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authorJianpeng Ma <majianpeng@gmail.com>2013-07-03 13:25:24 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-20 08:43:03 -0700
commita6ad83fce072869921cef7c6f4e86bd91639dc34 (patch)
tree4530efd7361b1a8e95229a84ccb2229e1035aba1 /include/linux
parentdead45bd0527751cc9e71c0547d8f19f498441ed (diff)
downloadvexpress-lsk-a6ad83fce072869921cef7c6f4e86bd91639dc34.tar.gz
elevator: Fix a race in elevator switching
commit d50235b7bc3ee0a0427984d763ea7534149531b4 upstream. 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> Cc: Jonghwan Choi <jhbird.choi@samsung.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/elevator.h6
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.