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block: Fix elv_support_iosched()

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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 <shinichiro.kawasaki@wdc.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Damien Le Moal 2019-10-09 07:39:54 +09:00 committed by Jens Axboe
parent 7adf4eaf60
commit 7a7c5e715e
1 changed files with 2 additions and 1 deletions
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3
block/elevator.c
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@ -616,7 +616,8 @@ out:
static inline bool elv_support_iosched(struct request_queue *q)
{
if (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED))
if (!q->mq_ops ||
(q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED)))
return false;
return true;
}