cfq-iosched: fix possible problem with jiffies wraparound
The RR service tree is indexed by a key that is relative to current jiffies.
This can cause problems on jiffies wraparound.
The patch fixes it using time_before comparison, and changing
the add_front path to use a relative number, too.
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e7f9e4e..ae14cba 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -512,8 +512,11 @@
rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key += cfqq->slice_resid;
cfqq->slice_resid = 0;
- } else
- rb_key = 0;
+ } else {
+ rb_key = -HZ;
+ __cfqq = cfq_rb_first(&cfqd->service_tree);
+ rb_key += __cfqq ? __cfqq->rb_key : jiffies;
+ }
if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
/*
@@ -547,7 +550,7 @@
n = &(*p)->rb_left;
else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
n = &(*p)->rb_right;
- else if (rb_key < __cfqq->rb_key)
+ else if (time_before(rb_key, __cfqq->rb_key))
n = &(*p)->rb_left;
else
n = &(*p)->rb_right;
