Re: [PATCH 04/10] btrfs: only track ref_heads in delayed_ref_updates

[Nikolay Borisov <nborisov@suse.com>]

On 3.12.18 г. 17:20 ч., Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> We use this number to figure out how many delayed refs to run, but
> __btrfs_run_delayed_refs really only checks every time we need a new
> delayed ref head, so we always run at least one ref head completely no
> matter what the number of items on it.  Fix the accounting to only be
> adjusted when we add/remove a ref head.

David,

I think also warrants a forward looking sentence stating that the number
is also going to be used to calculate the required number of bytes in
the delayed refs rsv. Something along the lines of:

In addition to using this number to limit the number of delayed refs
run, a future patch is also going to use it to calculate the amount of
space required for delayed refs space reservation.

> 
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> Signed-off-by: Josef Bacik <jbacik@fb.com>
> ---
>  fs/btrfs/delayed-ref.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
> index b3e4c9fcb664..48725fa757a3 100644
> --- a/fs/btrfs/delayed-ref.c
> +++ b/fs/btrfs/delayed-ref.c
> @@ -251,8 +251,6 @@ static inline void drop_delayed_ref(struct btrfs_trans_handle *trans,
>  	ref->in_tree = 0;
>  	btrfs_put_delayed_ref(ref);
>  	atomic_dec(&delayed_refs->num_entries);
> -	if (trans->delayed_ref_updates)
> -		trans->delayed_ref_updates--;
>  }
>  
>  static bool merge_ref(struct btrfs_trans_handle *trans,
> @@ -467,7 +465,6 @@ static int insert_delayed_ref(struct btrfs_trans_handle *trans,
>  	if (ref->action == BTRFS_ADD_DELAYED_REF)
>  		list_add_tail(&ref->add_list, &href->ref_add_list);
>  	atomic_inc(&root->num_entries);
> -	trans->delayed_ref_updates++;
>  	spin_unlock(&href->lock);
>  	return ret;
>  }
>