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| H A D | blk-sysfs.c | diff b410aff2bd9f101bc096069612391aecce204cd1 Tue Feb 14 21:27:38 CST 2017 Tahsin Erdogan <tahsin@google.com> block: do not allow updates through sysfs until registration completes
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.
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
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