On Wed, Apr 24, 2019 at 06:27:46PM +0200, Christoph Hellwig wrote: > On Wed, Apr 24, 2019 at 07:02:21PM +0800, Ming Lei wrote: > > Hennes reported the following kernel oops: > > Hannes? > > > + if (!blk_get_queue(ns->queue)) { > > + ret = -ENXIO; > > + goto out_free_queue; > > + } > > If we always need to hold a reference, shouldn't blk_mq_init_queue > return with that reference held (and yes, that means changes to > every driver, but it seems like we need to audit all of them anyway..) The issue is driver(NVMe) specific, the race window is just between between blk_cleanup_queue() and removing the ns from the controller namspace list in nvme_ns_remove() blk_mq_init_queue() does hold one refcount, and its counter-part is blk_cleanup_queue(). It is simply ugly to ask blk_mq_init_queue() to grab a refcnt for driver, then who is the counter-part for releasing the extra refcount? > > It seems like the queue lifetimes are a bit of a mess, and I'm not sure > if this just papers over the problem. Could you explain a bit what the mess is? Thanks, Ming