null_blk: add option for managing IO timeouts
Use the fault injection framework to provide a way for null_blk
to configure timeouts. This only works for queue_mode 1 and 2,
since the bio mode doesn't have code for tracking timeouts.
Let's say you want to have a 10% chance of timing out every
100,000 requests, and for 5 total timeouts, you could do:
modprobe null_blk timeout="100000,10,0,5"
This is useful for adding blktests to test that IO timeouts
are handled appropriately.
Signed-off-by: Jens Axboe <firstname.lastname@example.org>