Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753762Ab3GAKwK (ORCPT ); Mon, 1 Jul 2013 06:52:10 -0400 Received: from mail-pb0-f54.google.com ([209.85.160.54]:33822 "EHLO mail-pb0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752887Ab3GAKwI (ORCPT ); Mon, 1 Jul 2013 06:52:08 -0400 Date: Mon, 1 Jul 2013 18:52:04 +0800 From: majianpeng To: "Jens Axboe" Cc: linux-kernel Reply-To: majianpeng Subject: [PATCH V1] elevator: Fix a race about elevator switching. X-Priority: 3 X-GUID: A926625F-D679-46F2-9B69-649936A7A52D X-Has-Attach: no X-Mailer: Foxmail 7.0.1.90[en] Mime-Version: 1.0 Message-ID: <201307011851511379161@gmail.com> Content-Type: text/plain; charset="gb2312" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id r61AqKkb032132 Content-Length: 7251 Lines: 243 Thare'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 --- block/cfq-iosched.c | 17 ++++++++++++++--- block/deadline-iosched.c | 16 +++++++++++++--- block/elevator.c | 25 +++++-------------------- block/noop-iosched.c | 17 ++++++++++++++--- include/linux/elevator.h | 6 +++++- 5 files changed, 51 insertions(+), 30 deletions(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index e62e920..c7cfa34 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3960,18 +3960,28 @@ 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; @@ -4045,6 +4055,7 @@ 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 90037b5..1cfef5d 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 603b2c1..3e22301 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -154,7 +154,7 @@ 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; @@ -182,6 +182,7 @@ err: elevator_put(e); return NULL; } +EXPORT_SYMBOL(elevator_alloc); static void elevator_release(struct kobject *kobj) { @@ -234,16 +235,7 @@ 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); @@ -924,16 +916,9 @@ 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 5d1bf70..3de89d4 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; } diff --git a/include/linux/elevator.h b/include/linux/elevator.h index 1866206..c288a2f 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -6,6 +6,7 @@ #ifdef CONFIG_BLOCK struct io_cq; +struct elevator_type; typedef int (elevator_merge_fn) (struct request_queue *, struct request **, struct bio *); @@ -34,7 +35,8 @@ typedef void (elevator_put_req_fn) (struct request *); typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *); typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *); -typedef int (elevator_init_fn) (struct request_queue *); +typedef int (elevator_init_fn) (struct request_queue *, + struct elevator_type *e); typedef void (elevator_exit_fn) (struct elevator_queue *); struct elevator_ops @@ -152,6 +154,8 @@ extern int elevator_init(struct request_queue *, char *); extern void elevator_exit(struct elevator_queue *); extern int elevator_change(struct request_queue *, const char *); extern bool elv_rq_merge_ok(struct request *, struct bio *); +extern struct elevator_queue *elevator_alloc(struct request_queue *, + struct elevator_type *); /* * Helper functions. -- 1.7.9.5 ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?