bcachefs: Fix snapshot.c assertion for online fsck

c->curr_recovery_pass can go backwards; this adds a non rewinding
version, c->recovery_pass_done.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -1057,7 +1057,10 @@ struct bch_fs {
 	enum bch_recovery_pass	curr_recovery_pass;
 	/* bitmap of explicitly enabled recovery passes: */
 	u64			recovery_passes_explicit;
+	/* bitmask of recovery passes that we actually ran */
 	u64			recovery_passes_complete;
+	/* never rewinds version of curr_recovery_pass */
+	enum bch_recovery_pass	recovery_pass_done;
 	struct semaphore	online_fsck_mutex;
 
 	/* DEBUG JUNK */

fs/bcachefs/recovery.c

@@ -713,6 +713,7 @@ static int bch2_run_recovery_passes(struct bch_fs *c)
 			c->recovery_passes_complete |= BIT_ULL(c->curr_recovery_pass);
 		}
 		c->curr_recovery_pass++;
+		c->recovery_pass_done = max(c->recovery_pass_done, c->curr_recovery_pass);
 	}
 
 	return ret;
@@ -1197,6 +1198,8 @@ int bch2_fs_initialize(struct bch_fs *c)
 		goto err;
 	}
 
+	c->recovery_pass_done = ARRAY_SIZE(recovery_pass_fns) - 1;
+
 	if (enabled_qtypes(c)) {
 		ret = bch2_fs_quota_read(c);
 		if (ret)

fs/bcachefs/snapshot.c

@@ -123,7 +123,7 @@ bool __bch2_snapshot_is_ancestor(struct bch_fs *c, u32 id, u32 ancestor)
 	struct snapshot_table *t;
 	bool ret;
 
-	EBUG_ON(c->curr_recovery_pass <= BCH_RECOVERY_PASS_check_snapshots);
+	EBUG_ON(c->recovery_pass_done <= BCH_RECOVERY_PASS_check_snapshots);
 
 	rcu_read_lock();
 	t = rcu_dereference(c->snapshots);