ACK/Cmnt: [Bionic][PATCH v3 00/21] blk-mq scheduler fixes

[Stefan Bader]

On 15.05.2018 06:03, Jose Ricardo Ziviani wrote:
> From: Jose Ricardo Ziviani <joserz at linux.ibm.com>
> 
> Hello team!
> 
> Weeks ago I sent a patchset with:
>  * genirq/affinity: Spread irq vectors among present CPUs as far as possible
>  * blk-mq: simplify queue mapping & schedule with each possisble CPU
> 
> Unfortunately they broke some cases, in particular the hpsa driver, so they
> had to be reverted. However, the bugs in blk_mq are leading to a very
> unstable KVM/Qemu virtual machines whenever CPU hotplug/unplug and SMT
> changes are performed, also impacting live migration.
> 
> So, this is a new attempt to have the patches included. This new version
> includes all related fixes available upstream.
> 
> It's based on Ubuntu-4.15.0-21.22 tag.
> 
> V3:
>  - Added Buglink line in each commit
> 
> V2:
>  - Included all the fix necessary to blk_mq
> 
> Thank you!
> 
> Jose Ricardo Ziviani
> 
> Bart Van Assche (1):
>   blk-mq: Avoid that blk_mq_delay_run_hw_queue() introduces unintended
>     delays
> 
> Christoph Hellwig (2):
>   genirq/affinity: assign vectors to all possible CPUs
>   blk-mq: simplify queue mapping & schedule with each possisble CPU
> 
> Jens Axboe (1):
>   blk-mq: fix discard merge with scheduler attached
> 
> Ming Lei (16):
>   genirq/affinity: Rename *node_to_possible_cpumask as *node_to_cpumask
>   genirq/affinity: Move actual irq vector spreading into a helper
>     function
>   genirq/affinity: Allow irq spreading from a given starting point
>   genirq/affinity: Spread irq vectors among present CPUs as far as
>     possible
>   blk-mq: make sure hctx->next_cpu is set correctly
>   blk-mq: make sure that correct hctx->next_cpu is set
>   blk-mq: don't keep offline CPUs mapped to hctx 0
>   blk-mq: avoid to write intermediate result to hctx->next_cpu
>   blk-mq: introduce blk_mq_hw_queue_first_cpu() to figure out first cpu
>   blk-mq: don't check queue mapped in __blk_mq_delay_run_hw_queue()
>   nvme: pci: pass max vectors as num_possible_cpus() to
>     pci_alloc_irq_vectors
>   scsi: hpsa: fix selection of reply queue
>   scsi: megaraid_sas: fix selection of reply queue
>   scsi: core: introduce force_blk_mq
>   scsi: virtio_scsi: fix IO hang caused by automatic irq vector affinity
>   scsi: virtio_scsi: unify scsi_host_template
> 
> Thomas Gleixner (1):
>   genirq/affinity: Don't return with empty affinity masks on error
> 
>  block/blk-core.c                            |   2 +
>  block/blk-merge.c                           |  29 +++-
>  block/blk-mq-cpumap.c                       |   5 -
>  block/blk-mq.c                              |  65 +++++---
>  drivers/nvme/host/pci.c                     |   2 +-
>  drivers/scsi/hosts.c                        |   1 +
>  drivers/scsi/hpsa.c                         |  73 ++++++---
>  drivers/scsi/hpsa.h                         |   1 +
>  drivers/scsi/megaraid/megaraid_sas.h        |   1 +
>  drivers/scsi/megaraid/megaraid_sas_base.c   |  39 ++++-
>  drivers/scsi/megaraid/megaraid_sas_fusion.c |  12 +-
>  drivers/scsi/virtio_scsi.c                  | 129 ++-------------
>  include/scsi/scsi_host.h                    |   3 +
>  kernel/irq/affinity.c                       | 166 +++++++++++++-------
>  14 files changed, 296 insertions(+), 232 deletions(-)
> 

I went over the proposed changes and checked that there are currently no other
references in upstream pointing at the patches submitted. Two of those are by
now already applied (via stable):

* blk-mq: fix discard merge with scheduler attached
* blk-mq: don't keep offline CPUs mapped to hctx 0

The remaining changes are all either related to fixing the issue at hand or
follow-ups to address issues that had been introduced.

Acked-by: Stefan Bader <stefan.bader at canonical.com>

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