Re: [PATCH 2/2] btrfs: Use list_for_each_entry_safe in free_reloc_roots

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2020/2/21 下午9:11, Nikolay Borisov wrote:
> The function always works on a local copy of the reloc root list, which
> cannot be modified outside of it so using list_for_each_entry is fine.
> Additionally the macro handles empty lists so drop list_empty checks of
> callers. No semantic changes.
>
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> ---
>  fs/btrfs/relocation.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index e5cb64409f7c..f13b79adf6b0 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -2523,13 +2523,10 @@ int prepare_to_merge(struct reloc_control *rc, int err)
>  static noinline_for_stack
>  void free_reloc_roots(struct list_head *list)
>  {
> -	struct btrfs_root *reloc_root;
> +	struct btrfs_root *reloc_root, *tmp;
>
> -	while (!list_empty(list)) {
> -		reloc_root = list_entry(list->next, struct btrfs_root,
> -					root_list);
> +	list_for_each_entry_safe(reloc_root, tmp, list, root_list)
>  		__del_reloc_root(reloc_root);
> -	}
>  }
>
>  static noinline_for_stack
> @@ -2588,15 +2585,13 @@ void merge_reloc_roots(struct reloc_control *rc)
>  out:
>  	if (ret) {
>  		btrfs_handle_fs_error(fs_info, ret, NULL);
> -		if (!list_empty(&reloc_roots))
> -			free_reloc_roots(&reloc_roots);
> +		free_reloc_roots(&reloc_roots);
>
>  		/* new reloc root may be added */
>  		mutex_lock(&fs_info->reloc_mutex);
>  		list_splice_init(&rc->reloc_roots, &reloc_roots);
>  		mutex_unlock(&fs_info->reloc_mutex);
> -		if (!list_empty(&reloc_roots))
> -			free_reloc_roots(&reloc_roots);
> +		free_reloc_roots(&reloc_roots);
>  	}
>
>  	BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
> @@ -4689,8 +4684,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
>  out_free:
>  	kfree(rc);
>  out:
> -	if (!list_empty(&reloc_roots))
> -		free_reloc_roots(&reloc_roots);
> +	free_reloc_roots(&reloc_roots);
>
>  	btrfs_free_path(path);
>
>