On Nov 09, 2022 / 11:08, Christoph Hellwig wrote: > Use set->nr_hw_queues for the current number of tags, and remove the > duplicate set->nr_hw_queues update in the caller. Chaitanya found that blktests test cases block/029 and block/030 fail on linux-block/for-next branch [1]. The test cases modify null_blk devices' submit_queues number during test, and it caused the failures. [1] https://lore.kernel.org/linux-block/5183bc2c-746b-5806-9ace-31a3a7000e6d@xxxxxxxxxx/ I bisected and confirmed that this patch is the trigger. As I noted below, one of its hunks looks wrong for me. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > --- > block/blk-mq.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 8c630dbdf107e..9fa0b9a1435f2 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -4381,11 +4381,11 @@ static void blk_mq_update_queue_map(struct blk_mq_tag_set *set) > } > > static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set, > - int cur_nr_hw_queues, int new_nr_hw_queues) > + int new_nr_hw_queues) > { > struct blk_mq_tags **new_tags; > > - if (cur_nr_hw_queues >= new_nr_hw_queues) > + if (set->nr_hw_queues >= new_nr_hw_queues) > return 0; > When the condition of the if statement above is true, set->nr_hw_queues is no longer updated with new_nr_hw_queues. In nullb_update_nr_hw_queues(), null_blk calls blk_mq_update_nr_hw_queues() and refers set->nr_hw_queues. With unexpected set->nr_hw_queues value, null_blk fails to update submit_queues number. With a quick fix below, the blktests failures were avoided. Could you take look and see if this is the right fix? diff --git a/block/blk-mq.c b/block/blk-mq.c index a3a5fb4d4ef6..604e19be9648 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4384,8 +4384,10 @@ static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set, { struct blk_mq_tags **new_tags; - if (set->nr_hw_queues >= new_nr_hw_queues) + if (set->nr_hw_queues >= new_nr_hw_queues) { + set->nr_hw_queues = new_nr_hw_queues; return 0; + } new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *), GFP_KERNEL, set->numa_node); -- Shin'ichiro Kawasaki
