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authorTejun Heo <tj@kernel.org>2008-11-28 05:32:07 +0100
committerJens Axboe <jens.axboe@oracle.com>2008-12-29 08:28:45 +0100
commita185eb4bc84155fff35b602ce99602c010de9634 (patch)
treee052052cbac813166b614325b32584d8bb9beff0 /block
parentblock: simplify empty barrier implementation (diff)
downloadlinux-a185eb4bc84155fff35b602ce99602c010de9634.tar.xz
linux-a185eb4bc84155fff35b602ce99602c010de9634.zip
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 <tj@kernel.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-barrier.c14
1 files changed, 13 insertions, 1 deletions
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);