Re: [PATCH] blk-cgroup: wait for blkcg cleanup before initializing new disk

[Ming Lei <ming.lei@redhat.com>]

On Tue, Mar 10, 2026 at 06:20:25AM -0700, Christoph Hellwig wrote:
> On Mon, Mar 09, 2026 at 06:09:06PM +0800, Ming Lei wrote:
> > +	if (READ_ONCE(q->root_blkg)) {
> > +		/* 20s is a random timeout, disk_release() should be done well before */
> > +		unsigned long end = jiffies + msecs_to_jiffies(20000);
> > +
> > +		while (READ_ONCE(q->root_blkg) &&
> > +				time_before(jiffies, end))
> > +			msleep(1);
> > +		if (READ_ONCE(q->root_blkg))
> > +			return -EEXIST;
> 
> Random sleeps are almost never a good idea.  If you don't want to waste
> a waitqueue on this use wake_up_var/wait_on_var, but make it properly
> wait for an event.

The two wait variable helpers looks pretty handy, will take it in V2.

Thanks,
Ming