Re: [PATCH v3 3/8] blk-mq: Unregister debugfs attributes earlier

[Omar Sandoval <osandov@osandov.com>]

On Fri, Apr 21, 2017 at 03:16:28PM -0700, Omar Sandoval wrote:
> 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@sandisk.com>
> > Cc: Omar Sandoval <osandov@fb.com>
> > Cc: Hannes Reinecke <hare@suse.com>
> > ---
> >  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

I meant can you please rename blk_mq_debugfs_unregister_hctxs() to
blk_mq_debugfs_unregister_mq().