[dm-devel] trouble with generic/081

[Eric Sandeen]

On 12/16/16 2:15 AM, Christoph Hellwig wrote:
> On Thu, Dec 15, 2016 at 10:16:23AM +0100, Zdenek Kabelac wrote:
>> So let me explain the logic behind this 'amazingly stupid' idea.
> 
> And that logic doesn't make any sense at all.  invibly unmounting
> a file system behind the users back is actively harmful, as it is
> contradicting the principle of least surprise, and the xfstests mess
> is one simple example for it.  Add a callback in-kernel to tell the
> fs to shut down but NOT unmount and expose the namespace below it,
> which the administrator has probably intentionally hid.
> 
> Even worse unmount may trigger further writes and with fses not
> handling them the fs might now be stuck after being detached from
> the namespace without a way for the admin to detect or recover this.
> 
> What XFS did on IRIX was to let the volume manager call into the fs
> and shut it down.  At this point no further writes are possible,
> but we do not expose the namespace under the mount point, and the
> admin can fix the situation with all the normal tools.

<late to the party>

Is there a need for this kind of call-up when xfs now has the configurable
error handling so that it will shut down after X retries or Y seconds 
of a persistent error?

-Eric