From 3ac6c9f8a66726745136e46f63600550c3eb6cec Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 23 Apr 2009 12:14:56 +0200 Subject: [PATCH] cfq-iosched: fix bug with aliased request and cooperation detection cfq_prio_tree_lookup() should return the direct match, yet it always returns zero. Fix that. cfq_prio_tree_add() assumes that we don't get a direct match, while it is very possible that we do. Using O_DIRECT, you can have different cfqq with matching requests, since you don't have the page cache to serialize things for you. Fix this bug by only adding the cfqq if there isn't an existing match. Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 20a54b8..b0b754a 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -584,12 +584,13 @@ cfq_prio_tree_lookup(struct cfq_data *cfqd, int ioprio, sector_t sector, else break; p = n; + cfqq = NULL; } *ret_parent = parent; if (rb_link) *rb_link = p; - return NULL; + return cfqq; } static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) @@ -608,10 +609,10 @@ static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->ioprio, cfqq->next_rq->sector, &parent, &p); - BUG_ON(__cfqq); - - rb_link_node(&cfqq->p_node, parent, p); - rb_insert_color(&cfqq->p_node, root); + if (!__cfqq) { + rb_link_node(&cfqq->p_node, parent, p); + rb_insert_color(&cfqq->p_node, root); + } } /* -- 1.8.2.3