From 174364f6a8979655f71b04b6492657aec3762703 Mon Sep 17 00:00:00 2001 From: Damien Le Moal Date: Wed, 8 Jul 2020 09:20:22 +0900 Subject: dm zoned: Fix zone reclaim trigger Only triggering reclaim based on the percentage of unmapped cache zones can fail to detect cases where reclaim is needed, e.g. if the target has only 2 or 3 cache zones and only one unmapped cache zone, the percentage of free cache zones is higher than DMZ_RECLAIM_LOW_UNMAP_ZONES (30%) and reclaim does not trigger. This problem, combined with the fact that dmz_schedule_reclaim() is called from dmz_handle_bio() without the map lock held, leads to a race between zone allocation and dmz_should_reclaim() result. Depending on the workload applied, this race can lead to the write path waiting forever for a free zone without reclaim being triggered. Fix this by moving dmz_schedule_reclaim() inside dmz_alloc_zone() under the map lock. This results in checking the need for zone reclaim whenever a new data or buffer zone needs to be allocated. Also fix dmz_reclaim_percentage() to always return 0 if the number of unmapped cache (or random) zones is less than or equal to 1. Suggested-by: Shin'ichiro Kawasaki Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Signed-off-by: Mike Snitzer --- drivers/md/dm-zoned-metadata.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'drivers/md/dm-zoned-metadata.c') diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c index 5cf6f5f552e0..b298fefb022e 100644 --- a/drivers/md/dm-zoned-metadata.c +++ b/drivers/md/dm-zoned-metadata.c @@ -2217,8 +2217,15 @@ struct dm_zone *dmz_alloc_zone(struct dmz_metadata *zmd, unsigned int dev_idx, { struct list_head *list; struct dm_zone *zone; - int i = 0; + int i; + + /* Schedule reclaim to ensure free zones are available */ + if (!(flags & DMZ_ALLOC_RECLAIM)) { + for (i = 0; i < zmd->nr_devs; i++) + dmz_schedule_reclaim(zmd->dev[i].reclaim); + } + i = 0; again: if (flags & DMZ_ALLOC_CACHE) list = &zmd->unmap_cache_list; -- cgit v1.2.3