dm cache: age and write back cache entries even without active IO

The policy tick() method is normally called from interrupt context.
Both the mq and smq policies do some bottom half work for the tick
method in their map functions.  However if no IO is going through the
cache, then that bottom half work doesn't occur.  With these policies
this means recently hit entries do not age and do not get written
back as early as we'd like.

Fix this by introducing a new 'can_block' parameter to the tick()
method.  When this is set the bottom half work occurs immediately.
'can_block' is set when the tick method is called every second by the
core target (not in interrupt context).

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

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/dm-cache-policy-internal.h b/drivers/md/dm-cache-policy-internal.h
index ccbe852d5362..2816018faa7f 100644
--- a/drivers/md/dm-cache-policy-internal.h
+++ b/drivers/md/dm-cache-policy-internal.h
@@ -83,10 +83,10 @@ static inline dm_cblock_t policy_residency(struct dm_cache_policy *p)
 	return p->residency(p);
 }
 
-static inline void policy_tick(struct dm_cache_policy *p)
+static inline void policy_tick(struct dm_cache_policy *p, bool can_block)
 {
 	if (p->tick)
-		return p->tick(p);
+		return p->tick(p, can_block);
 }
 
 static inline int policy_emit_config_values(struct dm_cache_policy *p, char *result,