[dm-devel] block: Fix a WRITE SAME BUG_ON

[Christoph Hellwig]

On Thu, Jan 31, 2019 at 02:41:52PM -0500, John Dorminy wrote:
> > On Wed, Jan 30, 2019 at 09:08:50AM -0500, John Dorminy wrote:
> > > (I use WRITE_SAME to fill devices with a particular pattern in order
> > > to catch failures to initialize disk structures appropriately,
> > > personally, but it's just for convenience/speed.)
> >
> > How do you use it?  We don't have a user interface to generate
> > REQ_OP_WRITE_SAME requests.
> 
> A not-checked-in test module, similar to Zhang Xiaoxu's reproducer,
> exposing a sysfs node to trigger filling a block device with a test
> pattern.

Any reason you don't just use SCSI/NVMe passthrough directly from
userspace for that?