dm: handle requests beyond end of device instead of using BUG_ON

The access beyond the end of device BUG_ON that was introduced to
dm_request_fn via commit 29e4013de7ad950280e4b2208 ("dm: implement
REQ_FLUSH/FUA support for request-based dm") was an overly
drastic (but simple) response to this situation.

I have received a report that this BUG_ON was hit and now think
it would be better to use dm_kill_unmapped_request() to fail the clone
and original request with -EIO.

map_request() will assign the valid target returned by
dm_table_find_target to tio->ti.  But when the target
isn't valid tio->ti is never assigned (because map_request isn't
called); so add a check for tio->ti != NULL to dm_done().

Reported-by: Mike Christie <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Signed-off-by: Jun'ichi Nomura <[email protected]>
Cc: [email protected] # v2.6.37+
Signed-off-by: Alasdair G Kergon <[email protected]>

0 files changed, 0 insertions, 0 deletions