Re: IBM request to allow unprivledged ioctls [Was: Revert "dm mpath: fix stalls when handling invalid ioctls"]

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/11/2015 08:28, Hannes Reinecke wrote:
> 
> With the original code we would need to wait for path activation
> before we would be able to figure out if the ioctl is valid.
> However, the callback to verify the ioctl is sd_ioctl(), which as
> a first step calls scsi_verify_ioctl().
> So my reasoning was that we can as well call scsi_verify_ioctl()
> early, and allow it to filter out known invalid ioctls.
> Then we wouldn't need to wait for path activation and return
> immediately.

That in principle makes sense.  Unfortunately, before path activation
you can only find out if a ioctl is valid.  You cannot find out which
ioctls are _in_valid, because path activation sets the bdev and that
might make all ioctls valid.

> Incidentally, in the 'r == -ENOTCONN' case, we're waiting
> for path activation, but then just bail out with -ENOTCONN.
> As we're not resetting -ENOTCONN, where's the point in activate the
> paths here?
> Shouldn't we retry to figure out if -ENOTCONN is still true?

That makes sense too.  You've done the work, might as well reap the
benefits...

Paolo