From: Tejun Heo Date: Fri, 28 Nov 2008 04:32:07 +0000 (+0900) Subject: block: fix empty barrier on write-through w/ ordered tag X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a185eb4bc84155fff35b602ce99602c010de9634;p=linux-beck.git block: fix empty barrier on write-through w/ ordered tag Empty barrier on write-through (or no cache) w/ ordered tag has no command to execute and without any command to execute ordered tag is never issued to the device and the ordering is never achieved. Force draining for such cases. Signed-off-by: Tejun Heo Signed-off-by: Jens Axboe --- diff --git a/block/blk-barrier.c b/block/blk-barrier.c index c63044e9c4c0..8eba4e43bb0c 100644 --- a/block/blk-barrier.c +++ b/block/blk-barrier.c @@ -166,9 +166,21 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp) * For an empty barrier, there's no actual BAR request, which * in turn makes POSTFLUSH unnecessary. Mask them off. */ - if (!rq->hard_nr_sectors) + if (!rq->hard_nr_sectors) { q->ordered &= ~(QUEUE_ORDERED_DO_BAR | QUEUE_ORDERED_DO_POSTFLUSH); + /* + * Empty barrier on a write-through device w/ ordered + * tag has no command to issue and without any command + * to issue, ordering by tag can't be used. Drain + * instead. + */ + if ((q->ordered & QUEUE_ORDERED_BY_TAG) && + !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) { + q->ordered &= ~QUEUE_ORDERED_BY_TAG; + q->ordered |= QUEUE_ORDERED_BY_DRAIN; + } + } /* stash away the original request */ elv_dequeue_request(q, rq);