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

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Date: Thu, 7 Mar 2024 22:36:03 +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: <linux-kernel@...r.kernel.org>, <louhongxiang@...wei.com>
Subject: Re: [PATCH v3 4/4] scsi: scsi_core: Fix IO hang when device removing

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@...wei.com>
> ---
>   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);
>   }
>