On 04/27/2016 06:06 AM, xiakaixu wrote:
+void __wbt_done(struct rq_wb *rwb)
+{
+ int inflight, limit = rwb->wb_normal;
+
+ /*
+ * If the device does write back caching, drop further down
+ * before we wake people up.
+ */
+ if (rwb->wc && !atomic_read(&rwb->bdi->wb.dirty_sleeping))
+ limit = 0;
+ else
+ limit = rwb->wb_normal;
+
+ /*
+ * Don't wake anyone up if we are above the normal limit. If
+ * throttling got disabled (limit == 0) with waiters, ensure
+ * that we wake them up.
+ */
+ inflight = atomic_dec_return(&rwb->inflight);
+ if (limit && inflight >= limit) {
+ if (!rwb->wb_max)
+ wake_up_all(&rwb->wait);
+ return;
+ }
+
Hi Jens,
Just a little confused about this. The rwb->wb_max can't be 0 if the variable
'limit' does not equal to 0. So the if (!rwb->wb_max) branch maybe does not
make sense.
You are right, it doesn't make a lot of sense. I think it suffers from
code shuffling. How about the attached? The important part is that we
wake up waiters, if wbt got disabled while we had tracked IO in flight.
--
Jens Axboe
diff --git a/lib/wbt.c b/lib/wbt.c
index 650da911f24f..a6b80c135510 100644
--- a/lib/wbt.c
+++ b/lib/wbt.c
@@ -98,18 +98,23 @@ void __wbt_done(struct rq_wb *rwb)
else
limit = rwb->wb_normal;
+ inflight = atomic_dec_return(&rwb->inflight);
+
/*
- * Don't wake anyone up if we are above the normal limit. If
- * throttling got disabled (limit == 0) with waiters, ensure
- * that we wake them up.
+ * wbt got disabled with IO in flight. Wake up any potential
+ * waiters, we don't have to do more than that.
*/
- inflight = atomic_dec_return(&rwb->inflight);
- if (limit && inflight >= limit) {
- if (!rwb->wb_max)
- wake_up_all(&rwb->wait);
+ if (!rwb_enabled(rwb)) {
+ wake_up_all(&rwb->wait);
return;
}
+ /*
+ * Don't wake anyone up if we are above the normal limit.
+ */
+ if (inflight >= limit)
+ return;
+
if (waitqueue_active(&rwb->wait)) {
int diff = limit - inflight;
