linux-kernel - Re: [PATCH v4] scsi: sd: retry command SYNC CACHE if format in progress

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Message-ID: <676e37ba-a9c3-3d52-5c3b-0fa86cf1402e@huawei.com>
Date: Mon, 19 Aug 2024 14:44:37 +0800
From: Yihang Li <liyihang9@...wei.com>
To: Damien Le Moal <dlemoal@...nel.org>,
	<James.Bottomley@...senPartnership.com>, <martin.petersen@...cle.com>
CC: <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<bvanassche@....org>, <linuxarm@...wei.com>, <prime.zeng@...wei.com>,
	<stable@...r.kernel.org>, <liyihang9@...wei.com>
Subject: Re: [PATCH v4] scsi: sd: retry command SYNC CACHE if format in
 progress



On 2024/8/19 12:17, Damien Le Moal wrote:
> On 8/19/24 13:07, Yihang Li wrote:
>>
>>
>> On 2024/8/19 7:55, Damien Le Moal wrote:
>>> On 8/17/24 10:50, Yihang Li wrote:
>>>> If formatting a suspended disk (such as formatting with different DIF
>>>> type), the disk will be resuming first, and then the format command will
>>>> submit to the disk through SG_IO ioctl.
>>>>
>>>> When the disk is processing the format command, the system does not submit
>>>> other commands to the disk. Therefore, the system attempts to suspend the
>>>> disk again and sends the SYNC CACHE command. However, the SYNC CACHE
>>>
>>> Why would the system try to suspend the disk with a request in flight ? Sounds
>>> like there is a bug with PM reference counting, no ?
>>
>> According to my understand and test, the format command request is finished,
>> so it is not in flight for the kernel. And the command need a few time to processing
>> in the disk while no other commands are being sent.
> 
> OK, fine. But I think that retrying SYNC CACHE if the drive is formatting makes
> absolutely no sense at all because there is nothing to flush in that case.
> So what about simply ignoring the error ? I.e. something like this:
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 699f4f9674d9..1da267b8cd8a 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -1824,12 +1824,14 @@ static int sd_sync_cache(struct scsi_disk *sdkp)
>                                 /* this is no error here */
>                                 return 0;
>                         /*
> -                        * This drive doesn't support sync and there's not much
> -                        * we can do because this is called during shutdown
> -                        * or suspend so just return success so those operations
> -                        * can proceed.
> +                        * If a format is in progress (asc = LOGICAL UNIT NOT
> +                        * READY, ascq = FORMAT IN PROGRESS) or if the drive
> +                        * does not support sync, there is not much we can do
> +                        * because this is called during shutdown or suspend. So
> +                        * just return success so those operations can proceed.
>                          */
> -                       if (sshdr.sense_key == ILLEGAL_REQUEST)
> +                       if ((sshdr.asc == 0x04 && sshdr.ascq == 0x04) ||
> +                           sshdr.sense_key == ILLEGAL_REQUEST)
>                                 return 0;
>                 }
> 

Thanks for your suggestion, it seems like good.
I will send a new version based on this later.

Thanks,

Yihang.