blk-cgroup: clear the throttle queue on fork

We were hitting a panic in production where we put too many times on the
request queue.  This is because we'd get the throttle_queue of the
parent if we fork()'ed while we needed to be throttled, but we didn't
have a reference on it.  Instead just clear these flags on fork so the
child doesn't pay for the sins of its father.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/kernel/fork.c b/kernel/fork.c
index 9440d61b925ca08faa3beb7d3a02fedfdd0a9b84..694ae0e56866d3ce0015e892580a75a87927385b 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -843,6 +843,11 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
        tsk->fail_nth = 0;
 #endif
 
+#ifdef CONFIG_BLK_CGROUP
+       tsk->throttle_queue = NULL;
+       tsk->use_memdelay = 0;
+#endif
+
        return tsk;
 
 free_stack: