Re: [PATCH v3 3/3] dm zoned: keep polling for idle reclaim after a reclaim pass

[Hannes Reinecke <hare@suse.de>]

On 10/11/26 7:54 PM, Kyrylo Biryuk wrote:
> dmz_reclaim_work() re-arms its DMZ_IDLE_PERIOD poll only when
> dmz_should_reclaim() returns false at the start of a pass. After a pass
> it calls dmz_schedule_reclaim(), which queues the work only if reclaim
> is needed right now. When a pass ends while the target is still busy and
> has enough free zones, nothing is queued at all. Once the target goes
> idle, nothing re-evaluates dmz_should_reclaim() until new I/O arrives or
> user space sends a "reclaim" message, so the random or cache zones that
> filled up under load stay full.
> 
> Seen on md RAID5 members on 27 TB host-managed drives: after heavy
> writes the random zones stayed full for hours on idle targets; the
> workaround was a timer sending "dmsetup message <dev> 0 reclaim". With
> this patch the emptied and filled zones were reclaimed within minutes of
> the targets going idle, without the timer.
> 
> After a pass, requeue the work immediately if reclaim is still needed,
> otherwise re-arm the idle poll.
> 
> Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target")
> Assisted-by: LLM
> Signed-off-by: Kyrylo Biryuk <illofspeed@gmail.com>
> ---
>   drivers/md/dm-zoned-reclaim.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/dm-zoned-reclaim.c b/drivers/md/dm-zoned-reclaim.c
> index 88d56d3c86d..5084e10ea7e 100644
> --- a/drivers/md/dm-zoned-reclaim.c
> +++ b/drivers/md/dm-zoned-reclaim.c
> @@ -556,7 +556,16 @@ static void dmz_reclaim_work(struct work_struct *work)
>   		}
>   	}
>   
> -	dmz_schedule_reclaim(zrc);
> +	/*
> +	 * Keep the worker alive: when a pass ends while the target is busy
> +	 * with enough free zones, dmz_schedule_reclaim() queues nothing and
> +	 * the idle poll is never re-armed, so zones filled under load are not
> +	 * reclaimed once the target goes idle.
> +	 */
> +	if (dmz_should_reclaim(zrc, dmz_reclaim_percentage(zrc)))
> +		mod_delayed_work(zrc->wq, &zrc->work, 0);
> +	else
> +		mod_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
>   }
>   
>   /*

You could simply reschedule here
(ie call 'mod_delayed_work(zrc->wq, &zrc->work, 0)' directly),
as the second branch of the condition will be exercised at the
start of the function anyway.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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