bcachefs: Fix hidden btree errors when reading roots

We silence btree errors in btree_node_scan, since it's probing and
errors are expected: add a fake pass so that btree_node_scan is no
longer recovery pass 0, and we don't think we're in btree node scan when
reading btree roots.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/recovery_passes.c

@@ -27,6 +27,12 @@ const char * const bch2_recovery_passes[] = {
 	NULL
 };
 
+/* Fake recovery pass, so that scan_for_btree_nodes isn't 0: */
+static int bch2_recovery_pass_empty(struct bch_fs *c)
+{
+	return 0;
+}
+
 static int bch2_set_may_go_rw(struct bch_fs *c)
 {
 	struct journal_keys *keys = &c->journal_keys;

fs/bcachefs/recovery_passes_types.h

@@ -13,6 +13,7 @@
  * must never change:
  */
 #define BCH_RECOVERY_PASSES()							\
+	x(recovery_pass_empty,			41, PASS_SILENT)		\
 	x(scan_for_btree_nodes,			37, 0)				\
 	x(check_topology,			 4, 0)				\
 	x(accounting_read,			39, PASS_ALWAYS)		\