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authorJianpeng Ma <majianpeng@gmail.com>2013-07-03 13:25:24 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-20 08:43:03 -0700
commita6ad83fce072869921cef7c6f4e86bd91639dc34 (patch)
tree4530efd7361b1a8e95229a84ccb2229e1035aba1 /block/deadline-iosched.c
parentdead45bd0527751cc9e71c0547d8f19f498441ed (diff)
downloadlinux-linaro-stable-a6ad83fce072869921cef7c6f4e86bd91639dc34.tar.gz
elevator: Fix a race in elevator switching
commit d50235b7bc3ee0a0427984d763ea7534149531b4 upstream. There's a race between elevator switching and normal io operation. Because the allocation of struct elevator_queue and struct elevator_data don't in a atomic operation.So there are have chance to use NULL ->elevator_data. For example: Thread A: Thread B blk_queu_bio elevator_switch spin_lock_irq(q->queue_block) elevator_alloc elv_merge elevator_init_fn Because call elevator_alloc, it can't hold queue_lock and the ->elevator_data is NULL.So at the same time, threadA call elv_merge and nedd some info of elevator_data.So the crash happened. Move the elevator_alloc into func elevator_init_fn, it make the operations in a atomic operation. Using the follow method can easy reproduce this bug 1:dd if=/dev/sdb of=/dev/null 2:while true;do echo noop > scheduler;echo deadline > scheduler;done The test method also use this method. Signed-off-by: Jianpeng Ma <majianpeng@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Cc: Jonghwan Choi <jhbird.choi@samsung.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block/deadline-iosched.c')
-rw-r--r--block/deadline-iosched.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index ba19a3afab79..20614a332362 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -337,13 +337,21 @@ static void deadline_exit_queue(struct elevator_queue *e)
/*
* initialize elevator private data (deadline_data).
*/
-static int deadline_init_queue(struct request_queue *q)
+static int deadline_init_queue(struct request_queue *q, struct elevator_type *e)
{
struct deadline_data *dd;
+ struct elevator_queue *eq;
+
+ eq = elevator_alloc(q, e);
+ if (!eq)
+ return -ENOMEM;
dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
- if (!dd)
+ if (!dd) {
+ kobject_put(&eq->kobj);
return -ENOMEM;
+ }
+ eq->elevator_data = dd;
INIT_LIST_HEAD(&dd->fifo_list[READ]);
INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
@@ -355,7 +363,9 @@ static int deadline_init_queue(struct request_queue *q)
dd->front_merges = 1;
dd->fifo_batch = fifo_batch;
- q->elevator->elevator_data = dd;
+ spin_lock_irq(q->queue_lock);
+ q->elevator = eq;
+ spin_unlock_irq(q->queue_lock);
return 0;
}