@@ -123,7 +123,7 @@ static void apply_map_update(RelMapFile *map, Oid relationId, Oid fileNode,
123123bool add_okay );
124124static void merge_map_updates (RelMapFile * map ,const RelMapFile * updates ,
125125bool add_okay );
126- static void load_relmap_file (bool shared );
126+ static void load_relmap_file (bool shared , bool lock_held );
127127static void write_relmap_file (bool shared ,RelMapFile * newmap ,
128128bool write_wal ,bool send_sinval ,bool preserve_files ,
129129Oid dbid ,Oid tsid ,const char * dbpath );
@@ -393,12 +393,12 @@ RelationMapInvalidate(bool shared)
393393if (shared )
394394{
395395if (shared_map .magic == RELMAPPER_FILEMAGIC )
396- load_relmap_file (true);
396+ load_relmap_file (true, false );
397397}
398398else
399399{
400400if (local_map .magic == RELMAPPER_FILEMAGIC )
401- load_relmap_file (false);
401+ load_relmap_file (false, false );
402402}
403403}
404404
413413RelationMapInvalidateAll (void )
414414{
415415if (shared_map .magic == RELMAPPER_FILEMAGIC )
416- load_relmap_file (true);
416+ load_relmap_file (true, false );
417417if (local_map .magic == RELMAPPER_FILEMAGIC )
418- load_relmap_file (false);
418+ load_relmap_file (false, false );
419419}
420420
421421/*
@@ -594,7 +594,7 @@ RelationMapInitializePhase2(void)
594594/*
595595 * Load the shared map file, die on error.
596596 */
597- load_relmap_file (true);
597+ load_relmap_file (true, false );
598598}
599599
600600/*
@@ -615,7 +615,7 @@ RelationMapInitializePhase3(void)
615615/*
616616 * Load the local map file, die on error.
617617 */
618- load_relmap_file (false);
618+ load_relmap_file (false, false );
619619}
620620
621621/*
@@ -627,7 +627,7 @@ RelationMapInitializePhase3(void)
627627 * Note that the local case requires DatabasePath to be set up.
628628 */
629629static void
630- load_relmap_file (bool shared )
630+ load_relmap_file (bool shared , bool lock_held )
631631{
632632RelMapFile * map ;
633633char mapfilename [MAXPGPATH ];
@@ -656,12 +656,15 @@ load_relmap_file(bool shared)
656656mapfilename )));
657657
658658/*
659- *Note: we could take RelationMappingLock in shared mode here, but it
660- *seems unnecessary since our read() should be atomic against any
661- *concurrent updater's write(). If thefile is updated shortly after we
662- *look, the sinval signaling mechanism will make us re-read it before we
663- *are able to access any relation that's affected by the change.
659+ *Grab the lock to prevent the file from being updated while we read it,
660+ *unless the caller is already holding the lock. If the file is updated
661+ *shortly after we look, thesinval signaling mechanism will make us
662+ *re-read it before we are able to access any relation that's affected by
663+ * the change.
664664 */
665+ if (!lock_held )
666+ LWLockAcquire (RelationMappingLock ,LW_SHARED );
667+
665668pgstat_report_wait_start (WAIT_EVENT_RELATION_MAP_READ );
666669if (read (fd ,map ,sizeof (RelMapFile ))!= sizeof (RelMapFile ))
667670ereport (FATAL ,
@@ -670,6 +673,9 @@ load_relmap_file(bool shared)
670673mapfilename )));
671674pgstat_report_wait_end ();
672675
676+ if (!lock_held )
677+ LWLockRelease (RelationMappingLock );
678+
673679CloseTransientFile (fd );
674680
675681/* check for correct magic number, etc */
@@ -888,7 +894,7 @@ perform_relmap_update(bool shared, const RelMapFile *updates)
888894LWLockAcquire (RelationMappingLock ,LW_EXCLUSIVE );
889895
890896/* Be certain we see any other updates just made */
891- load_relmap_file (shared );
897+ load_relmap_file (shared , true );
892898
893899/* Prepare updated data in a local variable */
894900if (shared )