On 02/14/2017 08:27 PM, Tahsin Erdogan wrote: > When a new disk shows up, sysfs queue directory is created before elevator > is registered. This allows a user to attempt a scheduler switch even though > the initial registration hasn't completed yet. > > In one scenario, blk_register_queue() calls elv_register_queue() and > right before cfq_registered_queue() is called, another process executes > elevator_switch() and replaces q->elevator with deadline scheduler. When > cfq_registered_queue() executes it interprets e->elevator_data as struct > cfq_data even though it is actually struct deadline_data. > > Grab q->sysfs_lock in blk_register_queue() to synchronize with sysfs > callers. Thanks, this looks good to me - both the grabbing of the lock, and the ordering wrt UDEV_ADD. Queued up. -- Jens Axboe
