dm thin: wake worker when discard is prepared

When discards are prepared it is best to directly wake the worker that
will process them.  The worker will be woken anyway, via periodic
commit, but there is no reason to not wake_worker here.

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

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 41c9e81ba74a..aeb9e20f5978 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2676,10 +2676,13 @@ static int thin_endio(struct dm_target *ti,
         if (h->all_io_entry) {
                 INIT_LIST_HEAD(&work);
                 dm_deferred_entry_dec(h->all_io_entry, &work);
-                spin_lock_irqsave(&pool->lock, flags);
-                list_for_each_entry_safe(m, tmp, &work, list)
-                        list_add(&m->list, &pool->prepared_discards);
-                spin_unlock_irqrestore(&pool->lock, flags);
+                if (!list_empty(&work)) {
+                        spin_lock_irqsave(&pool->lock, flags);
+                        list_for_each_entry_safe(m, tmp, &work, list)
+                                list_add(&m->list, &pool->prepared_discards);
+                        spin_unlock_irqrestore(&pool->lock, flags);
+                        wake_worker(pool);
+                }
         }
 
         mempool_free(h, pool->endio_hook_pool);