On Fri, Feb 05, 2021 at 03:24:06PM +0100, Ulf Hansson wrote: > On Thu, 21 Jan 2021 at 09:13, Liu Xiang <liu.xiang@xxxxxxxxxxxxxx> wrote: > > > > After commit "40d09b53bfc557af7481b9d80f060a7ac9c7d314", request is > > completed in softirq. This may cause the system to suffer bad preemptoff > > time. > > The mmc driver has its own complete workqueue, but it can not work > > well now. > > The REQ_HIPRI flag can be used to complete request directly in its own > > complete workqueue and the preemptoff problem could be avoided. > > I am trying to understand all of the problem, but I don't quite get > it, sorry. Would it be possible for you to extend the description in > the commit message a bit? Yes, the message sounds weird. The mentioned commit should obviously not make any difference for drivers not using it. > More exactly, what will happen if we tag a request with REQ_HIPRI > before completing it? Apologize for my ignorance, but I am currently a > bit overwhelmed with work, so I didn't have the time to really look it > up myself. Drivers must never set REQ_HIPRI! This is a flag that is set by the submitter, and actually cleared for most drivers that don't support it by the block layer.
