On Thu, Jun 07, 2012 at 04:35:22PM +1000, NeilBrown wrote: > 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 ? For example, ops_complete_biofill() will change dev->read which isn't protected by STRIPE_ACTIVE. add_stripe_bio() checks ->toread ->towrite, which isn't protected by the bit too. Am I missing anything? -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
