Follow-up to MDEV-12266: Remove latch_t::m_temp_fsp

There is only one temporary tablespace. Reserving a data member in
each read-write lock object for a Boolean flag seems like a huge waste,
especially because this field was only actually used in debug builds.

LatchDebug::check_order(): Compare to fil_system.temp_space->latch.

storage/innobase/fil/fil0fil.cc

@@ -1480,7 +1480,6 @@ fil_space_create(
 	rw_lock_create(fil_space_latch_key, &space->latch, SYNC_FSP);
 
 	if (space->purpose == FIL_TYPE_TEMPORARY) {
-		ut_d(space->latch.set_temp_fsp());
 		/* SysTablespace::open_or_create() would pass
 		size!=0 to fil_node_create(), so first_time_open
 		would not hold in fil_node_open_file(), and we

storage/innobase/include/sync0types.h

@@ -979,8 +979,7 @@ struct latch_t {
 		UNIV_NOTHROW
 		:
 		m_id(id),
-		m_rw_lock(),
-		m_temp_fsp() { }
+		m_rw_lock() {}
 
 	/** Destructor */
 	virtual ~latch_t() UNIV_NOTHROW { }
@@ -1014,24 +1013,6 @@ struct latch_t {
 		return(sync_latch_get_level(m_id));
 	}
 
-	/** @return true if the latch is for a temporary file space*/
-	bool is_temp_fsp() const
-		UNIV_NOTHROW
-	{
-		return(m_temp_fsp);
-	}
-
-	/** Set the temporary tablespace flag. (For internal temporary
-	tables, MySQL 5.7 does not always acquire the index->lock. We
-	need to figure out the context and add some special rules
-	during the checks.) */
-	void set_temp_fsp()
-		UNIV_NOTHROW
-	{
-		ut_ad(get_id() == LATCH_ID_FIL_SPACE);
-		m_temp_fsp = true;
-	}
-
 	/** @return the latch name, m_id must be set  */
 	const char* get_name() const
 		UNIV_NOTHROW
@@ -1047,9 +1028,6 @@ struct latch_t {
 	/** true if it is a rw-lock. In debug mode, rw_lock_t derives from
 	this class and sets this variable. */
 	bool		m_rw_lock;
-
-	/** true if it is an temporary space latch */
-	bool		m_temp_fsp;
 };
 
 /** Subclass this to iterate over a thread's acquired latch levels. */

storage/innobase/sync/sync0debug.cc

@@ -35,6 +35,7 @@ Created 2012-08-21 Sunny Bains
 
 #include "ut0new.h"
 #include "srv0start.h"
+#include "fil0fil.h"
 
 #include <map>
 #include <vector>
@@ -910,19 +911,10 @@ LatchDebug::check_order(
 
 	case SYNC_TREE_NODE:
 
-		{
-			const latch_t*	fsp_latch;
-
-			fsp_latch = find(latches, SYNC_FSP);
-
-			ut_a((fsp_latch != NULL
-			      && fsp_latch->is_temp_fsp())
-			     || find(latches, SYNC_INDEX_TREE) != 0
-			     || find(latches, SYNC_DICT_OPERATION)
-			     || basic_check(latches,
-					    level, SYNC_TREE_NODE - 1));
-		}
-
+		ut_a(find(latches, SYNC_FSP) == &fil_system.temp_space->latch
+		     || find(latches, SYNC_INDEX_TREE)
+		     || find(latches, SYNC_DICT_OPERATION)
+		     || basic_check(latches, level, SYNC_TREE_NODE - 1));
 		break;
 
 	case SYNC_TREE_NODE_NEW: