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 <majianp...@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
