::map<
	uint32_t,
	file_name_t,
	std::less<uint32_t>,
	ut_allocator<std::pair<const uint32_t, file_name_t> > >	recv_spaces_t;

static recv_spaces_t	recv_spaces;

/** The last parsed FILE_RENAME records */
static std::map<uint32_t,std::string> renamed_spaces;

/** Files for which fil_ibd_load() returned FIL_LOAD_DEFER */
static struct
{
  /** Maintains the last opened defer file name along with lsn */
  struct item
  {
    /** Log sequence number of latest add() called by fil_name_process() */
    lsn_t lsn;
    /** File name from the FILE_ record */
    std::string file_name;
    /** whether a FILE_DELETE record was encountered */
    mutable bool deleted;
  };

  using map= std::map<const uint32_t, item, std::less<const uint32_t>,
                      ut_allocator<std::pair<const uint32_t, item> > >;

  /** Map of defer tablespaces */
  map defers;

  /** Add the deferred space only if it is latest one
  @param space  space identifier
  @param f_name file name
  @param lsn    log sequence number of the FILE_ record */
  void add(uint32_t space, const std::string &f_name, lsn_t lsn)
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    const char *filename= f_name.c_str();

    if (srv_operation == SRV_OPERATION_RESTORE)
    {
      /* Replace absolute DATA DIRECTORY file paths with
      short names relative to the backup directory. */
      if (const char *name= strrchr(filename, '/'))
      {
        while (--name > filename && *name != '/');
        if (name > filename)
          filename= name + 1;
      }
    }

    char *fil_path= fil_make_filepath(nullptr, {filename, strlen(filename)},
                                      IBD, false);
    const item defer{lsn, fil_path, false};
    ut_free(fil_path);

    /* The file name must be unique. Keep the one with the latest LSN. */
    auto d= defers.begin();

    while (d != defers.end())
    {
      if (d->second.file_name != defer.file_name)
        ++d;
      else if (d->first == space)
      {
        /* Neither the file name nor the tablespace ID changed.
        Update the LSN if needed. */
        if (d->second.lsn < lsn)
          d->second.lsn= lsn;
        return;
      }
      else if (d->second.lsn < lsn)
      {
        /* Reset the old tablespace name in recovered spaces list */
        recv_spaces_t::iterator it{recv_spaces.find(d->first)};
        if (it != recv_spaces.end() &&
            it->second.name == d->second.file_name)
          it->second.name = "";
        defers.erase(d++);
      }
      else
      {
        ut_ad(d->second.lsn != lsn);
        return; /* A later tablespace already has this name. */
      }
    }

    auto p= defers.emplace(space, defer);
    if (!p.second && p.first->second.lsn <= lsn)
    {
      p.first->second.lsn= lsn;
      p.first->second.file_name= defer.file_name;
    }
    /* Add the newly added defered space and change the file name */
    recv_spaces_t::iterator it{recv_spaces.find(space)};
    if (it != recv_spaces.end())
      it->second.name = defer.file_name;
  }

  void remove(uint32_t space)
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    defers.erase(space);
  }

  /** Look up a tablespace that was found corrupted during recovery.
  @param id   tablespace id
  @return tablespace whose creation was deferred
  @retval nullptr if no such tablespace was found */
  item *find(uint32_t id)
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    auto it= defers.find(id);
    if (it != defers.end())
      return &it->second;
    return nullptr;
  }

  void clear()
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    defers.clear();
  }

  /** Initialize all deferred tablespaces.
  @return whether any deferred initialization failed */
  bool reinit_all()
  {
retry:
    log_sys.latch.wr_unlock();
    fil_space_t *space= fil_system.sys_space;
    buf_block_t *free_block= buf_LRU_get_free_block(false);
    log_sys.latch.wr_lock(SRW_LOCK_CALL);
    mysql_mutex_lock(&recv_sys.mutex);

    for (auto d= defers.begin(); d != defers.end(); )
    {
      const uint32_t space_id{d->first};
      recv_sys_t::map::iterator p{recv_sys.pages.lower_bound({space_id,0})};

      if (d->second.deleted ||
          p == recv_sys.pages.end() || p->first.space() != space_id)
      {
        /* We found a FILE_DELETE record for the tablespace, or
        there were no buffered records. Either way, we must create a
        dummy tablespace with the latest known name,
        for dict_drop_index_tree(). */
        recv_sys.pages_it_invalidate(space_id);
        while (p != recv_sys.pages.end() && p->first.space() == space_id)
        {
          ut_ad(!p->second.being_processed);
          recv_sys_t::map::iterator r= p++;
          recv_sys.erase(r);
        }
        recv_spaces_t::iterator it{recv_spaces.find(space_id)};
        if (it != recv_spaces.end())
        {
          const std::string *name= &d->second.file_name;
          if (d->second.deleted)
          {
            const auto r= renamed_spaces.find(space_id);
            if (r != renamed_spaces.end())
              name= &r->second;
            bool exists;
            os_file_type_t ftype;
            if (!os_file_status(name->c_str(), &exists, &ftype) || !exists)
              goto processed;
          }
          if (create(it, *name, static_cast<uint32_t>
                     (1U << FSP_FLAGS_FCRC32_POS_MARKER |
                      FSP_FLAGS_FCRC32_PAGE_SSIZE()), nullptr, 0))
            mysql_mutex_unlock(&fil_system.mutex);
        }
      }
      else
        space= recv_sys.recover_deferred(p, d->second.file_name, free_block);
processed:
      auto e= d++;
      defers.erase(e);
      if (!space)
        break;
      if (space != fil_system.sys_space)
        space->release();
      if (free_block)
        continue;
      mysql_mutex_unlock(&recv_sys.mutex);
      goto retry;
    }

    clear();
    mysql_mutex_unlock(&recv_sys.mutex);
    if (free_block)
      buf_pool.free_block(free_block);
    return !space;
  }

  /** Create tablespace metadata for a data file that was initially
  found corrupted during recovery.
  @param it         tablespace iterator
  @param name       latest file name
  @param flags      FSP_SPACE_FLAGS
  @param crypt_data encryption metadata
  @param size       tablespace size in pages
  @return tablespace; the caller must release fil_system.mutex
  @retval nullptr   if crypt_data is invalid */
  static fil_space_t *create(const recv_spaces_t::const_iterator &it,
                             const std::string &name, uint32_t flags,
                             fil_space_crypt_t *crypt_data, uint32_t size)
  {
    if (crypt_data && !fil_crypt_check(crypt_data, name.c_str()))
      return nullptr;
    mysql_mutex_lock(&fil_system.mutex);
    fil_space_t *space= fil_space_t::create(it->first, flags, false,
                                            crypt_data);
    ut_ad(space);
    const char *filename= name.c_str();
    if (srv_operation == SRV_OPERATION_RESTORE)
    {
      if (const char *tbl_name= strrchr(filename, '/'))
      {
        while (--tbl_name > filename && *tbl_name != '/');
        if (tbl_name > filename)
          filename= tbl_name + 1;
      }
    }
    pfs_os_file_t handle= OS_FILE_CLOSED;
    if (srv_operation == SRV_OPERATION_RESTORE)
    {
      /* During mariadb-backup --backup, a table could be renamed,
      created and dropped, and we may be missing the file at this
      point of --prepare. Try to create the file if it does not exist
      already. If the file exists, we'll pass handle=OS_FILE_CLOSED
      and the file will be opened normally in fil_space_t::acquire()
      inside recv_sys_t::recover_deferred(). */
      bool success;
      handle= os_file_create(innodb_data_file_key, filename,
                             OS_FILE_CREATE_SILENT,
                             OS_DATA_FILE, false, &success);
    }
    space->add(filename, handle, size, false, false);
    space->recv_size= it->second.size;
    space->size_in_header= size;
    return space;
  }

  /** Attempt to recover pages from the doublewrite buffer.
  This is invoked if we found neither a valid first page in the
  data file nor redo log records that would initialize the first
  page. */
  void deferred_dblwr(lsn_t max_lsn)
  {
    for (auto d= defers.begin(); d != defers.end(); )
    {
      if (d->second.deleted)
      {
      next_item:
        d++;
        continue;
      }
      const page_id_t page_id{d->first, 0};
      const byte *page= recv_sys.dblwr.find_page(page_id, max_lsn);
      if (!page)
        goto next_item;
      const uint32_t space_id= mach_read_from_4(page + FIL_PAGE_SPACE_ID);
      const uint32_t flags= fsp_header_get_flags(page);
      const uint32_t page_no= mach_read_from_4(page + FIL_PAGE_OFFSET);
      const uint32_t size= fsp_header_get_field(page, FSP_SIZE);

      if (page_no == 0 && space_id == d->first && size >= 4 &&
          fil_space_t::is_valid_flags(flags, space_id) &&
          fil_space_t::logical_size(flags) == srv_page_size)
      {
        recv_spaces_t::iterator it {recv_spaces.find(d->first)};
        ut_ad(it != recv_spaces.end());

        fil_space_t *space= create(
          it, d->second.file_name.c_str(), flags,
          fil_space_read_crypt_data(fil_space_t::zip_size(flags), page),
          size);

        if (!space)
          goto next_item;

        space->free_limit= fsp_header_get_field(page, FSP_FREE_LIMIT);
        space->free_len= flst_get_len(FSP_HEADER_OFFSET + FSP_FREE + page);
        fil_node_t *node= UT_LIST_GET_FIRST(space->chain);
        mysql_mutex_unlock(&fil_system.mutex);
        if (!space->acquire())
        {
free_space:
          fil_space_free(it->first, false);
          goto next_item;
        }
        if (os_file_write(IORequestWrite, node->name, node->handle,
                          page, 0, fil_space_t::physical_size(flags)) !=
            DB_SUCCESS)
        {
          space->release();
          goto free_space;
        }
        space->release();
        it->second.space= space;
        defers.erase(d++);
        continue;
      }
      goto next_item;
    }
  }
}
deferred_spaces;

/** Report an operation to create, delete, or rename a file during backup.
@param[in]	space_id	tablespace identifier
@param[in]	type		redo log type
@param[in]	name		file name (not NUL-terminated)
@param[in]	len		length of name, in bytes
@param[in]	new_name	new file name (NULL if not rename)
@param[in]	new_len		length of new_name, in bytes (0 if NULL) */
void (*log_file_op)(uint32_t space_id, int type,
		    const byte* name, size_t len,
		    const byte* new_name, size_t new_len);

void (*undo_space_trunc)(uint32_t space_id);

void (*first_page_init)(uint32_t space_id);

/** Information about initializing page contents during redo log processing.
FIXME: Rely on recv_sys.pages! */
class mlog_init_t
{
  using map= std::map<const page_id_t, recv_init,
                      std::less<const page_id_t>,
                      ut_allocator<std::pair<const page_id_t, recv_init>>>;
  /** Map of page initialization operations.
  FIXME: Merge this to recv_sys.pages! */
  map inits;

  /** Iterator to the last add() or will_avoid_read(), for speeding up
  will_avoid_read(). */
  map::iterator i;
public:
  /** Constructor */
  mlog_init_t() : i(inits.end()) {}

  /** Record that a page will be initialized by the redo log.
  @param page_id     page identifier
  @param lsn         log sequence number
  @return whether the state was changed */
  bool add(const page_id_t page_id, lsn_t lsn)
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    const recv_init init = { lsn, false };
    std::pair<map::iterator, bool> p=
      inits.insert(map::value_type(page_id, init));
    ut_ad(!p.first->second.created);
    if (p.second) return true;
    if (p.first->second.lsn >= lsn) return false;
    p.first->second = init;
    i = p.first;
    return true;
  }

  /** Get the last stored lsn of the page id and its respective
  init/load operation.
  @param page_id    page identifier
  @return the latest page initialization;
  not valid after releasing recv_sys.mutex. */
  recv_init &last(page_id_t page_id)
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    return inits.find(page_id)->second;
  }

  /** Determine if a page will be initialized or freed after a time.
  @param page_id      page identifier
  @param lsn          log sequence number
  @return whether page_id will be freed or initialized after lsn */
  bool will_avoid_read(page_id_t page_id, lsn_t lsn)
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    if (i != inits.end() && i->first == page_id)
      return i->second.lsn > lsn;
    i = inits.lower_bound(page_id);
    return i != inits.end() && i->first == page_id && i->second.lsn > lsn;
  }

  /** At the end of each recovery batch, reset the 'created' flags. */
  void reset()
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);
    ut_ad(recv_no_ibuf_operations);
    for (map::value_type &i : inits)
      i.second.created= false;
  }

  /** During the last recovery batch, mark whether there exist
  buffered changes for the pages that were initialized
  by buf_page_create() and still reside in the buffer pool. */
  void mark_ibuf_exist()
  {
    mysql_mutex_assert_owner(&recv_sys.mutex);

    for (const map::value_type &i : inits)
      if (i.second.created)
      {
        auto &chain= buf_pool.page_hash.cell_get(i.first.fold());
        page_hash_latch &hash_lock= buf_pool.page_hash.lock_get(chain);

        hash_lock.lock_shared();
        buf_block_t *block= reinterpret_cast<buf_block_t*>
          (buf_pool.page_hash.get(i.first, chain));
        bool got_latch= block && block->page.lock.x_lock_try();
        hash_lock.unlock_shared();

        if (!block)
          continue;

        uint32_t state;

        if (!got_latch)
        {
          mysql_mutex_lock(&buf_pool.mutex);
          block= reinterpret_cast<buf_block_t*>
            (buf_pool.page_hash.get(i.first, chain));
          if (!block)
          {
            mysql_mutex_unlock(&buf_pool.mutex);
            continue;
          }

          state= block->page.fix();
          mysql_mutex_unlock(&buf_pool.mutex);
          if (state < buf_page_t::UNFIXED)
          {
            block->page.unfix();
            continue;
          }
          block->page.lock.x_lock();
          state= block->page.unfix();
          ut_ad(state < buf_page_t::READ_FIX);
          if (state >= buf_page_t::UNFIXED && block->page.id() == i.first)
            goto check_ibuf;
        }
        else
        {
          state= block->page.state();
          ut_ad(state >= buf_page_t::FREED);
          ut_ad(state < buf_page_t::READ_FIX);

          if (state >= buf_page_t::UNFIXED)
          {
          check_ibuf:
            mysql_mutex_unlock(&recv_sys.mutex);
            if (ibuf_page_exists(block->page.id(), block->zip_size()))
              block->page.set_ibuf_exist();
            mysql_mutex_lock(&recv_sys.mutex);
          }
        }

        block->page.lock.x_unlock();
      }
  }

  /** Clear the data structure */
  void clear() { inits.clear(); i = inits.end(); }
};

static mlog_init_t mlog_init;

/** Try to recover a tablespace that was not readable earlier
@param p          iterator to the page
@param name       tablespace file name
@param free_block spare buffer block
@return recovered tablespace
@retval nullptr if recovery failed */
fil_space_t *recv_sys_t::recover_deferred(const recv_sys_t::map::iterator &p,
                                          const std::string &name,
                                          buf_block_t *&free_block)
{
  mysql_mutex_assert_owner(&mutex);

  ut_ad(p->first.space());

  recv_spaces_t::iterator it{recv_spaces.find(p->first.space())};
  ut_ad(it != recv_spaces.end());

  if (!p->first.page_no() && p->second.skip_read)
  {
    mtr_t mtr;
    ut_ad(!p->second.being_processed);
    p->second.being_processed= 1;
    init &init= mlog_init.last(p->first);
    mysql_mutex_unlock(&mutex);
    buf_block_t *block= recover_low(p, mtr, free_block, init);
    mysql_mutex_lock(&mutex);
    p->second.being_processed= -1;
    ut_ad(block == free_block || block == reinterpret_cast<buf_block_t*>(-1));
    free_block= nullptr;
    if (UNIV_UNLIKELY(!block || block == reinterpret_cast<buf_block_t*>(-1)))
      goto fail;
    const byte *page= UNIV_LIKELY_NULL(block->page.zip.data)
      ? block->page.zip.data
      : block->page.frame;
    const uint32_t space_id= mach_read_from_4(page + FIL_PAGE_SPACE_ID);
    const uint32_t flags= fsp_header_get_flags(page);
    const uint32_t page_no= mach_read_from_4(page + FIL_PAGE_OFFSET);
    const uint32_t size= fsp_header_get_field(page, FSP_SIZE);

    if (page_id_t{space_id, page_no} == p->first && size >= 4 &&
        fil_space_t::is_valid_flags(flags, space_id) &&
        fil_space_t::logical_size(flags) == srv_page_size)
    {
      fil_space_t *space= deferred_spaces.create(it, name, flags,
                                                 fil_space_read_crypt_data
                                                 (fil_space_t::zip_size(flags),
                                                  page), size);
      if (!space)
        goto release_and_fail;
      space->free_limit= fsp_header_get_field(page, FSP_FREE_LIMIT);
      space->free_len= flst_get_len(FSP_HEADER_OFFSET + FSP_FREE + page);
      fil_node_t *node= UT_LIST_GET_FIRST(space->chain);
      node->deferred= true;
      mysql_mutex_unlock(&fil_system.mutex);
      if (!space->acquire())
        goto release_and_fail;
      fil_names_dirty(space);
      const bool is_compressed= fil_space_t::is_compressed(flags);
#ifdef _WIN32
      const bool is_sparse= is_compressed;
      if (is_compressed)
        os_file_set_sparse_win32(node->handle);
#else
      const bool is_sparse= is_compressed &&
        DB_SUCCESS == os_file_punch_hole(node->handle, 0, 4096) &&
        !my_test_if_thinly_provisioned(node->handle);
#endif
      /* Mimic fil_node_t::read_page0() in case the file exists and
      has already been extended to a larger size. */
      ut_ad(node->size == size);
      const os_offset_t file_size= os_file_get_size(node->handle);
      if (file_size != os_offset_t(-1))
      {
        const uint32_t n_pages=
          uint32_t(file_size / fil_space_t::physical_size(flags));
        if (n_pages > size)
        {
          mysql_mutex_lock(&fil_system.mutex);
          space->size= node->size= n_pages;
          space->set_committed_size();
          mysql_mutex_unlock(&fil_system.mutex);
          goto size_set;
        }
      }
      if (!os_file_set_size(node->name, node->handle,
                            (size * fil_space_t::physical_size(flags)) &
                            ~4095ULL, is_sparse))
      {
        space->release();
        goto release_and_fail;
      }
    size_set:
      node->deferred= false;
      it->second.space= space;
      block->page.lock.x_unlock();
      p->second.being_processed= -1;
      return space;
    }

  release_and_fail:
    block->page.lock.x_unlock();
  }

fail:
  ib::error() << "Cannot apply log to " << p->first
              << " of corrupted file '" << name << "'";
  return nullptr;
}

/** Process a record that indicates that a tablespace is
being shrunk in size.
@param page_id	first page identifier that is not in the file
@param lsn	log sequence number of the shrink operation */
inline void recv_sys_t::trim(const page_id_t page_id, lsn_t lsn)
{
  DBUG_ENTER("recv_sys_t::trim");
  DBUG_LOG("ib_log", "discarding log beyond end of tablespace "
           << page_id << " before LSN " << lsn);
  mysql_mutex_assert_owner(&mutex);
  if (pages_it != pages.end() && pages_it->first.space() == page_id.space())
    pages_it= pages.end();
  for (recv_sys_t::map::iterator p = pages.lower_bound(page_id);
       p != pages.end() && p->first.space() == page_id.space();)
  {
    recv_sys_t::map::iterator r = p++;
    if (r->second.trim(lsn))
    {
      ut_ad(!r->second.being_processed);
      pages.erase(r);
    }
  }
  DBUG_VOID_RETURN;
}

inline dberr_t recv_sys_t::read(os_offset_t total_offset, span<byte> buf)
{
  size_t file_idx= static_cast<size_t>(total_offset / log_sys.file_size);
  os_offset_t offset= total_offset % log_sys.file_size;
  return file_idx
    ? recv_sys.files[file_idx].read(offset, buf)
    : log_sys.log.read(offset, buf);
}

inline size_t recv_sys_t::files_size()
{
  ut_ad(!files.empty());
  return files.size();
}

/** Process a file name from a FILE_* record.
@param[in]	name		file name
@param[in]	len		length of the file name
@param[in]	space_id	the tablespace ID
@param[in]	ftype		FILE_MODIFY, FILE_DELETE, or FILE_RENAME
@param[in]	lsn		lsn of the redo log
@param[in]	if_exists	whether to check if the tablespace exists */
static void fil_name_process(const char *name, ulint len, uint32_t space_id,
                             mfile_type_t ftype, lsn_t lsn, bool if_exists)
{
	ut_ad(srv_operation <= SRV_OPERATION_EXPORT_RESTORED
	      || srv_operation == SRV_OPERATION_RESTORE
	      || srv_operation == SRV_OPERATION_RESTORE_EXPORT);

	/* We will also insert space=NULL into the map, so that
	further checks can ensure that a FILE_MODIFY record was
	scanned before applying any page records for the space_id. */

	const bool deleted{ftype == FILE_DELETE};
	const file_name_t fname(std::string(name, len), deleted);
	std::pair<recv_spaces_t::iterator,bool> p = recv_spaces.emplace(
		space_id, fname);
	ut_ad(p.first->first == space_id);

	file_name_t&	f = p.first->second;

	auto d = deferred_spaces.find(space_id);
	if (d) {
		if (deleted) {
			d->deleted = true;
			goto got_deleted;
		}
		goto reload;
	}

	if (deleted) {
got_deleted:
		/* Got FILE_DELETE */
		if (!p.second && f.status != file_name_t::DELETED) {
			f.status = file_name_t::DELETED;
			if (f.space != NULL) {
				fil_space_free(space_id, false);
				f.space = NULL;
			}
		}

		ut_ad(f.space == NULL);
	} else if (p.second // the first FILE_MODIFY or FILE_RENAME
		   || f.name != fname.name) {
reload:
		fil_space_t*	space;

		/* Check if the tablespace file exists and contains
		the space_id. If not, ignore the file after displaying
		a note. Abort if there are multiple files with the
		same space_id. */
		switch (fil_ibd_load(space_id, fname.name.c_str(), space)) {
		case FIL_LOAD_OK:
			ut_ad(space != NULL);

			deferred_spaces.remove(space_id);
			if (!f.space) {
				if (f.size
				    || f.flags != f.initial_flags) {
					fil_space_set_recv_size_and_flags(
						space->id, f.size, f.flags);
				}

				f.space = space;
				goto same_space;
			} else if (f.space == space) {
same_space:
				f.name = fname.name;
				f.status = file_name_t::NORMAL;
			} else {
				sql_print_error("InnoDB: Tablespace " UINT32PF
						" has been found"
						" in two places:"
						" '%.*s' and '%.*s'."
						" You must delete"
						" one of them.",
						space_id,
						int(f.name.size()),
						f.name.data(),
						int(fname.name.size()),
						fname.name.data());
				recv_sys.set_corrupt_fs();
			}
			break;

		case FIL_LOAD_ID_CHANGED:
			ut_ad(space == NULL);
			break;

		case FIL_LOAD_NOT_FOUND:
			/* No matching tablespace was found; maybe it
			was renamed, and we will find a subsequent
			FILE_* record. */
			ut_ad(space == NULL);

			if (srv_operation == SRV_OPERATION_RESTORE && d
			    && ftype == FILE_RENAME) {
rename:
				d->file_name = fname.name;
				f.name = fname.name;
				break;
			}

			if (srv_force_recovery
			    || srv_operation == SRV_OPERATION_RESTORE) {
				/* Without innodb_force_recovery,
				missing tablespaces will only be
				reported in
				recv_init_crash_recovery_spaces().
				Enable some more diagnostics when
				forcing recovery. */

				sql_print_information(
					"InnoDB: At LSN: " LSN_PF
					": unable to open file %.*s"
					" for tablespace " UINT32PF,
					recv_sys.lsn,
					int(fname.name.size()),
					fname.name.data(), space_id);
			}
			break;

		case FIL_LOAD_DEFER:
			if (d && ftype == FILE_RENAME
			    && srv_operation == SRV_OPERATION_RESTORE) {
				goto rename;
			}
			/* Skip the deferred spaces
			when lsn is already processed */
			if (!if_exists) {
				deferred_spaces.add(
					space_id, fname.name.c_str(), lsn);
			}
			break;
		case FIL_LOAD_INVALID:
			ut_ad(space == NULL);
			if (srv_force_recovery == 0) {
				sql_print_error("InnoDB: Recovery cannot access"
						" file %.*s (tablespace "
						UINT32PF ")", int(len), name,
						space_id);
				sql_print_information("InnoDB: You may set "
						      "innodb_force_recovery=1"
						      " to ignore this and"
						      " possibly get a"
						      " corrupted database.");
				recv_sys.set_corrupt_fs();
				break;
			}

			sql_print_warning("InnoDB: Ignoring changes to"
					  " file %.*s (tablespace "
					  UINT32PF ")"
					  " due to innodb_force_recovery",
					  int(len), name, space_id);
		}
	}
}

void recv_sys_t::close_files()
{
  for (auto &file : files)
    if (file.is_opened())
      file.close();
  files.clear();
  files.shrink_to_fit();
}

/** Clean up after recv_sys_t::create() */
void recv_sys_t::close()
{
  ut_ad(this == &recv_sys);

  if (is_initialised())
  {
    dblwr.pages.clear();
    ut_d(mysql_mutex_lock(&mutex));
    clear();
    deferred_spaces.clear();
    ut_d(mysql_mutex_unlock(&mutex));

    scanned_lsn= 0;
    mysql_mutex_destroy(&mutex);
  }

  recv_spaces.clear();
  renamed_spaces.clear();
  mlog_init.clear();
  close_files();
}

/** Initialize the redo log recovery subsystem. */
void recv_sys_t::create()
{
	ut_ad(this == &recv_sys);
	ut_ad(!is_initialised());
	mysql_mutex_init(recv_sys_mutex_key, &mutex, nullptr);

	apply_log_recs = false;

	len = 0;
	offset = 0;
	lsn = 0;
	scanned_lsn = 1;
	found_corrupt_log = false;
	found_corrupt_fs = false;
	file_checkpoint = 0;

	progress_time = time(NULL);
	ut_ad(pages.empty());
	pages_it = pages.end();

	memset(truncated_undo_spaces, 0, sizeof truncated_undo_spaces);
	UT_LIST_INIT(blocks, &buf_block_t::unzip_LRU);
}

/** Clear a fully processed set of stored redo log records. */
void recv_sys_t::clear()
{
  mysql_mutex_assert_owner(&mutex);
  apply_log_recs= false;
  ut_ad(!after_apply || found_corrupt_fs || !UT_LIST_GET_LAST(blocks));
  pages.clear();
  pages_it= pages.end();

  for (buf_block_t *block= UT_LIST_GET_LAST(blocks); block; )
  {
    buf_block_t *prev_block= UT_LIST_GET_PREV(unzip_LRU, block);
    ut_ad(block->page.state() == buf_page_t::MEMORY);
    block->page.hash= nullptr;
    UT_LIST_REMOVE(blocks, block);
    MEM_MAKE_ADDRESSABLE(block->page.frame, srv_page_size);
    buf_block_free(block);
    block= prev_block;
  }
}

/** Free most recovery data structures. */
void recv_sys_t::debug_free()
{
  ut_ad(this == &recv_sys);
  ut_ad(is_initialised());
  mysql_mutex_lock(&mutex);

  recovery_on= false;
  pages.clear();
  pages_it= pages.end();

  mysql_mutex_unlock(&mutex);
  log_sys.clear_mmap();
}


/** Free a redo log snippet.
@param data buffer allocated in add() */
inline void recv_sys_t::free(const void *data)
{
  ut_ad(!ut_align_offset(data, ALIGNMENT));
  mysql_mutex_assert_owner(&mutex);

  buf_block_t *block= buf_pool.block_from(data);
  ut_ad(block->page.frame == page_align(data));
  ut_ad(block->page.state() == buf_page_t::MEMORY);
  ut_ad(uint16_t(block->page.free_offset - 1) < srv_page_size);
  ut_ad(block->page.used_records);
  if (!--block->page.used_records)
  {
    block->page.hash= nullptr;
    UT_LIST_REMOVE(blocks, block);
    MEM_MAKE_ADDRESSABLE(block->page.frame, srv_page_size);
    buf_block_free(block);
  }
}


/** @return whether a log_t::FORMAT_10_5 log block checksum matches */
static bool recv_check_log_block(const byte *buf)
{
  return mach_read_from_4(my_assume_aligned<4>(508 + buf)) ==
    my_crc32c(0, buf, 508);
}

/** Calculate the checksum for a log block using the pre-10.2.2 algorithm. */
inline uint32_t log_block_calc_checksum_format_0(const byte *b)
{
  uint32_t sum= 1;
  const byte *const end= &b[512 - 4];

  for (uint32_t sh= 0; b < end; )
  {
    sum&= 0x7FFFFFFFUL;
    sum+= uint32_t{*b} << sh++;
    sum+= *b++;
    if (sh > 24)
      sh= 0;
  }

  return sum;
}

/** Determine if a redo log from before MariaDB 10.2.2 is clean.
@return error code
@retval DB_SUCCESS      if the redo log is clean
@retval DB_CORRUPTION   if the redo log is corrupted
@retval DB_ERROR        if the redo log is not empty */
ATTRIBUTE_COLD static dberr_t recv_log_recover_pre_10_2()
{
  uint64_t max_no= 0;

  ut_ad(log_sys.format == 0);

  /** Offset of the first checkpoint checksum */
  constexpr uint CHECKSUM_1= 288;
  /** Offset of the second checkpoint checksum */
  constexpr uint CHECKSUM_2= CHECKSUM_1 + 4;
  /** the checkpoint LSN field */
  constexpr uint CHECKPOINT_LSN= 8;
  /** Most significant bits of the checkpoint offset */
  constexpr uint OFFS_HI= CHECKSUM_2 + 12;
  /** Least significant bits of the checkpoint offset */
  constexpr uint OFFS_LO= 16;

  lsn_t source_offset= 0;
  const lsn_t log_size{(log_sys.file_size - 2048) * recv_sys.files_size()};
  for (size_t field= 512; field < 2048; field+= 1024)
  {
    const byte *buf= log_sys.buf + field;

    if (static_cast<uint32_t>(ut_fold_binary(buf, CHECKSUM_1)) !=
        mach_read_from_4(buf + CHECKSUM_1) ||
        static_cast<uint32_t>(ut_fold_binary(buf + CHECKPOINT_LSN,
                                             CHECKSUM_2 - CHECKPOINT_LSN)) !=
        mach_read_from_4(buf + CHECKSUM_2))
    {
      DBUG_PRINT("ib_log", ("invalid pre-10.2.2 checkpoint %zu", field));
      continue;
    }

    if (!log_crypt_101_read_checkpoint(buf))
    {
      sql_print_error("InnoDB: Decrypting checkpoint failed");
      continue;
    }

    const uint64_t checkpoint_no= mach_read_from_8(buf);

    DBUG_PRINT("ib_log", ("checkpoint " UINT64PF " at " LSN_PF " found",
                          checkpoint_no,
                          mach_read_from_8(buf + CHECKPOINT_LSN)));

    if (checkpoint_no < max_no)
      continue;

    const lsn_t o= lsn_t{mach_read_from_4(buf + OFFS_HI)} << 32 |
      mach_read_from_4(buf + OFFS_LO);
    if (o >= 0x80c && (o & ~511) + 512 < log_size)
    {
      max_no= checkpoint_no;
      log_sys.next_checkpoint_lsn= mach_read_from_8(buf + CHECKPOINT_LSN);
      source_offset= o;
    }
  }

  const char *uag= srv_operation == SRV_OPERATION_NORMAL
    ? "InnoDB: Upgrade after a crash is not supported."
    : "mariadb-backup --prepare is not possible.";

  if (!log_sys.next_checkpoint_lsn)
  {
    sql_print_error("%s"
                    " This redo log was created before MariaDB 10.2.2,"
                    " and we did not find a valid checkpoint."
                    " Please follow the instructions at"
                    " https://mariadb.com/kb/en/library/upgrading/", uag);
    return DB_ERROR;
  }

  static const char pre_10_2[]=
    " This redo log was created before MariaDB 10.2.2";

  byte *buf= const_cast<byte*>(field_ref_zero);

  if (source_offset < (log_sys.is_mmap() ? log_sys.file_size : 4096))
    memcpy_aligned<512>(buf, &log_sys.buf[source_offset & ~511], 512);
  else
    if (dberr_t err= recv_sys.read(source_offset & ~511, {buf, 512}))
      return err;

  if (log_block_calc_checksum_format_0(buf) !=
      mach_read_from_4(my_assume_aligned<4>(buf + 508)) &&
      !log_crypt_101_read_block(buf, log_sys.next_checkpoint_lsn))
  {
    sql_print_error("%s%s, and it appears corrupted.", uag, pre_10_2);
    return DB_CORRUPTION;
  }

  if (mach_read_from_2(buf + 4) == (source_offset & 511))
    return DB_SUCCESS;

  if (buf[20 + 32 * 9] == 2)
    sql_print_error("InnoDB: Cannot decrypt log for upgrading."
                    " The encrypted log was created before MariaDB 10.2.2.");
  else
    sql_print_error("%s%s. You must start up and shut down"
                    " MariaDB 10.1 or MySQL 5.6 or earlier"
                    " on the data directory.",
                    uag, pre_10_2);

  return DB_ERROR;
}

/** Determine if a redo log from MariaDB 10.2.2, 10.3, 10.4, or 10.5 is clean.
@param lsn_offset  checkpoint LSN offset
@return	error code
@retval	DB_SUCCESS	if the redo log is clean
@retval	DB_CORRUPTION	if the redo log is corrupted
@retval	DB_ERROR	if the redo log is not empty */
static dberr_t recv_log_recover_10_5(lsn_t lsn_offset)
{
  byte *buf= const_cast<byte*>(field_ref_zero);

  if (lsn_offset < (log_sys.is_mmap() ? log_sys.file_size : 4096))
    memcpy_aligned<512>(buf, &log_sys.buf[lsn_offset & ~511], 512);
  else
  {
    if (dberr_t err= recv_sys.read(lsn_offset & ~lsn_t{4095}, {buf, 4096}))
      return err;
    buf+= lsn_offset & 0xe00;
  }

  if (!recv_check_log_block(buf))
  {
    sql_print_error("InnoDB: Invalid log header checksum");
    return DB_CORRUPTION;
  }

  if (log_sys.is_encrypted() &&
      !log_decrypt(buf, log_sys.next_checkpoint_lsn & ~511, 512))
    return DB_ERROR;

  /* On a clean shutdown, the redo log will be logically empty
  after the checkpoint lsn. */

  if (mach_read_from_2(my_assume_aligned<2>(buf + 4)) != (lsn_offset & 511))
    return DB_ERROR;

  return DB_SUCCESS;
}

dberr_t recv_sys_t::find_checkpoint()
{
  bool wrong_size= false;
  byte *buf;

  ut_ad(pages.empty());
  pages_it= pages.end();

  if (files.empty())
  {
    file_checkpoint= 0;
    std::string path{get_log_file_path()};
    bool success;
    os_file_t file{os_file_create_func(path.c_str(),
                                       OS_FILE_OPEN,
                                       OS_LOG_FILE,
                                       srv_read_only_mode, &success)};
    if (file == OS_FILE_CLOSED)
      return DB_ERROR;
    const os_offset_t size{os_file_get_size(file)};
    if (!size)
    {
      if (srv_operation != SRV_OPERATION_NORMAL)
        goto too_small;
    }
    else if (size < log_t::START_OFFSET + SIZE_OF_FILE_CHECKPOINT)
    {
    too_small:
      sql_print_error("InnoDB: File %.*s is too small",
                      int(path.size()), path.data());
    err_exit:
      os_file_close(file);
      return DB_ERROR;
    }
    else if (!log_sys.attach(file, size))
      goto err_exit;
    else
      file= OS_FILE_CLOSED;

    recv_sys.files.emplace_back(file);
    for (int i= 1; i < 101; i++)
    {
      path= get_log_file_path(LOG_FILE_NAME_PREFIX).append(std::to_string(i));
      file= os_file_create_func(path.c_str(),
                                OS_FILE_OPEN_SILENT,
                                OS_LOG_FILE, true, &success);
      if (file == OS_FILE_CLOSED)
        break;
      const os_offset_t sz{os_file_get_size(file)};
      if (size != sz)
      {
        sql_print_error("InnoDB: Log file %.*s is of different size " UINT64PF
                        " bytes than other log files " UINT64PF " bytes!",
                        int(path.size()), path.data(), sz, size);
        wrong_size= true;
      }
      recv_sys.files.emplace_back(file);
    }

    if (!size)
    {
      if (wrong_size)
        return DB_CORRUPTION;
      lsn= log_sys.next_checkpoint_lsn;
      log_sys.format= log_t::FORMAT_3_23;
      goto upgrade;
    }
  }
  else
    ut_ad(srv_operation == SRV_OPERATION_BACKUP);
  log_sys.next_checkpoint_lsn= 0;
  lsn= 0;
  buf= my_assume_aligned<4096>(log_sys.buf);
  if (!log_sys.is_mmap())
    if (dberr_t err= log_sys.log.read(0, {buf, log_sys.START_OFFSET}))
      return err;
  /* Check the header page checksum. There was no
  checksum in the first redo log format (version 0). */
  log_sys.format= mach_read_from_4(buf + LOG_HEADER_FORMAT);
  if (log_sys.format == log_t::FORMAT_3_23)
  {
    if (wrong_size)
      return DB_CORRUPTION;
    if (dberr_t err= recv_log_recover_pre_10_2())
      return err;
  upgrade:
    memset_aligned<4096>(const_cast<byte*>(field_ref_zero), 0, 4096);
    /* Mark the redo log for upgrading. */
    log_sys.last_checkpoint_lsn= log_sys.next_checkpoint_lsn;
    log_sys.set_recovered_lsn(log_sys.next_checkpoint_lsn);
    lsn= file_checkpoint= log_sys.next_checkpoint_lsn;
    if (UNIV_LIKELY(lsn != 0))
      scanned_lsn= lsn;
    log_sys.next_checkpoint_no= 0;
    return DB_SUCCESS;
  }

  if (!recv_check_log_block(buf))
  {
    sql_print_error("InnoDB: Invalid log header checksum");
    return DB_CORRUPTION;
  }

  const lsn_t first_lsn{mach_read_from_8(buf + LOG_HEADER_START_LSN)};
  log_sys.set_first_lsn(first_lsn);
  char creator[LOG_HEADER_CREATOR_END - LOG_HEADER_CREATOR + 1];
  memcpy(creator, buf + LOG_HEADER_CREATOR, sizeof creator);
  /* Ensure that the string is NUL-terminated. */
  creator[LOG_HEADER_CREATOR_END - LOG_HEADER_CREATOR]= 0;

  lsn_t lsn_offset= 0;

  switch (log_sys.format) {
  default:
    sql_print_error("InnoDB: Unsupported redo log format."
                    " The redo log was created with %s.", creator);
    return DB_ERROR;
  case log_t::FORMAT_10_8:
    if (files.size() != 1)
    {
      sql_print_error("InnoDB: Expecting only ib_logfile0");
      return DB_CORRUPTION;
    }

    if (*reinterpret_cast<const uint32_t*>(buf + LOG_HEADER_FORMAT + 4) ||
        first_lsn < log_t::FIRST_LSN)
    {
      sql_print_error("InnoDB: Invalid ib_logfile0 header block;"
                      " the log was created with %s.", creator);
      return DB_CORRUPTION;
    }

    if (!mach_read_from_4(buf + LOG_HEADER_CREATOR_END));
    else if (!log_crypt_read_header(buf + LOG_HEADER_CREATOR_END))
    {
      sql_print_error("InnoDB: Reading log encryption info failed;"
                      " the log was created with %s.", creator);
      return DB_ERROR;
    }
    else
      log_sys.format= log_t::FORMAT_ENC_10_8;

    for (size_t field= log_t::CHECKPOINT_1; field <= log_t::CHECKPOINT_2;
         field+= log_t::CHECKPOINT_2 - log_t::CHECKPOINT_1)
    {
      buf= log_sys.buf + field;
      const lsn_t checkpoint_lsn{mach_read_from_8(buf)};
      const lsn_t end_lsn{mach_read_from_8(buf + 8)};
      if (checkpoint_lsn < first_lsn || end_lsn < checkpoint_lsn ||
          memcmp(buf + 16, field_ref_zero, 60 - 16) ||
          my_crc32c(0, buf, 60) != mach_read_from_4(buf + 60))
      {
        DBUG_PRINT("ib_log", ("invalid checkpoint at %zu", field));
        continue;
      }

      if (checkpoint_lsn >= log_sys.next_checkpoint_lsn)
      {
        log_sys.next_checkpoint_lsn= checkpoint_lsn;
        log_sys.next_checkpoint_no= field == log_t::CHECKPOINT_1;
        lsn= end_lsn;
      }
    }
    if (!log_sys.next_checkpoint_lsn)
      goto got_no_checkpoint;
    if (!memcmp(creator, "Backup ", 7))
      srv_start_after_restore= true;
    return DB_SUCCESS;
  case log_t::FORMAT_10_5:
  case log_t::FORMAT_10_5 | log_t::FORMAT_ENCRYPTED:
    if (files.size() != 1)
    {
      sql_print_error("InnoDB: Expecting only ib_logfile0");
      return DB_CORRUPTION;
    }
    /* fall through */
  case log_t::FORMAT_10_2:
  case log_t::FORMAT_10_2 | log_t::FORMAT_ENCRYPTED:
  case log_t::FORMAT_10_3:
  case log_t::FORMAT_10_3 | log_t::FORMAT_ENCRYPTED:
  case log_t::FORMAT_10_4:
  case log_t::FORMAT_10_4 | log_t::FORMAT_ENCRYPTED:
    uint64_t max_no= 0;
    const lsn_t log_size{(log_sys.file_size - 2048) * files.size()};
    for (size_t field= 512; field < 2048; field += 1024)
    {
      const byte *b = buf + field;

      if (!recv_check_log_block(b))
      {
        DBUG_PRINT("ib_log", ("invalid checkpoint checksum at %zu", field));
        continue;
      }

      if (log_sys.is_encrypted() && !log_crypt_read_checkpoint_buf(b))
      {
        sql_print_error("InnoDB: Reading checkpoint encryption info failed.");
        continue;
      }

      const uint64_t checkpoint_no= mach_read_from_8(b);
      const lsn_t checkpoint_lsn= mach_read_from_8(b + 8);
      DBUG_PRINT("ib_log", ("checkpoint " UINT64PF " at " LSN_PF " found",
                            checkpoint_no, checkpoint_lsn));
      const lsn_t o{mach_read_from_8(b + 16)};
      if (checkpoint_no >= max_no && o >= 0x80c && (o & ~511) + 512 < log_size)
      {
        max_no= checkpoint_no;
        log_sys.next_checkpoint_lsn= checkpoint_lsn;
        log_sys.next_checkpoint_no= field == 512;
        lsn_offset= mach_read_from_8(b + 16);
      }
    }
  }

  if (!log_sys.next_checkpoint_lsn)
  {
  got_no_checkpoint:
    sql_print_error("InnoDB: No valid checkpoint was found;"
                    " the log was created with %s.", creator);
    return DB_ERROR;
  }

  if (wrong_size)
    return DB_CORRUPTION;

  if (dberr_t err= recv_log_recover_10_5(lsn_offset))
  {
    const char *msg1, *msg2, *msg3;
    msg1= srv_operation == SRV_OPERATION_NORMAL
      ? "InnoDB: Upgrade after a crash is not supported."
      : "mariadb-backup --prepare is not possible.";

    if (err == DB_ERROR)
    {
      msg2= srv_operation == SRV_OPERATION_NORMAL
        ? ". You must start up and shut down MariaDB "
        : ". You must use mariadb-backup ";
      msg3= (log_sys.format & ~log_t::FORMAT_ENCRYPTED) == log_t::FORMAT_10_5
        ? "10.7 or earlier." : "10.4 or earlier.";
    }
    else
      msg2= ", and it appears corrupted.", msg3= "";

    sql_print_error("%s The redo log was created with %s%s%s",
                    msg1, creator, msg2, msg3);
    return err;
  }

  goto upgrade;
}

/** Trim old log records for a page.
@param start_lsn oldest log sequence number to preserve
@return whether all the log for the page was trimmed */
inline bool page_recv_t::trim(lsn_t start_lsn)
{
  while (log.head)
  {
    if (log.head->lsn > start_lsn) return false;
    last_offset= 1; /* the next record must not be same_page */
    log_rec_t *next= log.head->next;
    recv_sys.free(log.head);
    log.head= next;
  }
  log.tail= nullptr;
  return true;
}


void page_recv_t::recs_t::rewind(lsn_t start_lsn)
{
  mysql_mutex_assert_owner(&recv_sys.mutex);
  log_phys_t *trim= static_cast<log_phys_t*>(head);
  ut_ad(trim);
  while (log_phys_t *next= static_cast<log_phys_t*>(trim->next))
  {
    ut_ad(trim->start_lsn < start_lsn);
    if (next->start_lsn == start_lsn)
      break;
    trim= next;
  }
  tail= trim;
  log_rec_t *l= tail->next;
  tail->next= nullptr;
  while (l)
  {
    log_rec_t *next= l->next;
    recv_sys.free(l);
    l= next;
  }
}


void page_recv_t::recs_t::clear()
{
  mysql_mutex_assert_owner(&recv_sys.mutex);
  for (const log_rec_t *l= head; l; )
  {
    const log_rec_t *next= l->next;
    recv_sys.free(l);
    l= next;
  }
  head= tail= nullptr;
}

/** Ignore any earlier redo log records for this page. */
inline void page_recv_t::will_not_read()
{
  ut_ad(!being_processed);
  skip_read= true;
  log.clear();
}

void recv_sys_t::erase(map::iterator p)
{
  ut_ad(p->second.being_processed <= 0);
  p->second.log.clear();
  pages.erase(p);
}

/** Free log for processed pages. */
void recv_sys_t::garbage_collect()
{
  mysql_mutex_assert_owner(&mutex);

  if (pages_it != pages.end() && pages_it->second.being_processed < 0)
    pages_it= pages.end();

  for (map::iterator p= pages.begin(); p != pages.end(); )
  {
    if (p->second.being_processed < 0)
    {
      map::iterator r= p++;
      erase(r);
    }
    else
      p++;
  }
}

/** Allocate a block from the buffer pool for recv_sys.pages */
ATTRIBUTE_COLD buf_block_t *recv_sys_t::add_block()
{
  for (bool freed= false;;)
  {
    const auto rs= UT_LIST_GET_LEN(blocks) * 2;
    mysql_mutex_lock(&buf_pool.mutex);
    const auto bs=
      UT_LIST_GET_LEN(buf_pool.free) + UT_LIST_GET_LEN(buf_pool.LRU);
    if (UNIV_LIKELY(bs > BUF_LRU_MIN_LEN || rs < bs))
    {
      buf_block_t *block= buf_LRU_get_free_block(true);
      mysql_mutex_unlock(&buf_pool.mutex);
      return block;
    }
    /* out of memory: redo log occupies more than 1/3 of buf_pool
    and there are fewer than BUF_LRU_MIN_LEN pages left */
    mysql_mutex_unlock(&buf_pool.mutex);
    if (freed)
      return nullptr;
    freed= true;
    garbage_collect();
  }
}

/** Wait for buffer pool to become available. */
ATTRIBUTE_COLD void recv_sys_t::wait_for_pool(size_t pages)
{
  mysql_mutex_unlock(&mutex);
  os_aio_wait_until_no_pending_reads(false);
  mysql_mutex_lock(&mutex);
  garbage_collect();
  mysql_mutex_lock(&buf_pool.mutex);
  const size_t available= UT_LIST_GET_LEN(buf_pool.free);
  mysql_mutex_unlock(&buf_pool.mutex);
  if (available < pages)
    buf_flush_sync_batch(lsn);
}

/** Register a redo log snippet for a page.
@param it       page iterator
@param start_lsn start LSN of the mini-transaction
@param lsn      @see mtr_t::commit_lsn()
@param l        redo log snippet
@param len      length of l, in bytes
@return whether we ran out of memory */
ATTRIBUTE_NOINLINE
bool recv_sys_t::add(map::iterator it, lsn_t start_lsn, lsn_t lsn,
                     const byte *l, size_t len)
{
  mysql_mutex_assert_owner(&mutex);
  page_recv_t &recs= it->second;
  buf_block_t *block;

  switch (*l & 0x70) {
  case FREE_PAGE: case INIT_PAGE:
    recs.will_not_read();
    mlog_init.add(it->first, start_lsn); /* FIXME: remove this! */
    /* fall through */
  default:
    log_phys_t *tail= static_cast<log_phys_t*>(recs.log.last());
    if (!tail)
      break;
    if (tail->start_lsn != start_lsn)
      break;
    ut_ad(tail->lsn == lsn);
    block= UT_LIST_GET_LAST(blocks);
    ut_ad(block);
    const size_t used= uint16_t(block->page.free_offset - 1) + 1;
    ut_ad(used >= ALIGNMENT);
    const byte *end= const_cast<const log_phys_t*>(tail)->end();
    if (!((reinterpret_cast<size_t>(end + len) ^
           reinterpret_cast<size_t>(end)) & ~(ALIGNMENT - 1)))
    {
      /* Use already allocated 'padding' bytes */
append:
      MEM_MAKE_ADDRESSABLE(end + 1, len);
      /* Append to the preceding record for the page */
      tail->append(l, len);
      return false;
    }
    if (end <= &block->page.frame[used - ALIGNMENT] ||
        &block->page.frame[used] >= end)
      break; /* Not the last allocated record in the page */
    const size_t new_used= static_cast<size_t>
      (end - block->page.frame + len + 1);
    ut_ad(new_used > used);
    if (new_used > srv_page_size)
      break;
    block->page.free_offset=
      ut_calc_align<uint16_t>(static_cast<uint16_t>(new_used), ALIGNMENT);
    goto append;
  }

  const size_t size{log_phys_t::alloc_size(len)};
  ut_ad(size <= srv_page_size);
  void *buf;
  block= UT_LIST_GET_FIRST(blocks);
  if (UNIV_UNLIKELY(!block))
  {
  create_block:
    block= add_block();
    if (UNIV_UNLIKELY(!block))
      return true;
    block->page.used_records= 1;
    block->page.free_offset=
      ut_calc_align<uint16_t>(static_cast<uint16_t>(size), ALIGNMENT);
    static_assert(ut_is_2pow(ALIGNMENT), "ALIGNMENT must be a power of 2");
    UT_LIST_ADD_FIRST(blocks, block);
    MEM_MAKE_ADDRESSABLE(block->page.frame, size);
    MEM_NOACCESS(block->page.frame + size, srv_page_size - size);
    buf= block->page.frame;
  }
  else
  {
    size_t free_offset= block->page.free_offset;
    ut_ad(!ut_2pow_remainder(free_offset, ALIGNMENT));
    if (UNIV_UNLIKELY(!free_offset))
    {
      ut_ad(srv_page_size == 65536);
      goto create_block;
    }
    ut_ad(free_offset <= srv_page_size);
    free_offset+= size;

    if (free_offset > srv_page_size)
      goto create_block;

    block->page.used_records++;
    block->page.free_offset=
      ut_calc_align<uint16_t>(static_cast<uint16_t>(free_offset), ALIGNMENT);
    MEM_MAKE_ADDRESSABLE(block->page.frame + free_offset - size, size);
    buf= block->page.frame + free_offset - size;
  }

  recs.log.append(new (my_assume_aligned<ALIGNMENT>(buf))
                  log_phys_t{start_lsn, lsn, l, len});
  return false;
}

/** Store/remove the freed pages in fil_name_t of recv_spaces.
@param[in]	page_id		freed or init page_id
@param[in]	freed		TRUE if page is freed */
static void store_freed_or_init_rec(page_id_t page_id, bool freed)
{
  uint32_t space_id= page_id.space();
  uint32_t page_no= page_id.page_no();
  if (space_id == TRX_SYS_SPACE || srv_is_undo_tablespace(space_id))
  {
    if (srv_immediate_scrub_data_uncompressed)
      fil_space_get(space_id)->free_page(page_no, freed);
    return;
  }

  recv_spaces_t::iterator i= recv_spaces.lower_bound(space_id);
  if (i != recv_spaces.end() && i->first == space_id)
  {
    if (freed)
      i->second.add_freed_page(page_no);
    else
      i->second.remove_freed_page(page_no);
  }
}

/** Wrapper for log_sys.buf[] between recv_sys.offset and recv_sys.len */
struct recv_buf
{
  bool is_mmap() const noexcept { return log_sys.is_mmap(); }

  const byte *ptr;

  constexpr recv_buf(const byte *ptr) : ptr(ptr) {}
  constexpr bool operator==(const recv_buf other) const
  { return ptr == other.ptr; }

  static const byte *end() { return &log_sys.buf[recv_sys.len]; }

  const char *get_filename(byte*, size_t) const noexcept
  { return reinterpret_cast<const char*>(ptr); }

  bool is_eof(size_t len= 0) const noexcept { return ptr + len >= end(); }

  byte operator*() const noexcept
  {
    ut_ad(ptr >= log_sys.buf);
    ut_ad(ptr < end());
    return *ptr;
  }
  byte operator[](size_t size) const noexcept { return *(*this + size); }
  recv_buf operator+(size_t len) const noexcept
  { recv_buf r{*this}; return r+= len; }
  recv_buf &operator++() noexcept { return *this+= 1; }
  recv_buf &operator+=(size_t len) noexcept { ptr+= len; return *this; }

  size_t operator-(const recv_buf start) const noexcept
  {
    ut_ad(ptr >= start.ptr);
    return size_t(ptr - start.ptr);
  }

  uint32_t crc32c(const recv_buf start) const noexcept
  {
    return my_crc32c(0, start.ptr, ptr - start.ptr);
  }

  void *memcpy(void *buf, size_t size) const noexcept
  {
    ut_ad(size);
    ut_ad(!is_eof(size - 1));
    return ::memcpy(buf, ptr, size);
  }

  bool is_zero(size_t size) const noexcept
  {
    ut_ad(!is_eof(size));
    return !memcmp(ptr, field_ref_zero, size);
  }

  uint64_t read8() const noexcept
  { ut_ad(!is_eof(7)); return mach_read_from_8(ptr); }
  uint32_t read4() const noexcept
  { ut_ad(!is_eof(3)); return mach_read_from_4(ptr); }

  /** Update the pointer if the new pointer is within the buffer. */
  bool set_if_contains(const byte *pos) noexcept
  {
    if (pos > end() || pos < ptr)
      return false;
    ptr= pos;
    return true;
  }

  /** Get the contiguous, unencrypted buffer.
  @param buf         return value of copy_if_needed()
  @param start       start of the mini-transaction
  @param decrypt_buf possibly, a copy of the mini-transaction
  @return contiguous, non-encrypted buffer */
  const byte *get_buf(const byte *buf, const recv_buf start,
                      const byte *decrypt_buf) const noexcept
  { return ptr == buf ? start.ptr : decrypt_buf; }

  /** Copy and decrypt a log record if needed.
  @param iv    initialization vector
  @param tmp   buffer for the decrypted log record
  @param start un-encrypted start of the log record
  @param len   length of the possibly encrypted part, in bytes */
  const byte *copy_if_needed(const byte *iv, byte *tmp, recv_buf start,
                             size_t len)
  {
    ut_ad(*this - start + len <= srv_page_size);
    if (!len || !log_sys.is_encrypted())
      return ptr;
    const size_t s(*this - start);
    start.memcpy(tmp, s);
    return log_decrypt_buf(iv, tmp + s, ptr, static_cast<uint>(len));
  }
};

/** Ring buffer wrapper for log_sys.buf[]; recv_sys.len == log_sys.file_size */
struct recv_ring : public recv_buf
{
  static constexpr bool is_mmap() { return true; }

  constexpr recv_ring(const byte *ptr) : recv_buf(ptr) {}

  constexpr static bool is_eof() { return false; }
  constexpr static bool is_eof(size_t) { return false; }

  byte operator*() const noexcept
  {
    ut_ad(ptr >= &log_sys.buf[log_sys.START_OFFSET]);
    ut_ad(ptr < end());
    return *ptr;
  }
  byte operator[](size_t size) const noexcept { return *(*this + size); }
  recv_ring operator+(size_t len) const noexcept
  { recv_ring r{*this}; return r+= len; }
  recv_ring &operator++() noexcept { return *this+= 1; }
  recv_ring &operator+=(size_t len) noexcept
  {
    ut_ad(ptr < end());
    ut_ad(ptr >= &log_sys.buf[log_sys.START_OFFSET]);
    ut_ad(len < recv_sys.MTR_SIZE_MAX * 2);
    ptr+= len;
    if (ptr >= end())
    {
      ptr-= recv_sys.len - log_sys.START_OFFSET;
      ut_ad(ptr >= &log_sys.buf[log_sys.START_OFFSET]);
      ut_ad(ptr < end());
    }
    return *this;
  }
  size_t operator-(const recv_ring start) const noexcept
  {
    auto s= ptr - start.ptr;
    return s >= 0
      ? size_t(s)
      : size_t(s + recv_sys.len - log_sys.START_OFFSET);
  }

  uint32_t crc32c(const recv_ring start) const noexcept
  {
    return ptr >= start.ptr
      ? my_crc32c(0, start.ptr, ptr - start.ptr)
      : my_crc32c(my_crc32c(0, start.ptr, end() - start.ptr),
                  &log_sys.buf[log_sys.START_OFFSET],
                  ptr - &log_sys.buf[log_sys.START_OFFSET]);
  }

  void *memcpy(void *buf, size_t size) const noexcept
  {
    ut_ad(size);
    ut_ad(size < srv_page_size);

    auto s= ptr + size - end();
    if (s <= 0)
      return ::memcpy(buf, ptr, size);
    ::memcpy(buf, ptr, size - s);
    ::memcpy(static_cast<byte*>(buf) + size - s,
             &log_sys.buf[log_sys.START_OFFSET], s);
    return buf;
  }

  bool is_zero(size_t size) const noexcept
  {
    auto s= ptr + size - end();
    if (s <= 0)
      return !memcmp(ptr, field_ref_zero, size);
    return !memcmp(ptr, field_ref_zero, size - s) &&
      !memcmp(&log_sys.buf[log_sys.START_OFFSET], field_ref_zero, s);
  }

  uint64_t read8() const noexcept
  {
    if (UNIV_LIKELY(ptr + 8 <= end()))
      return mach_read_from_8(ptr);
    byte b[8];
    return mach_read_from_8(static_cast<const byte*>(memcpy(b, 8)));
  }
  uint32_t read4() const noexcept
  {
    if (UNIV_LIKELY(ptr + 4 <= end()))
      return mach_read_from_4(ptr);
    byte b[4];
    return mach_read_from_4(static_cast<const byte*>(memcpy(b, 4)));
  }

  /** Get the contiguous, unencrypted buffer.
  @param buf         return value of copy_if_needed()
  @param start       start of the mini-transaction
  @param decrypt_buf possibly, a copy of the mini-transaction
  @return contiguous, non-encrypted buffer */
  const byte *get_buf(const byte *buf, const recv_ring start,
                      const byte *decrypt_buf) const noexcept
  { return ptr == buf && start.ptr < ptr ? start.ptr : decrypt_buf; }

  const char *get_filename(byte* buf, size_t rlen) const noexcept
  {
    return UNIV_LIKELY(ptr + rlen <= end())
      ? reinterpret_cast<const char*>(ptr)
      : static_cast<const char*>(memcpy(buf, rlen));
  }

  /** Copy and decrypt a log record if needed.
  @param iv    initialization vector
  @param tmp   buffer for the decrypted log record
  @param start un-encrypted start of the log record
  @param len   length of the possibly encrypted part, in bytes */
  const byte *copy_if_needed(const byte *iv, byte *tmp, recv_ring start,
                             size_t len)
  {
    const size_t s(*this - start);
    ut_ad(s + len <= srv_page_size);
    if (!len || !log_sys.is_encrypted())
    {
      if (start.ptr + s == ptr && ptr + len <= end())
        return ptr;
      start.memcpy(tmp, s + len);
      return tmp + s;
    }

    start.memcpy(tmp, s);

    const byte *b= ptr;
    if (ptr + len > end())
      b= static_cast<byte*>(memcpy(alloca(len), len));
    return log_decrypt_buf(iv, tmp + s, b, static_cast<uint>(len));
  }
};

template<typename source>
void recv_sys_t::rewind(source &l, source &begin) noexcept
{
  ut_ad(srv_operation != SRV_OPERATION_BACKUP);
  mysql_mutex_assert_owner(&mutex);

  const source end= l;
  uint32_t rlen;
  for (l= begin; !(l == end); l+= rlen)
  {
    const source recs{l};
    ++l;
    const byte b= *recs;

    ut_ad(b > 1);
    ut_ad(UNIV_LIKELY((b & 0x70) != RESERVED) || srv_force_recovery);

    rlen= b & 0xf;
    if (!rlen)
    {
      const uint32_t lenlen= mlog_decode_varint_length(*l);
      const uint32_t addlen= mlog_decode_varint(l);
      ut_ad(addlen != MLOG_DECODE_ERROR);
      rlen= addlen + 15 - lenlen;
      l+= lenlen;
    }
    ut_ad(!l.is_eof(rlen));
    if (b & 0x80)
      continue;

    uint32_t idlen= mlog_decode_varint_length(*l);
    if (UNIV_UNLIKELY(idlen > 5 || idlen >= rlen))
      continue;
    const uint32_t space_id= mlog_decode_varint(l);
    if (UNIV_UNLIKELY(space_id == MLOG_DECODE_ERROR))
      continue;
    l+= idlen;
    rlen-= idlen;
    idlen= mlog_decode_varint_length(*l);
    if (UNIV_UNLIKELY(idlen > 5 || idlen > rlen))
      continue;
    const uint32_t page_no= mlog_decode_varint(l);
    if (UNIV_UNLIKELY(page_no == MLOG_DECODE_ERROR))
      continue;
    const page_id_t id{space_id, page_no};
    if (pages_it == pages.end() || pages_it->first != id)
    {
      pages_it= pages.find(id);
      if (pages_it == pages.end())
        continue;
    }

    ut_ad(!pages_it->second.being_processed);
    const log_phys_t *head=
      static_cast<log_phys_t*>(*pages_it->second.log.begin());
    if (!head || head->start_lsn == lsn)
    {
      erase(pages_it);
      pages_it= pages.end();
    }
    else
      pages_it->second.log.rewind(lsn);
  }

  l= begin;
  pages_it= pages.end();
}

/** Parse and register one log_t::FORMAT_10_8 mini-transaction.
@tparam storing   whether to store the records
@param  l         log data source
@param  if_exists if store: whether to check if the tablespace exists */
template<typename source,recv_sys_t::store storing>
inline
recv_sys_t::parse_mtr_result recv_sys_t::parse(source &l, bool if_exists)
  noexcept
{
restart:
  ut_ad(storing == BACKUP || log_sys.latch_have_wr());
  ut_ad(storing == BACKUP || !undo_space_trunc);
  ut_ad(storing == BACKUP || !log_file_op);
  ut_ad(storing == YES || !if_exists);
  ut_ad((storing == BACKUP) ==
        (srv_operation == SRV_OPERATION_BACKUP ||
         srv_operation == SRV_OPERATION_BACKUP_NO_DEFER));
  mysql_mutex_assert_owner(&mutex);
  ut_ad(log_sys.next_checkpoint_lsn);
  ut_ad(log_sys.is_latest());

  alignas(8) byte iv[MY_AES_BLOCK_SIZE];
  byte *decrypt_buf=
    static_cast<byte*>(alloca(storing == BACKUP
                              ? 1/*type,length*/ + 5/*space_id*/ +
                              5/*page_no*/ + 1/*rlen*/
                              : srv_page_size));
  const lsn_t start_lsn{lsn};

  /* Check that the entire mini-transaction is included within the buffer */
  if (l.is_eof(0))
    return PREMATURE_EOF;

  if (*l <= 1)
    return GOT_EOF; /* We should never write an empty mini-transaction. */

  source begin{l};
  uint32_t rlen;
  for (uint32_t total_len= 0; !l.is_eof(); l+= rlen, total_len+= rlen)
  {
    if (total_len >= MTR_SIZE_MAX)
      return GOT_EOF;
    if (*l <= 1)
      goto eom_found;
    rlen= *l & 0xf;
    ++l;
    if (!rlen)
    {
      if (l.is_eof(0))
        break;
      rlen= mlog_decode_varint_length(*l);
      if (l.is_eof(rlen))
        break;
      const uint32_t addlen= mlog_decode_varint(l);
      if (UNIV_UNLIKELY(addlen >= MTR_SIZE_MAX))
        return GOT_EOF;
      rlen= addlen + 15;
    }
  }

  /* Not the entire mini-transaction was present. */
  return PREMATURE_EOF;

 eom_found:
  if (*l != log_sys.get_sequence_bit((l - begin) + lsn))
    return GOT_EOF;

  if (l.is_eof(4))
    return PREMATURE_EOF;

  uint32_t crc{l.crc32c(begin)};

  if (log_sys.is_encrypted())
  {
    if (l.is_eof(8 + 4))
      return PREMATURE_EOF;
    (l + 1).memcpy(iv, 8);
    l+= 8;
    crc= my_crc32c(crc, iv, 8);
  }

  if (storing == BACKUP)
    DBUG_EXECUTE_IF("log_intermittent_checksum_mismatch",
                    {
                      static int c;
                      if (!c++)
                      {
                        sql_print_information("Invalid log block checksum");
                        return GOT_EOF;
                      }
                    });

  if (crc != (l + 1).read4())
    return GOT_EOF;

  l+= 5;
  ut_d(const source el{l});
  lsn+= l - begin;
  offset= l.ptr - log_sys.buf;
  if (!l.is_mmap());
  else if (offset == log_sys.file_size)
    offset= log_sys.START_OFFSET;
  else
    ut_ad(offset < log_sys.file_size);

  ut_d(std::set<page_id_t> freed);
#if 0 && defined UNIV_DEBUG /* MDEV-21727 FIXME: enable this */
  /* Pages that have been modified in this mini-transaction.
  If a mini-transaction writes INIT_PAGE for a page, it should not have
  written any log records for the page. Unfortunately, this does not
  hold for ROW_FORMAT=COMPRESSED pages, because page_zip_compress()
  can be invoked in a pessimistic operation, even after log has
  been written for other pages. */
  ut_d(std::set<page_id_t> modified);
#endif

  uint32_t space_id= 0, page_no= 0;
  /* The end offset the last write (always 0 in storing==BACKUP).
  The value 1 means that no "same page" record is allowed. */
  uint last_offset= 0;
  bool got_page_op= false;

  for (l= begin;; l+= rlen)
  {
    const source recs{l};
    ++l;
    const byte b= *recs;

    if (b <= 1)
      break;

    if (UNIV_LIKELY((b & 0x70) != RESERVED));
    else if (srv_force_recovery)
      sql_print_warning("InnoDB: Ignoring unknown log record at LSN " LSN_PF,
                        lsn);
    else
    {
      sql_print_error("InnoDB: Unknown log record at LSN " LSN_PF, lsn);
    corrupted:
      found_corrupt_log= true;
      return GOT_EOF;
    }

    rlen= b & 0xf;
    if (!rlen)
    {
      const uint32_t lenlen= mlog_decode_varint_length(*l);
      const uint32_t addlen= mlog_decode_varint(l);
      ut_ad(addlen != MLOG_DECODE_ERROR);
      rlen= addlen + 15 - lenlen;
      l+= lenlen;
    }
    ut_ad(!l.is_eof(rlen));

    uint32_t idlen;
    if ((b & 0x80) && got_page_op)
    {
      /* This record is for the same page as the previous one. */
      if (UNIV_UNLIKELY((b & 0x70) <= INIT_PAGE))
      {
      record_corrupted:
        /* FREE_PAGE,INIT_PAGE cannot be with same_page flag */
        if (!srv_force_recovery)
        {
        malformed:
          sql_print_error("InnoDB: Malformed log record at LSN " LSN_PF
                          "; set innodb_force_recovery=1 to ignore.", lsn);
          goto corrupted;
        }
        sql_print_warning("InnoDB: Ignoring malformed log record at LSN "
                          LSN_PF, lsn);
        /* the next record must not be same_page */
        if (storing != BACKUP) last_offset= 1;
        continue;
      }
      if (srv_operation == SRV_OPERATION_BACKUP)
        continue;
      DBUG_PRINT("ib_log",
                 ("scan " LSN_PF ": rec %x len %zu page %u:%u",
                  lsn, b, l - recs + rlen, space_id, page_no));
      goto same_page;
    }
    if (storing != BACKUP) last_offset= 0;
    idlen= mlog_decode_varint_length(*l);
    if (UNIV_UNLIKELY(idlen > 5 || idlen >= rlen))
    {
      if (!*l && b == FILE_CHECKPOINT + 1)
        continue;
    page_id_corrupted:
      if (!srv_force_recovery)
      {
        sql_print_error("InnoDB: Corrupted page identifier at " LSN_PF
                        "; set innodb_force_recovery=1 to ignore the record.",
                        lsn);
        goto corrupted;
      }
      sql_print_warning("InnoDB: Ignoring corrupted page identifier at LSN "
                        LSN_PF, lsn);
      continue;
    }
    space_id= mlog_decode_varint(l);
    if (UNIV_UNLIKELY(space_id == MLOG_DECODE_ERROR))
      goto page_id_corrupted;
    l+= idlen;
    rlen-= idlen;
    idlen= mlog_decode_varint_length(*l);
    if (UNIV_UNLIKELY(idlen > 5 || idlen > rlen))
      goto page_id_corrupted;
    page_no= mlog_decode_varint(l);
    if (UNIV_UNLIKELY(page_no == MLOG_DECODE_ERROR))
      goto page_id_corrupted;
    l+= idlen;
    rlen-= idlen;
    if (storing != BACKUP)
    {
      mach_write_to_4(iv + 8, space_id);
      mach_write_to_4(iv + 12, page_no);
    }
    DBUG_PRINT("ib_log",
               ("scan " LSN_PF ": rec %x len %zu page %u:%u",
                lsn, b, l - recs + rlen, space_id, page_no));
    got_page_op= !(b & 0x80);
    if (got_page_op)
    {
      if (storing == BACKUP)
      {
        if (page_no == 0 && (b & 0xf0) == INIT_PAGE && first_page_init)
          first_page_init(space_id);
        else if (rlen == 1 && undo_space_trunc)
        {
          mach_write_to_4(iv + 8, space_id);
          mach_write_to_4(iv + 12, page_no);
          if (*l.copy_if_needed(iv, decrypt_buf, recs, 1) == TRIM_PAGES)
            undo_space_trunc(space_id);
        }
        continue;
      }
      if (storing == YES && UNIV_LIKELY(space_id != TRX_SYS_SPACE) &&
          !srv_is_undo_tablespace(space_id))
      {
        ut_ad(file_checkpoint != 0);
        recv_spaces_t::iterator i= recv_spaces.lower_bound(space_id);
        if (i != recv_spaces.end() && i->first == space_id);
        else if (lsn < file_checkpoint)
          /* We have not seen all records between the checkpoint and
          FILE_CHECKPOINT. There should be a FILE_DELETE for this
          tablespace later. */
          recv_spaces.emplace_hint(i, space_id, file_name_t("", false));
        else
        {
          if (!srv_force_recovery)
          {
            sql_print_error("InnoDB: Missing FILE_DELETE or FILE_MODIFY for "
                            "[page id: space=" UINT32PF
                            ", page number=" UINT32PF "]"
                            " at " LSN_PF
                            "; set innodb_force_recovery=1 to"
                            " ignore the record.",
                            space_id, page_no, lsn);
            goto corrupted;
          }
          sql_print_warning("InnoDB: Ignoring record for "
                            "[page id: space=" UINT32PF
                            ", page number=" UINT32PF "] at " LSN_PF,
                            space_id, page_no, lsn);
          continue;
        }
      }
    same_page:
      if (!rlen);
      else if (UNIV_UNLIKELY(l - recs + rlen > srv_page_size))
        goto record_corrupted;
      const page_id_t id{space_id, page_no};
      ut_d(if ((b & 0x70) == INIT_PAGE || (b & 0x70) == OPTION)
             freed.erase(id));
      ut_ad(freed.find(id) == freed.end());
      const byte *cl= nullptr; /* avoid bogus -Wmaybe-uninitialized */
      switch (b & 0x70) {
      case FREE_PAGE:
        ut_ad(freed.emplace(id).second);
        /* the next record must not be same_page */
        if (storing != BACKUP) last_offset= 1;
        goto free_or_init_page;
      case INIT_PAGE:
        if (storing != BACKUP) last_offset= FIL_PAGE_TYPE;
      free_or_init_page:
        if (UNIV_UNLIKELY(rlen != 0))
          goto record_corrupted;
        store_freed_or_init_rec(id, (b & 0x70) == FREE_PAGE);

        if (storing == NO)
        {
          /* We must update mlog_init for the correct operation of
          multi-batch recovery, for example to avoid occasional
          failures of the test innodb.recovery_memory.

          For storing == YES, this will be invoked in recv_sys_t::add(). */
          mlog_init.add(id, start_lsn);

          /* recv_scan_log() may have stored some log for this page
          before entering the skip_the_rest: loop. Such records must
          be discarded, because reading an INIT_PAGE or FREE_PAGE
          record implies that the page can be recovered based on log
          records, without reading it from a data file. */

          if (pages_it == pages.end() || pages_it->first != id)
          {
            pages_it= pages.find(id);
            if (pages_it == pages.end())
              continue;
          }
          map::iterator r= pages_it++;
          ut_ad(!r->second.being_processed);
          erase(r);
          continue;
        }
        if (storing == YES)
          cl= l.copy_if_needed(iv, decrypt_buf, recs, rlen);
        break;
      case EXTENDED:
        if (storing == NO)
          /* We really only care about WRITE records to page 0, to
          invoke fil_space_set_recv_size_and_flags().  As of now, the
          EXTENDED records refer to index or undo log pages (which
          page 0 never can be), or we have the TRIM_PAGES subtype for
          shrinking a tablespace, to a larger number of pages than 0.
          Either way, we can ignore this record during the preparation
          for multi-batch recovery. */
          continue;
        if (UNIV_UNLIKELY(!rlen))
          goto record_corrupted;
        if (storing == YES || rlen == 1)
          cl= l.copy_if_needed(iv, decrypt_buf, recs, rlen);
        if (rlen == 1 && *cl == TRIM_PAGES)
        {
          if (!srv_is_undo_tablespace(space_id) ||
              page_no != SRV_UNDO_TABLESPACE_SIZE_IN_PAGES)
            goto record_corrupted;
          static_assert(UT_ARR_SIZE(truncated_undo_spaces) ==
                        TRX_SYS_MAX_UNDO_SPACES, "compatibility");
          /* The entire undo tablespace will be reinitialized by
          innodb_undo_log_truncate=ON. Discard old log for all pages. */
          trim({space_id, 0}, start_lsn);
          truncated_undo_spaces[space_id - srv_undo_space_id_start]=
            { start_lsn, page_no };
          /* the next record must not be same_page */
          if (storing != BACKUP) last_offset= 1;
          if (undo_space_trunc)
            undo_space_trunc(space_id);
          continue;
        }
        /* This record applies to an undo log or index page, and it
        may be followed by subsequent WRITE or similar records for the
        same page in the same mini-transaction. */
        if (storing != BACKUP) last_offset= FIL_PAGE_TYPE;
        break;
      case OPTION:
        /* OPTION records can be safely ignored in recovery */
        if (storing == YES &&
            rlen == 5/* OPT_PAGE_CHECKSUM and CRC-32C; see page_checksum() */)
        {
          cl= l.copy_if_needed(iv, decrypt_buf, recs, rlen);
          if (*cl == OPT_PAGE_CHECKSUM)
            break;
        }
        /* fall through */
      case RESERVED:
        continue;
      case WRITE:
      case MEMMOVE:
      case MEMSET:
        if (storing == BACKUP)
          continue;
        if (storing == NO && UNIV_LIKELY(page_no != 0))
          /* fil_space_set_recv_size_and_flags() is mandatory for storing==NO.
          It is only applicable to page_no == 0. Other than that, we can just
          ignore the payload and only compute the mini-transaction checksum;
          there will be a subsequent call with storing==YES. */
          continue;
        if (UNIV_UNLIKELY(rlen == 0 || last_offset == 1))
          goto record_corrupted;
        ut_d(const source payload{l});
        cl= l.copy_if_needed(iv, decrypt_buf, recs, rlen);
        const uint32_t olen= mlog_decode_varint_length(*cl);
        if (UNIV_UNLIKELY(olen >= rlen) || UNIV_UNLIKELY(olen > 3))
          goto record_corrupted;
        const uint32_t offset= mlog_decode_varint(cl);
        ut_ad(offset != MLOG_DECODE_ERROR);
        static_assert(FIL_PAGE_OFFSET == 4, "compatibility");
        if (UNIV_UNLIKELY(offset >= srv_page_size))
          goto record_corrupted;
        last_offset+= offset;
        if (UNIV_UNLIKELY(last_offset < 8 || last_offset >= srv_page_size))
          goto record_corrupted;
        cl+= olen;
        rlen-= olen;
        if ((b & 0x70) == WRITE)
        {
          if (UNIV_UNLIKELY(rlen + last_offset > srv_page_size))
            goto record_corrupted;
          if (UNIV_UNLIKELY(!page_no) && file_checkpoint)
          {
            const bool has_size= last_offset <= FSP_HEADER_OFFSET + FSP_SIZE &&
              last_offset + rlen >= FSP_HEADER_OFFSET + FSP_SIZE + 4;
            const bool has_flags= last_offset <=
              FSP_HEADER_OFFSET + FSP_SPACE_FLAGS &&
              last_offset + rlen >= FSP_HEADER_OFFSET + FSP_SPACE_FLAGS + 4;
            if (has_size || has_flags)
            {
              recv_spaces_t::iterator it= recv_spaces.find(space_id);
              const uint32_t size= has_size
                ? mach_read_from_4(FSP_HEADER_OFFSET + FSP_SIZE + cl -
                                   last_offset)
                : 0;
              const uint32_t flags= has_flags
                ? mach_read_from_4(FSP_HEADER_OFFSET + FSP_SPACE_FLAGS + cl -
                                   last_offset)
                : file_name_t::initial_flags;
              if (it == recv_spaces.end())
                ut_ad(storing == NO || space_id == TRX_SYS_SPACE ||
                      srv_is_undo_tablespace(space_id));
              else if (!it->second.space)
              {
                if (has_size)
                  it->second.size= size;
                if (has_flags)
                  it->second.flags= flags;
              }
              fil_space_set_recv_size_and_flags(space_id, size, flags);
            }
          }
        parsed_ok:
          last_offset+= rlen;
          ut_ad(l == payload);
          if (!l.set_if_contains(cl))
            (l= recs)+= cl - decrypt_buf;
          break;
        }
        uint32_t llen= mlog_decode_varint_length(*cl);
        if (UNIV_UNLIKELY(llen > rlen || llen > 3))
          goto record_corrupted;
        const uint32_t len= mlog_decode_varint(cl);
        ut_ad(len != MLOG_DECODE_ERROR);
        if (UNIV_UNLIKELY(last_offset + len > srv_page_size))
          goto record_corrupted;
        cl+= llen;
        rlen-= llen;
        llen= len;
        if ((b & 0x70) == MEMSET)
        {
          if (UNIV_UNLIKELY(rlen > llen))
            goto record_corrupted;
          goto parsed_ok;
        }
        const uint32_t slen= mlog_decode_varint_length(*cl);
        if (UNIV_UNLIKELY(slen != rlen || slen > 3))
          goto record_corrupted;
        uint32_t s= mlog_decode_varint(cl);
        ut_ad(slen != MLOG_DECODE_ERROR);
        if (s & 1)
          s= last_offset - (s >> 1) - 1;
        else
          s= last_offset + (s >> 1) + 1;
        if (UNIV_UNLIKELY(s < 8 || s + llen > srv_page_size))
          goto record_corrupted;
        goto parsed_ok;
      }
#if 0 && defined UNIV_DEBUG
      switch (b & 0x70) {
      case RESERVED:
        ut_ad(0); /* we did "continue" earlier */
        break;
      case OPTION:
      case FREE_PAGE:
        break;
      default:
        ut_ad(modified.emplace(id).second || (b & 0x70) != INIT_PAGE);
      }
#endif
      if (storing == YES)
      {
        if (if_exists)
        {
          if (fil_space_t *space= fil_space_t::get(space_id))
          {
            const auto size= space->get_size();
            space->release();
            if (!size)
              continue;
          }
          else if (!deferred_spaces.find(space_id))
            continue;
        }
        if (!mlog_init.will_avoid_read(id, start_lsn))
        {
          if (pages_it == pages.end() || pages_it->first != id)
            pages_it= pages.emplace(id, page_recv_t{}).first;
          if (UNIV_UNLIKELY(add(pages_it, start_lsn, lsn,
                                l.get_buf(cl, recs, decrypt_buf),
                                l - recs + rlen)))
          {
            lsn= start_lsn;
            if (lsn > log_sys.get_lsn())
              log_sys.set_recovered_lsn(start_lsn);
            l+= rlen;
            offset= begin.ptr - log_sys.buf;
            rewind(l, begin);
            if (if_exists)
            {
              apply(false);
              if (is_corrupt_fs())
                return GOT_EOF;
              goto restart;
            }
            sql_print_information("InnoDB: Multi-batch recovery needed at LSN "
                                  LSN_PF, start_lsn);
            return GOT_OOM;
          }
        }
      }
    }
    else if (rlen)
    {
      switch (b & 0xf0) {
      case FILE_CHECKPOINT:
        if (space_id || page_no || l[rlen] > 1);
        else if (rlen != 8)
        {
          if (rlen < UNIV_PAGE_SIZE_MAX && !l.is_zero(rlen))
            continue;
        }
        else if (storing == YES)
        {
          ut_ad(file_checkpoint);
          continue;
        }
        else if (const lsn_t c= l.read8())
        {
          if (UNIV_UNLIKELY(srv_print_verbose_log == 2))
            fprintf(stderr, "FILE_CHECKPOINT(" LSN_PF ") %s at " LSN_PF "\n",
                    c, c != log_sys.next_checkpoint_lsn
                    ? "ignored" : file_checkpoint ? "reread" : "read", lsn);

          DBUG_PRINT("ib_log",
                     ("FILE_CHECKPOINT(" LSN_PF ") %s at " LSN_PF,
                      c, c != log_sys.next_checkpoint_lsn
                      ? "ignored" : file_checkpoint ? "reread" : "read", lsn));

          if (c == log_sys.next_checkpoint_lsn)
          {
            /* There can be multiple FILE_CHECKPOINT for the same LSN. */
            if (file_checkpoint)
              continue;
            file_checkpoint= lsn;
            return GOT_EOF;
          }
          continue;
        }
        else
          continue;
        /* fall through */
      default:
        if (!srv_force_recovery)
          goto malformed;
        sql_print_warning("InnoDB: Ignoring malformed log record at LSN "
                          LSN_PF, lsn);
        continue;
      case FILE_DELETE:
      case FILE_MODIFY:
      case FILE_RENAME:
        if (UNIV_UNLIKELY(page_no != 0))
        {
        file_rec_error:
          if (!srv_force_recovery)
          {
            sql_print_error("InnoDB: Corrupted file-level record;"
                            " set innodb_force_recovery=1 to ignore.");
            goto corrupted;
          }

          sql_print_warning("InnoDB: Ignoring corrupted file-level record"
                            " at LSN " LSN_PF, lsn);
          continue;
        }
        /* fall through */
      case FILE_CREATE:
        if (UNIV_UNLIKELY(!space_id || page_no))
          goto file_rec_error;
        /* There is no terminating NUL character. Names must end in .ibd.
        For FILE_RENAME, there is a NUL between the two file names. */

        const char * const fn= l.get_filename(decrypt_buf, rlen);
        const char *fn2= static_cast<const char*>(memchr(fn, 0, rlen));

        if (UNIV_UNLIKELY((fn2 == nullptr) == ((b & 0xf0) == FILE_RENAME)))
          goto file_rec_error;

        const char * const fnend= fn2 ? fn2 : fn + rlen;
        const char * const fn2end= fn2 ? fn + rlen : nullptr;

        if (fn2)
        {
          fn2++;
          if (memchr(fn2, 0, fn2end - fn2))
            goto file_rec_error;
          if (fn2end - fn2 < 4 || memcmp(fn2end - 4, DOT_IBD, 4))
            goto file_rec_error;
        }

        if (space_id == TRX_SYS_SPACE || srv_is_undo_tablespace(space_id))
          goto file_rec_error;
        if (fnend - fn < 4 || memcmp(fnend - 4, DOT_IBD, 4))
          goto file_rec_error;

        if (UNIV_UNLIKELY(!recv_needed_recovery && srv_read_only_mode))
          continue;

        if (storing == BACKUP)
        {
          if ((b & 0xf0) < FILE_CHECKPOINT && log_file_op)
            log_file_op(space_id, b & 0xf0,
                        reinterpret_cast<const byte*>(fn),
                        static_cast<ulint>(fnend - fn),
                        reinterpret_cast<const byte*>(fn2),
                        fn2 ? static_cast<ulint>(fn2end - fn2) : 0);
          continue;
        }

        fil_name_process(fn, fnend - fn, space_id,
                         (b & 0xf0) == FILE_DELETE ? FILE_DELETE : FILE_MODIFY,
                         start_lsn, if_exists);

        if (fn2)
        {
          fil_name_process(fn2, fn2end - fn2, space_id,
                           FILE_RENAME, start_lsn, if_exists);
          if (file_checkpoint)
          {
            const size_t len= fn2end - fn2;
            auto r= renamed_spaces.emplace(space_id, std::string{fn2, len});
            if (!r.second)
              r.first->second= std::string{fn2, len};
          }
        }

        if (is_corrupt_fs())
          return GOT_EOF;
      }
    }
    else if (b == FILE_CHECKPOINT + 2 && !space_id && !page_no);
    else
      goto malformed;
  }

  l+= log_sys.is_encrypted() ? 4U + 8U : 4U;
  ut_ad(l == el);
  return OK;
}

template<recv_sys_t::store storing>
recv_sys_t::parse_mtr_result recv_sys_t::parse_mtr(bool if_exists) noexcept
{
  recv_buf s{&log_sys.buf[recv_sys.offset]};
  return recv_sys.parse<recv_buf,storing>(s, if_exists);
}

/** for mariadb-backup; @see xtrabackup_copy_logfile() */
template
recv_sys_t::parse_mtr_result
recv_sys_t::parse_mtr<recv_sys_t::store::BACKUP>(bool) noexcept;

template<recv_sys_t::store storing>
recv_sys_t::parse_mtr_result recv_sys_t::parse_mmap(bool if_exists) noexcept
{
  recv_sys_t::parse_mtr_result r{parse_mtr<storing>(if_exists)};
  if (UNIV_LIKELY(r != PREMATURE_EOF) || !log_sys.is_mmap())
    return r;
  ut_ad(recv_sys.len == log_sys.file_size);
  ut_ad(recv_sys.offset >= log_sys.START_OFFSET);
  ut_ad(recv_sys.offset <= recv_sys.len);
  recv_ring s
    {recv_sys.offset == recv_sys.len
     ? &log_sys.buf[log_sys.START_OFFSET]
     : &log_sys.buf[recv_sys.offset]};
  return recv_sys.parse<recv_ring,storing>(s, if_exists);
}

/** for mariadb-backup; @see xtrabackup_copy_mmap_logfile() */
template
recv_sys_t::parse_mtr_result
recv_sys_t::parse_mmap<recv_sys_t::store::BACKUP>(bool) noexcept;

/** Apply the hashed log records to the page, if the page lsn is less than the
lsn of a log record.
@param[in,out]	block		buffer pool page
@param[in,out]	mtr		mini-transaction
@param[in,out]	recs		log records to apply
@param[in,out]	space		tablespace, or NULL if not looked up yet
@param[in,out]	init		page initialization operation, or NULL
@return the recovered page
@retval nullptr on failure */
static buf_block_t *recv_recover_page(buf_block_t *block, mtr_t &mtr,
                                      page_recv_t &recs,
                                      fil_space_t *space,
                                      recv_init *init)
{
	mysql_mutex_assert_not_owner(&recv_sys.mutex);
	ut_ad(recv_sys.apply_log_recs);
	ut_ad(recv_needed_recovery);
	ut_ad(!init || init->created);
	ut_ad(!init || init->lsn);
	ut_ad(recs.being_processed == 1);
	ut_ad(!space || space->id == block->page.id().space());
	ut_ad(log_sys.is_latest());

	if (UNIV_UNLIKELY(srv_print_verbose_log == 2)) {
		ib::info() << "Applying log to page " << block->page.id();
	}

	DBUG_PRINT("ib_log", ("Applying log to page %u:%u",
			      block->page.id().space(),
			      block->page.id().page_no()));

	byte *frame = UNIV_LIKELY_NULL(block->page.zip.data)
		? block->page.zip.data
		: block->page.frame;
	const lsn_t page_lsn = init
		? 0
		: mach_read_from_8(frame + FIL_PAGE_LSN);
	bool free_page = false;
	lsn_t start_lsn = 0, end_lsn = 0;
	ut_d(lsn_t recv_start_lsn = 0);
	const lsn_t init_lsn = init ? init->lsn : 0;

	bool skipped_after_init = false;

	for (const log_rec_t* recv : recs.log) {
		const log_phys_t* l = static_cast<const log_phys_t*>(recv);
		ut_ad(l->lsn);
		ut_ad(end_lsn <= l->lsn);
		ut_ad(l->lsn <= recv_sys.lsn);

		ut_ad(l->start_lsn);
		ut_ad(recv_start_lsn <= l->start_lsn);
		ut_d(recv_start_lsn = l->start_lsn);

		if (l->start_lsn < page_lsn) {
			/* This record has already been applied. */
			DBUG_PRINT("ib_log", ("apply skip %u:%u LSN " LSN_PF
					      " < " LSN_PF,
					      block->page.id().space(),
					      block->page.id().page_no(),
					      l->start_lsn, page_lsn));
			skipped_after_init = true;
			end_lsn = l->lsn;
			continue;
		}

		if (l->start_lsn < init_lsn) {
			DBUG_PRINT("ib_log", ("init skip %u:%u LSN " LSN_PF
					      " < " LSN_PF,
					      block->page.id().space(),
					      block->page.id().page_no(),
					      l->start_lsn, init_lsn));
			skipped_after_init = false;
			end_lsn = l->lsn;
			continue;
		}

		/* There is no need to check LSN for just initialized pages. */
		if (skipped_after_init) {
			skipped_after_init = false;
			ut_ad(end_lsn == page_lsn);
			if (end_lsn != page_lsn) {
				sql_print_information(
					"InnoDB: The last skipped log record"
					" LSN " LSN_PF
					" is not equal to page LSN " LSN_PF,
					end_lsn, page_lsn);
			}
		}

		end_lsn = l->lsn;

		if (UNIV_UNLIKELY(srv_print_verbose_log == 2)) {
			ib::info() << "apply " << l->start_lsn
				   << ": " << block->page.id();
		}

		DBUG_PRINT("ib_log", ("apply " LSN_PF ": %u:%u",
				      l->start_lsn,
				      block->page.id().space(),
				      block->page.id().page_no()));

		log_phys_t::apply_status a= l->apply(*block, recs.last_offset);

		switch (a) {
		case log_phys_t::APPLIED_NO:
			ut_ad(!mtr.has_modifications());
			free_page = true;
			start_lsn = 0;
			continue;
		case log_phys_t::APPLIED_YES:
		case log_phys_t::APPLIED_CORRUPTED:
			goto set_start_lsn;
		case log_phys_t::APPLIED_TO_FSP_HEADER:
		case log_phys_t::APPLIED_TO_ENCRYPTION:
			break;
		}

		if (fil_space_t* s = space
		    ? space
		    : fil_space_t::get(block->page.id().space())) {
			switch (a) {
			case log_phys_t::APPLIED_TO_FSP_HEADER:
				s->flags = mach_read_from_4(
					FSP_HEADER_OFFSET
					+ FSP_SPACE_FLAGS + frame);
				s->size_in_header = mach_read_from_4(
					FSP_HEADER_OFFSET + FSP_SIZE
					+ frame);
				s->free_limit = mach_read_from_4(
					FSP_HEADER_OFFSET
					+ FSP_FREE_LIMIT + frame);
				s->free_len = mach_read_from_4(
					FSP_HEADER_OFFSET + FSP_FREE
					+ FLST_LEN + frame);
				break;
			default:
				byte* b= frame
					+ fsp_header_get_encryption_offset(
						block->zip_size())
					+ FSP_HEADER_OFFSET;
				if (memcmp(b, CRYPT_MAGIC, MAGIC_SZ)) {
					break;
				}
				b += MAGIC_SZ;
				if (*b != CRYPT_SCHEME_UNENCRYPTED
				    && *b != CRYPT_SCHEME_1) {
					break;
				}
				if (b[1] != MY_AES_BLOCK_SIZE) {
					break;
				}
				if (b[2 + MY_AES_BLOCK_SIZE + 4 + 4]
				    > FIL_ENCRYPTION_OFF) {
					break;
				}
				fil_crypt_parse(s, b);
			}

			if (!space) {
				s->release();
			}
		}

set_start_lsn:
		if ((a == log_phys_t::APPLIED_CORRUPTED
		     || recv_sys.is_corrupt_log()) && !srv_force_recovery) {
			if (init) {
				init->created = false;
			}

			mtr.discard_modifications();
			mtr.commit();

			fil_space_t* s = space
				? space
				: fil_space_t::get(block->page.id().space());

			buf_pool.corrupted_evict(&block->page,
						 block->page.state() &
						 buf_page_t::LRU_MASK);
			if (!space) {
				s->release();
			}

			return nullptr;
		}

		if (!start_lsn) {
			start_lsn = l->start_lsn;
		}
	}

	if (start_lsn) {
		ut_ad(end_lsn >= start_lsn);
		ut_ad(!block->page.oldest_modification());
		mach_write_to_8(FIL_PAGE_LSN + frame, end_lsn);
		if (UNIV_LIKELY(!block->page.zip.data)) {
			mach_write_to_8(srv_page_size
					- FIL_PAGE_END_LSN_OLD_CHKSUM
					+ frame, end_lsn);
		} else {
			buf_zip_decompress(block, false);
		}
		/* The following is adapted from
		buf_pool_t::insert_into_flush_list() */
		mysql_mutex_lock(&buf_pool.flush_list_mutex);
		buf_pool.flush_list_bytes+= block->physical_size();
		block->page.set_oldest_modification(start_lsn);
		UT_LIST_ADD_FIRST(buf_pool.flush_list, &block->page);
		buf_pool.page_cleaner_wakeup();
		mysql_mutex_unlock(&buf_pool.flush_list_mutex);
	} else if (free_page && init) {
		/* There have been no operations that modify the page.
		Any buffered changes must not be merged. A subsequent
		buf_page_create() from a user thread should discard
		any buffered changes. */
		init->created = false;
		ut_ad(!mtr.has_modifications());
		block->page.set_freed(block->page.state());
	}

	/* Make sure that committing mtr does not change the modification
	lsn values of page */

	mtr.discard_modifications();
	mtr.commit();

	return block;
}

/** Remove records for a corrupted page.
@param page_id  corrupted page identifier
@param node     file for which an error is to be reported
@return whether an error message was reported */
ATTRIBUTE_COLD
bool recv_sys_t::free_corrupted_page(page_id_t page_id,
                                     const fil_node_t &node) noexcept
{
  if (!recovery_on)
    return false;

  mysql_mutex_lock(&mutex);
  map::iterator p= pages.find(page_id);
  if (p == pages.end())
  {
    mysql_mutex_unlock(&mutex);
    return false;
  }

  p->second.being_processed= -1;
  if (!srv_force_recovery)
    set_corrupt_fs();
  mysql_mutex_unlock(&mutex);

  (srv_force_recovery ? sql_print_warning : sql_print_error)
    ("InnoDB: Unable to apply log to corrupted page " UINT32PF
     " in file %s", page_id.page_no(), node.name);
  return true;
}

ATTRIBUTE_COLD void recv_sys_t::set_corrupt_log() noexcept
{
  mysql_mutex_lock(&mutex);
  found_corrupt_log= true;
  mysql_mutex_unlock(&mutex);
}

ATTRIBUTE_COLD void recv_sys_t::set_corrupt_fs() noexcept
{
  mysql_mutex_assert_owner(&mutex);
  if (!srv_force_recovery)
    sql_print_information("InnoDB: Set innodb_force_recovery=1"
                          " to ignore corrupted pages.");
  found_corrupt_fs= true;
}

/** Apply any buffered redo log to a page.
@param space     tablespace
@param bpage     buffer pool page
@return whether the page was recovered correctly */
bool recv_recover_page(fil_space_t* space, buf_page_t* bpage)
{
  mtr_t mtr;
  mtr.start();
  mtr.set_log_mode(MTR_LOG_NO_REDO);

  ut_ad(bpage->frame);
  /* Move the ownership of the x-latch on the page to this OS thread,
  so that we can acquire a second x-latch on it. This is needed for
  the operations to the page to pass the debug checks. */
  bpage->lock.claim_ownership();
  bpage->lock.x_lock_recursive();
  bpage->fix_on_recovery();
  mtr.memo_push(reinterpret_cast<buf_block_t*>(bpage), MTR_MEMO_PAGE_X_FIX);

  buf_block_t *success= reinterpret_cast<buf_block_t*>(bpage);

  mysql_mutex_lock(&recv_sys.mutex);
  if (recv_sys.apply_log_recs)
  {
    const page_id_t id{bpage->id()};
    recv_sys_t::map::iterator p= recv_sys.pages.find(id);
    if (p == recv_sys.pages.end());
    else if (p->second.being_processed < 0)
    {
      recv_sys.pages_it_invalidate(p);
      recv_sys.erase(p);
    }
    else
    {
      p->second.being_processed= 1;
      recv_sys_t::init *init= nullptr;
      if (p->second.skip_read)
        (init= &mlog_init.last(id))->created= true;
      mysql_mutex_unlock(&recv_sys.mutex);
      success= recv_recover_page(success, mtr, p->second, space, init);
      p->second.being_processed= -1;
      goto func_exit;
    }
  }

  mysql_mutex_unlock(&recv_sys.mutex);
  mtr.commit();
func_exit:
  ut_ad(mtr.has_committed());
  return success;
}

void IORequest::fake_read_complete(os_offset_t offset) const noexcept
{
  ut_ad(node);
  ut_ad(is_read());
  ut_ad(bpage);
  ut_ad(bpage->frame);
  ut_ad(recv_recovery_is_on());
  ut_ad(offset);

  mtr_t mtr;
  mtr.start();
  mtr.set_log_mode(MTR_LOG_NO_REDO);

  ut_ad(bpage->frame);
  /* Move the ownership of the x-latch on the page to this OS thread,
  so that we can acquire a second x-latch on it. This is needed for
  the operations to the page to pass the debug checks. */
  bpage->lock.claim_ownership();
  bpage->lock.x_lock_recursive();
  bpage->fix_on_recovery();
  mtr.memo_push(reinterpret_cast<buf_block_t*>(bpage), MTR_MEMO_PAGE_X_FIX);

  page_recv_t &recs= *reinterpret_cast<page_recv_t*>(slot);
  ut_ad(recs.being_processed == 1);
  recv_init &init= *reinterpret_cast<recv_init*>(offset);
  ut_ad(init.lsn > 1);
  init.created= true;

  if (recv_recover_page(reinterpret_cast<buf_block_t*>(bpage),
                        mtr, recs, node->space, &init))
  {
    ut_ad(bpage->oldest_modification() || bpage->is_freed());
    bpage->lock.x_unlock(true);
  }
  recs.being_processed= -1;
  ut_ad(mtr.has_committed());

  node->space->release();
}

/** @return whether a page has been freed */
inline bool fil_space_t::is_freed(uint32_t page) noexcept
{
  std::lock_guard<std::mutex> freed_lock(freed_range_mutex);
  return freed_ranges.contains(page);
}

bool recv_sys_t::report(time_t time)
{
  if (time - progress_time < 15)
    return false;
  progress_time= time;
  return true;
}

ATTRIBUTE_COLD
void recv_sys_t::report_progress() const
{
  mysql_mutex_assert_owner(&mutex);
  const size_t n{pages.size()};
  if (recv_sys.scanned_lsn == recv_sys.lsn)
  {
    sql_print_information("InnoDB: To recover: %zu pages", n);
    service_manager_extend_timeout(INNODB_EXTEND_TIMEOUT_INTERVAL,
                                   "To recover: %zu pages", n);
  }
  else
  {
    sql_print_information("InnoDB: To recover: LSN " LSN_PF
                          "/" LSN_PF "; %zu pages",
                          recv_sys.lsn, recv_sys.scanned_lsn, n);
    service_manager_extend_timeout(INNODB_EXTEND_TIMEOUT_INTERVAL,
                                   "To recover: LSN " LSN_PF
                                   "/" LSN_PF "; %zu pages",
                                   recv_sys.lsn, recv_sys.scanned_lsn, n);
  }
}

/** Apply a recovery batch.
@param space_id       current tablespace identifier
@param space          current tablespace
@param free_block     spare buffer block
@param last_batch     whether it is possible to write more redo log
@return whether the caller must provide a new free_block */
bool recv_sys_t::apply_batch(uint32_t space_id, fil_space_t *&space,
                             buf_block_t *&free_block, bool last_batch)
{
  mysql_mutex_assert_owner(&mutex);
  ut_ad(pages_it != pages.end());
  ut_ad(!pages_it->second.log.empty());

  mysql_mutex_lock(&buf_pool.mutex);
  size_t n= 0, max_n= std::min<size_t>(BUF_LRU_MIN_LEN,
                                       UT_LIST_GET_LEN(buf_pool.LRU) +
                                       UT_LIST_GET_LEN(buf_pool.free));
  mysql_mutex_unlock(&buf_pool.mutex);

  map::iterator begin= pages.end();
  page_id_t begin_id{~0ULL};

  while (pages_it != pages.end() && n < max_n)
  {
    ut_ad(!buf_dblwr.is_inside(pages_it->first));
    if (!pages_it->second.being_processed)
    {
      if (space_id != pages_it->first.space())
      {
        space_id= pages_it->first.space();
        if (space)
          space->release();
        space= fil_space_t::get(space_id);
        if (!space)
        {
          auto d= deferred_spaces.defers.find(space_id);
          if (d == deferred_spaces.defers.end() || d->second.deleted)
            /* For deleted files we preserve the deferred_spaces entry */;
          else if (!free_block)
            return true;
          else
          {
            space= recover_deferred(pages_it, d->second.file_name, free_block);
            deferred_spaces.defers.erase(d);
            if (!space && !srv_force_recovery)
            {
              set_corrupt_fs();
              return false;
            }
          }
        }
      }
      if (!space || space->is_freed(pages_it->first.page_no()))
        pages_it->second.being_processed= -1;
      else if (!n++)
      {
        begin= pages_it;
        begin_id= pages_it->first;
      }
    }
    pages_it++;
  }

  if (!last_batch)
    log_sys.latch.wr_unlock();

  pages_it= begin;

  if (report(time(nullptr)))
    report_progress();

  if (!n)
    goto wait;

  mysql_mutex_lock(&buf_pool.mutex);

  if (UNIV_UNLIKELY(UT_LIST_GET_LEN(buf_pool.free) < n))
  {
    mysql_mutex_unlock(&buf_pool.mutex);
  wait:
    wait_for_pool(n);
    if (n);
    else if (!last_batch)
      goto unlock_relock;
    else
      goto get_last;
    pages_it= pages.lower_bound(begin_id);
    ut_ad(pages_it != pages.end());
  }
  else
    mysql_mutex_unlock(&buf_pool.mutex);

  while (pages_it != pages.end())
  {
    ut_ad(!buf_dblwr.is_inside(pages_it->first));
    if (!pages_it->second.being_processed)
    {
      const page_id_t id{pages_it->first};

      if (space_id != id.space())
      {
        space_id= id.space();
        if (space)
          space->release();
        space= fil_space_t::get(space_id);
      }
      if (!space)
      {
	const auto it= deferred_spaces.defers.find(space_id);
	if (it != deferred_spaces.defers.end() && !it->second.deleted)
          /* The records must be processed after recover_deferred(). */
	  goto next;
        goto space_not_found;
      }
      else if (space->is_freed(id.page_no()))
      {
      space_not_found:
        pages_it->second.being_processed= -1;
        goto next;
      }
      else
      {
        page_recv_t &recs= pages_it->second;
        ut_ad(!recs.log.empty());
        recs.being_processed= 1;
        init *init= recs.skip_read ? &mlog_init.last(id) : nullptr;
        mysql_mutex_unlock(&mutex);
        buf_read_recover(space, id, recs, init);
      }

      if (!--n)
      {
        if (last_batch)
          goto relock_last;
        goto relock;
      }
      mysql_mutex_lock(&mutex);
      pages_it= pages.lower_bound(id);
    }
    else
    next:
      pages_it++;
  }

  if (!last_batch)
  {
  unlock_relock:
    mysql_mutex_unlock(&mutex);
  relock:
    log_sys.latch.wr_lock(SRW_LOCK_CALL);
  relock_last:
    mysql_mutex_lock(&mutex);
  get_last:
    pages_it= pages.lower_bound(begin_id);
  }

  return false;
}

/** Attempt to initialize a page based on redo log records.
@param p        iterator
@param mtr      mini-transaction
@param b        pre-allocated buffer pool block
@param init     page initialization
@return the recovered block
@retval nullptr if the page cannot be initialized based on log records
@retval -1      if the page cannot be recovered due to corruption */
inline buf_block_t *recv_sys_t::recover_low(const map::iterator &p, mtr_t &mtr,
                                            buf_block_t *b, init &init)
{
  mysql_mutex_assert_not_owner(&mutex);
  page_recv_t &recs= p->second;
  ut_ad(recs.skip_read);
  ut_ad(recs.being_processed == 1);
  buf_block_t* block= nullptr;
  const lsn_t end_lsn= recs.log.last()->lsn;
  if (end_lsn < init.lsn)
    DBUG_LOG("ib_log", "skip log for page " << p->first
             << " LSN " << end_lsn << " < " << init.lsn);
  fil_space_t *space= fil_space_t::get(p->first.space());

  mtr.start();
  mtr.set_log_mode(MTR_LOG_NO_REDO);

  ulint zip_size= space ? space->zip_size() : 0;

  if (!space)
  {
    if (p->first.page_no() != 0)
    {
    nothing_recoverable:
      mtr.commit();
      return nullptr;
    }
    auto it= recv_spaces.find(p->first.space());
    ut_ad(it != recv_spaces.end());
    uint32_t flags= it->second.flags;
    zip_size= fil_space_t::zip_size(flags);
    block= buf_page_create_deferred(p->first.space(), zip_size, &mtr, b);
    ut_ad(block == b);
    block->page.lock.x_lock_recursive();
  }
  else
  {
    block= buf_page_create(space, p->first.page_no(), zip_size, &mtr, b);

    if (UNIV_UNLIKELY(block != b))
    {
      /* The page happened to exist in the buffer pool, or it
      was just being read in. Before the exclusive page latch was acquired by
      buf_page_create(), all changes to the page must have been applied. */
      ut_d(mysql_mutex_lock(&mutex));
      ut_ad(pages.find(p->first) == pages.end());
      ut_d(mysql_mutex_unlock(&mutex));
      space->release();
      goto nothing_recoverable;
    }
  }

  ut_d(mysql_mutex_lock(&mutex));
  ut_ad(&recs == &pages.find(p->first)->second);
  ut_d(mysql_mutex_unlock(&mutex));
  init.created= true;
  block= recv_recover_page(block, mtr, recs, space, &init);
  ut_ad(mtr.has_committed());

  if (space)
    space->release();

  return block ? block : reinterpret_cast<buf_block_t*>(-1);
}

/** Attempt to initialize a page based on redo log records.
@param page_id  page identifier
@return recovered block
@retval nullptr if the page cannot be initialized based on log records */
ATTRIBUTE_COLD buf_block_t *recv_sys_t::recover_low(const page_id_t page_id)
{
  mysql_mutex_lock(&mutex);
  map::iterator p= pages.find(page_id);

  if (p != pages.end() && !p->second.being_processed && p->second.skip_read)
  {
    p->second.being_processed= 1;
    init &init= mlog_init.last(page_id);
    mysql_mutex_unlock(&mutex);
    buf_block_t *free_block= buf_LRU_get_free_block(false);
    mtr_t mtr;
    buf_block_t *block= recover_low(p, mtr, free_block, init);
    p->second.being_processed= -1;
    ut_ad(!block || block == reinterpret_cast<buf_block_t*>(-1) ||
          block == free_block);
    if (UNIV_UNLIKELY(!block))
      buf_pool.free_block(free_block);
    return block;
  }

  mysql_mutex_unlock(&mutex);
  return nullptr;
}

inline fil_space_t *fil_system_t::find(const char *path) const noexcept
{
  mysql_mutex_assert_owner(&mutex);
  for (fil_space_t &space : fil_system.space_list)
    if (space.chain.start && !strcmp(space.chain.start->name, path))
      return &space;
  return nullptr;
}

/** Thread-safe function which sorts flush_list by oldest_modification */
static void log_sort_flush_list() noexcept
{
  /* Ensure that oldest_modification() cannot change during std::sort() */
  {
    const double pct_lwm= srv_max_dirty_pages_pct_lwm;
    /* Disable "idle" flushing in order to minimize the wait time below. */
    srv_max_dirty_pages_pct_lwm= 0.0;

    for (;;)
    {
      os_aio_wait_until_no_pending_writes(false);
      mysql_mutex_lock(&buf_pool.flush_list_mutex);
      if (buf_pool.page_cleaner_active())
        my_cond_wait(&buf_pool.done_flush_list,
                     &buf_pool.flush_list_mutex.m_mutex);
      else if (!os_aio_pending_writes())
        break;
      mysql_mutex_unlock(&buf_pool.flush_list_mutex);
    }

    srv_max_dirty_pages_pct_lwm= pct_lwm;
  }

  const size_t size= UT_LIST_GET_LEN(buf_pool.flush_list);
  std::unique_ptr<buf_page_t *[]> list(new buf_page_t *[size]);

  /* Copy the dirty blocks from buf_pool.flush_list to an array for sorting. */
  size_t idx= 0;
  for (buf_page_t *p= UT_LIST_GET_FIRST(buf_pool.flush_list); p; )
  {
    const lsn_t lsn{p->oldest_modification()};
    ut_ad(lsn > 2 || lsn == 1);
    buf_page_t *n= UT_LIST_GET_NEXT(list, p);
    if (lsn > 1)
      list.get()[idx++]= p;
    else
      buf_pool.delete_from_flush_list(p);
    p= n;
  }

  std::sort(list.get(), list.get() + idx,
            [](const buf_page_t *lhs, const buf_page_t *rhs) {
              const lsn_t l{lhs->oldest_modification()};
              const lsn_t r{rhs->oldest_modification()};
              DBUG_ASSERT(l == 1 || l > 2); DBUG_ASSERT(r == 1 || r > 2);
              return r < l;
            });

  UT_LIST_INIT(buf_pool.flush_list, &buf_page_t::list);

  for (size_t i= 0; i < idx; i++)
  {
    buf_page_t *b= list[i];
    const lsn_t lsn{b->oldest_modification()};
    if (lsn == 1)
      continue;
    DBUG_ASSERT(lsn > 2);
    UT_LIST_ADD_LAST(buf_pool.flush_list, b);
  }

  mysql_mutex_unlock(&buf_pool.flush_list_mutex);
}

/** Apply buffered log to persistent data pages.
@param last_batch     whether it is possible to write more redo log */
void recv_sys_t::apply(bool last_batch)
{
  ut_ad(srv_operation <= SRV_OPERATION_EXPORT_RESTORED ||
        srv_operation == SRV_OPERATION_RESTORE ||
        srv_operation == SRV_OPERATION_RESTORE_EXPORT);

  mysql_mutex_assert_owner(&mutex);

  garbage_collect();

  for (auto id= srv_undo_tablespaces_open; id--;)
  {
    const trunc& t= truncated_undo_spaces[id];
    if (t.lsn)
    {
      /* The entire undo tablespace will be reinitialized by
      innodb_undo_log_truncate=ON. Discard old log for all pages.
      Even though we recv_sys_t::parse() already invoked trim(),
      this will be needed in case recovery consists of multiple batches
      (there was an invocation with !last_batch). */
      trim({id + srv_undo_space_id_start, 0}, t.lsn);
      if (fil_space_t *space = fil_space_get(id + srv_undo_space_id_start))
      {
        ut_ad(UT_LIST_GET_LEN(space->chain) == 1);
        ut_ad(space->recv_size >= t.pages);
        fil_node_t *file= UT_LIST_GET_FIRST(space->chain);
        ut_ad(file->is_open());
        os_file_truncate(file->name, file->handle,
                         os_offset_t{space->recv_size} <<
                         srv_page_size_shift, true);
      }
    }
  }

  if (!pages.empty())
  {
    recv_no_ibuf_operations = !last_batch ||
      srv_operation == SRV_OPERATION_RESTORE ||
      srv_operation == SRV_OPERATION_RESTORE_EXPORT;
    ut_ad(!last_batch || lsn == scanned_lsn);
    progress_time= time(nullptr);
    report_progress();

    apply_log_recs= true;

    fil_system.extend_to_recv_size();

    fil_space_t *space= nullptr;
    uint32_t space_id= ~0;
    buf_block_t *free_block= nullptr;

    for (pages_it= pages.begin(); pages_it != pages.end();
         pages_it= pages.begin())
    {
      if (!free_block)
      {
        if (!last_batch)
          log_sys.latch.wr_unlock();
        wait_for_pool(1);
        pages_it= pages.begin();
        mysql_mutex_unlock(&mutex);
        /* We must release log_sys.latch and recv_sys.mutex before
        invoking buf_LRU_get_free_block(). Allocating a block may initiate
        a redo log write and therefore acquire log_sys.latch. To avoid
        deadlocks, log_sys.latch must not be acquired while holding
        recv_sys.mutex. */
        free_block= buf_LRU_get_free_block(false);
        if (!last_batch)
          log_sys.latch.wr_lock(SRW_LOCK_CALL);
        mysql_mutex_lock(&mutex);
        pages_it= pages.begin();
      }

      while (pages_it != pages.end())
      {
        if (is_corrupt_fs() || is_corrupt_log())
        {
          if (space)
            space->release();
          if (free_block)
          {
            mysql_mutex_unlock(&mutex);
            mysql_mutex_lock(&buf_pool.mutex);
            buf_LRU_block_free_non_file_page(free_block);
            mysql_mutex_unlock(&buf_pool.mutex);
            mysql_mutex_lock(&mutex);
          }
          return;
        }
        if (apply_batch(space_id, space, free_block, last_batch))
          break;
      }
    }

    if (space)
      space->release();

    if (free_block)
    {
      mysql_mutex_lock(&buf_pool.mutex);
      buf_LRU_block_free_non_file_page(free_block);
      mysql_mutex_unlock(&buf_pool.mutex);
    }
  }

  if (last_batch)
  {
    if (!recv_no_ibuf_operations)
      /* We skipped this in buf_page_create(). */
      mlog_init.mark_ibuf_exist();
    mlog_init.clear();
    dblwr.pages.clear();
  }
  else
  {
    mlog_init.reset();
    log_sys.latch.wr_unlock();
  }

  mysql_mutex_unlock(&mutex);

  if (!last_batch)
  {
    buf_flush_sync_batch(lsn);
    buf_pool_invalidate();
    log_sys.latch.wr_lock(SRW_LOCK_CALL);
  }
  else if (srv_operation == SRV_OPERATION_RESTORE ||
           srv_operation == SRV_OPERATION_RESTORE_EXPORT)
    buf_flush_sync_batch(lsn);
  else
    /* Instead of flushing, last_batch sorts the buf_pool.flush_list
    in ascending order of buf_page_t::oldest_modification. */
    log_sort_flush_list();

#ifdef HAVE_PMEM
  if (last_batch && log_sys.is_mmap() && !log_sys.is_opened())
    mprotect(log_sys.buf, len, PROT_READ | PROT_WRITE);
#endif

  mysql_mutex_lock(&mutex);

  ut_d(after_apply= true);
  clear();
}

/** Scan log_t::FORMAT_10_8 log store records to the parsing buffer.
@param last_phase     whether changes can be applied to the tablespaces
@return whether rescan is needed (not everything was stored) */
static bool recv_scan_log(bool last_phase)
{
  DBUG_ENTER("recv_scan_log");

  ut_ad(log_sys.is_latest());
  const size_t block_size_1{log_sys.write_size - 1};

  mysql_mutex_lock(&recv_sys.mutex);
  if (!last_phase)
    recv_sys.clear();
  else
    ut_ad(recv_sys.file_checkpoint);

  bool store{recv_sys.file_checkpoint != 0};
  size_t buf_size= log_sys.buf_size;
  if (log_sys.is_mmap())
  {
    recv_sys.offset= size_t(log_sys.calc_lsn_offset(recv_sys.lsn));
    buf_size= size_t(log_sys.file_size);
    recv_sys.len= size_t(log_sys.file_size);
  }
  else
  {
    recv_sys.offset= size_t(recv_sys.lsn - log_sys.get_first_lsn()) &
      block_size_1;
    recv_sys.len= 0;
  }

  lsn_t rewound_lsn= 0;
  for (ut_d(lsn_t source_offset= 0);;)
  {
    ut_ad(log_sys.latch_have_wr());
#ifdef UNIV_DEBUG
    const bool wrap{source_offset + recv_sys.len == log_sys.file_size};
#endif
    if (size_t size= buf_size - recv_sys.len)
    {
#ifndef UNIV_DEBUG
      lsn_t
#endif
      source_offset=
        log_sys.calc_lsn_offset(recv_sys.lsn + recv_sys.len - recv_sys.offset);
      ut_ad(!wrap || source_offset == log_t::START_OFFSET);
      source_offset&= ~block_size_1;

      if (source_offset + size > log_sys.file_size)
        size= static_cast<size_t>(log_sys.file_size - source_offset);

      if (dberr_t err= log_sys.log.read(source_offset,
                                        {log_sys.buf + recv_sys.len, size}))
      {
        mysql_mutex_unlock(&recv_sys.mutex);
        ib::error() << "Failed to read log at " << source_offset
                    << ": " << err;
        recv_sys.set_corrupt_log();
        mysql_mutex_lock(&recv_sys.mutex);
      }
      else
        recv_sys.len+= size;
    }

    if (recv_sys.report(time(nullptr)))
    {
      sql_print_information("InnoDB: Read redo log up to LSN=" LSN_PF,
                            recv_sys.lsn);
      service_manager_extend_timeout(INNODB_EXTEND_TIMEOUT_INTERVAL,
                                     "Read redo log up to LSN=" LSN_PF,
                                     recv_sys.lsn);
    }

    recv_sys_t::parse_mtr_result r;

    if (UNIV_UNLIKELY(!recv_needed_recovery))
    {
      ut_ad(!last_phase);
      ut_ad(recv_sys.lsn >= log_sys.next_checkpoint_lsn);

      if (!store)
      {
        ut_ad(!recv_sys.file_checkpoint);
        for (;;)
        {
          const byte& b{log_sys.buf[recv_sys.offset]};
          r= recv_sys.parse_mmap<recv_sys_t::store::NO>(false);
          switch (r) {
          case recv_sys_t::PREMATURE_EOF:
            goto read_more;
          default:
            ut_ad(r == recv_sys_t::GOT_EOF);
            break;
          case recv_sys_t::OK:
            if (b == FILE_CHECKPOINT + 2 + 8 || (b & 0xf0) == FILE_MODIFY)
              continue;
          }

          const lsn_t end{recv_sys.file_checkpoint};
          ut_ad(!end || end == recv_sys.lsn);
          bool corrupt_fs= recv_sys.is_corrupt_fs();
          mysql_mutex_unlock(&recv_sys.mutex);

          if (!end && !corrupt_fs)
          {
            recv_sys.set_corrupt_log();
            sql_print_error("InnoDB: Missing FILE_CHECKPOINT(" LSN_PF
                            ") at " LSN_PF, log_sys.next_checkpoint_lsn,
                            recv_sys.lsn);
          }
          DBUG_RETURN(true);
        }
      }
      else
      {
        ut_ad(recv_sys.file_checkpoint != 0);
        switch ((r= recv_sys.parse_mmap<recv_sys_t::store::YES>(false))) {
        case recv_sys_t::PREMATURE_EOF:
          goto read_more;
        case recv_sys_t::GOT_EOF:
          break;
        default:
          ut_ad(r == recv_sys_t::OK);
          recv_needed_recovery= true;
          if (srv_read_only_mode)
          {
            mysql_mutex_unlock(&recv_sys.mutex);
            DBUG_RETURN(false);
          }
          sql_print_information("InnoDB: Starting crash recovery from"
                                " checkpoint LSN="  LSN_PF,
                                log_sys.next_checkpoint_lsn);
        }
      }
    }

    if (!store)
    skip_the_rest:
      while ((r= recv_sys.parse_mmap<recv_sys_t::store::NO>(false)) ==
             recv_sys_t::OK);
    else
    {
      uint16_t count= 0;
      while ((r= recv_sys.parse_mmap<recv_sys_t::store::YES>(last_phase)) ==
             recv_sys_t::OK)
        if (!++count && recv_sys.report(time(nullptr)))
        {
          const size_t n= recv_sys.pages.size();
          sql_print_information("InnoDB: Parsed redo log up to LSN=" LSN_PF
                                "; to recover: %zu pages", recv_sys.lsn, n);
          service_manager_extend_timeout(INNODB_EXTEND_TIMEOUT_INTERVAL,
                                         "Parsed redo log up to LSN=" LSN_PF
                                         "; to recover: %zu pages",
                                         recv_sys.lsn, n);
        }
      if (r == recv_sys_t::GOT_OOM)
      {
        ut_ad(!last_phase);
        rewound_lsn= recv_sys.lsn;
        store= false;
        if (recv_sys.scanned_lsn <= 1)
          goto skip_the_rest;
        ut_ad(recv_sys.file_checkpoint);
        goto func_exit;
      }
    }

    if (r != recv_sys_t::PREMATURE_EOF)
    {
      ut_ad(r == recv_sys_t::GOT_EOF);
    got_eof:
      ut_ad(recv_sys.is_initialised());
      if (recv_sys.scanned_lsn > 1)
      {
        ut_ad(recv_sys.is_corrupt_fs() ||
              recv_sys.scanned_lsn == recv_sys.lsn);
        break;
      }
      recv_sys.scanned_lsn= recv_sys.lsn;
      sql_print_information("InnoDB: End of log at LSN=" LSN_PF, recv_sys.lsn);
      break;
    }

  read_more:
    if (log_sys.is_mmap())
      break;

    if (recv_sys.is_corrupt_log())
      break;

    if (recv_sys.offset < log_sys.write_size &&
        recv_sys.lsn == recv_sys.scanned_lsn)
      goto got_eof;

    if (recv_sys.offset > buf_size / 4 ||
        (recv_sys.offset > block_size_1 &&
         recv_sys.len >= buf_size - recv_sys.MTR_SIZE_MAX))
    {
      const size_t ofs{recv_sys.offset & ~block_size_1};
      memmove_aligned<64>(log_sys.buf, log_sys.buf + ofs, recv_sys.len - ofs);
      recv_sys.len-= ofs;
      recv_sys.offset&= block_size_1;
    }
  }

  if (last_phase)
  {
    ut_ad(!rewound_lsn);
    ut_ad(recv_sys.lsn >= recv_sys.file_checkpoint);
    log_sys.set_recovered_lsn(recv_sys.lsn);
  }
  else if (rewound_lsn)
  {
    ut_ad(!store);
    ut_ad(recv_sys.file_checkpoint);
    recv_sys.lsn= rewound_lsn;
  }
func_exit:
  ut_d(recv_sys.after_apply= last_phase);
  mysql_mutex_unlock(&recv_sys.mutex);
  DBUG_RETURN(!store);
}

/** Report a missing tablespace for which page-redo log exists.
@param[in]	err	previous error code
@param[in]	i	tablespace descriptor
@return new error code */
static
dberr_t
recv_init_missing_space(dberr_t err, const recv_spaces_t::const_iterator& i)
{
	switch (srv_operation) {
	default:
		break;
	case SRV_OPERATION_RESTORE:
	case SRV_OPERATION_RESTORE_EXPORT:
		if (i->second.name.find("/#sql") != std::string::npos) {
			sql_print_warning("InnoDB: Tablespace " UINT32PF
					  " was not found at %.*s when"
					  " restoring a (partial?) backup."
					  " All redo log"
					  " for this file will be ignored!",
					  i->first, int(i->second.name.size()),
					  i->second.name.data());
		}
		return(err);
	}

	if (srv_force_recovery == 0) {
		sql_print_error("InnoDB: Tablespace " UINT32PF " was not"
				" found at %.*s.", i->first,
				int(i->second.name.size()),
				i->second.name.data());

		if (err == DB_SUCCESS) {
			sql_print_information(
				"InnoDB: Set innodb_force_recovery=1 to"
				" ignore this and to permanently lose"
				" all changes to the tablespace.");
			err = DB_TABLESPACE_NOT_FOUND;
		}
	} else {
		sql_print_warning("InnoDB: Tablespace " UINT32PF
				  " was not found at %.*s"
				  ", and innodb_force_recovery was set."
				  " All redo log for this tablespace"
				  " will be ignored!",
				  i->first, int(i->second.name.size()),
				  i->second.name.data());
	}

	return(err);
}

/** Report the missing tablespace and discard the redo logs for the deleted
tablespace.
@param[in]	rescan			rescan of redo logs is needed
					if hash table ran out of memory
@param[out]	missing_tablespace	missing tablespace exists or not
@return error code or DB_SUCCESS. */
static MY_ATTRIBUTE((warn_unused_result))
dberr_t
recv_validate_tablespace(bool rescan, bool& missing_tablespace)
{
	dberr_t err = DB_SUCCESS;

	mysql_mutex_lock(&recv_sys.mutex);

	for (recv_sys_t::map::iterator p = recv_sys.pages.begin();
	     p != recv_sys.pages.end();) {
		ut_ad(!p->second.log.empty());
		const uint32_t space = p->first.space();
		if (space == TRX_SYS_SPACE || srv_is_undo_tablespace(space)) {
next:
			p++;
			continue;
		}

		recv_spaces_t::iterator i = recv_spaces.find(space);
		ut_ad(i != recv_spaces.end());

		if (deferred_spaces.find(space)) {
			/* Skip redo logs belonging to
			incomplete tablespaces */
			goto next;
		}

		switch (i->second.status) {
		case file_name_t::NORMAL:
			goto next;
		case file_name_t::MISSING:
			err = recv_init_missing_space(err, i);
			i->second.status = file_name_t::DELETED;
			/* fall through */
		case file_name_t::DELETED:
			recv_sys_t::map::iterator r = p++;
			recv_sys.pages_it_invalidate(r);
			recv_sys.erase(r);
			continue;
		}
		ut_ad(0);
	}

	if (err != DB_SUCCESS) {
func_exit:
		mysql_mutex_unlock(&recv_sys.mutex);
		return(err);
	}

	/* When rescan is not needed, recv_sys.pages will contain the
	entire redo log. If rescan is needed or innodb_force_recovery
	is set, we can ignore missing tablespaces. */
	for (const recv_spaces_t::value_type& rs : recv_spaces) {
		if (UNIV_LIKELY(rs.second.status != file_name_t::MISSING)) {
			continue;
		}

		if (deferred_spaces.find(static_cast<uint32_t>(rs.first))) {
			continue;
		}

		if (srv_force_recovery) {
			sql_print_warning("InnoDB: Tablespace " UINT32PF
					  " was not found at %.*s,"
					  " and innodb_force_recovery was set."
					  " All redo log for this tablespace"
					  " will be ignored!",
					  rs.first, int(rs.second.name.size()),
					  rs.second.name.data());
			continue;
		}

		if (!rescan) {
			sql_print_information("InnoDB: Tablespace " UINT32PF
					      " was not found at '%.*s',"
					      " but there were"
					      " no modifications either.",
					      rs.first,
					      int(rs.second.name.size()),
					      rs.second.name.data());
		} else {
			missing_tablespace = true;
		}
	}

	goto func_exit;
}

/** Check if all tablespaces were found for crash recovery.
@param[in]	rescan			rescan of redo logs is needed
@param[out]	missing_tablespace	missing table exists
@return error code or DB_SUCCESS */
static MY_ATTRIBUTE((warn_unused_result))
dberr_t
recv_init_crash_recovery_spaces(bool rescan, bool& missing_tablespace)
{
	bool		flag_deleted	= false;

	ut_ad(!srv_read_only_mode);
	ut_ad(recv_needed_recovery);

	for (recv_spaces_t::value_type& rs : recv_spaces) {
		ut_ad(!is_predefined_tablespace(rs.first));
		ut_ad(rs.second.status != file_name_t::DELETED
		      || !rs.second.space);

		if (rs.second.status == file_name_t::DELETED) {
			/* The tablespace was deleted,
			so we can ignore any redo log for it. */
			flag_deleted = true;
		} else if (rs.second.space != NULL) {
			/* The tablespace was found, and there
			are some redo log records for it. */
			fil_names_dirty(rs.second.space);

			/* Add the freed page ranges in the respective
			tablespace */
			if (!rs.second.freed_ranges.empty()
			    && (srv_immediate_scrub_data_uncompressed
				|| rs.second.space->is_compressed())) {

				rs.second.space->add_free_ranges(
					std::move(rs.second.freed_ranges));
			}
		} else if (rs.second.name == "") {
			sql_print_error("InnoDB: Missing FILE_CREATE,"
					" FILE_DELETE or FILE_MODIFY"
					" before FILE_CHECKPOINT"
					" for tablespace " UINT32PF, rs.first);
			recv_sys.set_corrupt_log();
			return(DB_CORRUPTION);
		} else {
			rs.second.status = file_name_t::MISSING;
			flag_deleted = true;
		}

		ut_ad(rs.second.status == file_name_t::DELETED
		      || rs.second.name != "");
	}

	if (flag_deleted) {
		return recv_validate_tablespace(rescan, missing_tablespace);
	}

	return DB_SUCCESS;
}

/** Apply any FILE_RENAME records */
static dberr_t recv_rename_files()
{
  mysql_mutex_assert_owner(&recv_sys.mutex);
  ut_ad(log_sys.latch_have_wr());

  dberr_t err= DB_SUCCESS;

  for (auto i= renamed_spaces.begin(); i != renamed_spaces.end(); )
  {
    const auto &r= *i;
    const uint32_t id= r.first;
    fil_space_t *space= fil_space_t::get(id);
    if (!space)
    {
      i++;
      continue;
    }
    ut_ad(UT_LIST_GET_LEN(space->chain) == 1);
    char *old= space->chain.start->name;
    if (r.second != old)
    {
      bool exists;
      os_file_type_t ftype;
      const char *new_name= r.second.c_str();
      mysql_mutex_lock(&fil_system.mutex);
      const fil_space_t *other= nullptr;
      if (!space->chain.start->is_open() && space->chain.start->deferred &&
          (other= fil_system.find(new_name)) &&
          (other->chain.start->is_open() || !other->chain.start->deferred))
        other= nullptr;

      if (other)
      {
        /* Multiple tablespaces use the same file name. This should
        only be possible if the recovery of both files was deferred
        (no valid page 0 is contained in either file). We shall not
        rename the file, just rename the metadata. */
        sql_print_information("InnoDB: Renaming tablespace metadata " UINT32PF
                              " from '%s' to '%s' that is also associated"
                              " with tablespace " UINT32PF,
                              id, old, new_name, other->id);
        space->chain.start->name= mem_strdup(new_name);
        ut_free(old);
      }
      else if (!os_file_status(new_name, &exists, &ftype) || exists)
      {
        sql_print_error("InnoDB: Cannot replay rename of tablespace " UINT32PF
                        " from '%s' to '%s'%s",
                        id, old, new_name, exists ?
                        " because the target file exists" : "");
        err= DB_TABLESPACE_EXISTS;
      }
      else
      {
        mysql_mutex_unlock(&fil_system.mutex);
        err= space->rename(new_name, false);
        if (err != DB_SUCCESS)
          sql_print_error("InnoDB: Cannot replay rename of tablespace "
                          UINT32PF " to '%s': %s", id, new_name, ut_strerr(err));
        goto done;
      }
      mysql_mutex_unlock(&fil_system.mutex);
    }
done:
    space->release();
    if (err != DB_SUCCESS)
    {
      recv_sys.set_corrupt_fs();
      break;
    }
    renamed_spaces.erase(i++);
  }
  return err;
}

dberr_t recv_recovery_read_checkpoint()
{
  ut_ad(srv_operation <= SRV_OPERATION_EXPORT_RESTORED ||
        srv_operation == SRV_OPERATION_RESTORE ||
        srv_operation == SRV_OPERATION_RESTORE_EXPORT);
  ut_ad(!recv_sys.recovery_on);
  ut_d(mysql_mutex_lock(&buf_pool.mutex));
  ut_ad(UT_LIST_GET_LEN(buf_pool.LRU) == 0);
  ut_ad(UT_LIST_GET_LEN(buf_pool.unzip_LRU) == 0);
  ut_d(mysql_mutex_unlock(&buf_pool.mutex));

  if (srv_force_recovery >= SRV_FORCE_NO_LOG_REDO)
  {
    sql_print_information("InnoDB: innodb_force_recovery=6"
                          " skips redo log apply");
    return DB_SUCCESS;
  }

  log_sys.latch.wr_lock(SRW_LOCK_CALL);
  dberr_t err= recv_sys.find_checkpoint();
  log_sys.latch.wr_unlock();
  return err;
}

inline void log_t::set_recovered() noexcept
{
  ut_ad(get_flushed_lsn() == get_lsn());
  ut_ad(recv_sys.lsn == get_lsn());
  size_t offset{recv_sys.offset};
  if (!is_mmap())
  {
    const size_t bs{log_sys.write_size}, bs_1{bs - 1};
    memmove_aligned<512>(buf, buf + (offset & ~bs_1), bs);
    offset&= bs_1;
  }
#ifndef _WIN32
  else
    mprotect(buf, size_t(file_size), PROT_READ | PROT_WRITE);
#endif
  set_buf_free(offset);
}

inline bool recv_sys_t::validate_checkpoint() const noexcept
{
  if (lsn >= file_checkpoint && lsn >= log_sys.next_checkpoint_lsn)
    return false;
  sql_print_error("InnoDB: The log was only scanned up to "
                  LSN_PF ", while the current LSN at the "
                  "time of the latest checkpoint " LSN_PF
                  " was " LSN_PF "!",
                  lsn, log_sys.next_checkpoint_lsn, file_checkpoint);
  return true;
}

/** Start recovering from a redo log checkpoint.
of first system tablespace page
@return error code or DB_SUCCESS */
dberr_t recv_recovery_from_checkpoint_start()
{
	bool rescan = false;
	dberr_t err = DB_SUCCESS;

	ut_ad(srv_operation <= SRV_OPERATION_EXPORT_RESTORED
	      || srv_operation == SRV_OPERATION_RESTORE
	      || srv_operation == SRV_OPERATION_RESTORE_EXPORT);
	ut_d(mysql_mutex_lock(&buf_pool.flush_list_mutex));
	ut_ad(UT_LIST_GET_LEN(buf_pool.LRU) == 0);
	ut_ad(UT_LIST_GET_LEN(buf_pool.unzip_LRU) == 0);
	ut_d(mysql_mutex_unlock(&buf_pool.flush_list_mutex));

	if (srv_force_recovery >= SRV_FORCE_NO_LOG_REDO) {
		sql_print_information("InnoDB: innodb_force_recovery=6"
				      " skips redo log apply");
		return err;
	}

	recv_sys.recovery_on = true;

	log_sys.latch.wr_lock(SRW_LOCK_CALL);
	log_sys.set_capacity();

	/* Start reading the log from the checkpoint lsn. */

	ut_ad(recv_sys.pages.empty());

	if (log_sys.format == log_t::FORMAT_3_23) {
func_exit:
		log_sys.latch.wr_unlock();
		return err;
	}

	if (log_sys.is_latest()) {
		const bool rewind = recv_sys.lsn
			!= log_sys.next_checkpoint_lsn;
		log_sys.last_checkpoint_lsn = log_sys.next_checkpoint_lsn;

		recv_scan_log(false);
		if (recv_needed_recovery) {
read_only_recovery:
			sql_print_warning("InnoDB: innodb_read_only"
					  " prevents crash recovery");
			err = DB_READ_ONLY;
			goto func_exit;
		}
		if (recv_sys.is_corrupt_log()) {
			sql_print_error("InnoDB: Log scan aborted at LSN "
					LSN_PF, recv_sys.lsn);
                        goto err_exit;
		}
		if (recv_sys.is_corrupt_fs()) {
			goto err_exit;
		}
		ut_ad(recv_sys.file_checkpoint);
		ut_ad(log_sys.get_lsn() >= recv_sys.scanned_lsn);
		if (rewind) {
			recv_sys.lsn = log_sys.next_checkpoint_lsn;
			recv_sys.offset = 0;
			recv_sys.len = 0;
		}
		rescan = recv_scan_log(false);

		if (srv_read_only_mode && recv_needed_recovery) {
			goto read_only_recovery;
		}

		if ((recv_sys.is_corrupt_log() && !srv_force_recovery)
		    || recv_sys.is_corrupt_fs()) {
			goto err_exit;
		}
	}

	log_sys.set_recovered_lsn(recv_sys.scanned_lsn);

	if (recv_needed_recovery) {
		bool missing_tablespace = false;

		err = recv_init_crash_recovery_spaces(
			rescan, missing_tablespace);

		if (err != DB_SUCCESS) {
			goto func_exit;
		}

		if (missing_tablespace) {
			ut_ad(rescan);
			/* If any tablespaces seem to be missing,
			validate the remaining log records. */

			do {
				rescan = recv_scan_log(false);

				if (recv_sys.is_corrupt_log() ||
				    recv_sys.is_corrupt_fs()) {
					goto err_exit;
				}

				missing_tablespace = false;

				err = recv_validate_tablespace(
					rescan, missing_tablespace);

				if (err != DB_SUCCESS) {
					goto func_exit;
				}
			} while (missing_tablespace);

			rescan = true;
			/* Because in the loop above we overwrote the
			initially stored recv_sys.pages, we must
			restart parsing the log from the very beginning. */

			/* FIXME: Use a separate loop for checking for
			tablespaces (not individual pages), while retaining
			the initial recv_sys.pages. */
			mysql_mutex_lock(&recv_sys.mutex);
			ut_ad(log_sys.get_lsn() >= recv_sys.lsn);
			recv_sys.clear();
			recv_sys.lsn = log_sys.next_checkpoint_lsn;
			mysql_mutex_unlock(&recv_sys.mutex);
		}

		if (srv_operation <= SRV_OPERATION_EXPORT_RESTORED) {
			mysql_mutex_lock(&recv_sys.mutex);
			deferred_spaces.deferred_dblwr(log_sys.get_lsn());
			buf_dblwr.recover();
			mysql_mutex_unlock(&recv_sys.mutex);
		}

		ut_ad(srv_force_recovery <= SRV_FORCE_NO_UNDO_LOG_SCAN);

		if (rescan) {
			recv_scan_log(true);
			if ((recv_sys.is_corrupt_log()
			     && !srv_force_recovery)
			    || recv_sys.is_corrupt_fs()) {
				goto err_exit;
			}

			/* In case of multi-batch recovery,
			redo log for the last batch is not
			applied yet. */
			ut_d(recv_sys.after_apply = false);
		}
	} else {
		ut_ad(recv_sys.pages.empty());
	}

	if (!log_sys.is_latest()) {
	} else if (recv_sys.validate_checkpoint()) {
err_exit:
		err = DB_ERROR;
		goto func_exit;
	}

	if (!srv_read_only_mode && log_sys.is_latest()) {
		log_sys.set_recovered();
		if (recv_needed_recovery
		    && srv_operation <= SRV_OPERATION_EXPORT_RESTORED
		    && recv_sys.lsn - log_sys.next_checkpoint_lsn
		    < log_sys.log_capacity) {
			/* Write a FILE_CHECKPOINT marker as the first thing,
			before generating any other redo log. This ensures
			that subsequent crash recovery will be possible even
			if the server were killed soon after this. */
			fil_names_clear(log_sys.next_checkpoint_lsn);
		}
	}

	DBUG_EXECUTE_IF("before_final_redo_apply", goto err_exit;);
	mysql_mutex_lock(&recv_sys.mutex);
	if (UNIV_UNLIKELY(recv_sys.scanned_lsn != recv_sys.lsn)
	    && log_sys.is_latest()) {
		ut_ad("log parsing error" == 0);
		mysql_mutex_unlock(&recv_sys.mutex);
		err = DB_CORRUPTION;
		goto func_exit;
	}
	recv_sys.apply_log_recs = true;
	recv_no_ibuf_operations = false;
	ut_d(recv_no_log_write = srv_operation == SRV_OPERATION_RESTORE
	     || srv_operation == SRV_OPERATION_RESTORE_EXPORT);
	if (srv_operation == SRV_OPERATION_NORMAL) {
		err = recv_rename_files();
	}

	mysql_mutex_unlock(&recv_sys.mutex);

	/* The database is now ready to start almost normal processing of user
	transactions: transaction rollbacks and the application of the log
	records in the hash table can be run in background. */
	if (err == DB_SUCCESS && deferred_spaces.reinit_all()
	    && !srv_force_recovery) {
		err = DB_CORRUPTION;
	}

	goto func_exit;
}

bool recv_dblwr_t::validate_page(const page_id_t page_id, lsn_t max_lsn,
                                 const fil_space_t *space,
                                 const byte *page, byte *tmp_buf)
  const noexcept
{
  mysql_mutex_assert_owner(&recv_sys.mutex);
  uint32_t flags;

  if (page_id.page_no() == 0)
  {
    flags= fsp_header_get_flags(page);
    if (!fil_space_t::is_valid_flags(flags, page_id.space()))
    {
      uint32_t cflags= fsp_flags_convert_from_101(flags);
      if (cflags == UINT32_MAX)
      {
        ib::warn() << "Ignoring a doublewrite copy of page " << page_id
                   << "due to invalid flags " << ib::hex(flags);
        return false;
      }

      flags= cflags;
    }

    /* Page 0 is never page_compressed or encrypted. */
    goto check_if_corrupted;
  }

  flags= space->flags;

  if (space->full_crc32())
  check_if_corrupted:
    return !buf_page_is_corrupted(max_lsn < LSN_MAX, page, flags);

  ut_ad(tmp_buf);
  byte *tmp_frame= tmp_buf;
  byte *tmp_page= tmp_buf + srv_page_size;
  const uint16_t page_type= mach_read_from_2(page + FIL_PAGE_TYPE);
  const bool expect_encrypted= space->crypt_data &&
    space->crypt_data->type != CRYPT_SCHEME_UNENCRYPTED;

  if (expect_encrypted &&
      mach_read_from_4(page + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION))
  {
    if (!fil_space_verify_crypt_checksum(page, space->zip_size()))
      return false;
    if (page_type != FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED)
      return true;
    if (space->zip_size())
      return false;
    memcpy(tmp_page, page, space->physical_size());
    if (!fil_space_decrypt(space, tmp_frame, tmp_page))
      return false;
  }

  switch (page_type) {
  case FIL_PAGE_PAGE_COMPRESSED:
    memcpy(tmp_page, page, space->physical_size());
    /* fall through */
  case FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED:
    if (space->zip_size())
      return false; /* ROW_FORMAT=COMPRESSED cannot be page_compressed */
    ulint decomp= fil_page_decompress(tmp_frame, tmp_page, space->flags);
    if (!decomp)
      return false; /* decompression failed */
    if (decomp == srv_page_size)
      return false; /* the page was not compressed (invalid page type) */
    page= tmp_page;
  }

  goto check_if_corrupted;
}

ATTRIBUTE_COLD
byte *recv_dblwr_t::find_deferred_page(const fil_node_t &node,
                                       uint32_t page_no,
                                       byte *buf) noexcept
{
  ut_ad(node.space->full_crc32());
  mysql_mutex_lock(&recv_sys.mutex);
  byte *result_page= nullptr;
  bool is_encrypted= node.space->crypt_data &&
                     node.space->crypt_data->is_encrypted();
  for (list::iterator page_it= pages.begin(); page_it != pages.end();
       page_it++)
  {
    if (page_get_page_no(*page_it) != page_no ||
        buf_page_is_corrupted(true, *page_it, node.space->flags))
      continue;

    if (is_encrypted &&
        !mach_read_from_4(*page_it + FIL_PAGE_FCRC32_KEY_VERSION))
      continue;

    memcpy(buf, *page_it, node.space->physical_size());
    buf_tmp_buffer_t *slot= buf_pool.io_buf_reserve(false);
    ut_a(slot);
    slot->allocate();

    bool invalidate= false;
    if (is_encrypted)
    {
      invalidate= !fil_space_decrypt(node.space, slot->crypt_buf, buf);
      if (!invalidate && node.space->is_compressed())
        goto decompress;
    }
    else
decompress:
      invalidate= !fil_page_decompress(slot->crypt_buf, buf,
                                       node.space->flags);
    slot->release();

    if (invalidate ||
        mach_read_from_4(buf + FIL_PAGE_SPACE_ID) != node.space->id)
      continue;

    result_page= *page_it;
    pages.erase(page_it);
    break;
  }
  mysql_mutex_unlock(&recv_sys.mutex);
  if (result_page)
    sql_print_information("InnoDB: Recovered page [page id: space="
                          UINT32PF ", page number=" UINT32PF "] "
                          "to '%s' from the doublewrite buffer.",
                          uint32_t(node.space->id), page_no,
                          node.name);
  return result_page;
}

const byte *recv_dblwr_t::find_page(const page_id_t page_id, lsn_t max_lsn,
                                    const fil_space_t *space, byte *tmp_buf)
  const noexcept
{
  mysql_mutex_assert_owner(&recv_sys.mutex);

  for (byte *page : pages)
  {
    if (page_get_page_no(page) != page_id.page_no() ||
        page_get_space_id(page) != page_id.space())
      continue;
    const lsn_t lsn= mach_read_from_8(page + FIL_PAGE_LSN);
    if (page_id.page_no() == 0)
    {
      if (!lsn)
        continue;
      uint32_t flags= mach_read_from_4(
        FSP_HEADER_OFFSET + FSP_SPACE_FLAGS + page);
      if (!fil_space_t::is_valid_flags(flags, page_id.space()))
        continue;
    }

    if (lsn > max_lsn || lsn < log_sys.next_checkpoint_lsn ||
        !validate_page(page_id, max_lsn, space, page, tmp_buf))
    {
      /* Mark processed for subsequent iterations in buf_dblwr_t::recover() */
      memset_aligned<8>(page + FIL_PAGE_LSN, 0, 8);
      continue;
    }

    return page;
  }

  return nullptr;
}