Re: [PATCH] Btrfs: remove redundant btrfs_trans_release_metadata"

[Nikolay Borisov <nborisov@suse.com>]

On  5.09.2018 04:14, Liu Bo wrote:
> __btrfs_end_transaction() has done the metadata release twice,
> probably because it used to process delayed refs in between, but now
> that we don't process delayed refs any more, the 2nd release is always
> a noop.
> 
> Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/transaction.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index bb1b9f526e98..94b036a74d11 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -826,12 +826,6 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
>  		return 0;
>  	}
>  
> -	btrfs_trans_release_metadata(trans);
> -	trans->block_rsv = NULL;
> -
> -	if (!list_empty(&trans->new_bgs))
> -		btrfs_create_pending_block_groups(trans);
> -

The only code which can have any implications to the transaction reserve
is the btrfs_Create_pending_block_groups since it does insert items. But
at this point trans->block_rsv is already null and additionally even if
more reservations are made for this transaction further down either
btrfs_commit_transaction is called or the transaction kthread is called
which is going to commit it. So this change really seems inconsequential.

>  	trans->delayed_ref_updates = 0;
>  	if (!trans->sync) {
>  		must_run_delayed_refs =
>