Re: [PATCH v3 4/4] scsi: scsi_core: Fix IO hang when device removing

[Wenchao Hao]

On 2023/10/16 10:03, Wenchao Hao wrote:
> shost_for_each_device() would skip devices which is in progress of
> removing, so scsi_run_queue() for these devices would be skipped in
> scsi_run_host_queues() after blocking hosts' IO.
>
> 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)
>    ...
>    sd_remove()
>    del_gendisk()
>    blk_mq_freeze_queue_wait()
>    					    scsi_eh_flush_done_q()
> 					      scsi_queue_insert(scmd,...)
>
> scsi_queue_insert() would not kick device's queue since commit
> 8b566edbdbfb ("scsi: core: Only kick the requeue list if necessary")
>
> After scsi_unjam_host(), the scsi error handler would call
> scsi_run_host_queues() to trigger run queue for devices, while it
> would not run queue for devices which is in progress of removing
> because shost_for_each_device() would skip them.
>
> So the requests added to these queues would not be handled any more,
> and the removing device process would hang too.
>
> Fix this issue by using shost_for_each_device_include_deleted() in
> scsi_run_host_queues() to trigger a run queue for devices in removing.

This issue is fixed by commit '6df0e077d76bd (scsi: core: Kick the requeue
list after inserting when flushing)', so do not need any more.

> Signed-off-by: Wenchao Hao <haowenchao2@xxxxxxxxxx>
> ---
>   drivers/scsi/scsi_lib.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 195ca80667d0..40f407ffd26f 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -466,7 +466,7 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
>   {
>   	struct scsi_device *sdev;
>   
> -	shost_for_each_device(sdev, shost)
> +	shost_for_each_device_include_deleted(sdev, shost)
>   		scsi_run_queue(sdev->request_queue);
>   }
>