Re: [PATCH 1/7] fs/writeback: avoid to writeback non-expired inode in kupdate writeback

[Tim Chen]

On Fri, 2024-02-09 at 01:20 +0800, Kemeng Shi wrote:
> 
>  
> +static void filter_expired_io(struct bdi_writeback *wb)
> +{
> +	struct inode *inode, *tmp;
> +	unsigned long expired_jiffies = jiffies -
> +		msecs_to_jiffies(dirty_expire_interval * 10);

We have kupdate trigger time hard coded with a factor of 10 to expire interval here.
The kupdate trigger time "mssecs_to_jiffies(dirty_expire_interval * 10)" is
also used in wb_writeback().  It will be better to have a macro or #define
to encapsulate the trigger time so if for any reason we need
to tune the trigger time, we just need to change it at one place.

Tim

> +
> +	spin_lock(&wb->list_lock);
> +	list_for_each_entry_safe(inode, tmp, &wb->b_io, i_io_list)
> +		if (inode_dirtied_after(inode, expired_jiffies))
> +			redirty_tail(inode, wb);
> +
> +	list_for_each_entry_safe(inode, tmp, &wb->b_more_io, i_io_list)
> +		if (inode_dirtied_after(inode, expired_jiffies))
> +			redirty_tail(inode, wb);
> +	spin_unlock(&wb->list_lock);
> +}
> +
>  /*
>   * Explicit flushing or periodic writeback of "old" data.
>   *
> @@ -2070,6 +2087,9 @@ static long wb_writeback(struct bdi_writeback *wb,
>  	long progress;
>  	struct blk_plug plug;
>  
> +	if (work->for_kupdate)
> +		filter_expired_io(wb);
> +
>  	blk_start_plug(&plug);
>  	for (;;) {
>  		/*