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authorTejun Heo <tj@kernel.org>2008-11-28 13:32:06 +0900
committerJens Axboe <jens.axboe@oracle.com>2008-12-29 08:28:45 +0100
commit58eea927d2de43dc6f03d1ba2c46e55854b31540 (patch)
treebb43f43891a3154741bb6a116dc2956342160f15 /block
parent8f11b3e99a1136fcbb67316c3260f085299c0bff (diff)
downloadlinux-2.6.34-ux500-58eea927d2de43dc6f03d1ba2c46e55854b31540.tar.gz
block: simplify empty barrier implementation
Empty barrier required special handling in __elv_next_request() to complete it without letting the low level driver see it. With previous changes, barrier code is now flexible enough to skip the BAR step using the same barrier sequence selection mechanism. Drop the special handling and mask off q->ordered from start_ordered(). Remove blk_empty_barrier() test which now has no user. 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.c16
-rw-r--r--block/elevator.c8
2 files changed, 10 insertions, 14 deletions
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index b03d88013e1..c63044e9c4c 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -162,6 +162,14 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
q->ordered = q->next_ordered;
q->ordseq |= QUEUE_ORDSEQ_STARTED;
+ /*
+ * For an empty barrier, there's no actual BAR request, which
+ * in turn makes POSTFLUSH unnecessary. Mask them off.
+ */
+ if (!rq->hard_nr_sectors)
+ q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
+ QUEUE_ORDERED_DO_POSTFLUSH);
+
/* stash away the original request */
elv_dequeue_request(q, rq);
q->orig_bar_rq = rq;
@@ -171,13 +179,9 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
* Queue ordered sequence. As we stack them at the head, we
* need to queue in reverse order. Note that we rely on that
* no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
- * request gets inbetween ordered sequence. If this request is
- * an empty barrier, we don't need to do a postflush ever since
- * there will be no data written between the pre and post flush.
- * Hence a single flush will suffice.
+ * request gets inbetween ordered sequence.
*/
- if ((q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) &&
- !blk_empty_barrier(q->orig_bar_rq)) {
+ if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
rq = &q->post_flush_rq;
} else
diff --git a/block/elevator.c b/block/elevator.c
index 261ffaaf47b..ff60177a3ba 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -755,14 +755,6 @@ struct request *elv_next_request(struct request_queue *q)
int ret;
while ((rq = __elv_next_request(q)) != NULL) {
- /*
- * Kill the empty barrier place holder, the driver must
- * not ever see it.
- */
- if (blk_empty_barrier(rq)) {
- __blk_end_request(rq, 0, blk_rq_bytes(rq));
- continue;
- }
if (!(rq->cmd_flags & REQ_STARTED)) {
/*
* This is the first time the device driver