Re: [PATCH] btrfs: simplify expression in btrfs_csum_bytes_to_leaves()

[Byongho Lee <bhlee.kernel@gmail.com>]

Hi Stefan,

Stefan Behrens writes:

> The result of the calculation is different, which doesn't look right.
>
The expression comes out this way.
  (root->nodesize + root->nodesize * (BTRFS_MAX_LEVEL - 1)) * 2 * num_items
->(root->nodesize * (1 + BTRFS_MAX_LEVEL - 1)) * 2 * num_items
->(root->nodesize * (BTRFS_MAX_LEVEL)) * 2 * num_items
=>root->nodesize * BTRFS_MAX_LEVEL * 2 * num_items

Am I missing?

>
> On Tue, 26 Jan 2016 16:13:17 +0900, Byongho Lee wrote:
>> Simplify expression in btrfs_csum_bytes_to_leaves().
>> 
>> Signed-off-by: Byongho Lee <bhlee.kernel@gmail.com>
>> ---
>>  fs/btrfs/ctree.h | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>> 
>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>> index a9496644f47d..3ab8026280a2 100644
>> --- a/fs/btrfs/ctree.h
>> +++ b/fs/btrfs/ctree.h
>> @@ -3448,8 +3448,7 @@ u64 btrfs_csum_bytes_to_leaves(struct btrfs_root *root, u64 csum_bytes);
>>  static inline u64 btrfs_calc_trans_metadata_size(struct btrfs_root *root,
>>  						 unsigned num_items)
>>  {
>> -	return (root->nodesize + root->nodesize * (BTRFS_MAX_LEVEL - 1)) *
>> -		2 * num_items;
>> +	return root->nodesize * BTRFS_MAX_LEVEL * 2 * num_items;
>>  }
>>  
>>  /*
>>