On Thu, May 06, 2021 at 03:34:17PM +0800, Ming Lei wrote:
> > {
> > struct blk_mq_tags *drv_tags = set->tags[hctx_idx];
> > unsigned int i = 0;
> > unsigned long flags;
> >
> > spin_lock_irqsave(&drv_tags->lock, flags);
> > for (i = 0; i < set->queue_depth; i++)
> > WARN_ON_ONCE(refcount_read(&drv_tags->rqs[i]->ref) != 0);
> > drv_tags->rqs[i] = NULL;
>
> drv_tags->rqs[] may be assigned from another LUN at the same time, then
> the simple clearing will overwrite the active assignment. We just need
> to clear mapping iff the stored rq will be freed.
So. Even a different LUN shares the same tagset. So I can see the
need for the cmpxchg (please document it!), but I don't see the need
for the complex iteration. All the rqs are freed in one single loop,
so we can just iterate through them sequentially.
Btw, I think ->lock might better be named ->clear_lock to document its
purpose better.
