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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
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')
-rw-r--r--block/cfq-iosched.c17
-rw-r--r--block/deadline-iosched.c16
-rw-r--r--block/elevator.c25
-rw-r--r--block/noop-iosched.c17
4 files changed, 46 insertions, 29 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index d5cd3131c57a..d5bbdcfd0dab 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -4347,18 +4347,28 @@ static void cfq_exit_queue(struct elevator_queue *e)
kfree(cfqd);
}
-static int cfq_init_queue(struct request_queue *q)
+static int cfq_init_queue(struct request_queue *q, struct elevator_type *e)
{
struct cfq_data *cfqd;
struct blkcg_gq *blkg __maybe_unused;
int i, ret;
+ struct elevator_queue *eq;
+
+ eq = elevator_alloc(q, e);
+ if (!eq)
+ return -ENOMEM;
cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
- if (!cfqd)
+ if (!cfqd) {
+ kobject_put(&eq->kobj);
return -ENOMEM;
+ }
+ eq->elevator_data = cfqd;
cfqd->queue = q;
- q->elevator->elevator_data = cfqd;
+ spin_lock_irq(q->queue_lock);
+ q->elevator = eq;
+ spin_unlock_irq(q->queue_lock);
/* Init root service tree */
cfqd->grp_service_tree = CFQ_RB_ROOT;
@@ -4433,6 +4443,7 @@ static int cfq_init_queue(struct request_queue *q)
out_free:
kfree(cfqd);
+ kobject_put(&eq->kobj);
return ret;
}
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;
}
diff --git a/block/elevator.c b/block/elevator.c
index eba5b04c29b1..668394d18588 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -150,7 +150,7 @@ void __init load_default_elevator_module(void)
static struct kobj_type elv_ktype;
-static struct elevator_queue *elevator_alloc(struct request_queue *q,
+struct elevator_queue *elevator_alloc(struct request_queue *q,
struct elevator_type *e)
{
struct elevator_queue *eq;
@@ -170,6 +170,7 @@ err:
elevator_put(e);
return NULL;
}
+EXPORT_SYMBOL(elevator_alloc);
static void elevator_release(struct kobject *kobj)
{
@@ -221,16 +222,7 @@ int elevator_init(struct request_queue *q, char *name)
}
}
- q->elevator = elevator_alloc(q, e);
- if (!q->elevator)
- return -ENOMEM;
-
- err = e->ops.elevator_init_fn(q);
- if (err) {
- kobject_put(&q->elevator->kobj);
- return err;
- }
-
+ err = e->ops.elevator_init_fn(q, e);
return 0;
}
EXPORT_SYMBOL(elevator_init);
@@ -935,16 +927,9 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
spin_unlock_irq(q->queue_lock);
/* allocate, init and register new elevator */
- err = -ENOMEM;
- q->elevator = elevator_alloc(q, new_e);
- if (!q->elevator)
- goto fail_init;
-
- err = new_e->ops.elevator_init_fn(q);
- if (err) {
- kobject_put(&q->elevator->kobj);
+ err = new_e->ops.elevator_init_fn(q, new_e);
+ if (err)
goto fail_init;
- }
if (registered) {
err = elv_register_queue(q);
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index 5d1bf70e33d5..3de89d4690f3 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -59,16 +59,27 @@ noop_latter_request(struct request_queue *q, struct request *rq)
return list_entry(rq->queuelist.next, struct request, queuelist);
}
-static int noop_init_queue(struct request_queue *q)
+static int noop_init_queue(struct request_queue *q, struct elevator_type *e)
{
struct noop_data *nd;
+ struct elevator_queue *eq;
+
+ eq = elevator_alloc(q, e);
+ if (!eq)
+ return -ENOMEM;
nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
- if (!nd)
+ if (!nd) {
+ kobject_put(&eq->kobj);
return -ENOMEM;
+ }
+ eq->elevator_data = nd;
INIT_LIST_HEAD(&nd->queue);
- q->elevator->elevator_data = nd;
+
+ spin_lock_irq(q->queue_lock);
+ q->elevator = eq;
+ spin_unlock_irq(q->queue_lock);
return 0;
}