[PATCH stable 4.19 0/1] fix io hung for scsi

[PATCH stable 4.19 0/1] fix io hung for scsi

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

One of our product reported a io hung problem, turns out the problem
can be fixed by the patch.

I'm not sure why this patch is not backported yet, however, please
consider it in 4.19 lts.

Ming Lei (1):
  scsi: core: Fix race between handling STS_RESOURCE and completion

 drivers/scsi/scsi_lib.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

-- 
2.31.1

[PATCH stable 4.19 1/1] scsi: core: Fix race between handling STS_RESOURCE and completion

[Yu Kuai]

From: Ming Lei <ming.lei@redhat.com>

commit 673235f915318ced5d7ec4b2bfd8cb909e6a4a55 upstream.

When queuing I/O request to LLD, STS_RESOURCE may be returned because:

 - Host is in recovery or blocked

 - Target queue throttling or target is blocked

 - LLD rejection

In these scenarios BLK_STS_DEV_RESOURCE is returned to the block layer to
avoid an unnecessary re-run of the queue. However, all of the requests
queued to this SCSI device may complete immediately after reading
'sdev->device_busy' and BLK_STS_DEV_RESOURCE is returned to block layer. In
that case the current I/O won't get a chance to get queued since it is
invisible at that time for both scsi_run_queue_async() and blk-mq's
RESTART.

Fix the issue by not returning BLK_STS_DEV_RESOURCE in this situation.

Link: https://lore.kernel.org/r/20201202100419.525144-1-ming.lei@redhat.com
Fixes: 86ff7c2a80cd ("blk-mq: introduce BLK_STS_DEV_RESOURCE")
Cc: Hannes Reinecke <hare@suse.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Ewan Milne <emilne@redhat.com>
Cc: Long Li <longli@microsoft.com>
Reported-by: John Garry <john.garry@huawei.com>
Tested-by: "chenxiang (M)" <chenxiang66@hisilicon.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 drivers/scsi/scsi_lib.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0191708c9dd4..ace4a7230bcf 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2157,8 +2157,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	case BLK_STS_OK:
 		break;
 	case BLK_STS_RESOURCE:
-		if (atomic_read(&sdev->device_busy) ||
-		    scsi_device_blocked(sdev))
+		if (scsi_device_blocked(sdev))
 			ret = BLK_STS_DEV_RESOURCE;
 		break;
 	default:
-- 
2.31.1

Re: [PATCH stable 4.19 0/1] fix io hung for scsi

[Greg KH]

On Sat, Jul 30, 2022 at 04:46:50PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> One of our product reported a io hung problem, turns out the problem
> can be fixed by the patch.
> 
> I'm not sure why this patch is not backported yet, however, please
> consider it in 4.19 lts.

It was not backported as it did not apply as-is.  Can you also provide a
version for 5.4.y so that if someone were to upgrade to a newer kernel
version, they would not have a regression?  Once we have that, then we
can accept this 4.19.y version.

thanks,

greg k-h

Re: [PATCH stable 4.19 0/1] fix io hung for scsi

[Yu Kuai]

Hi, Greg

在 2022/07/31 18:46, Greg KH 写道:
> On Sat, Jul 30, 2022 at 04:46:50PM +0800, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> One of our product reported a io hung problem, turns out the problem
>> can be fixed by the patch.
>>
>> I'm not sure why this patch is not backported yet, however, please
>> consider it in 4.19 lts.
> 
> It was not backported as it did not apply as-is.  Can you also provide a
> version for 5.4.y so that if someone were to upgrade to a newer kernel
> version, they would not have a regression?  Once we have that, then we
> can accept this 4.19.y version.
> 
Of courest, thanks for your notice.

Kuai
> thanks,
> 
> greg k-h
> .
>