Messages in this thread Patch in this message | | | Date | Thu, 21 Feb 2013 16:42:45 +0800 | From | majianpeng <> | Subject | elevator: Fix a race about elevator switching. |
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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@gmail.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. -- 1.7.9.5 | |