Hi Christoph

On 06/21/2018 04:19 PM, Christoph Hellwig wrote:

On Thu, Jun 21, 2018 at 09:43:26AM +0800, jianchao.wang wrote:

quoted

So we have to preserve the ability of block layer that it could prevent
IO completion path from entering a timeout request.

With scsi-debug module, I tried to simulate a scenario where timeout and IO
completion path could occur concurrently, the system ran into crash easily.

Trace, please.  With the latest kernel.  I'm not saying that there
is nothing to fix, but the mode of never completing once timeout
requests as currently done is SCSI is clearly broken.

Sorry, I don't quite get your point.
Do you mean we should do the modification in the scsi layer ?
Actually, I used to look at the code to try to stop io completion on timeout request
in scsi-mid layer, but it looks like difficult, especially, scsi eh would try
to borrow the command to issue admin command such as get sense, test unit,etc.

Thanks
Jianchao