On Wed, Jan 02, 2013 at 02:27:00PM -0500, Vivek Goyal wrote: > On Fri, Dec 28, 2012 at 12:35:43PM -0800, Tejun Heo wrote: > > Instead of holding blkcg->lock while walking ->blkg_list and executing > > prfill(), RCU walk ->blkg_list and hold the blkg's queue lock while > > executing prfill(). This makes prfill() implementations easier as > > stats are mostly protected by queue lock. > > > > This will be used to implement hierarchical stats. > > > > Hi Tejun, > > I think dropping blkcg->lock might be a problem. Using RCU we have made > sure that blkg and q are around. But what about blkg->q.backing_dev_info.dev. > > We can follow bdi->dev pointer in blkg_dev_name(). I am not sure if we > ever clear it from q or not when device goes away. If the queue is dead, it wouldn't have policy enabled bit set which is tested while holding queue lock, so I don't think it's gonna be a problem. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
