Re: [PATCH 05/14] xfs: refactor the ioend merging code

[Darrick J. Wong]

On Thu, Oct 17, 2019 at 07:56:15PM +0200, Christoph Hellwig wrote:
> Introduce two nicely abstracted helper, which can be moved to the iomap
> code later.  Also use list_first_entry_or_null to simplify the code a
> bit.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>

--D

> ---
>  fs/xfs/xfs_aops.c | 73 +++++++++++++++++++++++++++--------------------
>  1 file changed, 42 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 91899de2be09..c29ef69d1e51 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -116,6 +116,22 @@ xfs_destroy_ioend(
>  	}
>  }
>  
> +static void
> +xfs_destroy_ioends(
> +	struct xfs_ioend	*ioend,
> +	int			error)
> +{
> +	struct list_head	tmp;
> +
> +	list_replace_init(&ioend->io_list, &tmp);
> +	xfs_destroy_ioend(ioend, error);
> +	while ((ioend = list_first_entry_or_null(&tmp, struct xfs_ioend,
> +			io_list))) {
> +		list_del_init(&ioend->io_list);
> +		xfs_destroy_ioend(ioend, error);
> +	}
> +}
> +
>  /*
>   * Fast and loose check if this write could update the on-disk inode size.
>   */
> @@ -230,7 +246,6 @@ STATIC void
>  xfs_end_ioend(
>  	struct xfs_ioend	*ioend)
>  {
> -	struct list_head	ioend_list;
>  	struct xfs_inode	*ip = XFS_I(ioend->io_inode);
>  	xfs_off_t		offset = ioend->io_offset;
>  	size_t			size = ioend->io_size;
> @@ -275,16 +290,7 @@ xfs_end_ioend(
>  done:
>  	if (ioend->io_append_trans)
>  		error = xfs_setfilesize_ioend(ioend, error);
> -	list_replace_init(&ioend->io_list, &ioend_list);
> -	xfs_destroy_ioend(ioend, error);
> -
> -	while (!list_empty(&ioend_list)) {
> -		ioend = list_first_entry(&ioend_list, struct xfs_ioend,
> -				io_list);
> -		list_del_init(&ioend->io_list);
> -		xfs_destroy_ioend(ioend, error);
> -	}
> -
> +	xfs_destroy_ioends(ioend, error);
>  	memalloc_nofs_restore(nofs_flag);
>  }
>  
> @@ -333,17 +339,18 @@ xfs_ioend_try_merge(
>  	struct xfs_ioend	*ioend,
>  	struct list_head	*more_ioends)
>  {
> -	struct xfs_ioend	*next_ioend;
> +	struct xfs_ioend	*next;
> +
> +	INIT_LIST_HEAD(&ioend->io_list);
>  
> -	while (!list_empty(more_ioends)) {
> -		next_ioend = list_first_entry(more_ioends, struct xfs_ioend,
> -				io_list);
> -		if (!xfs_ioend_can_merge(ioend, next_ioend))
> +	while ((next = list_first_entry_or_null(more_ioends, struct xfs_ioend,
> +			io_list))) {
> +		if (!xfs_ioend_can_merge(ioend, next))
>  			break;
> -		list_move_tail(&next_ioend->io_list, &ioend->io_list);
> -		ioend->io_size += next_ioend->io_size;
> -		if (next_ioend->io_append_trans)
> -			xfs_ioend_merge_append_transactions(ioend, next_ioend);
> +		list_move_tail(&next->io_list, &ioend->io_list);
> +		ioend->io_size += next->io_size;
> +		if (next->io_append_trans)
> +			xfs_ioend_merge_append_transactions(ioend, next);
>  	}
>  }
>  
> @@ -366,29 +373,33 @@ xfs_ioend_compare(
>  	return 0;
>  }
>  
> +static void
> +xfs_sort_ioends(
> +	struct list_head	*ioend_list)
> +{
> +	list_sort(NULL, ioend_list, xfs_ioend_compare);
> +}
> +
>  /* Finish all pending io completions. */
>  void
>  xfs_end_io(
>  	struct work_struct	*work)
>  {
> -	struct xfs_inode	*ip;
> +	struct xfs_inode	*ip =
> +		container_of(work, struct xfs_inode, i_ioend_work);
>  	struct xfs_ioend	*ioend;
> -	struct list_head	completion_list;
> +	struct list_head	tmp;
>  	unsigned long		flags;
>  
> -	ip = container_of(work, struct xfs_inode, i_ioend_work);
> -
>  	spin_lock_irqsave(&ip->i_ioend_lock, flags);
> -	list_replace_init(&ip->i_ioend_list, &completion_list);
> +	list_replace_init(&ip->i_ioend_list, &tmp);
>  	spin_unlock_irqrestore(&ip->i_ioend_lock, flags);
>  
> -	list_sort(NULL, &completion_list, xfs_ioend_compare);
> -
> -	while (!list_empty(&completion_list)) {
> -		ioend = list_first_entry(&completion_list, struct xfs_ioend,
> -				io_list);
> +	xfs_sort_ioends(&tmp);
> +	while ((ioend = list_first_entry_or_null(&tmp, struct xfs_ioend,
> +			io_list))) {
>  		list_del_init(&ioend->io_list);
> -		xfs_ioend_try_merge(ioend, &completion_list);
> +		xfs_ioend_try_merge(ioend, &tmp);
>  		xfs_end_ioend(ioend);
>  	}
>  }
> -- 
> 2.20.1
>