On Tue, Mar 28, 2017 at 11:43:04AM +0800, Ming Lei wrote: > On Mon, Mar 27, 2017 at 10:43:59AM -0700, Omar Sandoval wrote: > > From: Omar Sandoval <[email protected]> > > > > CONFIG_DEBUG_TEST_DRIVER_REMOVE found a possible leak of q->rq_wb in a > > couple of cases: when a request queue is reregistered and when gendisks > > share a request_queue. This has been a problem since wbt was introduced, > > but the WARN_ON(!list_empty(&stats->callbacks)) in the blk-stat rework > > exposed it. The fix is unfortunately a hack until we fix all of the > > drivers sharing a request_queue. > > > > Fixes: 87760e5eef35 ("block: hook up writeback throttling") > > Signed-off-by: Omar Sandoval <[email protected]> > > --- > > block/blk-sysfs.c | 16 +++++++++++++++- > > 1 file changed, 15 insertions(+), 1 deletion(-) > > > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > > index fa831cb2fc30..a187e3f70028 100644 > > --- a/block/blk-sysfs.c > > +++ b/block/blk-sysfs.c > > @@ -893,7 +893,21 @@ int blk_register_queue(struct gendisk *disk) > > > > kobject_uevent(&q->kobj, KOBJ_ADD); > > > > - blk_wb_init(q); > > + /* > > + * There are two cases where wbt may have already been initialized: > > + * 1. A call sequence of blk_register_queue(); blk_unregister_queue(); > > + * blk_register_queue(). > > + * 2. Multiple gendisks sharing a request_queue. > > + * > > + * To fix case 1, we'd like to call wbt_exit() in > > + * blk_unregister_queue(). However, that's unsafe for case 2. So, we're > > + * forced to do this and call wbt_exit() in blk_release_queue() instead. > > + * > > + * Note that in case 2, wbt will account across disks until those legacy > > + * drivers are fixed. > > + */ > > + if (!q->rq_wb) > > + blk_wb_init(q); > > Since 'rq_wb' is per-queue and its life time is same with queue's, I > am wondering why blk_wb_init() isn't put into blk_alloc_queue_node() or > queue's initialization api(blk_init_allocated_queue(), or > blk_mq_init_allocated_queue())?
Doing it at queue init time might be cleaner, I'll try that.
