Re: [PATCH 1/2] writeback: reset dirtied_when when switching wbs

[Tejun Heo <tj@kernel.org>]

On Fri, Oct 16, 2026 at 07:52:29PM +0800, Julian Sun wrote:
> When switching a dirty inode to another wb, inode_do_switch_wbs() puts
> it at the newest end of the target b_dirty list instead of searching
> for its sorted position. This requires updating dirtied_when, which
> move_expired_inodes() uses to decide where to stop scanning.
>
> However, the switch updates dirtied_time_when instead. This leaves
> b_dirty out of order and can make the scan stop before reaching older
> inodes. It also resets the lazytime expiration timestamp, potentially
> delaying timestamp writeback.
>
> Update dirtied_when instead, preserving both the constant-time insertion
> and the lazytime expiration timestamp. Correct the field name in the
> comment and document the distinction between the two inode timestamps.
>
> Fixes: 9a6ebbdbd412 ("writeback: Avoid excessively long inode switching times")
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Julian Sun <sunjunchao@bytedance.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun