dm cache: wake the worker thread every time we free a migration object

When the cache is idle, writeback work was only being issued every
second.  With this change outstanding writebacks are streamed
constantly.  This offers a writeback performance improvement.

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

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 7829d947ef01..6d36ed3c46a0 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -418,10 +418,13 @@ static struct dm_cache_migration *alloc_migration(struct cache *cache)
 
 static void free_migration(struct dm_cache_migration *mg)
 {
-        if (atomic_dec_and_test(&mg->cache->nr_allocated_migrations))
-                wake_up(&mg->cache->migration_wait);
+        struct cache *cache = mg->cache;
+
+        if (atomic_dec_and_test(&cache->nr_allocated_migrations))
+                wake_up(&cache->migration_wait);
 
-        mempool_free(mg, mg->cache->migration_pool);
+        mempool_free(mg, cache->migration_pool);
+        wake_worker(cache);
 }
 
 static int prealloc_data_structs(struct cache *cache, struct prealloc *p)