Re: [PATCH RFC v3 00/22] blk-mq/libata/scsi: SCSI driver tagging improvements Part I

[John Garry <john.garry@huawei.com>]

On 25/10/2022 11:17, John Garry wrote:

Hi all,

I meant to say that this is just an update for where I got to here. I am 
actually changing employer soon, but will continue in upstream linux 
storage domain. So I don't want people to think that I am just throwing 
some stuff over the wall for the community to deal with. I would still 
like people to check this.

Thanks,
John

> Currently SCSI low-level drivers are required to manage tags for commands
> which do not come via the block layer - libata internal commands would be
> an example of one of these. We want to make blk-mq manage these tags also.
> 
> There was some work to provide "reserved commands" support in such series
> as https://lore.kernel.org/linux-scsi/20211125151048.103910-1-hare@suse.de/
> 
> This was based on allocating a request for the lifetime of the "internal"
> command.
> 
> This series tries to solve that problem by not just allocating the request
> but also sending it as a request through the block layer. Reasons to do
> this:
> - Normal flow of a request and also commonality for regular scsi command
>    lifetime
> - We don't leave request and scsi_cmnd fields dangling as when we just
>    allocate and free the request for the lifetime of the "internal" command
> - For poll mode support we can only poll in block layer, so could not send
>    internal commands on poll mode queues if we did not do this, which is a
>    problem
> - Can get rid of duplicated code like libsas internal command timeout
>    handling
> 
> Series part I contains core SCSI midlayer, libata, and libsas changes to
> queue libsas "slow" tasks as requests.
> 
> Series part II of this series focused on changing libata to queue internal
> commands as requests.
> 
> Testing:
> QEMU with AHCI with disk and cdrom attached, hisi_sas, pm8001.
> 
> Branch containing all patches is at:
> https://github.com/hisilicon/kernel-dev/commits/private-topic-sas-6.1-block
> 
> v2 was here:
> https://lore.kernel.org/linux-scsi/1654770559-101375-1-git-send-email-john.garry@huawei.com/
> 
> Hannes Reinecke (1):
>    scsi: core: Implement reserved command handling
> 
> John Garry (21):
>    blk-mq: Don't get budget for reserved requests
>    scsi: core: Add scsi_get_dev()
>    scsi: core: Add support to send reserved commands
>    scsi: core: Add support for reserved command timeout handling
>    scsi: libsas: Improve sas_ex_discover_expander() error handling
>    scsi: libsas: Notify LLDD expander found before calling sas_rphy_add()
>    scsi: scsi_transport_sas: Alloc sdev for expander
>    scsi: libsas: Add sas_alloc_slow_task_rq()
>    scsi: libsas: Add sas_queuecommand_internal()
>    scsi: libsas: Add sas_internal_timeout()
>    scsi: core: Use SCSI_SCAN_RESCAN in  __scsi_add_device()
>    scsi: scsi_transport_sas: Allocate end device target id in the rphy
>      alloc
>    ata: libata-scsi: Add ata_scsi_setup_sdev()
>    scsi: libsas: Add sas_ata_setup_device()
>    ata: libata-scsi: Allocate sdev early in port probe
>    scsi: libsas drivers: Reserve tags
>    scsi: libsas: Queue SMP commands as requests
>    scsi: libsas: Queue TMF commands as requests
>    scsi: core: Add scsi_alloc_request_hwq()
>    scsi: libsas: Queue internal abort commands as requests
>    scsi: libsas: Delete sas_task_slow.timer
> 
>   block/blk-mq.c                         |   4 +-
>   drivers/ata/libata-eh.c                |   1 +
>   drivers/ata/libata-scsi.c              |  49 ++++++++----
>   drivers/ata/libata.h                   |   1 +
>   drivers/scsi/aic94xx/aic94xx_init.c    |   3 +
>   drivers/scsi/hisi_sas/hisi_sas_main.c  |  40 +++++-----
>   drivers/scsi/hisi_sas/hisi_sas_v1_hw.c |   3 +
>   drivers/scsi/hisi_sas/hisi_sas_v2_hw.c |   3 +
>   drivers/scsi/hisi_sas/hisi_sas_v3_hw.c |   7 ++
>   drivers/scsi/hosts.c                   |  16 ++++
>   drivers/scsi/isci/init.c               |   3 +
>   drivers/scsi/libsas/sas_ata.c          |  20 +++++
>   drivers/scsi/libsas/sas_expander.c     | 101 ++++++++++++++-----------
>   drivers/scsi/libsas/sas_init.c         |  61 ++++++++++++++-
>   drivers/scsi/libsas/sas_internal.h     |   5 ++
>   drivers/scsi/libsas/sas_scsi_host.c    |  93 ++++++++++++-----------
>   drivers/scsi/mvsas/mv_init.c           |   7 ++
>   drivers/scsi/pm8001/pm8001_init.c      |   8 +-
>   drivers/scsi/scsi_error.c              |   3 +
>   drivers/scsi/scsi_lib.c                |  42 +++++++++-
>   drivers/scsi/scsi_scan.c               |  29 ++++++-
>   drivers/scsi/scsi_transport_sas.c      |  34 ++++++---
>   include/linux/libata.h                 |   2 +
>   include/scsi/libsas.h                  |   8 +-
>   include/scsi/scsi_cmnd.h               |   3 +
>   include/scsi/scsi_host.h               |  21 ++++-
>   26 files changed, 424 insertions(+), 143 deletions(-)
>