On Tue 21-02-17 19:53:29, Bart Van Assche wrote: > On 02/21/2017 09:55 AM, Jan Kara wrote: > > diff --git a/block/blk-core.c b/block/blk-core.c > > index 47104f6a398b..9a901dcfdd5c 100644 > > --- a/block/blk-core.c > > +++ b/block/blk-core.c > > @@ -580,8 +580,6 @@ void blk_cleanup_queue(struct request_queue *q) > > q->queue_lock = &q->__queue_lock; > > spin_unlock_irq(lock); > > > > - bdi_unregister(q->backing_dev_info); > > - > > /* @q is and will stay empty, shutdown and put */ > > blk_put_queue(q); > > } > > diff --git a/block/genhd.c b/block/genhd.c > > index f6c4d4400759..68c613edb93a 100644 > > --- a/block/genhd.c > > +++ b/block/genhd.c > > @@ -660,6 +660,13 @@ void del_gendisk(struct gendisk *disk) > > disk->flags &= ~GENHD_FL_UP; > > > > sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi"); > > + /* > > + * Unregister bdi before releasing device numbers (as they can get > > + * reused and we'd get clashes in sysfs) but after bdev inodes are > > + * unhashed and thus will be soon destroyed as bdev inode's reference > > + * to wb_writeback can block bdi_unregister(). > > + */ > > + bdi_unregister(disk->queue->backing_dev_info); > > blk_unregister_queue(disk); > > blk_unregister_region(disk_devt(disk), disk->minors); > > This change looks suspicious to me. There are drivers that create a > block layer queue but neither call device_add_disk() nor del_gendisk(), > e.g. drivers/scsi/st.c. Although bdi_init() will be called for the > queues created by these drivers, this patch will cause the > bdi_unregister() call to be skipped for these drivers. Well, the thing is that bdi_unregister() is the counterpart to bdi_register(). Unless you call bdi_register(), which happens only in device_add_disk() (and some filesystems which create their private bdis), there's no point in calling bdi_unregister(). Counterpart to bdi_init() is bdi_exit() and that gets called always once bdi reference count drops to 0. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
