On Tue, Apr 18, 2017 at 04:29:44PM -0700, Bart Van Assche wrote:
> One of the debugfs attributes allows to run a queue. Since running
> a queue after a queue has entered the "dead" state is not allowed
> and even can cause a kernel crash, unregister the debugfs attributes
> before a queue reaches the "dead" state.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> Cc: Omar Sandoval <osandov@xxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> ---
> block/blk-mq-sysfs.c | 31 ++++++-------------------------
> block/blk-sysfs.c | 3 +--
> 2 files changed, 7 insertions(+), 27 deletions(-)
>
> diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
> index 727e3b675130..1b2107f229ee 100644
> --- a/block/blk-mq-sysfs.c
> +++ b/block/blk-mq-sysfs.c
> @@ -258,7 +258,7 @@ static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
> queue_for_each_hw_ctx(q, hctx, i)
> blk_mq_unregister_hctx(hctx);
>
> - blk_mq_debugfs_unregister_hctxs(q);
> + blk_mq_debugfs_unregister(q);
This isn't what we want to do. First of all, we can't get remove the
/sys/kernel/debug/block/$dev directory until after we shutdown blktrace.
You unregister the top-level directory in other places, too. That should
only be done in the blk_release_queue() like it was originally.
More importantly, this doesn't actually fix the issue at hand. The
blk_mq_debugfs_unregister_hctxs() call needs to be moved earlier.
Actually, can you please rename blk_mq_debugfs_unregister_mq() to make
it more obvious that it removes the /sys/kernel/debug/block/$dev/mq
directory.
> kobject_uevent(&q->mq_kobj, KOBJ_REMOVE);
> kobject_del(&q->mq_kobj);
> @@ -306,8 +306,7 @@ void blk_mq_sysfs_init(struct request_queue *q)
>
> int __blk_mq_register_dev(struct device *dev, struct request_queue *q)
> {
> - struct blk_mq_hw_ctx *hctx;
> - int ret, i;
> + int ret;
>
> WARN_ON_ONCE(!q->kobj.parent);
> lockdep_assert_held(&q->sysfs_lock);
> @@ -318,14 +317,7 @@ int __blk_mq_register_dev(struct device *dev, struct request_queue *q)
>
> kobject_uevent(&q->mq_kobj, KOBJ_ADD);
>
> - blk_mq_debugfs_register(q);
> -
> - queue_for_each_hw_ctx(q, hctx, i) {
> - ret = blk_mq_register_hctx(hctx);
> - if (ret)
> - break;
> - }
> -
This gets rid of the /sys/block/$dev/mq/* entries in sysfs?
