On Tue, Jun 4, 2013 at 11:04 AM, Martin K. Petersen
[off-list ref] wrote:

quoted

quoted

quoted

quoted

quoted

"hpa" == H Peter Anvin [off-list ref] writes:

hpa> One subdevice accepts it and the other doesn't, presumably.

Ah. Well fail the command and let the block layer deal with it. This is
really no different from the discard case.

Which md also does not handle if the device later returns "illegal
request" to a discard command.  My point about one device accepting
the write and another device dropping it is we now have an
inconsistent array and a write command to complete.  So I don't see
how md can wait/trust that the upper layer will retry and fix things
up?    Translate and retry internally for these command types, return
success to the original request, and disable future requests.