Messages in this thread | | | Date | Thu, 19 Jan 2012 11:46:41 -0500 | From | Vivek Goyal <> | Subject | Re: [PATCH 12/12] blkcg: kill the mind-bending blkg->dev |
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On Thu, Jan 19, 2012 at 08:30:56AM -0800, Tejun Heo wrote: > Hello, > > On Thu, Jan 19, 2012 at 10:49:19AM -0500, Vivek Goyal wrote: > > > Let stat and conf read functions get device name from > > > blkg->q->backing_dev_info.dev and pass it down to printing functions > > > and remove blkg->dev. > > > > I think one of the reasons for not using blkg->q->backing_dev_info.dev was > > that there were still drivers where multiple gendisks were sharing the > > request queue. > > Hmmm... is that relevant? The configurations / stats are per > cgroup-request_queue pair. How does multiple genhd's sharing a queue > make any difference? Also, the fill_dev_details functions were using > the same q->backing_dev_info to fill it in, so it's not like it was > using anything different.
You are right. Looks like it should not make any difference. Also looks like bdi->dev points to first disk on the queue and ignores later ones.
int bdi_register(struct backing_dev_info *bdi, struct device *parent, const char *fmt, ...) { if (bdi->dev) /* The driver needs to use separate queues per device */ return 0; }
So if a queue is being shared by multiple disks, then any throttling rule on the device will practically trated a rule on the queue and will be effective on all the devices cumulatively. So sounds fine.
Thanks Vivek
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