Makefile: add -Wshadow

Signed-off-by: Jens Axboe <axboe@fb.com>
t/btrace2fio: fix divide-by-zero in rate calculation

If usec is less than 1000, it'd crash.

Signed-off-by: Jens Axboe <axboe@fb.com>
t/btrace2fio: don't dec inflight for requeue

We don't inc it again on issue, so we'll end up with an assert
trigger on inflight going negative.

Signed-off-by: Jens Axboe <axboe@fb.com>
Add support for verify triggers and verify state saving

This allows you to (for instance) instantly terminate a verify
write workload, and then later that everything was written
correctly up to that very point. This can be useful for testing
powercut scenarios, which is often problematic on storage
devices.

The trigger part is a file based notification scheme, similar
to what is provided for the status dumps. When triggered,
fio will exit immediately and write the verify state safely
to disk. A trigger can be accompanied by a trigger command.
Say you wanted to test powercut safety, the trigger could be
something that immediately cut power to the machine.

The verify state is either saved locally (if run locally),
or saved over the network if run in client/server mode.

Signed-off-by: Jens Axboe <axboe@fb.com>
client: replace duplicate code with read_data()

Signed-off-by: Jens Axboe <axboe@fb.com>