Re: [PATCH] blk-mq: avoid to iterate over stale request

[Ming Lei <ming.lei@redhat.com>]

On Mon, Sep 06, 2021 at 02:50:03PM +0800, Ming Lei wrote:
> blk-mq can't run allocating driver tag and updating ->rqs[tag]
> atomically, meantime blk-mq doesn't clear ->rqs[tag] after the driver
> tag is released.
> 
> So there is chance to iterating over one stale request just after the
> tag is allocated and before updating ->rqs[tag].
> 
> scsi_host_busy_iter() calls scsi_host_check_in_flight() to count scsi
> in-flight requests after scsi host is blocked, so no new scsi command can
> be marked as SCMD_STATE_INFLIGHT. However, driver tag allocation still can
> be run by blk-mq core. One request is marked as SCMD_STATE_INFLIGHT,
> but this request may have been kept in another slot of ->rqs[], meantime
> the slot can be allocated out but ->rqs[] isn't updated yet. Then this
> in-flight request is counted twice as SCMD_STATE_INFLIGHT. This way causes
> trouble in handling scsi error.
> 
> Fixes the issue by not iterating over stale request.
> 
> Cc: linux-scsi@vger.kernel.org
> Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> Reported-by: luojiaxing <luojiaxing@huawei.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>

Hello Jens,

luojiaxiang has verified that this patch fixes his issue, any chance to
merge it?


Thanks,
Ming