SDEV_CANCEL is set when removing device and scsi_device_online() should
return false if sdev_state is SDEV_CANCEL.
IO hang would be caused if return true when state is SDEV_CANCEL with
following order:
T1: T2:scsi_error_handler
__scsi_remove_device()
scsi_device_set_state(sdev, SDEV_CANCEL)
scsi_eh_flush_done_q()
if (scsi_device_online(sdev))
scsi_queue_insert(scmd,...)
The command added by scsi_queue_insert() would never be handled any
more.
Signed-off-by: Wenchao Hao <[email protected]>
---
include/scsi/scsi_device.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 75b2235b99e2..c498a12f7715 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -517,7 +517,8 @@ static inline int scsi_device_online(struct scsi_device *sdev)
{
return (sdev->sdev_state != SDEV_OFFLINE &&
sdev->sdev_state != SDEV_TRANSPORT_OFFLINE &&
- sdev->sdev_state != SDEV_DEL);
+ sdev->sdev_state != SDEV_DEL &&
+ sdev->sdev_state != SDEV_CANCEL);
}
static inline int scsi_device_blocked(struct scsi_device *sdev)
{
--
2.32.0
On 9/22/23 02:36, Wenchao Hao wrote:
> SDEV_CANCEL is set when removing device and scsi_device_online() should
> return false if sdev_state is SDEV_CANCEL.
>
> IO hang would be caused if return true when state is SDEV_CANCEL with
> following order:
>
> T1: T2:scsi_error_handler
> __scsi_remove_device()
> scsi_device_set_state(sdev, SDEV_CANCEL)
> scsi_eh_flush_done_q()
> if (scsi_device_online(sdev))
> scsi_queue_insert(scmd,...)
>
> The command added by scsi_queue_insert() would never be handled any
> more.
Why not? I think the blk_mq_destroy_queue() call in
__scsi_remove_device() will cause it to fail.
Thanks,
Bart.
On 2023/9/22 23:23, Bart Van Assche wrote:
> On 9/22/23 02:36, Wenchao Hao wrote:
>> SDEV_CANCEL is set when removing device and scsi_device_online() should
>> return false if sdev_state is SDEV_CANCEL.
>>
>> IO hang would be caused if return true when state is SDEV_CANCEL with
>> following order:
>>
>> T1: T2:scsi_error_handler
>> __scsi_remove_device()
>> scsi_device_set_state(sdev, SDEV_CANCEL)
>> scsi_eh_flush_done_q()
>> if (scsi_device_online(sdev))
>> scsi_queue_insert(scmd,...)
>>
>> The command added by scsi_queue_insert() would never be handled any
>> more.
>
> Why not? I think the blk_mq_destroy_queue() call in __scsi_remove_device() will cause it to fail.
>
> Thanks,
>
> Bart.
>
Sorry, I did not describe in detail, the __scsi_remove_device() would be blocked
in blk_mq_freeze_queue_wait() to wait all block requests finished, so
blk_mq_destroy_queue() would not be called, and the task which try to remove
scsi_device would be hung.
On 2023/9/22 17:36, Wenchao Hao wrote:
> SDEV_CANCEL is set when removing device and scsi_device_online() should
> return false if sdev_state is SDEV_CANCEL.
>
> IO hang would be caused if return true when state is SDEV_CANCEL with
> following order:
>
> T1: T2:scsi_error_handler
> __scsi_remove_device()
> scsi_device_set_state(sdev, SDEV_CANCEL)
> scsi_eh_flush_done_q()
> if (scsi_device_online(sdev))
> scsi_queue_insert(scmd,...)
>
> The command added by scsi_queue_insert() would never be handled any
> more.
>
> Signed-off-by: Wenchao Hao <[email protected]>
> ---
> include/scsi/scsi_device.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index 75b2235b99e2..c498a12f7715 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -517,7 +517,8 @@ static inline int scsi_device_online(struct scsi_device *sdev)
> {
> return (sdev->sdev_state != SDEV_OFFLINE &&
> sdev->sdev_state != SDEV_TRANSPORT_OFFLINE &&
> - sdev->sdev_state != SDEV_DEL);
> + sdev->sdev_state != SDEV_DEL &&
> + sdev->sdev_state != SDEV_CANCEL);
> }
> static inline int scsi_device_blocked(struct scsi_device *sdev)
> {
Return false when if sdev_state is SDEV_CANCEL seems change some flow in
error handle, but I don't know if we should introduce these changes.
I think it's both ok to finish the failed command or try more recovery steps.
For example, in scsi_eh_bus_device_reset(), when scsi_try_bus_device_reset()
returned SUCCEED but the sdev_state is SDEV_CANCEL, should skip TUR and just
call scsi_eh_finish_cmd() to add this LUN's error command to done_q?
We can address the issue of IO hang described in this patch by running
scsi_device's queue regardless of the scsi_device's state and it seems
a better solution because the main reason of IO hang is as following:
scsi_restart_operations()
-> scsi_run_host_queues()
-> shost_for_each_device() // skip scsi_device with SDEV_DEL
// or SDEV_CANCEL state