@@ -136,7 +136,7 @@ static void apply_map_update(RelMapFile *map, Oid relationId, Oid fileNode,
136136bool add_okay );
137137static void merge_map_updates (RelMapFile * map ,const RelMapFile * updates ,
138138bool add_okay );
139- static void load_relmap_file (bool shared );
139+ static void load_relmap_file (bool shared , bool lock_held );
140140static void write_relmap_file (bool shared ,RelMapFile * newmap ,
141141bool write_wal ,bool send_sinval ,bool preserve_files ,
142142Oid dbid ,Oid tsid ,const char * dbpath );
@@ -405,12 +405,12 @@ RelationMapInvalidate(bool shared)
405405if (shared )
406406{
407407if (shared_map .magic == RELMAPPER_FILEMAGIC )
408- load_relmap_file (true);
408+ load_relmap_file (true, false );
409409}
410410else
411411{
412412if (local_map .magic == RELMAPPER_FILEMAGIC )
413- load_relmap_file (false);
413+ load_relmap_file (false, false );
414414}
415415}
416416
425425RelationMapInvalidateAll (void )
426426{
427427if (shared_map .magic == RELMAPPER_FILEMAGIC )
428- load_relmap_file (true);
428+ load_relmap_file (true, false );
429429if (local_map .magic == RELMAPPER_FILEMAGIC )
430- load_relmap_file (false);
430+ load_relmap_file (false, false );
431431}
432432
433433/*
@@ -612,7 +612,7 @@ RelationMapInitializePhase2(void)
612612/*
613613 * Load the shared map file, die on error.
614614 */
615- load_relmap_file (true);
615+ load_relmap_file (true, false );
616616}
617617
618618/*
@@ -633,7 +633,7 @@ RelationMapInitializePhase3(void)
633633/*
634634 * Load the local map file, die on error.
635635 */
636- load_relmap_file (false);
636+ load_relmap_file (false, false );
637637}
638638
639639/*
@@ -695,7 +695,7 @@ RestoreRelationMap(char *startAddress)
695695 * Note that the local case requires DatabasePath to be set up.
696696 */
697697static void
698- load_relmap_file (bool shared )
698+ load_relmap_file (bool shared , bool lock_held )
699699{
700700RelMapFile * map ;
701701char mapfilename [MAXPGPATH ];
@@ -725,12 +725,15 @@ load_relmap_file(bool shared)
725725mapfilename )));
726726
727727/*
728- *Note: we could take RelationMappingLock in shared mode here, but it
729- *seems unnecessary since our read() should be atomic against any
730- *concurrent updater's write(). If thefile is updated shortly after we
731- *look, the sinval signaling mechanism will make us re-read it before we
732- *are able to access any relation that's affected by the change.
728+ *Grab the lock to prevent the file from being updated while we read it,
729+ *unless the caller is already holding the lock. If the file is updated
730+ *shortly after we look, thesinval signaling mechanism will make us
731+ *re-read it before we are able to access any relation that's affected by
732+ * the change.
733733 */
734+ if (!lock_held )
735+ LWLockAcquire (RelationMappingLock ,LW_SHARED );
736+
734737pgstat_report_wait_start (WAIT_EVENT_RELATION_MAP_READ );
735738r = read (fd ,map ,sizeof (RelMapFile ));
736739if (r != sizeof (RelMapFile ))
@@ -747,6 +750,9 @@ load_relmap_file(bool shared)
747750}
748751pgstat_report_wait_end ();
749752
753+ if (!lock_held )
754+ LWLockRelease (RelationMappingLock );
755+
750756if (CloseTransientFile (fd )!= 0 )
751757ereport (FATAL ,
752758(errcode_for_file_access (),
@@ -969,7 +975,7 @@ perform_relmap_update(bool shared, const RelMapFile *updates)
969975LWLockAcquire (RelationMappingLock ,LW_EXCLUSIVE );
970976
971977/* Be certain we see any other updates just made */
972- load_relmap_file (shared );
978+ load_relmap_file (shared , true );
973979
974980/* Prepare updated data in a local variable */
975981if (shared )