Use a fd opened for read/write when syncing slots during startup, take 2.

anarazel · anarazel · commit a586cc4b6c56 · 2019-10-04T13:34:28.000-07:00
Cribbing from dfbaed4: Some operating systems, including the reporter's windows, return EBADFD or similar when fsync() is invoked on a O_RDONLY file descriptor. Unfortunately RestoreSlotFromDisk() does exactly that; which causes failures after restarts in at least some scenarios. If you hit the bug the error message will be something like ERROR: could not fsync file "pg_replslot/$name/state": Bad file descriptor Simply use O_RDWR instead of O_RDONLY when opening the relevant file descriptor to fix the bug. Unfortunately this fix was undone in 82a5649. Re-apply, and add a comment. Bug: 16039 Reported-By: Hans Buschmann Author: Andres Freund Discussion: https://postgr.es/m/16039-196fc97cc05e141c@postgresql.org Backpatch: 12-, as 82a5649
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
@@ -1386,7 +1386,8 @@ RestoreSlotFromDisk(const char *name)
 
 	elog(DEBUG1, "restoring replication slot from \"%s\"", path);
 
-	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
+	/* on some operating systems fsyncing a file requires O_RDWR */
+	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
 
 	/*
 	 * We do not need to handle this as we are rename()ing the directory into
