From: Jeff Moyer <jmoyer@redhat.com> Date: Tue, 3 Nov 2009 11:36:39 -0500 Subject: [block] cfq-iosched: fix aliased req & cooperation detect Message-id: 1257266206-24003-6-git-send-email-jmoyer@redhat.com O-Subject: [PATCH 05/12] cfq-iosched: fix bug with aliased request and cooperation detection Bugzilla: 456181 448130 427709 RH-Acked-by: Rik van Riel <riel@redhat.com> RH-Acked-by: Josef Bacik <josef@redhat.com> RH-Acked-by: Vivek Goyal <vgoyal@redhat.com> commit 3ac6c9f8a66726745136e46f63600550c3eb6cec Author: Jens Axboe <jens.axboe@oracle.com> Date: Thu Apr 23 12:14:56 2009 +0200 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 <jens.axboe@oracle.com> Signed-off-by: Jeff Moyer <jmoyer@redhat.com> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index b20eba7..7f3674d 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -497,12 +497,13 @@ 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 rb_erase_init(struct rb_node *n, struct rb_root *root) @@ -528,10 +529,10 @@ static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->ioprio, cfqq->next_crq->request->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); + } } static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)