Re: [PATCH 1/3] dm zoned: back off when reclaim finds no destination zone

[Hannes Reinecke <hare@suse.de>]

On 10/10/26 12:51 PM, illofspeed wrote:
> When dmz_do_reclaim() fails with -ENOSPC because no free zone is
> available to copy the data into, dmz_reclaim_work() still ends with
> dmz_schedule_reclaim(). If the target is idle, dmz_should_reclaim()
> keeps returning true, the work is queued again with no delay and the
> worker spins on the same failing pass.
> 
> Re-arm the idle poll instead, so that reclaim is retried after
> DMZ_IDLE_PERIOD. The next patch makes -ENOSPC the expected result when
> an idle target has random zones but no free sequential zone.
> 
> Tested on a 7.2.6 kernel as an out-of-tree dm-zoned module, together
> with the next two patches, on emulated host-managed drives (tcmu-runner
> ZBC handler) and on three 27 TB host-managed drives used as md RAID5
> members.
> 
> Assisted-by: LLM
> Signed-off-by: illofspeed <volvo.mail@gmail.com>
> ---
>   drivers/md/dm-zoned-reclaim.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/md/dm-zoned-reclaim.c b/drivers/md/dm-zoned-reclaim.c
> index c041413c729..315f0da99f3 100644
> --- a/drivers/md/dm-zoned-reclaim.c
> +++ b/drivers/md/dm-zoned-reclaim.c
> @@ -540,6 +540,14 @@ static void dmz_reclaim_work(struct work_struct *work)
>   	if (ret && ret != -EINTR) {
>   		if (!dmz_check_dev(zmd))
>   			return;
> +		if (ret == -ENOSPC) {
> +			/*
> +			 * No zone to copy into: nothing can progress now.
> +			 * Rescheduling immediately would spin; poll instead.
> +			 */
> +			mod_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
> +			return;
> +		}
>   	}
>   
>   	dmz_schedule_reclaim(zrc);

Reviewed-by: Hannes Reinecke <hare@kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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