[bug report] reimplement IDR and IDA using the radix tree

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Matthew Wilcox,

This is a semi-automatic email about new static checker warnings.

The patch 755edccbffa1: "reimplement IDR and IDA using the radix 
tree" from Dec 7, 2016, leads to the following Smatch complaint:

lib/radix-tree.c:2413 ida_remove()
	 warn: variable dereferenced before check 'node' (see line 2409)

lib/radix-tree.c
  2408		__clear_bit(offset, bitmap->bitmap);
  2409		node_tag_set(&ida->ida_rt, node, IDR_FREE, get_slot_offset(node, slot));
                                                                           ^^^^
Dereference.

  2410		if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
  2411			*slot = NULL;
  2412			kfree(bitmap);
  2413			if (node) {
                            ^^^^
Check.

  2414				node->count--;
  2415				__radix_tree_delete_node(&ida->ida_rt, node);

regards,
dan carpenter