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Message-ID: <bfc9e734-3a04-9600-58e7-91d7e7f53010@huawei.com>
Date: Thu, 14 Sep 2023 14:20:20 +0800
From: Wenchao Hao <haowenchao2@...wei.com>
To: "James E . J . Bottomley" <jejb@...ux.ibm.com>,
"Martin K . Petersen" <martin.petersen@...cle.com>,
<linux-scsi@...r.kernel.org>
CC: Hannes Reinecke <hare@...e.de>, <linux-kernel@...r.kernel.org>,
<louhongxiang@...wei.com>, <lixiaokeng@...wei.com>
Subject: Re: [RFC PATCH v2 00/18] scsi: scsi_error: Introduce new error handle
mechanism
On 2023/9/1 17:41, Wenchao Hao wrote:
> It's unbearable for systems with large scale scsi devices share HBAs to
> block all devices' IOs when handle error commands, we need a new error
> handle mechanism to address this issue.
>
> I consulted about this issue a year ago, the discuss link can be found in
> refenence. Hannes replied about why we have to block the SCSI host
> then perform error recovery kindly. I think it's unnecessary to block
> SCSI host for all drivers and can try a small level recovery(LUN based for
> example) first to avoid block the SCSI host.
>
> The new error handle mechanism introduced in this patchset has been
> developed and tested with out self developed hardware since one year
> ago, now we want this mechanism can be used by more drivers.
>
> Drivers can decide if using the new error handle mechanism and how to
> handle error commands when scsi_device are scanned,the new mechanism
> makes SCSI error handle more flexible.
>
> SCSI error recovery strategy after blocking host's IO is mainly
> following steps:
>
> - LUN reset
> - Target reset
> - Bus reset
> - Host reset
>
Mike gave some suggestions and I found a bug in fallback logic, I would
address these and resend in next few days.
> Some drivers did not implement callbacks for host reset, it's unnecessary
> to block host's IO for these drivers. For example, smartpqi only registered
> device reset, if device reset failed, it's meaningless to fallback to target
> reset, bus reset or host reset any more, because these steps would also
> failed.
>
> Here are some drivers we concerned:(there are too many kinds of drivers
> to figure out, so here I just list some drivers I am familiar with)
>
> +-------------+--------------+--------------+-----------+------------+
> | drivers | device_reset | target_reset | bus_reset | host_reset |
> +-------------+--------------+--------------+-----------+------------+
> | mpt3sas | Y | Y | N | Y |
> +-------------+--------------+--------------+-----------+------------+
> | smartpqi | Y | N | N | N |
> +-------------+--------------+--------------+-----------+------------+
> | megaraidsas | N | Y | N | Y |
> +-------------+--------------+--------------+-----------+------------+
> | virtioscsi | Y | N | N | N |
> +-------------+--------------+--------------+-----------+------------+
> | iscsi_tcp | Y | Y | N | N |
> +-------------+--------------+--------------+-----------+------------+
> | hisisas | Y | Y | N | N |
> +-------------+--------------+--------------+-----------+------------+
>
> For LUN based error handle, when scsi command is classified as error,
> we would block the scsi device's IO and try to recover this scsi
> device, if still can not recover all error commands, it might
> fallback to target or host level recovery.
>
> It's same for target based error handle, but target based error handle
> would block the scsi target's IO then try to recover the error commands
> of this target.
>
> The first patch defines basic framework to support LUN/target based error
> handle mechanism, three key operations are abstracted which are:
> - add error command
> - wake up error handle
> - block IOs when error command is added and recoverying.
>
> Drivers can implement these three function callbacks and setup to SCSI
> middle level; I also add a general LUN/target based error handle strategy
> which can be called directly from drivers to implement LUN/tartget based
> error handle.
>
> The changes of SCSI middle level's error handle are tested with scsi_debug
> which support single LUN error injection, the scsi_debug patches can be
> found in reference, following scenarios are tested.
>
> Scenario1: LUN based error handle is enabled:
> +-----------+---------+-------------------------------------------------------+
> | lun reset | TUR | Desired result |
> + --------- + ------- + ------------------------------------------------------+
> | success | success | retry or finish with EIO(may offline disk) |
> + --------- + ------- + ------------------------------------------------------+
> | success | fail | fallback to host recovery, retry or finish with |
> | | | EIO(may offline disk) |
> + --------- + ------- + ------------------------------------------------------+
> | fail | NA | fallback to host recovery, retry or finish with |
> | | | EIO(may offline disk) |
> + --------- + ------- + ------------------------------------------------------+
>
> Scenario2: target based error handle is enabled:
> +-----------+---------+--------------+---------+------------------------------+
> | lun reset | TUR | target reset | TUR | Desired result |
> +-----------+---------+--------------+---------+------------------------------+
> | success | success | NA | NA | retry or finish with |
> | | | | | EIO(may offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
> | success | fail | success | success | retry or finish with |
> | | | | | EIO(may offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
> | fail | NA | success | success | retry or finish with |
> | | | | | EIO(may offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
> | fail | NA | success | fail | fallback to host recovery, |
> | | | | | retry or finish with EIO(may |
> | | | | | offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
> | fail | NA | fail | NA | fallback to host recovery, |
> | | | | | retry or finish with EIO(may |
> | | | | | offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
>
> Scenario3: both LUN and target based error handle are enabled:
> +-----------+---------+--------------+---------+------------------------------+
> | lun reset | TUR | target reset | TUR | Desired result |
> +-----------+---------+--------------+---------+------------------------------+
> | success | success | NA | NA | retry or finish with |
> | | | | | EIO(may offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
> | success | fail | success | success | lun recovery fallback to |
> | | | | | target recovery, retry or |
> | | | | | finish with EIO(may offline |
> | | | | | disk |
> +-----------+---------+--------------+---------+------------------------------+
> | fail | NA | success | success | lun recovery fallback to |
> | | | | | target recovery, retry or |
> | | | | | finish with EIO(may offline |
> | | | | | disk |
> +-----------+---------+--------------+---------+------------------------------+
> | fail | NA | success | fail | lun recovery fallback to |
> | | | | | target recovery, then fall |
> | | | | | back to host recovery, retry |
> | | | | | or fhinsi with EIO(may |
> | | | | | offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
> | fail | NA | fail | NA | lun recovery fallback to |
> | | | | | target recovery, then fall |
> | | | | | back to host recovery, retry |
> | | | | | or fhinsi with EIO(may |
> | | | | | offline disk) |
> +-----------+---------+--------------+---------+------------------------------+
>
> References: https://lore.kernel.org/linux-scsi/20230815122316.4129333-1-haowenchao2@huawei.com/
> References: https://lore.kernel.org/linux-scsi/71e09bb4-ff0a-23fe-38b4-fe6425670efa@huawei.com/
>
> Wenchao Hao (19):
> scsi: scsi_error: Define framework for LUN/target based error handle
> scsi: scsi_error: Move complete variable eh_action from shost to sdevice
> scsi: scsi_error: Check if to do reset in scsi_try_xxx_reset
> scsi: scsi_error: Add helper scsi_eh_sdev_stu to do START_UNIT
> scsi: scsi_error: Add helper scsi_eh_sdev_reset to do lun reset
> scsi: scsi_error: Add flags to mark error handle steps has done
> scsi: scsi_error: Add helper to handle scsi device's error command list
> scsi: scsi_error: Add a general LUN based error handler
> scsi: core: increase/decrease target_busy without check can_queue
> scsi: scsi_error: Add helper to handle scsi target's error command list
> scsi: scsi_error: Add a general target based error handler
> scsi: scsi_debug: Add param to control LUN bassed error handler
> scsi: scsi_debug: Add param to control target based error handle
> scsi: mpt3sas: Add param to control LUN based error handle
> scsi: mpt3sas: Add param to control target based error handle
> scsi: smartpqi: Add param to control LUN based error handle
> scsi: megaraid_sas: Add param to control target based error handle
> scsi: virtio_scsi: Add param to control LUN based error handle
> scsi: iscsi_tcp: Add param to control LUN based error handle
>
> drivers/scsi/iscsi_tcp.c | 20 +
> drivers/scsi/megaraid/megaraid_sas_base.c | 20 +
> drivers/scsi/mpt3sas/mpt3sas_scsih.c | 28 +
> drivers/scsi/scsi_debug.c | 24 +
> drivers/scsi/scsi_error.c | 756 ++++++++++++++++++++--
> drivers/scsi/scsi_lib.c | 23 +-
> drivers/scsi/scsi_priv.h | 18 +
> drivers/scsi/smartpqi/smartpqi_init.c | 14 +
> drivers/scsi/virtio_scsi.c | 16 +-
> include/scsi/scsi_device.h | 97 +++
> include/scsi/scsi_eh.h | 8 +
> include/scsi/scsi_host.h | 2 -
> 12 files changed, 963 insertions(+), 63 deletions(-)
>
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