On 2026/10/13 16:55, Kyrylo Biryuk wrote:
> An idle target whose random (and cache) zones are all unmapped keeps its
> reclaim work running without pause:
>
> - since commit 90a9b8693f1b ("dm zoned: reclaim random zones when
> idle"), dmz_should_reclaim() returns true when the target is idle and
> the total number of random (and cache) zones is non-zero, whether or
> not any of them holds data;
> - dmz_do_reclaim() then finds no candidate and returns -EBUSY;
> - dmz_reclaim_work() runs dmz_check_dev(), which checks every device
> for media events (a TEST UNIT READY on SCSI disks), and
> dmz_schedule_reclaim() requeues the work with no delay because
> dmz_should_reclaim() is still true.
>
> Without the previous patch, a pass ending while the target is busy and
> has enough free zones can leave reclaim unqueued, which ends the loop;
> keeping the idle poll armed makes it recur whenever the target becomes
> idle. On three 27 TB host-managed drives used
> without cache devices (all random zones free) it kept about three CPUs
> busy and sent about 155,000 TEST UNIT READY commands per second to each
> drive while the target was idle.
>
> Only reclaim on idle when a random or cache zone actually holds data (the
> intent of the "p_unmap < 100" test that commit replaced), and
> handle -EBUSY like -ENOSPC: nothing can progress and no I/O failed, so
> poll again after the idle period instead of rescheduling at once, and
> skip the device check. Use queue_delayed_work() for that poll so work an
> allocation has already queued is not postponed.
>
> Fixes: 90a9b8693f1b ("dm zoned: reclaim random zones when idle")
> Assisted-by: LLM
> Signed-off-by: Kyrylo Biryuk <[email protected]>
This is undoing what patch 1 does. So can you squash this into patch 1 to avoid
the churn?
> ---
> drivers/md/dm-zoned-reclaim.c | 26 +++++++++++++++-----------
> 1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/md/dm-zoned-reclaim.c b/drivers/md/dm-zoned-reclaim.c
> index f1f9adf6039..0d62ade1466 100644
> --- a/drivers/md/dm-zoned-reclaim.c
> +++ b/drivers/md/dm-zoned-reclaim.c
> @@ -470,9 +470,10 @@ static unsigned int dmz_reclaim_percentage(struct
> dmz_reclaim *zrc)
> */
> static bool dmz_should_reclaim(struct dmz_reclaim *zrc, unsigned int p_unmap)
> {
> - unsigned int nr_reclaim;
> + unsigned int nr_reclaim, nr_unmap;
>
> nr_reclaim = dmz_nr_rnd_zones(zrc->metadata, zrc->dev_idx);
> + nr_unmap = dmz_nr_unmap_rnd_zones(zrc->metadata, zrc->dev_idx);
>
> if (dmz_nr_cache_zones(zrc->metadata)) {
> /*
> @@ -483,10 +484,11 @@ static bool dmz_should_reclaim(struct dmz_reclaim *zrc,
> unsigned int p_unmap)
> if (zrc->dev_idx == 0)
> return false;
> nr_reclaim += dmz_nr_cache_zones(zrc->metadata);
> + nr_unmap += dmz_nr_unmap_cache_zones(zrc->metadata);
> }
>
> - /* Reclaim when idle */
> - if (dmz_target_idle(zrc) && nr_reclaim)
> + /* Reclaim when idle, but only if a random or cache zone holds data */
> + if (dmz_target_idle(zrc) && nr_reclaim > nr_unmap)
> return true;
>
> /* If there are still plenty of cache zones, do not reclaim */
> @@ -543,17 +545,19 @@ static void dmz_reclaim_work(struct work_struct *work)
> dmz_nr_rnd_zones(zmd, zrc->dev_idx));
>
> ret = dmz_do_reclaim(zrc);
> + if (ret == -ENOSPC || ret == -EBUSY) {
> + /*
> + * No zone to copy into (-ENOSPC) or no zone to reclaim
> + * (-EBUSY): nothing can progress now and no I/O failed.
> + * Rescheduling immediately would spin; poll instead, without
> + * postponing work that an allocation has already queued.
> + */
> + queue_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
> + return;
> + }
> 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);
--
Damien Le Moal
Western Digital Research
