[dm-devel] [PATCH 0/2] Update command result handling

[Hannes Reinecke]

Currently we're updating the request result upon completion
only for BLK_PC requests. This makes it impossible for the
upper layers to reliable detect the real cause for an
I/O failure. By attaching the result and the sense to all
requests we can update multipathing to make some more elaborate
choices on how to handle I/O errors.
This also solves a potential data corruption with multipathing
and persistent reservations. When queue_if_no_path is active
multipath will queue any I/O failure (including those failed
with RESERVATION CONFLICT) until the reservation status changes.
But by then I/O might have been ongoing on the other paths,
thus the delayed submission will severely corrupt your data.

Signed-off-by: Hannes Reinecke <hare at suse.de>