MDEV-14795 InnoDB system tablespace cannot be shrunk

- Introduce the option :autoshrink attribute to be
added to innodb_data_file_path variable to allow
the shrinking of system tablespace during startup process.

Steps for shrinking the system tablespace:

1) Find the last used extent in system tablespace
by iterating through the BITMAP in extent descriptor pages

2) If the last used extent is lesser than user specified size
then set desired target size to user specified size.

3) Store the page contents of "to be modified" extent
descriptor pages, latches the "to be modified"
extent descriptor pages and check for buffer pool
memory availability

4) Make checkpoint to flush all pages in buffer pool, so
that pages in flush list doesn't have to use doublewrite
buffer and disable doublewrite buffer during shrinking process

5) Update the FSP_SIZE and FSP_FREE_LIMIT in header page

6) Remove the "to be truncated" pages from FSP_FREE and
FSP_FREE_FRAG list

7) Reset the bitmap in the last descriptor pages for the
"to be truncated" pages.

8) In case of multiple files, calculate the truncated last
file size and do the truncation in last file

9) Check whether mini-transaction log size doesn't exceed
the minimum value of innodb_log_buffer_size which is 2MB.
In that case, replace the modified buffer pool pages with
the page old content.

11) Commit the mini-transaction for shrinking the tablespace
and enable/disable the doublewrite buffer depends on user
specified value.

recv_sys_t::apply(): Handle the truncation of system tablespace
only if the recovered tablespace size is lesser than actual
existing size.

mysql-test/suite/innodb/r/sys_truncate.result

+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
+SET UNIQUE_CHECKS=0, FOREIGN_KEY_CHECKS=0;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+f3 INT NOT NULL, INDEX(f1),
+INDEX(f2), INDEX(f3))ENGINE=InnoDB;
+BEGIN;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+COMMIT;
+DROP TABLE t1;
+InnoDB		0 transactions not purged
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+NAME	FILE_SIZE
+innodb_system	77594624
+# restart
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+NAME	FILE_SIZE
+innodb_system	10485760

mysql-test/suite/innodb/r/sys_truncate_debug.result

+call mtr.add_suppression("InnoDB: Cannot shrink the system tablespace");
+call mtr.add_suppression("InnoDB: Plugin initialization aborted");
+call mtr.add_suppression("Plugin 'InnoDB' init function returned error");
+call mtr.add_suppression("Plugin 'InnoDB' registration as a STORAGE ENGINE failed");
+SET GLOBAL INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG=2;
+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
+SET UNIQUE_CHECKS=0, FOREIGN_KEY_CHECKS=0;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+f3 INT NOT NULL, INDEX(f1),
+INDEX(f2), INDEX(f3))ENGINE=InnoDB;
+BEGIN;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+COMMIT;
+DROP TABLE t1;
+InnoDB		0 transactions not purged
+SELECT NAME, FILE_SIZE FROM INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES WHERE SPACE = 0;
+NAME	FILE_SIZE
+innodb_system	540016640
+# restart: --debug_dbug=+d,sys_shrink_buffer_pool_full
+FOUND 1 /\[Warning\] InnoDB: Cannot shrink the system tablespace/ in mysqld.1.err
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+ENGINE	SUPPORT	COMMENT	TRANSACTIONS	XA	SAVEPOINTS
+InnoDB	YES	Supports transactions, row-level locking, foreign keys and encryption for tables	YES	YES	YES
+# restart: --debug_dbug=+d,mtr_log_max_size
+FOUND 1 /\[ERROR\] InnoDB: Cannot shrink the system tablespace/ in mysqld.1.err
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+ENGINE	SUPPORT	COMMENT	TRANSACTIONS	XA	SAVEPOINTS
+InnoDB	YES	Supports transactions, row-level locking, foreign keys and encryption for tables	YES	YES	YES
+# restart: --debug_dbug=+d,crash_after_sys_truncate
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+ENGINE	SUPPORT	COMMENT	TRANSACTIONS	XA	SAVEPOINTS
+# restart: --innodb_buffer_pool_size=5M
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+ENGINE	SUPPORT	COMMENT	TRANSACTIONS	XA	SAVEPOINTS
+InnoDB	YES	Supports transactions, row-level locking, foreign keys and encryption for tables	YES	YES	YES
+SELECT NAME, FILE_SIZE FROM INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES WHERE SPACE=0;
+NAME	FILE_SIZE
+innodb_system	3145728

mysql-test/suite/innodb/r/sys_truncate_large.result

+set global innodb_file_per_table=0;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
+set global innodb_limit_optimistic_insert_debug=2;
+set unique_checks=0, foreign_key_checks=0;
+create table t1(f1 int not null)engine=innodb;
+begin;
+insert into t1 select * from seq_1_to_8192;
+insert into t1 select * from seq_1_to_8192;
+insert into t1 select * from seq_1_to_65536;
+commit;
+create table t2(f1 int not null)engine=innodb;
+insert into t2 select * from seq_1_to_65536;
+create table t3(f1 int not null)engine=innodb;
+insert into t3 select * from seq_1_to_65536;
+CREATE TABLE t4(f1 int not null)engine=innodb;
+insert into t4 select * from seq_1_to_65536;
+drop table t2;
+drop table t4;
+InnoDB		0 transactions not purged
+# restart
+drop table t3, t1;

mysql-test/suite/innodb/t/sys_truncate.opt

+--innodb_data_file_path=ibdata1:10M:autoextend:autoshrink
+--innodb_sys_tablespaces

mysql-test/suite/innodb/t/sys_truncate.test

+--source include/have_innodb.inc
+--source include/have_sequence.inc
+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+SET UNIQUE_CHECKS=0, FOREIGN_KEY_CHECKS=0;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+                f3 INT NOT NULL, INDEX(f1),
+                INDEX(f2), INDEX(f3))ENGINE=InnoDB;
+BEGIN;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+COMMIT;
+DROP TABLE t1;
+--source include/wait_all_purged.inc
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+--source include/restart_mysqld.inc
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;

mysql-test/suite/innodb/t/sys_truncate_debug.opt

+--innodb_data_file_path=ibdata1:1M:autoextend:autoshrink
+--innodb_sys_tablespaces
+--innodb_page_size=4k

mysql-test/suite/innodb/t/sys_truncate_debug.test

+--source include/have_innodb.inc
+--source include/have_sequence.inc
+--source include/not_embedded.inc
+--source include/have_debug.inc
+--source include/not_windows.inc
+
+call mtr.add_suppression("InnoDB: Cannot shrink the system tablespace");
+call mtr.add_suppression("InnoDB: Plugin initialization aborted");
+call mtr.add_suppression("Plugin 'InnoDB' init function returned error");
+call mtr.add_suppression("Plugin 'InnoDB' registration as a STORAGE ENGINE failed");
+
+SET GLOBAL INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG=2;
+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+SET UNIQUE_CHECKS=0, FOREIGN_KEY_CHECKS=0;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+                f3 INT NOT NULL, INDEX(f1),
+                INDEX(f2), INDEX(f3))ENGINE=InnoDB;
+BEGIN;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+COMMIT;
+DROP TABLE t1;
+--source include/wait_all_purged.inc
+SELECT NAME, FILE_SIZE FROM INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES WHERE SPACE = 0;
+
+# Ran out of buffer pool
+let $restart_parameters=--debug_dbug="+d,sys_shrink_buffer_pool_full";
+--source include/restart_mysqld.inc
+
+--let SEARCH_PATTERN= \[Warning\] InnoDB: Cannot shrink the system tablespace
+let SEARCH_FILE= $MYSQLTEST_VARDIR/log/mysqld.1.err;
+--source include/search_pattern_in_file.inc
+
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+
+# Ran out of mtr log size
+let $restart_parameters=--debug_dbug="+d,mtr_log_max_size";
+--source include/restart_mysqld.inc
+
+--let SEARCH_PATTERN= \[ERROR\] InnoDB: Cannot shrink the system tablespace
+let SEARCH_FILE= $MYSQLTEST_VARDIR/log/mysqld.1.err;
+--source include/search_pattern_in_file.inc
+
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+
+# Crash after shrinking the system tablespace
+let $restart_parameters=--debug_dbug="+d,crash_after_sys_truncate";
+--source include/restart_mysqld.inc
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+
+let $restart_parameters=--innodb_buffer_pool_size=5M;
+--source include/restart_mysqld.inc
+SELECT * FROM INFORMATION_SCHEMA.ENGINES
+WHERE engine = 'innodb'
+AND support IN ('YES', 'DEFAULT', 'ENABLED');
+SELECT NAME, FILE_SIZE FROM INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES WHERE SPACE=0;

mysql-test/suite/innodb/t/sys_truncate_large.opt

+--innodb_data_file_path=ibdata1:1M:autoextend:autoshrink
+--innodb_page_size=4k

mysql-test/suite/innodb/t/sys_truncate_large.test

+--source include/big_test.inc
+--source include/have_innodb.inc
+--source include/have_sequence.inc
+--source include/not_valgrind.inc
+--source include/have_debug.inc
+
+set global innodb_file_per_table=0;
+set global innodb_limit_optimistic_insert_debug=2;
+set unique_checks=0, foreign_key_checks=0;
+
+create table t1(f1 int not null)engine=innodb;
+begin;
+insert into t1 select * from seq_1_to_8192;
+insert into t1 select * from seq_1_to_8192;
+insert into t1 select * from seq_1_to_65536;
+commit;
+
+create table t2(f1 int not null)engine=innodb;
+insert into t2 select * from seq_1_to_65536;
+
+create table t3(f1 int not null)engine=innodb;
+insert into t3 select * from seq_1_to_65536;
+
+CREATE TABLE t4(f1 int not null)engine=innodb;
+insert into t4 select * from seq_1_to_65536;
+
+drop table t2;
+drop table t4;
+--source include/wait_all_purged.inc
+--source include/restart_mysqld.inc
+drop table t3, t1;

mysql-test/suite/mariabackup/sys_truncate.opt

+--innodb_data_file_path=ibdata1:1M:autoextend:autoshrink
+--innodb_sys_tablespaces

mysql-test/suite/mariabackup/sys_truncate.result

+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+f3 INT NOT NULL, INDEX(f1),
+INDEX(f2), INDEX(f3))ENGINE=InnoDB;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+DROP TABLE t1;
+InnoDB		0 transactions not purged
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+NAME	FILE_SIZE
+innodb_system	70254592
+# restart
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+NAME	FILE_SIZE
+innodb_system	3145728
+# Incremental backup
+# Prepare full backup, apply incremental one
+# Restore and check results
+# shutdown server
+# remove datadir
+# xtrabackup move back
+# restart
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+NAME	FILE_SIZE
+innodb_system	3145728

mysql-test/suite/mariabackup/sys_truncate.test

+--source include/have_innodb.inc
+--source include/have_sequence.inc
+let basedir=$MYSQLTEST_VARDIR/tmp/backup;
+let incremental_dir=$MYSQLTEST_VARDIR/tmp/backup_inc1;
+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+CREATE TABLE t1(f1 INT NOT NULL, f2 INT NOT NULL,
+                f3 INT NOT NULL, INDEX(f1),
+                INDEX(f2), INDEX(f3))ENGINE=InnoDB;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+INSERT INTO t1 SELECT seq, seq, seq FROM seq_1_to_16384;
+DROP TABLE t1;
+--source ../innodb/include/wait_all_purged.inc
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+--disable_result_log
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --parallel=10 --target-dir=$basedir --throttle=1000;
+--enable_result_log
+--source include/restart_mysqld.inc
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+
+--echo # Incremental backup
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --parallel=2 --ftwrl-wait-timeout=5 --ftwrl-wait-threshold=300 --ftwrl-wait-query-type=all --target-dir=$incremental_dir --incremental-basedir=$basedir;
+
+--disable_result_log
+echo # Prepare full backup, apply incremental one;
+exec $XTRABACKUP --prepare --target-dir=$basedir;
+exec $XTRABACKUP --prepare --target-dir=$basedir --incremental-dir=$incremental_dir;
+
+echo # Restore and check results;
+let $targetdir=$basedir;
+-- source include/restart_and_restore.inc
+--enable_result_log
+SELECT NAME, FILE_SIZE FROM information_schema.innodb_sys_tablespaces WHERE SPACE = 0;
+# Cleanup
+rmdir $basedir;
+rmdir $incremental_dir;

storage/innobase/fil/fil0fil.cc

@@ -668,6 +668,19 @@ fil_space_extend_must_retry(
 	return false;
 }
 
+bool recv_sys_t::check_sys_truncate()
+{
+  mysql_mutex_assert_owner(&fil_system.mutex);
+  if (!truncated_sys_space.lsn)
+    return false;
+  if (fil_system.sys_space->size <= fil_system.sys_space->recv_size)
+  {
+    truncated_sys_space={0,0};
+    return false;
+  }
+  return true;
+}
+
 /** @return whether the file is usable for io() */
 ATTRIBUTE_COLD bool fil_space_t::prepare_acquired()
 {
@@ -684,6 +697,8 @@ ATTRIBUTE_COLD bool fil_space_t::prepare_acquired()
   else if (node->deferred);
   else if (auto desired_size= recv_size)
   {
+    if (id == TRX_SYS_SPACE && recv_sys.check_sys_truncate())
+      goto clear;
     bool success;
     while (fil_space_extend_must_retry(this, node, desired_size, &success))
       mysql_mutex_lock(&fil_system.mutex);

storage/innobase/fsp/fsp0fsp.cc

@@ -3065,3 +3065,614 @@ std::ostream &fseg_header::to_stream(std::ostream &out) const
   return out;
 }
 #endif /* UNIV_DEBUG */
+
+/** Get the latched extent descriptor page or
+acquire the extent descriptor page.
+@param page_no  page number to be acquired
+@param mtr      mini-transaction
+@param err      error code
+@return block descriptor */
+static
+buf_block_t *fsp_get_latched_xdes_page(
+  uint32_t page_no, mtr_t *mtr, dberr_t *err)
+{
+  buf_block_t *block= nullptr;
+  block= mtr->get_already_latched(
+    page_id_t{0, page_no}, MTR_MEMO_PAGE_SX_FIX);
+  if (block)
+    return block;
+  return buf_page_get_gen(
+    page_id_t{0, page_no}, 0, RW_SX_LATCH, nullptr,
+    BUF_GET_POSSIBLY_FREED, mtr, err);
+}
+
+/** Used during system tablespace truncation. Stores
+the "to be modified" extent descriptor page and its
+old page state */
+class fsp_xdes_old_page
+{
+  std::vector<buf_block_t*> m_old_xdes_pages;
+public:
+  ulint n_pages()
+  {
+    uint32_t count=0;
+    for (uint32_t i= 0; i < m_old_xdes_pages.size(); i++)
+      if (m_old_xdes_pages[i]) count++;
+    return count;
+  }
+
+  __attribute__((warn_unused_result))
+  dberr_t insert(uint32_t page_no, mtr_t *mtr)
+  {
+    uint32_t m_index= page_no >> srv_page_size_shift;
+    if (m_old_xdes_pages.size() > m_index &&
+        m_old_xdes_pages[m_index] != nullptr)
+      return DB_SUCCESS;
+
+    DBUG_EXECUTE_IF("sys_shrink_buffer_pool_full",
+                    return DB_OUT_OF_MEMORY;);
+    dberr_t err= DB_SUCCESS;
+    buf_block_t *block= fsp_get_latched_xdes_page(page_no, mtr, &err);
+    if (block)
+    {
+      buf_block_t *old= buf_LRU_get_free_block(have_no_mutex_soft);
+      if (!old) return DB_OUT_OF_MEMORY;
+
+      memcpy_aligned<UNIV_PAGE_SIZE_MIN>(
+        old->page.frame, block->page.frame, srv_page_size);
+
+      if (m_index >= m_old_xdes_pages.size())
+        m_old_xdes_pages.resize(m_index + 1);
+      m_old_xdes_pages[m_index] = old;
+    }
+    return err;
+  }
+
+  buf_block_t *search(uint32_t page_no)
+  {
+    uint32_t m_index= page_no >> srv_page_size_shift;
+    if (m_index > m_old_xdes_pages.size())
+      return nullptr;
+    return m_old_xdes_pages[m_index];
+  }
+
+  void restore(mtr_t *mtr)
+  {
+    for (uint32_t i= 0; i < m_old_xdes_pages.size(); i++)
+    {
+      if (m_old_xdes_pages[i] == nullptr) continue;
+      buf_block_t *block= mtr->get_already_latched(
+        page_id_t{0, i << srv_page_size_shift},
+        MTR_MEMO_PAGE_SX_FIX);
+      ut_ad(block);
+      memcpy_aligned<UNIV_PAGE_SIZE_MIN>(
+        block->page.frame, m_old_xdes_pages[i]->page.frame, srv_page_size);
+    }
+  }
+
+  fsp_xdes_old_page()=default;
+  ~fsp_xdes_old_page()
+  {
+    for (uint32_t i= 0; i < m_old_xdes_pages.size(); i++)
+      if (m_old_xdes_pages[i])
+        buf_block_free(m_old_xdes_pages[i]);
+  }
+};
+
+/** Update the current descriptor entry with last valid
+descriptor entry with skipped descriptor pages
+@param header          File segment header
+@param hdr_offset      FSP_FREE or FSP_FREE_FRAG
+@param cur_addr        current descriptor
+@param last_valid_addr last valid descriptor
+@param skip_len        number of truncated extent descriptor entry
+@param mtr             mini-transaction
+@return error code or DB_SUCCESS */
+__attribute__((warn_unused_result))
+static
+dberr_t fsp_lst_update_skip(
+  buf_block_t *header, uint16_t hdr_offset,
+  fil_addr_t cur_addr, fil_addr_t last_valid_addr,
+  uint32_t skip_len, mtr_t *mtr)
+{
+  dberr_t err= DB_SUCCESS;
+  buf_block_t *cur= fsp_get_latched_xdes_page(
+    cur_addr.page, mtr, &err);
+
+  if (!cur) return err;
+  if (last_valid_addr.page == FIL_NULL)
+  {
+    /* First node, so update the FIRST pointer of base
+    with current extent descriptor and update
+    the PREV pointer of last valid descriptor with
+    FIL_NULL */
+    flst_write_addr(
+      *header,
+      header->page.frame + hdr_offset + FLST_FIRST,
+      cur_addr.page, cur_addr.boffset, mtr);
+
+    flst_write_addr(
+      *cur,
+      cur->page.frame + cur_addr.boffset + FLST_PREV,
+      last_valid_addr.page, last_valid_addr.boffset, mtr);
+  }
+  else
+  {
+    buf_block_t *prev= nullptr;
+    if (cur->page.id().page_no() == last_valid_addr.page)
+      prev= cur;
+    else
+    {
+      prev= fsp_get_latched_xdes_page(
+              last_valid_addr.page, mtr, &err);
+      if (!prev) return err;
+    }
+
+    /* Update the NEXT pointer of last valid extent
+    descriptor entry with current extent descriptor */
+    flst_write_addr(
+      *prev,
+      prev->page.frame + last_valid_addr.boffset + FLST_NEXT,
+      cur_addr.page, cur_addr.boffset, mtr);
+
+    /* Update the PREV pointer of current extent
+    descriptor entry with last valid extent descriptor */
+    flst_write_addr(
+      *cur,
+      cur->page.frame + cur_addr.boffset + FLST_PREV,
+      last_valid_addr.page, last_valid_addr.boffset, mtr);
+  }
+
+  byte *len_bytes= &header->page.frame[hdr_offset + FLST_LEN];
+  uint32_t len= mach_read_from_4(len_bytes);
+  ut_ad(len > skip_len);
+  mtr->write<4>(*header, len_bytes, len - skip_len);
+  return DB_SUCCESS;
+}
+
+/** Write the FLST_NEXT pointer of the last valid node with FIL_NULL
+@param header          File segment header
+@param hdr_offset      FSP_HEADER_OFFSET + FSP_FREE or FSP_FREE_FRAG
+@param cur_addr        current descriptor
+@param skip_len        number of truncated extent descriptor entry
+@param orig_len        original length of the list
+@param mtr             mini-transaction
+@return error code or DB_SUCCESS */
+__attribute__((warn_unused_result))
+dberr_t
+fsp_lst_write_end(
+  buf_block_t *header, uint16_t hdr_offset,
+  fil_addr_t cur_addr, uint32_t skip_len, uint32_t orig_len,
+  mtr_t *mtr)
+{
+  dberr_t err= DB_SUCCESS;
+  byte *len_bytes= &header->page.frame[hdr_offset + FLST_LEN];
+  uint32_t len= mach_read_from_4(len_bytes);
+  if (skip_len == 0)
+  {
+func_exit:
+    if (hdr_offset == FSP_FREE_FRAG + FSP_HEADER_OFFSET)
+    {
+      byte *frag_used_byte= &header->page.frame[
+        FSP_HEADER_OFFSET + FSP_FRAG_N_USED];
+      uint32_t n_used_frag= mach_read_from_4(frag_used_byte);
+      /* Update the FSP_FRAG_N_USED value after removing
+      the truncated pages from FSP_FREE_FRAG list */
+      if (len != orig_len)
+        mtr->write<4>(*header, frag_used_byte,
+                      n_used_frag - ((orig_len - len) * 2));
+    }
+    return DB_SUCCESS;
+  }
+
+  if (cur_addr.page == FIL_NULL)
+  {
+    /* There is no list, so reset base node */
+    mtr->memset(
+      header,
+      FLST_FIRST + FIL_ADDR_PAGE + hdr_offset, 4, 0xff);
+    mtr->memset(
+      header,
+      FLST_LAST + FIL_ADDR_PAGE + hdr_offset, 4, 0xff);
+  }
+  else
+  {
+    /* Update the FLST_LAST pointer in base node with current
+    valid extent descriptor and mark the FIL_NULL as next in
+    current extent descriptr */
+    flst_write_addr(
+      *header,
+      header->page.frame + hdr_offset + FLST_LAST,
+      cur_addr.page, cur_addr.boffset, mtr);
+
+    buf_block_t *cur_block= fsp_get_latched_xdes_page(
+      cur_addr.page, mtr, &err);
+
+    if (!cur_block) return err;
+
+    flst_write_addr(
+      *cur_block,
+      cur_block->page.frame + cur_addr.boffset + FLST_NEXT,
+      FIL_NULL, 0, mtr);
+  }
+
+  ut_ad(len >= skip_len);
+  len-= skip_len;
+  mtr->write<4>(*header, len_bytes, len);
+  goto func_exit;
+}
+
+/** Remove the truncated extents from the FSP_FREE list
+@param header     tablespace header
+@param hdr_offset FSP_FREE or FSP_FREE_FRAG
+@param threshold  Remove the pages from the list which is
+                  greater than threshold
+@param mtr        mini-transaction to remove the extents
+@return DB_SUCCESS on success or error code */
+__attribute__((warn_unused_result))
+static
+dberr_t fsp_shrink_list(buf_block_t *header, uint16_t hdr_offset,
+                        uint32_t threshold, mtr_t *mtr)
+{
+  ut_ad(mach_read_from_4(header->page.frame + FIL_PAGE_OFFSET) == 0);
+  const uint32_t len= flst_get_len(hdr_offset + header->page.frame);
+  if (len == 0)
+    return DB_SUCCESS;
+
+  buf_block_t *descr_block= nullptr;
+  dberr_t err= DB_SUCCESS;
+  uint32_t skip_len= 0;
+  fil_addr_t last_valid_addr {FIL_NULL, 0}, next_addr{FIL_NULL, 0};
+  fil_addr_t addr= flst_get_first(header->page.frame + hdr_offset);
+
+  for (uint32_t i= len; i > 0; i--)
+  {
+    ut_ad(addr.page < fil_system.sys_space->size);
+    ut_ad(!(addr.page & (srv_page_size - 1)));
+    if (!descr_block || descr_block->page.id().page_no() != addr.page)
+    {
+      descr_block= fsp_get_latched_xdes_page(
+                     addr.page, mtr, &err);
+      if (!descr_block)
+        return err;
+    }
+
+    if (addr.page < threshold)
+    {
+      /* Update only if only non-truncated page */
+      if (skip_len)
+      {
+        err= fsp_lst_update_skip(
+          header, hdr_offset, addr, last_valid_addr, skip_len, mtr);
+        if (err) return err;
+        skip_len= 0;
+      }
+
+      if (threshold <= xdes_get_offset(
+            descr_block->page.frame + addr.boffset - XDES_FLST_NODE))
+        skip_len++;
+      else last_valid_addr= addr;
+    }
+    else skip_len++;
+
+    next_addr= flst_get_next_addr(
+      descr_block->page.frame + addr.boffset);
+    if (next_addr.page != addr.page && addr.page >= threshold)
+    {
+      mtr->release_last_page();
+      descr_block= nullptr;
+    }
+
+    if (next_addr.page == FIL_NULL)
+    {
+      err= fsp_lst_write_end(header, hdr_offset, last_valid_addr,
+                             skip_len, len, mtr);
+      break;
+    }
+    addr= next_addr;
+  }
+  ut_d(if (err == DB_SUCCESS) flst_validate(header, hdr_offset, mtr););
+  return err;
+}
+
+/** Reset the XDES_BITMAP for the truncated extents
+@param  space      tablespace to be truncated
+@param  threshold  truncated size
+@param  mtr        mini-transaction to reset XDES_BITMAP
+@return DB_SUCCESS or error code on failure */
+__attribute__((warn_unused_result))
+static
+dberr_t fsp_xdes_reset(fil_space_t *space, uint32_t threshold, mtr_t *mtr)
+{
+  if (!(threshold & (srv_page_size - 1)))
+    return DB_SUCCESS;
+
+  uint32_t cur_descr_page= xdes_calc_descriptor_page(0, threshold);
+  ulint descr_offset= XDES_ARR_OFFSET + XDES_SIZE
+          * xdes_calc_descriptor_index(0, threshold);
+  ulint last_descr_offset= XDES_ARR_OFFSET + XDES_SIZE
+          * xdes_calc_descriptor_index(
+               0, (cur_descr_page + srv_page_size - 1));
+  last_descr_offset+= XDES_SIZE;
+  dberr_t err= DB_SUCCESS;
+  buf_block_t *block= fsp_get_latched_xdes_page(
+                        cur_descr_page, mtr, &err);
+  if (!block)
+    return err;
+  mtr->memset(
+    block, descr_offset, (last_descr_offset - descr_offset), 0);
+  return err;
+}
+
+/** This function does 2 things by traversing all the used
+extents in the system tablespace
+1) Find the last used extent
+2) Store the old page frame of the "to be modified" extent
+descriptor pages.
+@param space             system tablespace
+@param last_used_extent  value is 0 in case of finding the last used
+                         extent; else it could be last used extent
+@param old_xdes_entry    nullptr or object to store the
+                         old page content of "to be modified"
+                         extent descriptor pages
+@return DB_SUCCESS or error code */
+__attribute__((warn_unused_result))
+dberr_t fsp_traverse_extents(
+  fil_space_t *space, uint32_t *last_used_extent, mtr_t *mtr,
+  fsp_xdes_old_page *old_xdes_entry= nullptr)
+{
+  dberr_t err= DB_SUCCESS;
+  bool find_last_used_extent= (old_xdes_entry == nullptr);
+  uint32_t threshold= *last_used_extent;
+  uint32_t last_descr_page_no= xdes_calc_descriptor_page(
+    0, space->free_limit - 1);
+
+  if (find_last_used_extent)
+    *last_used_extent= space->free_limit;
+  else
+  {
+    err= old_xdes_entry->insert(0, mtr);
+    if (err) return err;
+    if (threshold & (srv_page_size - 1))
+      err= old_xdes_entry->insert(
+        xdes_calc_descriptor_page(0, threshold), mtr);
+  }
+
+  buf_block_t *block= nullptr;
+  std::vector<uint32_t> modified_xdes;
+
+  for (uint32_t cur_extent=
+       ((space->free_limit - 1)/ FSP_EXTENT_SIZE) * FSP_EXTENT_SIZE;
+       cur_extent >= threshold;)
+  {
+    if (!block)
+    {
+      block= fsp_get_latched_xdes_page(last_descr_page_no, mtr, &err);
+      if (!block) return err;
+    }
+
+    xdes_t *descr= XDES_ARR_OFFSET + XDES_SIZE
+      * xdes_calc_descriptor_index(0, cur_extent)
+      + block->page.frame;
+
+    if (find_last_used_extent)
+    {
+      ulint state= xdes_get_state(descr);
+      if (state == XDES_FREE)
+        *last_used_extent= cur_extent;
+      else if (state == XDES_FREE_FRAG &&
+               !(cur_extent & (srv_page_size - 1)) &&
+               xdes_get_n_used(descr) == 2)
+        /* Extent Descriptor Page */
+        *last_used_extent= cur_extent;
+      else return DB_SUCCESS;
+    }
+    else
+    {
+      fil_addr_t prev_addr= flst_get_prev_addr(
+                              descr + XDES_FLST_NODE);
+      ut_ad(prev_addr.page < fil_system.sys_space->size ||
+            prev_addr.page == FIL_NULL);
+      ut_ad(prev_addr.page == FIL_NULL ||
+            !(prev_addr.page & (srv_page_size - 1)));
+
+      fil_addr_t next_addr= flst_get_next_addr(
+                              descr + XDES_FLST_NODE);
+      ut_ad(next_addr.page < fil_system.sys_space->size ||
+            next_addr.page == FIL_NULL);
+      ut_ad(next_addr.page == FIL_NULL ||
+            !(next_addr.page & (srv_page_size - 1)));
+
+      if (prev_addr.page < threshold)
+        modified_xdes.push_back(prev_addr.page);
+
+      if (next_addr.page < threshold)
+        modified_xdes.push_back(next_addr.page);
+    }
+
+    cur_extent-= FSP_EXTENT_SIZE;
+    uint32_t cur_descr_page= xdes_calc_descriptor_page(0, cur_extent);
+    if (last_descr_page_no != cur_descr_page)
+    {
+      if (last_descr_page_no >= threshold)
+        mtr->release_last_page();
+      last_descr_page_no= cur_descr_page;
+      block= nullptr;
+    }
+  }
+
+  if (!find_last_used_extent)
+  {
+    for (auto it : modified_xdes)
+    {
+      err= old_xdes_entry->insert(it, mtr);
+      if (err) return err;
+    }
+    modified_xdes.clear();
+  }
+  return err;
+}
+
+#ifdef UNIV_DEBUG
+/** Validate the system tablespace list */
+__attribute__((warn_unused_result))
+dberr_t fsp_sys_tablespace_validate()
+{
+  /* Validate all FSP list in system tablespace */
+  mtr_t local_mtr;
+  dberr_t err= DB_SUCCESS;
+  local_mtr.start();
+  if (buf_block_t *header= fsp_get_header(
+        fil_system.sys_space, &local_mtr, &err))
+  {
+    flst_validate(header, FSP_FREE + FSP_HEADER_OFFSET, &local_mtr);
+    flst_validate(header, FSP_FREE_FRAG + FSP_HEADER_OFFSET,
+                  &local_mtr);
+    flst_validate(header, FSP_HEADER_OFFSET + FSP_FULL_FRAG,
+                  &local_mtr);
+    flst_validate(header, FSP_HEADER_OFFSET + FSP_SEG_INODES_FULL,
+                  &local_mtr);
+    flst_validate(header, FSP_HEADER_OFFSET + FSP_SEG_INODES_FREE,
+                  &local_mtr);
+  }
+  local_mtr.commit();
+  return err;
+}
+#endif /* UNIV_DEBUG */
+
+void fsp_system_tablespace_truncate()
+{
+  uint32_t last_used_extent= 0;
+  fil_space_t *space= fil_system.sys_space;
+  mtr_t mtr;
+  mtr.start();
+  mtr.x_lock_space(space);
+  dberr_t err= fsp_traverse_extents(space, &last_used_extent, &mtr);
+  if (err != DB_SUCCESS)
+  {
+func_exit:
+    sql_print_warning("InnoDB: Cannot shrink the system tablespace "
+                      "due to %s", ut_strerr(err));
+    mtr.commit();
+    return;
+  }
+  uint32_t fixed_size= srv_sys_space.get_min_size(),
+           header_size= space->size_in_header;
+  mtr.commit();
+
+  if (last_used_extent >= header_size || fixed_size >= header_size)
+    /* Tablespace is being used within fixed size */
+    return;
+
+  /* Set fixed size as threshold to truncate */
+  if (fixed_size > last_used_extent)
+    last_used_extent= fixed_size;
+
+  my_bool old_dblwr_buf= srv_use_doublewrite_buf;
+  /* Flush all pages in buffer pool, so that it doesn't have to
+  use doublewrite buffer and disable dblwr and there should
+  be enough space in redo log */
+  log_make_checkpoint();
+  srv_use_doublewrite_buf= false;
+
+  buf_block_t *header= nullptr;
+  ut_ad(!fsp_sys_tablespace_validate());
+
+  mtr.start();
+  mtr.x_lock_space(space);
+
+  {
+    /* Take the rough estimation of modified extent
+    descriptor page and store their old state */
+    fsp_xdes_old_page old_xdes_list;
+    err= fsp_traverse_extents(space, &last_used_extent, &mtr, &old_xdes_list);
+
+    if (err == DB_OUT_OF_MEMORY)
+    {
+      mtr.commit();
+      sql_print_warning("InnoDB: Cannot shrink the system "
+                        "tablespace from " UINT32PF" to "
+                        UINT32PF " pages due to insufficient "
+                        "innodb_buffer_pool_size", space->size,
+                        last_used_extent);
+      return;
+    }
+
+    sql_print_information("InnoDB: Truncating system tablespace from "
+                          UINT32PF " to " UINT32PF " pages", space->size,
+                          last_used_extent);
+
+    header= fsp_get_latched_xdes_page(0, &mtr, &err);
+    if (!header)
+      goto func_exit;
+
+    mtr.write<4, mtr_t::FORCED>(
+      *header, FSP_HEADER_OFFSET + FSP_SIZE + header->page.frame,
+      last_used_extent);
+
+    if (space->free_limit > last_used_extent)
+      mtr.write<4,mtr_t::MAYBE_NOP>(*header, FSP_HEADER_OFFSET
+                                    + FSP_FREE_LIMIT + header->page.frame,
+                                    last_used_extent);
+    err= fsp_shrink_list(
+      header, FSP_HEADER_OFFSET + FSP_FREE, last_used_extent, &mtr);
+    if (err != DB_SUCCESS)
+      goto func_exit;
+
+    err= fsp_shrink_list(
+      header, FSP_HEADER_OFFSET + FSP_FREE_FRAG, last_used_extent, &mtr);
+    if (err != DB_SUCCESS)
+      goto func_exit;
+
+    err= fsp_xdes_reset(space, last_used_extent, &mtr);
+    if (err != DB_SUCCESS)
+      goto func_exit;
+
+    mtr.trim_pages(page_id_t(0, last_used_extent));
+    size_t shrink_redo_size= mtr.get_log_size();
+
+    DBUG_EXECUTE_IF("mtr_log_max_size", goto mtr_max;);
+    if (shrink_redo_size >
+          (2 << 20) - 8 /* encryption nonce */ - 5 /* EOF, checksum */)
+    {
+#ifndef DBUG_OFF
+mtr_max:
+#endif
+      /* Replace the modified copy from buffer pool with
+      original copy of the pages. */
+      old_xdes_list.restore(&mtr);
+      mtr.discard_modifications();
+      mtr.commit();
+      ut_ad(!fsp_sys_tablespace_validate());
+      sql_print_error(
+        "InnoDB: Cannot shrink the system tablespace "
+        "because the mini-transaction log size (%zu bytes) "
+        "exceeds 2 MiB", shrink_redo_size + 8 + 5);
+      return;
+    }
+  }
+  mysql_mutex_lock(&fil_system.mutex);
+
+  space->size= last_used_extent;
+  if (space->free_limit > last_used_extent)
+    space->free_limit= space->size;
+
+  space->free_len= flst_get_len(
+    FSP_HEADER_OFFSET + FSP_FREE+ header->page.frame);
+
+  /* Last file new size after truncation */
+  uint32_t new_last_file_size=
+    last_used_extent -
+    (fixed_size - srv_sys_space.m_files.at(
+       srv_sys_space.m_files.size() - 1).param_size());
+
+  space->size_in_header= space->size;
+  space->is_being_truncated= true;
+  space->set_stopping();
+  space->chain.end->size= new_last_file_size;
+  srv_sys_space.set_last_file_size(new_last_file_size);
+  mysql_mutex_unlock(&fil_system.mutex);
+  mtr.commit_shrink(*space);
+  sql_print_information("InnoDB: System tablespace truncated successfully");
+  srv_use_doublewrite_buf= old_dblwr_buf;
+}

storage/innobase/fsp/fsp0sysspace.cc

@@ -100,6 +100,7 @@ SysTablespace::parse_params(
 
 	ut_ad(m_last_file_size_max == 0);
 	ut_ad(!m_auto_extend_last_file);
+	ut_ad(!m_auto_shrink);
 
 	char*	new_str = mem_strdup(filepath_spec);
 	char*	str = new_str;
@@ -146,6 +147,11 @@ SysTablespace::parse_params(
 				str = parse_units(str, &size);
 			}
 
+		        if (0 == strncmp(str, ":autoshrink",
+	                         (sizeof ":autoshrink") - 1)) {
+			   str += (sizeof ":autoshrink") - 1;
+			}
+
 			if (*str != '\0') {
 				ut_free(new_str);
 				ib::error()
@@ -266,6 +272,12 @@ SysTablespace::parse_params(
 				str = parse_units(str, &m_last_file_size_max);
 			}
 
+		        if (0 == strncmp(str, ":autoshrink",
+	                         (sizeof ":autoshrink") - 1)) {
+			   str += (sizeof ":autoshrink") - 1;
+			   m_auto_shrink = true;
+			}
+
 			if (*str != '\0') {
 				ut_free(new_str);
 				ib::error() << "syntax error in file path or"
@@ -333,6 +345,7 @@ SysTablespace::shutdown()
 	m_created_new_raw = 0;
 	m_is_tablespace_full = false;
 	m_sanity_checks_done = false;
+	m_auto_shrink = false;
 }
 
 /** Verify the size of the physical file.
@@ -974,6 +987,7 @@ SysTablespace::normalize_size()
 	for (files_t::iterator it = m_files.begin(); it != end; ++it) {
 
 		it->m_size <<= (20U - srv_page_size_shift);
+		it->m_user_param_size = it->m_size;
 	}
 
 	m_last_file_size_max <<= (20U - srv_page_size_shift);

storage/innobase/fut/fut0lst.cc

@@ -35,8 +35,8 @@ Created 11/28/1995 Heikki Tuuri
 @param[in]      page    page number
 @param[in]      boffset byte offset
 @param[in,out]  mtr     mini-transaction */
-static void flst_write_addr(const buf_block_t& block, byte *faddr,
-                            uint32_t page, uint16_t boffset, mtr_t* mtr)
+void flst_write_addr(const buf_block_t &block, byte *faddr,
+                     uint32_t page, uint16_t boffset, mtr_t *mtr)
 {
   ut_ad(mtr->memo_contains_page_flagged(faddr, MTR_MEMO_PAGE_X_FIX |
                                         MTR_MEMO_PAGE_SX_FIX));

storage/innobase/include/fsp0file.h

@@ -317,6 +317,8 @@ class Datafile {
 	void set_space_id(uint32_t space_id) { m_space_id= space_id; }
 
 	void set_flags(uint32_t flags) { m_flags = flags; }
+
+	uint32_t param_size() const { return m_user_param_size; }
 private:
 	/** Free the filepath buffer. */
 	void free_filepath();
@@ -406,6 +408,9 @@ class Datafile {
 	pages in SysTablespace::normalize_size() */
 	uint32_t		m_size;
 
+	/** Size in pages; Initial parameter size */
+	uint32_t		m_user_param_size;
+
 	/** ordinal position of this datafile in the tablespace */
 	ulint			m_order;
 

storage/innobase/include/fsp0fsp.h

@@ -573,6 +573,9 @@ inline void fsp_init_file_page(
 	mtr->init(block);
 }
 
+/** Truncate the system tablespace */
+void fsp_system_tablespace_truncate();
+
 #ifndef UNIV_DEBUG
 # define fsp_init_file_page(space, block, mtr) fsp_init_file_page(block, mtr)
 #endif

storage/innobase/include/fsp0sysspace.h

@@ -119,6 +119,12 @@ class SysTablespace : public Tablespace
 		return(m_auto_extend_last_file);
 	}
 
+	/** @return auto shrink */
+	bool can_auto_shrink() const
+	{
+		return m_auto_shrink;
+	}
+
 	/** Set the last file size.
 	@param[in]	size	the size to set */
 	void set_last_file_size(uint32_t size)
@@ -143,6 +149,16 @@ class SysTablespace : public Tablespace
 			<< (20 - srv_page_size_shift);
 	}
 
+	/**
+	@return user specified tablespace size */
+	uint32_t get_min_size() const
+	{
+	  uint32_t full_size= 0;
+	  for (uint32_t i= 0; i < m_files.size(); i++)
+	    full_size+= m_files.at(i).m_user_param_size;
+	  return full_size;
+	}
+
 	/**
 	@return next increment size */
 	uint32_t get_increment() const;
@@ -251,6 +267,10 @@ class SysTablespace : public Tablespace
 
 	/** if false, then sanity checks are still pending */
 	bool		m_sanity_checks_done;
+
+	/** Shrink the system tablespace if the value is
+	enabled */
+	bool		m_auto_shrink;
 };
 
 /* GLOBAL OBJECTS */

storage/innobase/include/fut0lst.h

@@ -148,6 +148,15 @@ inline fil_addr_t flst_get_prev_addr(const flst_node_t *node)
   return flst_read_addr(node + FLST_PREV);
 }
 
+/** Write a file address.
+@param[in]      block   file page
+@param[in,out]  faddr   file address location
+@param[in]      page    page number
+@param[in]      boffset byte offset
+@param[in,out]  mtr     mini-transaction */
+void flst_write_addr(const buf_block_t &block, byte *faddr,
+                     uint32_t page, uint16_t boffset, mtr_t *mtr);
+
 # ifdef UNIV_DEBUG
 /** Validate a file-based list. */
 void flst_validate(const buf_block_t *base, uint16_t boffset, mtr_t *mtr);

storage/innobase/include/log0recv.h

@@ -235,7 +235,10 @@ struct recv_sys_t
     lsn_t lsn;
     /** truncated size of the tablespace, or 0 if not truncated */
     unsigned pages;
-  } truncated_undo_spaces[127];
+  };
+
+  trunc truncated_undo_spaces[127];
+  trunc truncated_sys_space;
 
 public:
   /** The contents of the doublewrite buffer */
@@ -260,6 +263,12 @@ struct recv_sys_t
       pages_it= pages.end();
   }
 
+  /** Allow to apply system tablespace truncate redo log only
+  if the size to be extended is lesser than current size.
+  @retval true  To apply the truncate shrink redo log record
+  @retval false otherwise */
+  bool check_sys_truncate();
+
 private:
   /** Attempt to initialize a page based on redo log records.
   @param p        iterator

storage/innobase/log/log0recv.cc

@@ -1319,6 +1319,7 @@ void recv_sys_t::create()
 	recv_max_page_lsn = 0;
 
 	memset(truncated_undo_spaces, 0, sizeof truncated_undo_spaces);
+	truncated_sys_space= {0, 0};
 	UT_LIST_INIT(blocks, &buf_block_t::unzip_LRU);
 }
 
@@ -2665,23 +2666,28 @@ recv_sys_t::parse_mtr_result recv_sys_t::parse(source &l, bool if_exists)
         cl= l.copy_if_needed(iv, decrypt_buf, recs, rlen);
         if (rlen == 1 && *cl == TRIM_PAGES)
         {
-#if 0 /* For now, we can only truncate an undo log tablespace */
-          if (UNIV_UNLIKELY(!space_id || !page_no))
-            goto record_corrupted;
-#else
-          if (!srv_is_undo_tablespace(space_id) ||
-              page_no != SRV_UNDO_TABLESPACE_SIZE_IN_PAGES)
+          if (srv_is_undo_tablespace(space_id))
+	  {
+	    if (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. */
+            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 };
-          if (!store && undo_space_trunc)
+              { start_lsn, page_no};
+	  }
+	  else if (space_id != 0) goto record_corrupted;
+	  else
+	  {
+	    /* Shrink the system tablespace */
+            trim({space_id, page_no}, start_lsn);
+            truncated_sys_space= {start_lsn, page_no};
+	  }
+          static_assert(UT_ARR_SIZE(truncated_undo_spaces) ==
+                        TRX_SYS_MAX_UNDO_SPACES, "compatibility");
+          if (!store && undo_space_trunc && space_id)
             undo_space_trunc(space_id);
-#endif
           last_offset= 1; /* the next record must not be same_page  */
           continue;
         }
@@ -3723,6 +3729,30 @@ void recv_sys_t::apply(bool last_batch)
 
     apply_log_recs= true;
 
+    if (truncated_sys_space.lsn)
+    {
+      trim({0, truncated_sys_space.pages}, truncated_sys_space.lsn);
+      fil_node_t *file= UT_LIST_GET_LAST(fil_system.sys_space->chain);
+      ut_ad(file->is_open());
+
+      /* Last file new size after truncation */
+      uint32_t new_last_file_size=
+        truncated_sys_space.pages -
+          (srv_sys_space.get_min_size()
+           - srv_sys_space.m_files.at(
+               srv_sys_space.m_files.size() - 1). param_size());
+
+      os_file_truncate(
+        file->name, file->handle,
+        os_offset_t{new_last_file_size} << srv_page_size_shift, true);
+      mysql_mutex_lock(&fil_system.mutex);
+      fil_system.sys_space->size= truncated_sys_space.pages;
+      fil_system.sys_space->chain.end->size= new_last_file_size;
+      srv_sys_space.set_last_file_size(new_last_file_size);
+      truncated_sys_space={0, 0};
+      mysql_mutex_unlock(&fil_system.mutex);
+    }
+
     for (auto id= srv_undo_tablespaces_open; id--;)
     {
       const trunc& t= truncated_undo_spaces[id];

storage/innobase/mtr/mtr0mtr.cc

@@ -495,12 +495,11 @@ void mtr_t::commit_shrink(fil_space_t &space)
   ut_ad(is_active());
   ut_ad(!high_level_read_only);
   ut_ad(m_modifications);
-  ut_ad(m_made_dirty);
+  ut_ad(!space.id || m_made_dirty);
   ut_ad(!m_memo.empty());
   ut_ad(!recv_recovery_is_on());
   ut_ad(m_log_mode == MTR_LOG_ALL);
   ut_ad(!m_freed_pages);
-  ut_ad(UT_LIST_GET_LEN(space.chain) == 1);
 
   log_write_and_flush_prepare();
   m_latch_ex= true;
@@ -515,8 +514,9 @@ void mtr_t::commit_shrink(fil_space_t &space)
   ut_ad(log_sys.latch.is_write_locked());
 #endif
 
-  os_file_truncate(space.chain.start->name, space.chain.start->handle,
-                   os_offset_t{space.size} << srv_page_size_shift, true);
+  os_file_truncate(
+    space.chain.end->name, space.chain.end->handle,
+    os_offset_t{space.chain.end->size} << srv_page_size_shift, true);
 
   space.clear_freed_ranges();
 

storage/innobase/srv/srv0start.cc

@@ -1733,6 +1733,13 @@ dberr_t srv_start(bool create_new_db)
 		ut_ad(high_level_read_only
 		      || srv_force_recovery < SRV_FORCE_NO_UNDO_LOG_SCAN);
 
+		if (!high_level_read_only
+		    && srv_sys_space.can_auto_shrink()) {
+			fsp_system_tablespace_truncate();
+			DBUG_EXECUTE_IF("crash_after_sys_truncate",
+					return srv_init_abort(DB_ERROR););
+		}
+
 		/* Validate a few system page types that were left
 		uninitialized before MySQL or MariaDB 5.5. */
 		if (!high_level_read_only