[dm-devel] [PATCH 1/2] dm-log-writes: don't use all the cpu

[josef at toxicpanda.com]

From: Josef Bacik <jbacik at fb.com>

The check to see if the logging kthread needs to go to sleep is wrong,
it checks lc->pending_blocks, which will be non-0 if there are any
blocks that are pending, whether they are ready to be logged or not.
What we really want is to go to sleep until it's time to log blocks, so
change this check so we do actually go to sleep in between flushes.

Signed-off-by: Josef Bacik <jbacik at fb.com>
---
 drivers/md/dm-log-writes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index a1da0eb..9aab510 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -399,7 +399,7 @@ static int log_writes_kthread(void *arg)
 		if (!try_to_freeze()) {
 			set_current_state(TASK_INTERRUPTIBLE);
 			if (!kthread_should_stop() &&
-			    !atomic_read(&lc->pending_blocks))
+			    list_empty(&lc->logging_blocks))
 				schedule();
 			__set_current_state(TASK_RUNNING);
 		}
-- 
2.7.4