[dm-devel] [PATCH 0/8] mutipath: handle nvme:tcp paths better

[Benjamin Marzinski]

nvme:tcp devices set BLK_MQ_F_BLOCKING (they are the only block devices
which multipath supports that do so), meaning that block_mq expects that
they can block at certain points while servicing a request.  However,
due to the way device-mapper sets up its queue, it is not able to set
BLK_MQ_F_BLOCKING when it includes paths that set this flag.  Patches
were written to address this issue but they were rejected upstream

https://lore.kernel.org/linux-block/YcH%2FE4JNag0QYYAa@infradead.org/T/#t

The proposed solution was to have multipath use the bio queue_mode for
multipath devices that include nvme:tcp paths.

Multipathd currently doesn't handle queue_mode as well as it could. Once
a multipath device is created, queue_mode cannot be changed, but
multipath doesn't enforce this. This patchset improves multipath's
handling of the queue_mode feature, and then makes sure that if a
multipath device includes a nvme:tcp path, it will have queue_mode
set to bio.

Benjamin Marzinski (8):
  libmultipath: cleanup remove_feature
  libmultipath: cleanup add_feature
  multipath tests: tests for adding and removing features
  libmultipath: fix queue_mode feature handling
  multipath tests: tests for reconcile_features_with_queue_mode
  libmultipath: prepare proto_id for use by non-scsi devivces
  libmultipath: get nvme path transport protocol
  libmultipath: enforce queue_mode bio for nmve:tcp paths

 libmultipath/configure.c   |  28 +-
 libmultipath/discovery.c   |  31 ++-
 libmultipath/dmparser.c    |   2 +
 libmultipath/print.c       |   6 +-
 libmultipath/propsel.c     |  55 ++++
 libmultipath/structs.c     | 155 +++++------
 libmultipath/structs.h     |  44 ++-
 libmultipath/structs_vec.c |   7 +
 multipath/multipath.conf.5 |  17 +-
 multipathd/fpin_handlers.c |   2 +-
 tests/Makefile             |   4 +-
 tests/features.c           | 549 +++++++++++++++++++++++++++++++++++++
 12 files changed, 784 insertions(+), 116 deletions(-)
 create mode 100644 tests/features.c

-- 
2.17.2