tdb2: save open_flags instead of mmap_flags.

It's more consistent with what tdb1 does, and slightly more encapsulated.

ccan/tdb2/io.c

@@ -42,16 +42,23 @@ void tdb_munmap(struct tdb_file *file)
 
 void tdb_mmap(struct tdb_context *tdb)
 {
+	int mmap_flags;
+
 	if (tdb->flags & TDB_INTERNAL)
 		return;
 
 	if (tdb->flags & TDB_NOMMAP)
 		return;
 
+	if ((tdb->open_flags & O_ACCMODE) == O_RDONLY)
+		mmap_flags = PROT_READ;
+	else
+		mmap_flags = PROT_READ | PROT_WRITE;
+
 	/* size_t can be smaller than off_t. */
 	if ((size_t)tdb->file->map_size == tdb->file->map_size) {
 		tdb->file->map_ptr = mmap(NULL, tdb->file->map_size,
-					  tdb->mmap_flags,
+					  mmap_flags,
 					  MAP_SHARED, tdb->file->fd, 0);
 	} else
 		tdb->file->map_ptr = MAP_FAILED;

ccan/tdb2/open.c

@@ -369,6 +369,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	tdb->log_fn = NULL;
 	tdb->transaction = NULL;
 	tdb->access = NULL;
+	tdb->open_flags = open_flags;
 	tdb->last_error = TDB_SUCCESS;
 	tdb->file = NULL;
 	tdb->lock_fn = tdb_fcntl_lock;
@@ -416,11 +417,9 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 
 	if ((open_flags & O_ACCMODE) == O_RDONLY) {
 		tdb->read_only = true;
-		tdb->mmap_flags = PROT_READ;
 		openlock = F_RDLCK;
 	} else {
 		tdb->read_only = false;
-		tdb->mmap_flags = PROT_READ | PROT_WRITE;
 		openlock = F_WRLCK;
 	}
 

ccan/tdb2/private.h

@@ -334,8 +334,8 @@ struct tdb_context {
 	/* Operating read-only? (Opened O_RDONLY, or in traverse_read) */
 	bool read_only;
 
-	/* mmap read only? */
-	int mmap_flags;
+	/* Open flags passed to tdb_open. */
+	int open_flags;
 
 	/* the flags passed to tdb_open, for tdb_reopen. */
 	uint32_t flags;