kyber: avoid q->disk dereferences in trace points

q->disk becomes invalid after the gendisk is removed.  Work around this
by caching the dev_t for the tracepoints.  The real fix would be to
properly tear down the I/O schedulers with the gendisk, but that is
a much more invasive change.

Signed-off-by: Christoph Hellwig <>
Tested-by: Yi Zhang <>
Signed-off-by: Jens Axboe <>
2 files changed