block: Fix elv_support_iosched()

A BIO based request queue does not have a tag_set, which prevent testing
for the flag BLK_MQ_F_NO_SCHED indicating that the queue does not
require an elevator. This leads to an incorrect initialization of a
default elevator in some cases such as BIO based null_blk
(queue_mode == BIO) with zoned mode enabled as the default elevator in
this case is mq-deadline instead of "none".

Fix this by testing for a NULL queue mq_ops field which indicates that
the queue is BIO based and should not have an elevator.

Reported-by: Shinichiro Kawasaki <[email protected]>
Reviewed-by: Bob Liu <[email protected]>
Signed-off-by: Damien Le Moal <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

0 files changed, 0 insertions, 0 deletions