From 1b5ed5e1f1315e37380e55102f58bcae3344d2a7 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 10 Nov 2005 08:49:19 +0100 Subject: [BLOCK] cfq-iosched: cfq forced dispatching fix cfq forced dispatching might not return all requests on the queue. This bug can hang elevator switchinig and corrupt request ordering during flush sequence. Signed-off-by: Tejun Heo Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 54 ++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 45 insertions(+), 9 deletions(-) (limited to 'block') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index ecacca9c877e..452538644bce 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -999,7 +999,7 @@ cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) /* * get next queue for service */ -static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd, int force) +static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) { unsigned long now = jiffies; struct cfq_queue *cfqq; @@ -1023,7 +1023,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd, int force) */ if (!RB_EMPTY(&cfqq->sort_list)) goto keep_queue; - else if (!force && cfq_cfqq_class_sync(cfqq) && + else if (cfq_cfqq_class_sync(cfqq) && time_before(now, cfqq->slice_end)) { if (cfq_arm_slice_timer(cfqd, cfqq)) return NULL; @@ -1091,6 +1091,42 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, return dispatched; } +static int +cfq_forced_dispatch_cfqqs(struct list_head *list) +{ + int dispatched = 0; + struct cfq_queue *cfqq, *next; + struct cfq_rq *crq; + + list_for_each_entry_safe(cfqq, next, list, cfq_list) { + while ((crq = cfqq->next_crq)) { + cfq_dispatch_insert(cfqq->cfqd->queue, crq); + dispatched++; + } + BUG_ON(!list_empty(&cfqq->fifo)); + } + return dispatched; +} + +static int +cfq_forced_dispatch(struct cfq_data *cfqd) +{ + int i, dispatched = 0; + + for (i = 0; i < CFQ_PRIO_LISTS; i++) + dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]); + + dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr); + dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr); + dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr); + + cfq_slice_expired(cfqd, 0); + + BUG_ON(cfqd->busy_queues); + + return dispatched; +} + static int cfq_dispatch_requests(request_queue_t *q, int force) { @@ -1100,7 +1136,10 @@ cfq_dispatch_requests(request_queue_t *q, int force) if (!cfqd->busy_queues) return 0; - cfqq = cfq_select_queue(cfqd, force); + if (unlikely(force)) + return cfq_forced_dispatch(cfqd); + + cfqq = cfq_select_queue(cfqd); if (cfqq) { int max_dispatch; @@ -1115,12 +1154,9 @@ cfq_dispatch_requests(request_queue_t *q, int force) cfq_clear_cfqq_wait_request(cfqq); del_timer(&cfqd->idle_slice_timer); - if (!force) { - max_dispatch = cfqd->cfq_quantum; - if (cfq_class_idle(cfqq)) - max_dispatch = 1; - } else - max_dispatch = INT_MAX; + max_dispatch = cfqd->cfq_quantum; + if (cfq_class_idle(cfqq)) + max_dispatch = 1; return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); } -- cgit v1.2.3-70-g09d2