dm cache policy smq: stop preemptively demoting blocks

It causes a lot of churn if the working set's size is close to the fast
device's size.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 5 insertions, 12 deletions

diff --git a/drivers/md/dm-cache-policy-smq.c b/drivers/md/dm-cache-policy-smq.c
index 54421a846a0c..758480a1893d 100644
--- a/drivers/md/dm-cache-policy-smq.c
+++ b/drivers/md/dm-cache-policy-smq.c
@@ -1134,13 +1134,10 @@ static bool clean_target_met(struct smq_policy *mq, bool idle)
                 percent_to_target(mq, CLEAN_TARGET);
 }
 
-static bool free_target_met(struct smq_policy *mq, bool idle)
+static bool free_target_met(struct smq_policy *mq)
 {
         unsigned nr_free;
 
-        if (!idle)
-                return true;
-
         nr_free = from_cblock(mq->cache_size) - mq->cache_alloc.nr_allocated;
         return (nr_free + btracker_nr_demotions_queued(mq->bg_work)) >=
                 percent_to_target(mq, FREE_TARGET);
@@ -1220,7 +1217,7 @@ static void queue_promotion(struct smq_policy *mq, dm_oblock_t oblock,
                  * We always claim to be 'idle' to ensure some demotions happen
                  * with continuous loads.
                  */
-                if (!free_target_met(mq, true))
+                if (!free_target_met(mq))
                         queue_demotion(mq);
                 return;
         }
@@ -1421,14 +1418,10 @@ static int smq_get_background_work(struct dm_cache_policy *p, bool idle,
         spin_lock_irqsave(&mq->lock, flags);
         r = btracker_issue(mq->bg_work, result);
         if (r == -ENODATA) {
-                /* find some writeback work to do */
-                if (mq->migrations_allowed && !free_target_met(mq, idle))
-                        queue_demotion(mq);
-
-                else if (!clean_target_met(mq, idle))
+                if (!clean_target_met(mq, idle)) {
                         queue_writeback(mq);
-
-                r = btracker_issue(mq->bg_work, result);
+                        r = btracker_issue(mq->bg_work, result);
+                }
         }
         spin_unlock_irqrestore(&mq->lock, flags);