[PATCH V5 0/3] blk-mq: fix blk_mq_alloc_request_hctx

[Ming Lei <ming.lei@redhat.com>]

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
allowing to allocate request when all CPUs of this hctx are offline.

Wen Xiong has verified V4 in her nvmef test.

V5:
	- take John Garry's suggestion to replace device field with
	new helper of device_has_managed_msi_irq()
V4:
	- remove patches for cleanup queue map helpers
	- take Christoph's suggestion to add field into 'struct device' for
	describing if managed irq is allocated from one device

V3:
	- cleanup map queues helpers, and remove pci/virtio/rdma queue
	  helpers
	- store use managed irq info into qmap

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 (3):
  driver core: add device_has_managed_msi_irq
  blk-mq: mark if one queue map uses managed irq
  blk-mq: don't deactivate hctx if managed irq isn't used

 block/blk-mq-pci.c                     |  1 +
 block/blk-mq-rdma.c                    |  3 +++
 block/blk-mq-virtio.c                  |  1 +
 block/blk-mq.c                         | 27 ++++++++++++++++----------
 block/blk-mq.h                         |  8 ++++++++
 drivers/base/core.c                    | 15 ++++++++++++++
 drivers/scsi/hisi_sas/hisi_sas_v2_hw.c |  1 +
 include/linux/blk-mq.h                 |  3 ++-
 include/linux/device.h                 |  2 ++
 9 files changed, 50 insertions(+), 11 deletions(-)

-- 
2.31.1