[PATCH 0/2] fixes for the updating nr_hw_queues

From: Jianchao Wang
Date: Wed Aug 15 2018 - 03:24:09 EST

Two fixes for updating nr_hw_queues.

The first patch fixes the following scenario:
Kyber depends on the mapping between cpu and nr_hw_queues. When
update nr_hw_queues, elevator_type->ops.mq.init_hctx will be
invoked before the mapping is adapted correctly, this would cause
panic in kyber.

The second patch fixes the following scenario:
part_in_flight/rw will invoke blk_mq_in_flight/rw to account the
inflight requests. It will access the queue_hw_ctx and nr_hw_queues
w/o any protection. When updating nr_hw_queues and blk_mq_in_flight
/rw occur concurrently, panic comes up.

Jianchao Wang (2)
blk-mq: init hctx sched after update cpu & nr_hw_queues
blk-mq: sync the update nr_hw_queues with part_in_flight

block/blk-mq.c | 40 ++++++++++++++++++++++++++++++++--------
block/blk.h | 2 ++
block/elevator.c | 20 ++++++++++++--------
block/genhd.c | 10 ++++++++--
include/linux/blkdev.h | 4 ++++
5 files changed, 58 insertions(+), 18 deletions(-)