Hi,
In cfq_find_next_crq(), when determining rbnext, if
rb_next(&last->rb_node) is NULL, rb_first() is used without checking
if it equals last. If it equals last, rbnext should be NULL not last.
This bug is masked by duplicate calls to cfq_find_next_crq which ends
up clearing cfqq->next_crq as, on the second call, last isn't on rb
tree.
This patch fixes cfq_find_next_crq() and removes extra calls to
cfq_update_next_crq().
Signed-off-by: Tejun Heo <[email protected]>
Index: blk-fixes/drivers/block/cfq-iosched.c
===================================================================
--- blk-fixes.orig/drivers/block/cfq-iosched.c 2005-07-26 14:35:41.000000000 +0900
+++ blk-fixes/drivers/block/cfq-iosched.c 2005-07-26 14:43:14.000000000 +0900
@@ -195,7 +195,6 @@ struct cfq_rq {
static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned long);
static void cfq_dispatch_sort(request_queue_t *, struct cfq_rq *);
-static void cfq_update_next_crq(struct cfq_rq *);
static void cfq_put_cfqd(struct cfq_data *cfqd);
/*
@@ -235,8 +234,6 @@ static void cfq_remove_merge_hints(reque
if (q->last_merge == crq->request)
q->last_merge = NULL;
-
- cfq_update_next_crq(crq);
}
static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
@@ -380,8 +377,11 @@ cfq_find_next_crq(struct cfq_data *cfqd,
if (!ON_RB(&last->rb_node))
return NULL;
- if ((rbnext = rb_next(&last->rb_node)) == NULL)
+ if ((rbnext = rb_next(&last->rb_node)) == NULL) {
rbnext = rb_first(&cfqq->sort_list);
+ if (rbnext == &last->rb_node)
+ rbnext = NULL;
+ }
rbprev = rb_prev(&last->rb_node);
@@ -721,7 +721,6 @@ cfq_merged_requests(request_queue_t *q,
}
}
- cfq_update_next_crq(cnext);
cfq_remove_request(q, next);
}
-
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