[PATCH 0/5] blk-mq/scsi-mq: support global tags & introduce force_blk_mq

Ming Lei
2018-02-03T04:21:07Z

Hi All,

This patchset supports global tags which was started by Hannes originally:

https://marc.info/?l=linux-block&m=149132580511346&w=2

Also inroduce 'force_blk_mq' to 'struct scsi_host_template', so that
driver can avoid to support two IO paths(legacy and blk-mq), especially
recent discusion mentioned that SCSI_MQ will be enabled at default soon.

https://marc.info/?l=linux-scsi&m=151727684915589&w=2

With the above two changes, it should be easier to convert SCSI drivers'
reply queue into blk-mq's hctx, then the automatic irq affinity issue can
be solved easily, please see detailed descrption in commit log.

Also drivers may require to complete request on the submission CPU
for avoiding hard/soft deadlock, which can be done easily with blk_mq
too.

https://marc.info/?t=151601851400001&r=1&w=2

The final patch uses the introduced 'force_blk_mq' to fix virtio_scsi
so that IO hang issue can be avoided inside legacy IO path, this issue is
a bit generic, at least HPSA/virtio-scsi are found broken with v4.15+.

Thanks
Ming

Ming Lei (5):
blk-mq: tags: define several fields of tags as pointer
blk-mq: introduce BLK_MQ_F_GLOBAL_TAGS
block: null_blk: introduce module parameter of 'g_global_tags'
scsi: introduce force_blk_mq
scsi: virtio_scsi: fix IO hang by irq vector automatic affinity

block/bfq-iosched.c | 4 +--
block/blk-mq-debugfs.c | 11 ++++----
block/blk-mq-sched.c | 2 +-
block/blk-mq-tag.c | 67 +++++++++++++++++++++++++++++-----------------
block/blk-mq-tag.h | 15 ++++++++---
block/blk-mq.c | 31 ++++++++++++++++-----
block/blk-mq.h | 3 ++-
block/kyber-iosched.c | 2 +-
drivers/block/null_blk.c | 6 +++++
drivers/scsi/hosts.c | 1 +
drivers/scsi/virtio_scsi.c | 59 +++-------------------------------------
include/linux/blk-mq.h | 2 ++
include/scsi/scsi_host.h | 3 +++
13 files changed, 105 insertions(+), 101 deletions(-)

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2.9.5