[PATCH V2 0/6] blk-mq: fix blk_mq_alloc_request_hctx

[Ming Lei]

Hi,

blk_mq_alloc_request_hctx() is used by NVMe fc/rdma/tcp/loop to connect
io queue. Also the sw ctx is chosen as the 1st online cpu in hctx->cpumask.
However, all cpus in hctx->cpumask may be offline.

This usage model isn't well supported by blk-mq which supposes allocator is
always done on one online CPU in hctx->cpumask. This assumption is
related with managed irq, which also requires blk-mq to drain inflight
request in this hctx when the last cpu in hctx->cpumask is going to
offline.

However, NVMe fc/rdma/tcp/loop don't use managed irq, so we should allow
them to ask for request allocation when the specified hctx is inactive
(all cpus in hctx->cpumask are offline).

Fix blk_mq_alloc_request_hctx() by adding/passing flag of BLK_MQ_F_MANAGED_IRQ. 

Meantime optimize blk-mq cpu hotplug handling for non-managed irq.

V2:
	- use flag of BLK_MQ_F_MANAGED_IRQ
	- pass BLK_MQ_F_MANAGED_IRQ from driver explicitly
	- kill BLK_MQ_F_STACKING

Ming Lei (6):
  blk-mq: prepare for not deactivating hctx if managed irq isn't used
  nvme: pci: pass BLK_MQ_F_MANAGED_IRQ to blk-mq
  scsi: add flag of .use_managed_irq to 'struct Scsi_Host'
  scsi: set shost->use_managed_irq if driver uses managed irq
  virtio: add one field into virtio_device for recording if device uses
    managed irq
  blk-mq: don't deactivate hctx if managed irq isn't used

 block/blk-mq-debugfs.c                    |  2 +-
 block/blk-mq.c                            | 27 +++++++++++++----------
 drivers/block/loop.c                      |  2 +-
 drivers/block/virtio_blk.c                |  2 ++
 drivers/md/dm-rq.c                        |  2 +-
 drivers/nvme/host/pci.c                   |  3 ++-
 drivers/scsi/aacraid/linit.c              |  3 +++
 drivers/scsi/be2iscsi/be_main.c           |  3 +++
 drivers/scsi/csiostor/csio_init.c         |  3 +++
 drivers/scsi/hisi_sas/hisi_sas_v3_hw.c    |  1 +
 drivers/scsi/hpsa.c                       |  3 +++
 drivers/scsi/lpfc/lpfc.h                  |  1 +
 drivers/scsi/lpfc/lpfc_init.c             |  4 ++++
 drivers/scsi/megaraid/megaraid_sas_base.c |  3 +++
 drivers/scsi/mpt3sas/mpt3sas_scsih.c      |  3 +++
 drivers/scsi/qla2xxx/qla_isr.c            |  5 ++++-
 drivers/scsi/scsi_lib.c                   | 12 +++++-----
 drivers/scsi/smartpqi/smartpqi_init.c     |  3 +++
 drivers/scsi/virtio_scsi.c                |  1 +
 drivers/virtio/virtio_pci_common.c        |  1 +
 include/linux/blk-mq.h                    |  6 +----
 include/linux/virtio.h                    |  1 +
 include/scsi/scsi_host.h                  |  3 +++
 23 files changed, 67 insertions(+), 27 deletions(-)

-- 
2.31.1