bcachefs: Fix bch2_mount error path

In the bch2_mount() error path, we were calling
deactivate_locked_super(), which calls ->kill_sb(), which in our case
was calling bch2_fs_free() without __bch2_fs_stop().

This changes bch2_mount() to just call bch2_fs_stop() directly.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs.c

@@ -1906,7 +1906,10 @@ static struct dentry *bch2_mount(struct file_system_type *fs_type,
 	return dget(sb->s_root);
 
 err_put_super:
+	sb->s_fs_info = NULL;
+	c->vfs_sb = NULL;
 	deactivate_locked_super(sb);
+	bch2_fs_stop(c);
 	return ERR_PTR(bch2_err_class(ret));
 }
 
@@ -1914,7 +1917,10 @@ static void bch2_kill_sb(struct super_block *sb)
 {
 	struct bch_fs *c = sb->s_fs_info;
 
+	if (c)
+		c->vfs_sb = NULL;
 	generic_shutdown_super(sb);
+	if (c)
 		bch2_fs_free(c);
 }
 

fs/bcachefs/super.c

@@ -581,6 +581,8 @@ void bch2_fs_free(struct bch_fs *c)
 {
 	unsigned i;
 
+	BUG_ON(!test_bit(BCH_FS_STOPPING, &c->flags));
+
 	mutex_lock(&bch_fs_list_lock);
 	list_del(&c->list);
 	mutex_unlock(&bch_fs_list_lock);