[block:for-5.15/block 38/39] block/elevator.c:637 elevator_get_default() error: we previously assumed 'q->tag_set' could be null (see line 633)

[kernel test robot <lkp@intel.com>]

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CC: kbuild-all(a)lists.01.org
CC: linux-kernel(a)vger.kernel.org
TO: Bart Van Assche <bvanassche@acm.org>
CC: Jens Axboe <axboe@kernel.dk>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-5.15/block
head:   2112f5c1330a671fa852051d85cb9eadc05d7eb7
commit: 90b7198001f23ea37d3b46dc631bdaa2357a20b1 [38/39] blk-mq: Introduce the BLK_MQ_F_NO_SCHED_BY_DEFAULT flag
:::::: branch date: 15 hours ago
:::::: commit date: 15 hours ago
config: ia64-randconfig-m031-20210804 (attached as .config)
compiler: ia64-linux-gcc (GCC) 10.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
block/elevator.c:637 elevator_get_default() error: we previously assumed 'q->tag_set' could be null (see line 633)

vim +637 block/elevator.c

61db437d1cc16c4 Damien Le Moal    2019-09-05  626  
131d08e122eaaba Christoph Hellwig 2018-05-31  627  /*
a0958ba7fcdc316 Damien Le Moal    2019-09-05  628   * For single queue devices, default to using mq-deadline. If we have multiple
a0958ba7fcdc316 Damien Le Moal    2019-09-05  629   * queues or mq-deadline is not available, default to "none".
a0958ba7fcdc316 Damien Le Moal    2019-09-05  630   */
a0958ba7fcdc316 Damien Le Moal    2019-09-05  631  static struct elevator_type *elevator_get_default(struct request_queue *q)
a0958ba7fcdc316 Damien Le Moal    2019-09-05  632  {
90b7198001f23ea Bart Van Assche   2021-08-05 @633  	if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT)
90b7198001f23ea Bart Van Assche   2021-08-05  634  		return NULL;
90b7198001f23ea Bart Van Assche   2021-08-05  635  
580dca8143d2159 Ming Lei          2021-04-06  636  	if (q->nr_hw_queues != 1 &&
580dca8143d2159 Ming Lei          2021-04-06 @637  			!blk_mq_is_sbitmap_shared(q->tag_set->flags))
a0958ba7fcdc316 Damien Le Moal    2019-09-05  638  		return NULL;
a0958ba7fcdc316 Damien Le Moal    2019-09-05  639  
a0958ba7fcdc316 Damien Le Moal    2019-09-05  640  	return elevator_get(q, "mq-deadline", false);
a0958ba7fcdc316 Damien Le Moal    2019-09-05  641  }
a0958ba7fcdc316 Damien Le Moal    2019-09-05  642  

:::::: The code at line 637 was first introduced by commit
:::::: 580dca8143d215977811bd2ff881e1e4f6ff39f0 blk-mq: set default elevator as deadline in case of hctx shared tagset

:::::: TO: Ming Lei <ming.lei@redhat.com>
:::::: CC: Jens Axboe <axboe@kernel.dk>

---
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