tree dbc881f131ae6981d736023cf1ba9fc59e292ed5
parent 76aa1d341257c1beb6ecfdd67fecdaac7e2aee25
author huhai <huhai@kylinos.cn> 1526653950 -0600
committer Jens Axboe <axboe@kernel.dk> 1526654138 -0600

blk-mq: clear hctx->dispatch_from when mappings change

When the number of hardware queues is changed, the drivers will call
blk_mq_update_nr_hw_queues() to remap hardware queues. This changes
the ctx mappings, but the current code doesn't clear the
->dispatch_from hint. This can result in dispatch_from pointing to
a ctx that isn't mapped to the hctx anymore.

Fixes: b347689ffbca ("blk-mq-sched: improve dispatching from sw queue")
Signed-off-by: huhai <huhai@kylinos.cn>
Reviewed-by: Ming Lei <ming.lei@redhat.com>

Moved the placement of the clearing to where we clear other items
pertaining to the existing mapping, added Fixes line, and reworded
the commit message.

Signed-off-by: Jens Axboe <axboe@kernel.dk>