[dm-devel] [PATCH 2/6] dm: introduce dm_accept_partial_bio

[Mike Snitzer]

On Mon, Mar 17 2014 at  3:18pm -0400,
Mikulas Patocka <mpatocka at redhat.com> wrote:

> 
> 
> On Mon, 17 Mar 2014, Mike Snitzer wrote:
> 
> > On Mon, Mar 17 2014 at  1:43pm -0400,
> > Mike Snitzer <snitzer at redhat.com> wrote:
> > 
> > > On Mon, Mar 17 2014 at  1:08pm -0400,
> > > Mikulas Patocka <mpatocka at redhat.com> wrote:
> > > 
> > > > 
> > > > Regarding REQ_FLUSH - it would already crash on NULL pointer dereference 
> > > > when accessing *tio->len_ptr.
> > 
> > I realize if any of these BUG_ON checks hits the calling target code has
> > a bug.  I just think it a fairly harsh response to BUG the system.  But
> > I can let this issue go.
> > 
> > I do however want you to add yet another BUG_ON for any bio that isn't
> > meant to be sent to this interface (only one so far is REQ_FLUSH AFAIK).
> 
> Then, it triggers NULL pointer dereference. You don't have to add BUG_ON 
> for it, it crashes anyway.

I understand it'll NULL pointer, but that is _always_ confusing for
someone who wasn't the original developer.  Please add the explicit
BUG_ON() for REQ_FLUSH.