btrfs: remove unnecessary extent root check in btrfs_defrag_leaves

We only defrag leaves on roots that have SHAREABLE set, so we don't need
to check if we're the extent root as it doesn't have SHAREABLE set.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/tree-defrag.c

@@ -27,14 +27,6 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
 	int next_key_ret = 0;
 	u64 last_ret = 0;
 
-	if (root->fs_info->extent_root == root) {
-		/*
-		 * there's recursion here right now in the tree locking,
-		 * we can't defrag the extent root without deadlock
-		 */
-		goto out;
-	}
-
 	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
 		goto out;