[fnst-kernel 10816] Found several problems while reading btrfs code

[liubo <liubo2009@cn.fujitsu.com>]

Hi, Chris,

We've found several tiny problems while reading btrfs code.

These problems are mainly about uncheck return value or BUG_ON check. 
They really have an impact on codes' quality, though they will not be 
hit in normal cases.

Here comes some examples:

1. memory allocation check
May cause -ENOMEM, btrfs BUG_ON().

static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
...
        path = btrfs_alloc_path();
        BUG_ON(!path);

2. return value's BUG_ON() check

static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
...
        if (btrfs_block_can_be_shared(root, buf)) {
                ret = btrfs_lookup_extent_info(trans, root, buf->start,
                                               buf->len, &refs, &flags);
                BUG_ON(ret);
                BUG_ON(refs == 0);



Is there a plan to improve the above? 
We are helpful on this:)


thanks, 
liubo