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

Hannes Reinecke
2018-02-05T06:58:29Z

On 02/03/2018 05:21 AM, Ming Lei wrote:
> 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(-)
>
Thanks Ming for picking this up.

I'll give it a shot and see how it behaves on other hardware.

Cheers,

Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
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