linux-kernel - Re: [PATCH v4 00/11] Enhance libsas hotplug feature

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Date:   Wed, 6 Sep 2017 14:07:57 +0100
From:   John Garry <john.garry@...wei.com>
To:     Jason Yan <yanaijie@...wei.com>, <martin.petersen@...cle.com>,
        <jejb@...ux.vnet.ibm.com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chenweilong@...wei.com>, <zhaohongjiang@...wei.com>,
        <hare@...e.com>, <dan.j.williams@...el.com>, <jthumshirn@...e.de>,
        <Raj.Dinesh@...rosemi.com>, <hch@....de>,
        <huangdaode@...ilicon.com>, <chenxiang66@...ilicon.com>
Subject: Re: [PATCH v4 00/11] Enhance libsas hotplug feature

On 06/09/2017 10:15, Jason Yan wrote:
> Hello all, Yijing Wang handed over this topic to me. We are working
> on it the last two months. We have tested the patchset for a long
> time. Here is the new version.
>
> Now the libsas hotplug has some issues, Dan Williams report
> a similar bug here before
> https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg39187.html
>
> The issues we have found
> 1. if LLDD burst reports lots of phy-up/phy-down sas events, some events
>    may lost because a same sas events is pending now, finally libsas topo
>    may different the hardware.
> 2. receive a phy down sas event, libsas call sas_deform_port to remove
>    devices, it would first delete the sas port, then put a destruction
>    discovery event in a new work, and queue it at the tail of workqueue,
>    once the sas port be deleted, its children device will be deleted too,
>    when the destruction work start, it will found the target device has
>    been removed, and report a sysfs warnning.
> 3. since a hotplug process will be divided into several works, if a phy up
>    sas event insert into phydown works, like
>    destruction work  ---> PORTE_BYTES_DMAED (sas_form_port) ---->PHYE_LOSS_OF_SIGNAL
>    the hot remove flow would broken by PORTE_BYTES_DMAED event, it's not
>    we expected, and issues would occur.
>
> v3->v4: -get rid of unused ha event and do some cleanup
>         -use dynamic alloced work and support shutting down the phy if active event reached the threshold
> 		-use flush_workqueue instead of wait-completion to process discover events synchronously
> 		-direct call probe and destruct function
> 		-other small code improvements
> v2->v3: some code improvements suggested by Johannes and John,
> 	    split v2 patch 2 into several small patches.
> v1->v2: some code improvements suggested by John Garry
>
> Jason Yan (10):
>   libsas: kill useless ha_event and do some cleanup
>   libsas: remove the numbering for each event enum
>   libsas: remove unused port_gone_completion and DISCE_PORT_GONE
>   libsas: rename notify_port_event() for consistency
>   libsas: Use dynamic alloced work to avoid sas event lost
>   libsas: shut down the PHY if events reached the threshold
>   libsas: make the event threshold configurable
>   libsas: Use new workqueue to run sas event and disco event
>   libsas: libsas: use flush_workqueue to process disco events
>     synchronously
>   libsas: direct call probe and destruct
>
> chenxiang (1):
>   libsas: add event to defer list tail instead of head when draining
>

Regardless of the fate of the rest of the patches in this series, I 
think patches 1,2,3,4,11/11 can be taken in isolation (subject to 
review, of course). It would save maintaining them out-of-tree.

John

>  drivers/scsi/aic94xx/aic94xx_hwi.c    |   3 -
>  drivers/scsi/hisi_sas/hisi_sas_main.c |   7 ++-
>  drivers/scsi/libsas/sas_ata.c         |   1 -
>  drivers/scsi/libsas/sas_discover.c    |  36 +++++++-----
>  drivers/scsi/libsas/sas_dump.c        |  10 ----
>  drivers/scsi/libsas/sas_dump.h        |   1 -
>  drivers/scsi/libsas/sas_event.c       |  97 +++++++++++++++++++-------------
>  drivers/scsi/libsas/sas_expander.c    |   2 +-
>  drivers/scsi/libsas/sas_init.c        | 101 +++++++++++++++++++++++++++++-----
>  drivers/scsi/libsas/sas_internal.h    |   7 +++
>  drivers/scsi/libsas/sas_phy.c         |  73 ++++++++++++------------
>  drivers/scsi/libsas/sas_port.c        |  25 +++++----
>  include/scsi/libsas.h                 |  81 ++++++++++++---------------
>  include/scsi/scsi_transport_sas.h     |   1 +
>  14 files changed, 270 insertions(+), 175 deletions(-)
>