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Date: Mon, 15 Apr 2013 18:52:19 +0800
From: majianpeng <majianpeng@...il.com>
To: Jens Axboe <jaxboe@...ionio.com>
CC: linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: elevator: Fix a race about elevator switching.
Hi Jens,
How about this patch? It was a long time.
Thanks!
Jianpeng Ma
> 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_flush_plug_list elevator_switch
> __elv_add_request)
> blk_peek_request elevator_alloc
> noop_dispatch
> elevator_init_fn
> Because call elevator_alloc, it can't hold queue_lock and the
> ->elevator_data is NULL after allocating.So at the same time, threadA call elv_merge and
> nedd some info of elevator_data.So the crash happened.
> [ 196.125709] BUG: unable to handle kernel
> [ 196.126046] Modules linked in: netconsole configfs nfsd lockd auth_rpcgss sunrpc exportfs raid1 btrfs zlib_deflate libcrc32c
> [ 196.126046] CPU 2
> [ 196.126046] Pid: 6747, comm: dd Not tainted 3.8.0+ #107 To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M.
> [ 196.126046] RIP: 0010:[<ffffffff812a8c63>] [<ffffffff812a8c63>] noop_dispatch+0x13/0x40
> [ 196.126046] RSP: 0018:ffff8800a6fef838 EFLAGS: 00010046
> [ 196.126046] RAX: 0000000000000000 RBX: ffff8800b53abf20 RCX: 0000000000000000
> [ 196.126046] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8800b53abf20
> [ 196.126046] RBP: ffff8800a6fef838 R08: 0000000000000000 R09: 0000000000000000
> [ 196.126046] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8800b53abf20
> [ 196.126046] R13: ffff8800a6feffd8 R14: ffff8800a6feffd8 R15: ffff8800b3c68090
> [ 196.126046] FS: 00007f6ef48d6700(0000) GS:ffff8800ba000000(0000) knlGS:0000000000000000
> [ 196.126046] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [ 196.126046] CR2: 0000000000000000 CR3: 00000000a83a1000 CR4: 00000000000407e0
> [ 196.126046] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 196.126046] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 196.126046] Process dd (pid: 6747, threadinfo ffff8800a6fee000, task ffff88009e2a2840)
> [ 196.126046] Stack:
> [ 196.126046] ffff8800a6fef888 ffffffff81297a54 ffff8800b50de7b0 ffff8800b3c68090
> [ 196.126046] ffff8800a6fef888 ffff8800b3c68000 ffff8800b53abf20 0000000000000000
> [ 196.126046] ffff8800b50de7b0 ffff8800b3c68090 ffff8800a6fef8f8 ffffffff8140fe5a
> [ 196.126046] Call Trace:
> [ 196.126046] [<ffffffff81297a54>] blk_peek_request+0x194/0x250
> [ 196.126046] [<ffffffff8140fe5a>] scsi_request_fn+0x4a/0x4f0
> [ 196.126046] [<ffffffff810995ef>] ? __lock_is_held+0x5f/0x80
> [ 196.126046] [<ffffffff81290d37>] __blk_run_queue+0x37/0x50
> [ 196.126046] [<ffffffff812904cd>] __elv_add_request+0xad/0x2d0
> [ 196.126046] [<ffffffff81297ecc>] blk_flush_plug_list+0x1bc/0x260
> [ 196.126046] [<ffffffff81297f88>] blk_finish_plug+0x18/0x50
> [ 196.126046] [<ffffffff81195f1e>] do_blockdev_direct_IO+0x18be/0x20e0
> [ 196.126046] [<ffffffff81077cd8>] ? sched_clock_cpu+0xa8/0x120
> [ 196.126046] [<ffffffff811913d0>] ? I_BDEV+0x10/0x10
> [ 196.126046] [<ffffffff810d0868>] ? rcu_irq_exit+0x68/0xb0
> [ 196.126046] [<ffffffff81196795>] __blockdev_direct_IO+0x55/0x60
> [ 196.126046] [<ffffffff811913d0>] ? I_BDEV+0x10/0x10
> [ 196.126046] [<ffffffff81191c67>] blkdev_direct_IO+0x57/0x60
> [ 196.126046] [<ffffffff811913d0>] ? I_BDEV+0x10/0x10
> [ 196.126046] [<ffffffff81106633>] generic_file_aio_read+0x703/0x770
> [ 196.126046] [<ffffffff811915c1>] blkdev_aio_read+0x51/0x80
> [ 196.126046] [<ffffffff81095d45>] ? lock_release_holdtime.part.23+0x15/0x1a0
> [ 196.126046] [<ffffffff81157bb3>] do_sync_read+0xa3/0xe0
> [ 196.126046] [<ffffffff81158343>] vfs_read+0xb3/0x180
> [ 196.126046] [<ffffffff81158465>] sys_read+0x55/0xa0
> [ 196.126046] [<ffffffff816f4242>] system_call_fastpath+0x16/0x1b
> [ 196.126046] Code: 48 83 c4 08 5b 5d c3 90 b8 10 00 00 00 eb e0 b8 f4 ff ff ff eb ea 66 90 66 66 66 66 90 48 8b 47 18 55 48 89 e5 48 8b 50 08 31 c0 <48> 8b 32 48 39 f2 74 1f 48 8b 46 08 48 8b 16 48 89 42 08 48 89
> [ 196.126046] RIP [<ffffffff812a8c63>] noop_dispatch+0x13/0x40
> [ 196.126046] RSP <ffff8800a6fef838>
> [ 196.126046] CR2: 0000000000000000
>
> 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@...il.com>
> ---
> 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.
--
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