On Thu, Aug 23, 2018 at 04:49:11PM +0100, David Howells wrote: > I'm seeing the attached message generated from this line: > > btrfs_debug_in_rcu(fs_info, > "btrfs_map_bio: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u", > bio_op(bio), bio->bi_opf, (u64)bio->bi_iter.bi_sector, > (u_long)dev->bdev->bd_dev, rcu_str_deref(dev->name), dev->devid, > bio->bi_iter.bi_size); > > in submit_stripe_bio(). I'm not sure exactly why, but I suspect > rcu_str_deref() is the point from where it is generated. Yes, the macro is rcu_dereference in disguise. The code previously had explicit rcu_lock/unlock, now it uses the btrfs_debug_in_rcu helper which is supposed to provide that. It's possible that the helper is missing it due to some #ifdef mess, but I don't see it.
