btrfs: qgroup: don't use extent changeset when not needed

The local extent changeset is passed to clear_record_extent_bits() where
it may have some additional memory dynamically allocated for ulist. When
qgroup is disabled, the memory is leaked because in this case the
changeset is not released upon __btrfs_qgroup_release_data() return.

Since the recorded contents of the changeset are not used thereafter, just
don't pass it.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Reported-by: syzbot+81670362c283f3dd889c@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000aa8c0c060ade165e@google.com
Fixes: af0e2aab ("btrfs: qgroup: flush reservations during quota disable")
CC: stable@vger.kernel.org # 6.10+
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/qgroup.c

@@ -4346,10 +4346,9 @@ static int __btrfs_qgroup_release_data(struct btrfs_inode *inode,
 	int ret;
 
 	if (btrfs_qgroup_mode(inode->root->fs_info) == BTRFS_QGROUP_MODE_DISABLED) {
-		extent_changeset_init(&changeset);
 		return clear_record_extent_bits(&inode->io_tree, start,
 						start + len - 1,
-						EXTENT_QGROUP_RESERVED, &changeset);
+						EXTENT_QGROUP_RESERVED, NULL);
 	}
 
 	/* In release case, we shouldn't have @reserved */