[PATCH v5 0/2] improve nvme quiesce time for large amount of namespaces

[Sagi Grimberg]

This set improves the quiesce time when using a large set of
namespaces, which also improves I/O failover time in a multipath environment.

We improve for both non-blocking hctxs and blocking hctxs introducing
blk_mq_[un]quiesce_tagset which works on all request queues over a given
tagset in parallel (which is the case in nvme) for both tagset types (blocking
and non-blocking);

Changes from v4:
- introduce blk_mq_[un]quiesce_tagset as one interface
- move nvme core to use this interface

Changes from v3:
- make hctx->rcu_sync dynamically allocated from the heap instead
  of a static member function

Changes from v2:
- made blk_mq_quiesce_queue_async operate on both blocking and
  non-blocking hctxs.
- removed separation between blocking vs. non-blocking queues
- dropeed patch from Chao
- dropped nvme-rdma test patch

Changes from v1:
- trivial typo fixes

*** SUBJECT HERE ***

*** BLURB HERE ***

Sagi Grimberg (2):
  blk-mq: add tagset quiesce interface
  nvme: use blk_mq_[un]quiesce_tagset

 block/blk-mq.c           | 66 ++++++++++++++++++++++++++++++++++++++++
 drivers/nvme/host/core.c | 14 ++-------
 include/linux/blk-mq.h   |  4 +++
 3 files changed, 72 insertions(+), 12 deletions(-)

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2.25.1