On Thu, Jan 20, 2022 at 11:52:48AM +0100, Daniel Wagner wrote: > The request queues can be freed while we operate on them. Make sure we It shouldn't be freed here. > hold a reference when using blk_mq_queue_tag_busy_iter. > > RIP: blk_mq_queue_tag_busy_iter Any chance to pose the whole stack trace? > Call Trace: > ? blk_mq_hctx_mark_pending > ? diskstats_show > ? blk_mq_hctx_mark_pending > blk_mq_in_flight > diskstats_show > ? klist_next > seq_read > proc_reg_read > vfs_read > ksys_read > do_syscall_64 > entry_SYSCALL_64_after_hwframe > > Signed-off-by: Daniel Wagner <dwagner@xxxxxxx> > --- > block/genhd.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/block/genhd.c b/block/genhd.c > index c9d4386dd177..0e163055a4e6 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -1167,10 +1167,13 @@ static int diskstats_show(struct seq_file *seqf, void *v) > if (bdev_is_partition(hd) && !bdev_nr_sectors(hd)) > continue; > part_stat_read_all(hd, &stat); > + if (blk_queue_enter(gp->queue, BLK_MQ_REQ_NOWAIT)) > + continue; The disk device's refcnt is supposed to be grabbed by class device iterator code, so queue shouldn't be released in diskstats_show(). Not mention blk_queue_enter() won't prevent disk from being released... thanks, Ming
