On Mon, Mar 27, 2017 at 10:43:59AM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> 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 <osandov@xxxxxx>
> ---
> 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())?
Thanks,
Ming
