On Thu, 7 Jun 2012 14:29:39 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote: > On Thu, Jun 07, 2012 at 10:54:10AM +1000, NeilBrown wrote: > > On Mon, 04 Jun 2012 16:01:53 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote: > > > > > Add a per-stripe lock to protect stripe specific data, like dev->read, > > > written, ... The purpose is to reduce lock contention of conf->device_lock. > > > > I'm not convinced that you need to add a lock. > > I am convinced that if you do add one you need to explain exactly what it is > > protecting. > > > > The STRIPE_ACTIVE bit serves as a lock and ensures that only one process can > > be in handle_stripe at a time. > > So I don't think dev->read actually needs any protection (though I haven't > > checked thoroughly). > > > > I think the only things that device_lock protects are things shared by > > multiple stripes, so adding a per-stripe spinlock isn't going to help remove > > device_lock. > > This sounds not true to me. both the async callbacks and request completion > access stripe data, like dev->read. Such things are not protected by > STRIPE_ACTIVE bit. Thought we can delete STRIPE_ACTIVE bit with stripe lock > introduced. Please give specifics. What race do you see with access to dev->read that is not protected by STRIPE_ACTIVE ? NeilBrown
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