For v4 with regard to suspend/resume: Tested-by: Oleksandr Natalenko <[email protected]>
On pondělí 11. září 2017 13:10:11 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 comming, 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 wait forever, > meantime scsi_device_resume() waits for completion of RQF_PREEMPT, > then system hangs forever, such as during system suspend or > sending SCSI domain alidation. > > Both IO hang inside system suspend[1] or SCSI domain validation > were reported before. > > This patch introduces preempt freeze, and solves the issue > by preempt freezing block queue during SCSI quiesce, and allows > to allocate request of RQF_PREEMPT when queue is in this state. > > Oleksandr verified that V3 does fix the hang during suspend/resume, > and Cathy verified that revised V3 fixes hang in sending > SCSI domain validation. > > Both SCSI and SCSI_MQ have this IO deadlock issue, this patch fixes > them all by introducing/unifying blk_freeze_queue_preempt() and > blk_unfreeze_queue_preempt(), and cleanup is done together. > > The patchset can be found in the following gitweb: > > https://github.com/ming1/linux/tree/blk_safe_scsi_quiesce_V4 > > V4: > - reorganize patch order to make it more reasonable > - support nested preempt freeze, as required by SCSI transport spi > - check preempt freezing in slow path of of blk_queue_enter() > - add "SCSI: transport_spi: resume a quiesced device" > - wake up freeze queue in setting dying for both blk-mq and legacy > - rename blk_mq_[freeze|unfreeze]_queue() in one patch > - rename .mq_freeze_wq and .mq_freeze_depth > - improve comment > > V3: > - introduce q->preempt_unfreezing to fix one bug of preempt freeze > - call blk_queue_enter_live() only when queue is preempt frozen > - cleanup a bit on the implementation of preempt freeze > - only patch 6 and 7 are changed > > 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 > > > Thanks, > Ming > > > Ming Lei (10): > blk-mq: only run hw queues for blk-mq > block: tracking request allocation with q_usage_counter > blk-mq: rename blk_mq_[freeze|unfreeze]_queue > blk-mq: rename blk_mq_freeze_queue_wait as blk_freeze_queue_wait > block: rename .mq_freeze_wq and .mq_freeze_depth > block: pass flags to blk_queue_enter() > block: introduce preempt version of blk_[freeze|unfreeze]_queue > block: allow to allocate req with RQF_PREEMPT when queue is preempt > frozen > SCSI: transport_spi: resume a quiesced device > SCSI: preempt freeze block queue when SCSI device is put into quiesce > > block/bfq-iosched.c | 2 +- > block/blk-cgroup.c | 8 +- > block/blk-core.c | 95 ++++++++++++++++---- > block/blk-mq.c | 180 > ++++++++++++++++++++++++++++---------- block/blk-mq.h | > 1 - > block/blk-timeout.c | 2 +- > block/blk.h | 12 +++ > block/elevator.c | 4 +- > drivers/block/loop.c | 24 ++--- > drivers/block/rbd.c | 2 +- > drivers/nvme/host/core.c | 8 +- > drivers/scsi/scsi_lib.c | 25 +++++- > drivers/scsi/scsi_transport_spi.c | 3 + > fs/block_dev.c | 4 +- > include/linux/blk-mq.h | 15 ++-- > include/linux/blkdev.h | 32 +++++-- > 16 files changed, 313 insertions(+), 104 deletions(-)
