On 06/04/2013 11:56 AM, Dan Williams wrote:

On Tue, Jun 4, 2013 at 11:38 AM, H. Peter Anvin [off-list ref] wrote:

quoted

Well, if that is what the block device layer is defined to do then that
is what the block layer does.  It makes sense from the point of view of
a disk, there block layer has to translate and redo, so if the block
layer is defined to do that, why not rely on it?

I'm just hung up on when we can safely mark the array as not dirty.
At a minimum this means raid needs a "I have an ignored-write-failure
in-flight, awaiting retry from upper layer" state.

Ah yes, if you rely on the block layer to retry on you you don't see the
beginnings and ends of the entire transaction, and at least ideally the
RAID -- and the specific blocks -- should be marked dirty during that
operation.  The same applies to DISCARD presumably.

Yuck, this suddenly got complex.  Perhaps WRITE SAME should simply be
disabled on raid1/raid10 until this can be addressed?  Do we need to do
the same for DISCARD?

	-hpa