Messages in this thread Patch in this message | | | Date | Thu, 07 Oct 2010 09:42:56 +0200 | From | Jens Axboe <> | Subject | [GIT PULL] single block fix for 2.6.36 |
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Hi Linus,
The API that was added for drivers to switch IO schedulers when loaded does not work if the driver isn't in a fully initialized state. The in-kernel ones call it right after blk_init_queue(), which will result in an oops when the elevator core tries to unregister unregistered kobjects.
Add a registered bit and only do the unregister/register dance in elevator_switch() if we need to. The other call path for this is the sysfs parts to allow online switching, which can only be called with a fully setup driver.
Please pull, this is a regression introduced in this series.
are available in the git repository at: git://git.kernel.dk/linux-2.6-block.git for-linus
Jens Axboe (1): elevator: fix oops on early call to elevator_change()
block/elevator.c | 12 ++++++++---- include/linux/elevator.h | 1 + 2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/block/elevator.c b/block/elevator.c index 205b09a..4e11559 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -938,6 +938,7 @@ int elv_register_queue(struct request_queue *q) } } kobject_uevent(&e->kobj, KOBJ_ADD); + e->registered = 1; } return error; } @@ -947,6 +948,7 @@ static void __elv_unregister_queue(struct elevator_queue *e) { kobject_uevent(&e->kobj, KOBJ_REMOVE); kobject_del(&e->kobj); + e->registered = 0; } void elv_unregister_queue(struct request_queue *q) @@ -1042,11 +1044,13 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) spin_unlock_irq(q->queue_lock); - __elv_unregister_queue(old_elevator); + if (old_elevator->registered) { + __elv_unregister_queue(old_elevator); - err = elv_register_queue(q); - if (err) - goto fail_register; + err = elv_register_queue(q); + if (err) + goto fail_register; + } /* * finally exit old elevator and turn off BYPASS. diff --git a/include/linux/elevator.h b/include/linux/elevator.h index 926b503..4fd978e 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -93,6 +93,7 @@ struct elevator_queue struct elevator_type *elevator_type; struct mutex sysfs_lock; struct hlist_head *hash; + unsigned int registered:1; }; /* -- Jens Axboe
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