MDEV-24142: Replace InnoDB rw_lock_t with sux_lock

InnoDB buffer pool block and index tree latches depend on a
special kind of read-update-write lock that allows reentrant
(recursive) acquisition of the 'update' and 'write' locks
as well as an upgrade from 'update' lock to 'write' lock.
The 'update' lock allows any number of reader locks from
other threads, but no concurrent 'update' or 'write' lock.

If there were no requirement to support an upgrade from 'update'
to 'write', we could compose the lock out of two srw_lock
(implemented as any type of native rw-lock, such as SRWLOCK on
Microsoft Windows). Removing this requirement is very difficult,
so in commit f7e7f487d4b06695f91f6fbeb0396b9d87fc7bbf we
implemented an 'update' mode to our srw_lock.

Re-entrant or recursive locking is mostly needed when writing or
freeing BLOB pages, but also in crash recovery or when merging
buffered changes to an index page. The re-entrancy allows us to
attach a previously acquired page to a sub-mini-transaction that
will be committed before whatever else is holding the page latch.

The SUX lock supports Shared ('read'), Update, and eXclusive ('write')
locking modes. The S latches are not re-entrant, but a single S latch
may be acquired even if the thread already holds an U latch.

The idea of the U latch is to allow a write of something that concurrent
readers do not care about (such as the contents of BTR_SEG_LEAF,
BTR_SEG_TOP and other page allocation metadata structures, or
the MDEV-6076 PAGE_ROOT_AUTO_INC). (The PAGE_ROOT_AUTO_INC field
is only updated when a dict_table_t for the table exists, and only
read when a dict_table_t for the table is being added to dict_sys.)

block_lock::u_lock_try(bool for_io=true) is used in buf_flush_page()
to allow concurrent readers but no concurrent modifications while the
page is being written to the data file. That latch will be released
by buf_page_write_complete() in a different thread. Hence, we use
the special lock owner value FOR_IO.

The index_lock::u_lock() improves concurrency on operations that
involve non-leaf index pages.

The interface has been cleaned up a little. We will use
x_lock_recursive() instead of x_lock() when we know that a
lock is already held by the current thread. Similarly,
a lock upgrade from U to X is only allowed via u_x_upgrade()
or x_lock_upgraded() but not via x_lock().

We will disable the LatchDebug and sync_array interfaces to
InnoDB rw-locks.

The SEMAPHORES section of SHOW ENGINE INNODB STATUS output
will no longer include any information about InnoDB rw-locks,
only TTASEventMutex (cmake -DMUTEXTYPE=event) waits.
This will make a part of the 'innotop' script dead code.

The block_lock buf_block_t::lock will not be covered by any
PERFORMANCE_SCHEMA instrumentation.

SHOW ENGINE INNODB MUTEX and INFORMATION_SCHEMA.INNODB_MUTEXES
will no longer output source code file names or line numbers.
The dict_index_t::lock will be identified by index and table names,
which should be much more useful. PERFORMANCE_SCHEMA is lumping
information about all dict_index_t::lock together as
event_name='wait/synch/sxlock/innodb/index_tree_rw_lock'.

buf_page_free(): Remove the file,line parameters. The sux_lock will
not store such diagnostic information.

buf_block_dbg_add_level(): Define as empty macro, to be removed
in a subsequent commit.

Unless the build was configured with cmake -DPLUGIN_PERFSCHEMA=NO
the index_lock dict_index_t::lock will be instrumented via
PERFORMANCE_SCHEMA. Similar to
commit 1669c88
we will distinguish lock waits by registering shared_lock,exclusive_lock
events instead of try_shared_lock,try_exclusive_lock.
Actual 'try' operations will not be instrumented at all.

rw_lock_list: Remove. After MDEV-24167, this only covered
buf_block_t::lock and dict_index_t::lock. We will output their
information by traversing buf_pool or dict_sys.

Author: dr-m

mysql-test/suite/innodb/disabled.def

@@ -11,3 +11,4 @@
 ##############################################################################
 
 create-index-debug : MDEV-13680 InnoDB may crash when btr_page_alloc() fails
+innodb_wl6326_big : MDEV-24142 FIXME: no instrumentation

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

@@ -243,15 +243,6 @@ innodb_dict_lru_count_idle	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NU
 innodb_dblwr_writes	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of doublewrite operations that have been performed (innodb_dblwr_writes)
 innodb_dblwr_pages_written	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of pages that have been written for doublewrite operations (innodb_dblwr_pages_written)
 innodb_page_size	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	value	InnoDB page size in bytes (innodb_page_size)
-innodb_rwlock_s_spin_waits	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rwlock spin waits due to shared latch request
-innodb_rwlock_x_spin_waits	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rwlock spin waits due to exclusive latch request
-innodb_rwlock_sx_spin_waits	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rwlock spin waits due to sx latch request
-innodb_rwlock_s_spin_rounds	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rwlock spin loop rounds due to shared latch request
-innodb_rwlock_x_spin_rounds	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rwlock spin loop rounds due to exclusive latch request
-innodb_rwlock_sx_spin_rounds	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rwlock spin loop rounds due to sx latch request
-innodb_rwlock_s_os_waits	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of OS waits due to shared latch request
-innodb_rwlock_x_os_waits	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of OS waits due to exclusive latch request
-innodb_rwlock_sx_os_waits	server	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of OS waits due to sx latch request
 dml_reads	dml	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rows read
 dml_inserts	dml	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rows inserted
 dml_deletes	dml	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Number of rows deleted
@@ -373,7 +364,7 @@ SPACE	NAME	ENCRYPTION_SCHEME	KEYSERVER_REQUESTS	MIN_KEY_VERSION	CURRENT_KEY_VERS
 Warnings:
 Warning	1012	InnoDB: SELECTing from INFORMATION_SCHEMA.innodb_tablespaces_encryption but the InnoDB storage engine is not installed
 select * from information_schema.innodb_mutexes;
-NAME	CREATE_FILE	CREATE_LINE	OS_WAITS
+NAME	OS_WAITS
 Warnings:
 Warning	1012	InnoDB: SELECTing from INFORMATION_SCHEMA.innodb_mutexes but the InnoDB storage engine is not installed
 select * from information_schema.innodb_sys_semaphore_waits;

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

@@ -209,15 +209,6 @@ innodb_dict_lru_count_idle	disabled
 innodb_dblwr_writes	disabled
 innodb_dblwr_pages_written	disabled
 innodb_page_size	disabled
-innodb_rwlock_s_spin_waits	disabled
-innodb_rwlock_x_spin_waits	disabled
-innodb_rwlock_sx_spin_waits	disabled
-innodb_rwlock_s_spin_rounds	disabled
-innodb_rwlock_x_spin_rounds	disabled
-innodb_rwlock_sx_spin_rounds	disabled
-innodb_rwlock_s_os_waits	disabled
-innodb_rwlock_x_os_waits	disabled
-innodb_rwlock_sx_os_waits	disabled
 dml_reads	disabled
 dml_inserts	disabled
 dml_deletes	disabled
@@ -272,15 +263,6 @@ lock_row_lock_time	disabled
 lock_row_lock_time_max	disabled
 lock_row_lock_waits	disabled
 lock_row_lock_time_avg	disabled
-innodb_rwlock_s_spin_waits	disabled
-innodb_rwlock_x_spin_waits	disabled
-innodb_rwlock_sx_spin_waits	disabled
-innodb_rwlock_s_spin_rounds	disabled
-innodb_rwlock_x_spin_rounds	disabled
-innodb_rwlock_sx_spin_rounds	disabled
-innodb_rwlock_s_os_waits	disabled
-innodb_rwlock_x_os_waits	disabled
-innodb_rwlock_sx_os_waits	disabled
 set global innodb_monitor_enable = "%lock*";
 ERROR 42000: Variable 'innodb_monitor_enable' can't be set to the value of '%lock*'
 set global innodb_monitor_enable="%%%%%%%%%%%%%%%%%%%%%%%%%%%";

mysql-test/suite/innodb_i_s/innodb_mutexes.result

@@ -2,7 +2,5 @@ SHOW CREATE TABLE INFORMATION_SCHEMA.INNODB_MUTEXES;
 Table	Create Table
 INNODB_MUTEXES	CREATE TEMPORARY TABLE `INNODB_MUTEXES` (
   `NAME` varchar(4000) NOT NULL DEFAULT '',
-  `CREATE_FILE` varchar(4000) NOT NULL DEFAULT '',
-  `CREATE_LINE` int(11) unsigned NOT NULL DEFAULT 0,
   `OS_WAITS` bigint(21) unsigned NOT NULL DEFAULT 0
 ) ENGINE=MEMORY DEFAULT CHARSET=utf8

mysql-test/suite/perfschema/r/sxlock_func.result

@@ -39,14 +39,14 @@ ORDER BY event_name;
 event_name
 wait/synch/rwlock/innodb/dict_operation_lock
 wait/synch/rwlock/innodb/fil_space_latch
-select operation from performance_schema.events_waits_history_long
-where event_name like "wait/synch/sxlock/%"
-  and operation = "shared_lock" limit 1;
-operation
-shared_lock
-select operation from performance_schema.events_waits_history_long
-where event_name like "wait/synch/sxlock/%"
-  and operation = "exclusive_lock" limit 1;
-operation
-exclusive_lock
+SELECT event_name FROM performance_schema.events_waits_history_long
+WHERE event_name = 'wait/synch/sxlock/innodb/index_tree_rw_lock'
+AND operation IN ('try_shared_lock','shared_lock') LIMIT 1;
+event_name
+wait/synch/sxlock/innodb/index_tree_rw_lock
+SELECT event_name from performance_schema.events_waits_history_long
+WHERE event_name = 'wait/synch/sxlock/innodb/index_tree_rw_lock'
+AND operation IN ('try_exclusive_lock','exclusive_lock') LIMIT 1;
+event_name
+wait/synch/sxlock/innodb/index_tree_rw_lock
 UPDATE performance_schema.setup_instruments SET enabled = 'YES', timed = 'YES';

mysql-test/suite/perfschema/t/sxlock_func.test

@@ -52,26 +52,15 @@ ORDER BY event_name;
 
 # Make sure some shared_lock operations have been executed
 
-select operation from performance_schema.events_waits_history_long
-  where event_name like "wait/synch/sxlock/%"
-  and operation = "shared_lock" limit 1;
+SELECT event_name FROM performance_schema.events_waits_history_long
+WHERE event_name = 'wait/synch/sxlock/innodb/index_tree_rw_lock'
+AND operation IN ('try_shared_lock','shared_lock') LIMIT 1;
 
 # Make sure some exclusive_lock operations have been executed
 
-select operation from performance_schema.events_waits_history_long
-  where event_name like "wait/synch/sxlock/%"
-  and operation = "exclusive_lock" limit 1;
-
-# The following operations are not verified in this test:
-# - shared_exclusive_lock
-# - try_shared_lock
-# - try_shared_exclusive_lock
-# - try_exclusive_lock
-# because to observe them:
-# - there must be an actual code path using the operation
-#   (this affects try operations, which are not all used)
-# - there must be a repeatable scenario to trigger the
-#   code path, to use as payload in the test script
+SELECT event_name from performance_schema.events_waits_history_long
+WHERE event_name = 'wait/synch/sxlock/innodb/index_tree_rw_lock'
+AND operation IN ('try_exclusive_lock','exclusive_lock') LIMIT 1;
 
 # Cleanup
 

storage/innobase/CMakeLists.txt

@@ -234,6 +234,7 @@ SET(INNOBASE_SOURCES
 	include/row0upd.h
 	include/row0upd.ic
 	include/row0vers.h
+	include/rw_lock.h
 	include/srv0mon.h
 	include/srv0mon.ic
 	include/srv0srv.h
@@ -242,8 +243,7 @@ SET(INNOBASE_SOURCES
 	include/sync0arr.ic
 	include/sync0debug.h
 	include/sync0policy.h
-	include/sync0rw.h
-	include/sync0rw.ic
+	include/sux_lock.h
 	include/sync0sync.h
 	include/sync0types.h
 	include/trx0i_s.h
@@ -329,7 +329,6 @@ SET(INNOBASE_SOURCES
 	srv/srv0start.cc
 	sync/srw_lock.cc
 	sync/sync0arr.cc
-	sync/sync0rw.cc
 	sync/sync0debug.cc
 	sync/sync0sync.cc
 	trx/trx0i_s.cc

storage/innobase/btr/btr0btr.cc

@@ -299,8 +299,6 @@ btr_height_get(
 
 		/* Release the S latch on the root page. */
 		mtr->memo_release(root_block, MTR_MEMO_PAGE_S_FIX);
-
-		ut_d(sync_check_unlock(&root_block->lock));
 	}
 
 	return(height);
@@ -728,7 +726,7 @@ void btr_page_free(dict_index_t* index, buf_block_t* block, mtr_t* mtr,
 					  : PAGE_HEADER + PAGE_BTR_SEG_TOP];
 	fseg_free_page(seg_header,
 		       index->table->space, id.page_no(), mtr, space_latched);
-	buf_page_free(id, mtr, __FILE__, __LINE__);
+	buf_page_free(id, mtr);
 
 	/* The page was marked free in the allocation bitmap, but it
 	should remain exclusively latched until mtr_t::commit() or until it
@@ -2782,8 +2780,7 @@ btr_page_split_and_insert(
 	ut_ad(!dict_index_is_online_ddl(cursor->index)
 	      || (flags & BTR_CREATE_FLAG)
 	      || dict_index_is_clust(cursor->index));
-	ut_ad(rw_lock_own_flagged(dict_index_get_lock(cursor->index),
-				  RW_LOCK_FLAG_X | RW_LOCK_FLAG_SX));
+	ut_ad(cursor->index->lock.have_u_or_x());
 
 	block = btr_cur_get_block(cursor);
 	page = buf_block_get_frame(block);
@@ -2933,9 +2930,8 @@ btr_page_split_and_insert(
 	    && page_is_leaf(page)
 	    && !dict_index_is_online_ddl(cursor->index)) {
 
-		mtr->memo_release(
-			dict_index_get_lock(cursor->index),
-			MTR_MEMO_X_LOCK | MTR_MEMO_SX_LOCK);
+		mtr->memo_release(&cursor->index->lock,
+				  MTR_MEMO_X_LOCK | MTR_MEMO_SX_LOCK);
 
 		/* NOTE: We cannot release root block latch here, because it
 		has segment header and already modified in most of cases.*/

storage/innobase/btr/btr0bulk.cc

@@ -834,7 +834,7 @@ PageBulk::release()
 	finish();
 
 	/* We fix the block because we will re-pin it soon. */
-	buf_block_buf_fix_inc(m_block, __FILE__, __LINE__);
+	buf_block_buf_fix_inc(m_block);
 
 	/* No other threads can modify this block. */
 	m_modify_clock = buf_block_get_modify_clock(m_block);
@@ -949,9 +949,7 @@ BtrBulk::pageCommit(
 		page_bulk->set_modified();
 	}
 
-	ut_ad(!rw_lock_own_flagged(&m_index->lock,
-				   RW_LOCK_FLAG_X | RW_LOCK_FLAG_SX
-				   | RW_LOCK_FLAG_S));
+	ut_ad(!m_index->lock.have_any());
 
 	/* Compress page if it's a compressed table. */
 	if (page_bulk->getPageZip() != NULL && !page_bulk->compress()) {

storage/innobase/btr/btr0cur.cc

@@ -344,9 +344,9 @@ btr_cur_latch_leaves(
 	case BTR_MODIFY_PREV:
 		mode = latch_mode == BTR_SEARCH_PREV ? RW_S_LATCH : RW_X_LATCH;
 		/* latch also left sibling */
-		rw_lock_s_lock(&block->lock);
+		block->lock.s_lock();
 		left_page_no = btr_page_get_prev(block->frame);
-		rw_lock_s_unlock(&block->lock);
+		block->lock.s_unlock();
 
 		if (left_page_no != FIL_NULL) {
 			latch_leaves.savepoints[0] = mtr_set_savepoint(mtr);
@@ -783,14 +783,14 @@ btr_cur_optimistic_latch_leaves(
 				modify_clock, file, line, mtr));
 	case BTR_SEARCH_PREV:
 	case BTR_MODIFY_PREV:
-		rw_lock_s_lock(&block->lock);
+		block->lock.s_lock();
 		if (block->modify_clock != modify_clock) {
-			rw_lock_s_unlock(&block->lock);
+			block->lock.s_unlock();
 			return false;
 		}
 		const uint32_t curr_page_no = block->page.id().page_no();
 		const uint32_t left_page_no = btr_page_get_prev(block->frame);
-		rw_lock_s_unlock(&block->lock);
+		block->lock.s_unlock();
 
 		const rw_lock_type_t mode = *latch_mode == BTR_SEARCH_PREV
 			? RW_S_LATCH : RW_X_LATCH;
@@ -1481,27 +1481,31 @@ btr_cur_search_to_nth_level_func(
 		upper_rw_latch = RW_X_LATCH;
 		break;
 	case BTR_CONT_MODIFY_TREE:
-	case BTR_CONT_SEARCH_TREE:
-		/* Do nothing */
 		ut_ad(srv_read_only_mode
 		      || mtr->memo_contains_flagged(&index->lock,
 						    MTR_MEMO_X_LOCK
 						    | MTR_MEMO_SX_LOCK));
-		if (dict_index_is_spatial(index)
-		    && latch_mode == BTR_CONT_MODIFY_TREE) {
-			/* If we are about to locating parent page for split
+		if (index->is_spatial()) {
+			/* If we are about to locate parent page for split
 			and/or merge operation for R-Tree index, X latch
 			the parent */
 			upper_rw_latch = RW_X_LATCH;
-		} else {
-			upper_rw_latch = RW_NO_LATCH;
+			break;
 		}
+		/* fall through */
+	case BTR_CONT_SEARCH_TREE:
+		/* Do nothing */
+		ut_ad(srv_read_only_mode
+		      || mtr->memo_contains_flagged(&index->lock,
+						    MTR_MEMO_X_LOCK
+						    | MTR_MEMO_SX_LOCK));
+		upper_rw_latch = RW_NO_LATCH;
 		break;
 	default:
 		if (!srv_read_only_mode) {
 			if (s_latch_by_caller) {
-				ut_ad(rw_lock_own(dict_index_get_lock(index),
-				              RW_LOCK_S));
+				ut_ad(mtr->memo_contains_flagged(
+					      &index->lock, MTR_MEMO_S_LOCK));
 			} else if (!modify_external) {
 				/* BTR_SEARCH_TREE is intended to be used with
 				BTR_ALREADY_S_LATCHED */
@@ -1710,9 +1714,9 @@ btr_cur_search_to_nth_level_func(
 
 		rw_latch = upper_rw_latch;
 
-		rw_lock_s_lock(&block->lock);
+		block->lock.s_lock();
 		left_page_no = btr_page_get_prev(buf_block_get_frame(block));
-		rw_lock_s_unlock(&block->lock);
+		block->lock.s_unlock();
 
 		if (left_page_no != FIL_NULL) {
 			ut_ad(prev_n_blocks < leftmost_from_level);
@@ -1856,7 +1860,7 @@ btr_cur_search_to_nth_level_func(
 				needs to keep tree sx-latch */
 				mtr_release_s_latch_at_savepoint(
 					mtr, savepoint,
-					dict_index_get_lock(index));
+					&index->lock);
 			}
 
 			/* release upper blocks */
@@ -2013,14 +2017,14 @@ btr_cur_search_to_nth_level_func(
 		lock_mutex_exit();
 
 		if (rw_latch == RW_NO_LATCH && height != 0) {
-			rw_lock_s_lock(&(block->lock));
+			block->lock.s_lock();
 		}
 
 		lock_prdt_lock(block, &prdt, index, LOCK_S,
 			       LOCK_PREDICATE, cursor->thr);
 
 		if (rw_latch == RW_NO_LATCH && height != 0) {
-			rw_lock_s_unlock(&(block->lock));
+			block->lock.s_unlock();
 		}
 	}
 
@@ -2094,7 +2098,7 @@ btr_cur_search_to_nth_level_func(
 					ut_ad(mtr->memo_contains_flagged(
 						&index->lock, MTR_MEMO_X_LOCK
 						| MTR_MEMO_SX_LOCK));
-					rw_lock_s_lock(&block->lock);
+					block->lock.s_lock();
 					add_latch = true;
 				}
 
@@ -2126,7 +2130,7 @@ btr_cur_search_to_nth_level_func(
 				}
 
 				if (add_latch) {
-					rw_lock_s_unlock(&block->lock);
+					block->lock.s_unlock();
 				}
 
 				ut_ad(!page_rec_is_supremum(node_ptr));
@@ -3042,7 +3046,7 @@ btr_cur_open_at_rnd_pos_func(
 				if (!srv_read_only_mode) {
 					mtr_release_s_latch_at_savepoint(
 						mtr, savepoint,
-						dict_index_get_lock(index));
+						&index->lock);
 				}
 
 				/* release upper blocks */
@@ -5147,7 +5151,7 @@ btr_cur_pessimistic_update(
 		    && page_is_leaf(block->frame)
 		    && !dict_index_is_online_ddl(index)) {
 
-			mtr_memo_release(mtr, dict_index_get_lock(index),
+			mtr_memo_release(mtr, &index->lock,
 					 MTR_MEMO_X_LOCK | MTR_MEMO_SX_LOCK);
 
 			/* NOTE: We cannot release root block latch here, because it
@@ -5884,7 +5888,7 @@ btr_cur_pessimistic_delete(
 	    && page_is_leaf(page)
 	    && !dict_index_is_online_ddl(index)) {
 
-		mtr_memo_release(mtr, dict_index_get_lock(index),
+		mtr_memo_release(mtr, &index->lock,
 				 MTR_MEMO_X_LOCK | MTR_MEMO_SX_LOCK);
 
 		/* NOTE: We cannot release root block latch here, because it
@@ -7120,7 +7124,7 @@ struct btr_blob_log_check_t {
 		if (UNIV_UNLIKELY(m_op == BTR_STORE_INSERT_BULK)) {
 			offs = page_offset(*m_rec);
 			page_no = (*m_block)->page.id().page_no();
-			buf_block_buf_fix_inc(*m_block, __FILE__, __LINE__);
+			buf_block_buf_fix_inc(*m_block);
 			ut_ad(page_no != FIL_NULL);
 		} else {
 			btr_pcur_store_position(m_pcur, m_mtr);
@@ -7662,9 +7666,6 @@ btr_free_externally_stored_field(
 	ut_ad(rec || !block->page.zip.data);
 
 	for (;;) {
-#ifdef UNIV_DEBUG
-		buf_block_t*	rec_block;
-#endif /* UNIV_DEBUG */
 		buf_block_t*	ext_block;
 
 		mtr_start(&mtr);
@@ -7679,9 +7680,9 @@ btr_free_externally_stored_field(
 		const page_id_t	page_id(page_get_space_id(p),
 					page_get_page_no(p));
 
-#ifdef UNIV_DEBUG
-		rec_block =
-#endif /* UNIV_DEBUG */
+#if 0
+		buf_block_t* rec_block =
+#endif
 		buf_page_get(page_id, rec_zip_size, RW_X_LATCH, &mtr);
 
 		buf_block_dbg_add_level(rec_block, SYNC_NO_ORDER_CHECK);