diff options
| author | Jianpeng Ma <majianpeng@gmail.com> | 2013-07-03 13:25:24 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2013-07-03 13:25:24 +0200 |
| commit | d50235b7bc3ee0a0427984d763ea7534149531b4 (patch) | |
| tree | acf1916e7926c1a0dddbe08db11ca2426a3816cc /include/linux | |
| parent | a6b3f7614ca690e49e934c291f707b0c19312194 (diff) | |
elevator: Fix a race in elevator switching
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>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/elevator.h | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/elevator.h b/include/linux/elevator.h index acd0312d46f..306dd8cd0b6 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -7,6 +7,7 @@ #ifdef CONFIG_BLOCK struct io_cq; +struct elevator_type; typedef int (elevator_merge_fn) (struct request_queue *, struct request **, struct bio *); @@ -35,7 +36,8 @@ 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 @@ -155,6 +157,8 @@ 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. |