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authorTejun Heo <tj@kernel.org>2008-11-28 13:32:05 +0900
committerJens Axboe <jens.axboe@oracle.com>2008-12-29 08:28:45 +0100
commit8f11b3e99a1136fcbb67316c3260f085299c0bff (patch)
treebb9b12fe23aceac19e24f674786612d0fcad2142 /block/elevator.c
parentf671620e7d895af221bdfeda751d54fa55ed9546 (diff)
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block: make barrier completion more robust
Barrier completion had the following assumptions. * start_ordered() couldn't finish the whole sequence properly. If all actions are to be skipped, q->ordseq is set correctly but the actual completion was never triggered thus hanging the barrier request. * Drain completion in elv_complete_request() assumed that there's always at least one request in the queue when drain completes. Both assumptions are true but these assumptions need to be removed to improve empty barrier implementation. This patch makes the following changes. * Make start_ordered() use blk_ordered_complete_seq() to mark skipped steps complete and notify __elv_next_request() that it should fetch the next request if the whole barrier has completed inside start_ordered(). * Make drain completion path in elv_complete_request() check whether the queue is empty. Empty queue also indicates drain completion. * While at it, convert 0/1 return from blk_do_ordered() to false/true. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/elevator.c')
-rw-r--r--block/elevator.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/block/elevator.c b/block/elevator.c
index 86836dd179c..261ffaaf47b 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -944,10 +944,14 @@ void elv_completed_request(struct request_queue *q, struct request *rq)
* drained for flush sequence.
*/
if (unlikely(q->ordseq)) {
- struct request *first_rq = list_entry_rq(q->queue_head.next);
- if (q->in_flight == 0 &&
+ struct request *next = NULL;
+
+ if (!list_empty(&q->queue_head))
+ next = list_entry_rq(q->queue_head.next);
+
+ if (!q->in_flight &&
blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
- blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
+ (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
blk_start_queueing(q);
}