On Tue, May 05, 2020 at 10:09:19AM +0800, Ming Lei wrote: > Hi, > > Thomas mentioned: > " > That was the constraint of managed interrupts from the very beginning: > > The driver/subsystem has to quiesce the interrupt line and the associated > queue _before_ it gets shutdown in CPU unplug and not fiddle with it > until it's restarted by the core when the CPU is plugged in again. > " > > But no drivers or blk-mq do that before one hctx becomes inactive(all > CPUs for one hctx are offline), and even it is worse, blk-mq stills tries > to run hw queue after hctx is dead, see blk_mq_hctx_notify_dead(). > > This patchset tries to address the issue by two stages: > > 1) add one new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE > > - mark the hctx as internal stopped, and drain all in-flight requests > if the hctx is going to be dead. > > 2) re-submit IO in the state of CPUHP_BLK_MQ_DEAD after the hctx becomes dead > > - steal bios from the request, and resubmit them via generic_make_request(), > then these IO will be mapped to other live hctx for dispatch > > Thanks John Garry for running lots of tests on arm64 with this patchset > and co-working on investigating all kinds of issues. > > Thanks Christoph's review on V7 & V8. > > Please comment & review, thanks! > > https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-improve-cpu-hotplug > > V10: > - fix double bio complete in request resubmission(10/11) > - add tested-by tag > > V9: > - add Reviewed-by tag > - document more on memory barrier usage between getting driver tag > and handling cpu offline(7/11) > - small code cleanup as suggested by Chritoph(7/11) > - rebase against for-5.8/block(1/11, 2/11) > V8: > - add patches to share code with blk_rq_prep_clone > - code re-organization as suggested by Christoph, most of them are > in 04/11, 10/11 > - add reviewed-by tag > > V7: > - fix updating .nr_active in get_driver_tag > - add hctx->cpumask check in cpuhp handler > - only drain requests which tag is >= 0 > - pass more aggressive cpuhotplug&io test > > V6: > - simplify getting driver tag, so that we can drain in-flight > requests correctly without using synchronize_rcu() > - handle re-submission of flush & passthrough request correctly > > V5: > - rename BLK_MQ_S_INTERNAL_STOPPED as BLK_MQ_S_INACTIVE > - re-factor code for re-submit requests in cpu dead hotplug handler > - address requeue corner case > > V4: > - resubmit IOs in dispatch list in case that this hctx is dead > > V3: > - re-organize patch 2 & 3 a bit for addressing Hannes's comment > - fix patch 4 for avoiding potential deadlock, as found by Hannes > > V2: > - patch4 & patch 5 in V1 have been merged to block tree, so remove > them > - address comments from John Garry and Minwoo > > Ming Lei (11): > block: clone nr_integrity_segments and write_hint in blk_rq_prep_clone > block: add helper for copying request > blk-mq: mark blk_mq_get_driver_tag as static > blk-mq: assign rq->tag in blk_mq_get_driver_tag > blk-mq: support rq filter callback when iterating rqs > blk-mq: prepare for draining IO when hctx's all CPUs are offline > blk-mq: stop to handle IO and drain IO before hctx becomes inactive > block: add blk_end_flush_machinery > blk-mq: add blk_mq_hctx_handle_dead_cpu for handling cpu dead > blk-mq: re-submit IO in case that hctx is inactive > block: deactivate hctx when the hctx is actually inactive > > block/blk-core.c | 27 ++- > block/blk-flush.c | 141 ++++++++++++--- > block/blk-mq-debugfs.c | 2 + > block/blk-mq-tag.c | 39 ++-- > block/blk-mq-tag.h | 4 + > block/blk-mq.c | 356 +++++++++++++++++++++++++++++-------- > block/blk-mq.h | 22 ++- > block/blk.h | 11 +- > drivers/block/loop.c | 2 +- > drivers/md/dm-rq.c | 2 +- > include/linux/blk-mq.h | 6 + > include/linux/cpuhotplug.h | 1 + > 12 files changed, 481 insertions(+), 132 deletions(-) > > Cc: John Garry <john.garry@xxxxxxxxxx> > Cc: Bart Van Assche <bvanassche@xxxxxxx> > Cc: Hannes Reinecke <hare@xxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Hi Jens, This patches have been worked and discussed for a while, so any chance to make it in 5.8 if no any further comments? Thanks, Ming
