With regard to suspend/resume cycle: Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx> On pátek 1. září 2017 20:49:49 CEST Ming Lei wrote: > Hi, > > The current SCSI quiesce isn't safe and easy to trigger I/O deadlock. > > Once SCSI device is put into QUIESCE, no new request except for RQF_PREEMPT > can be dispatched to SCSI successfully, and scsi_device_quiesce() just > simply waits for completion of I/Os dispatched to SCSI stack. It isn't > enough at all. > > Because new request still can be allocated, but all the allocated > requests can't be dispatched successfully, so request pool can be > consumed up easily. > > Then request with RQF_PREEMPT can't be allocated, and system may > hang forever, such as during system suspend or SCSI domain alidation. > > Both IO hang inside system suspend[1] or SCSI domain validation > were reported before. > > This patch tries to solve the issue by freezing block queue during > SCSI quiescing, and allowing to allocate request of RQF_PREEMPT > when queue is frozen. > > Both SCSI and SCSI_MQ have this IO deadlock issue, this patch fixes > them all by introducing preempt version of blk_freeze_queue() and > blk_unfreeze_queue(). > > V2: > - drop the 1st patch in V1 because percpu_ref_is_dying() is > enough as pointed by Tejun > > - introduce preempt version of blk_[freeze|unfreeze]_queue > > - sync between preempt freeze and normal freeze > > - fix warning from percpu-refcount as reported by Oleksandr > > > [1] https://marc.info/?t=150340250100013&r=3&w=2 > > > > Ming Lei (8): > blk-mq: rename blk_mq_unfreeze_queue as blk_unfreeze_queue > blk-mq: rename blk_mq_freeze_queue as blk_freeze_queue > blk-mq: only run hw queues for blk-mq > blk-mq: rename blk_mq_freeze_queue_wait as blk_freeze_queue_wait > block: tracking request allocation with q_usage_counter > block: allow to allocate req with REQF_PREEMPT when queue is frozen > block: introduce preempt version of blk_[freeze|unfreeze]_queue > SCSI: freeze block queue when SCSI device is put into quiesce > > block/bfq-iosched.c | 2 +- > block/blk-cgroup.c | 8 ++-- > block/blk-core.c | 50 ++++++++++++++++---- > block/blk-mq.c | 119 > ++++++++++++++++++++++++++++++++++++----------- block/blk-mq.h | > 1 - > block/blk.h | 6 +++ > block/elevator.c | 4 +- > drivers/block/loop.c | 16 +++---- > drivers/block/rbd.c | 2 +- > drivers/nvme/host/core.c | 8 ++-- > drivers/scsi/scsi_lib.c | 21 ++++++++- > include/linux/blk-mq.h | 15 +++--- > include/linux/blkdev.h | 20 +++++++- > 13 files changed, 206 insertions(+), 66 deletions(-)
