Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1448543
| From | Roger Pau Monné <roger.pau@citrix.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources |
| Date | 2016-07-22 13:50 +0200 |
| Message-ID | <rXH7P-5hk-3@gated-at.bofh.it> (permalink) |
| References | (3 earlier) <rXj5v-63Y-7@gated-at.bofh.it> <rXDnz-2NF-9@gated-at.bofh.it> <rXDQC-3e4-7@gated-at.bofh.it> <rXF62-3XU-17@gated-at.bofh.it> <rXFfI-429-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, Jul 22, 2016 at 05:43:32PM +0800, Bob Liu wrote:
>
> On 07/22/2016 05:34 PM, Roger Pau Monné wrote:
> > On Fri, Jul 22, 2016 at 04:17:48PM +0800, Bob Liu wrote:
> >>
> >> On 07/22/2016 03:45 PM, Roger Pau Monné wrote:
> >>> On Thu, Jul 21, 2016 at 06:08:05PM +0800, Bob Liu wrote:
> >>>>
> >>>> On 07/21/2016 04:57 PM, Roger Pau Monné wrote:
> >> ..[snip]..
> >>>>>> +
> >>>>>> +static ssize_t dynamic_reconfig_device(struct blkfront_info *info, ssize_t count)
> >>>>>> +{
> >>>>>> + unsigned int i;
> >>>>>> + int err = -EBUSY;
> >>>>>> +
> >>>>>> + /*
> >>>>>> + * Make sure no migration in parallel, device lock is actually a
> >>>>>> + * mutex.
> >>>>>> + */
> >>>>>> + if (!device_trylock(&info->xbdev->dev)) {
> >>>>>> + pr_err("Fail to acquire dev:%s lock, may be in migration.\n",
> >>>>>> + dev_name(&info->xbdev->dev));
> >>>>>> + return err;
> >>>>>> + }
> >>>>>> +
> >>>>>> + /*
> >>>>>> + * Prevent new requests and guarantee no uncompleted reqs.
> >>>>>> + */
> >>>>>> + blk_mq_freeze_queue(info->rq);
> >>>>>> + if (part_in_flight(&info->gd->part0))
> >>>>>> + goto out;
> >>>>>> +
> >>>>>> + /*
> >>>>>> + * Front Backend
> >>>>>> + * Switch to XenbusStateClosed
> >>>>>> + * frontend_changed():
> >>>>>> + * case XenbusStateClosed:
> >>>>>> + * xen_blkif_disconnect()
> >>>>>> + * Switch to XenbusStateClosed
> >>>>>> + * blkfront_resume():
> >>>>>> + * frontend_changed():
> >>>>>> + * reconnect
> >>>>>> + * Wait until XenbusStateConnected
> >>>>>> + */
> >>>>>> + info->reconfiguring = true;
> >>>>>> + xenbus_switch_state(info->xbdev, XenbusStateClosed);
> >>>>>> +
> >>>>>> + /* Poll every 100ms, 1 minute timeout. */
> >>>>>> + for (i = 0; i < 600; i++) {
> >>>>>> + /*
> >>>>>> + * Wait backend enter XenbusStateClosed, blkback_changed()
> >>>>>> + * will clear reconfiguring.
> >>>>>> + */
> >>>>>> + if (!info->reconfiguring)
> >>>>>> + goto resume;
> >>>>>> + schedule_timeout_interruptible(msecs_to_jiffies(100));
> >>>>>> + }
> >>>>>
> >>>>> Instead of having this wait, could you just set info->reconfiguring = 1, set
> >>>>> the frontend state to XenbusStateClosed and mimic exactly what a resume from
> >>>>> suspension does? blkback_changed would have to set the frontend state to
> >>>>> InitWait when it detects that the backend has switched to Closed, and call
> >>>>> blkfront_resume.
> >>>>
> >>>>
> >>>> I think that won't work.
> >>>> In the real "resume" case, the power management system will trigger all ->resume() path.
> >>>> But there is no place for dynamic configuration.
> >>>
> >>> Hello,
> >>>
> >>> I think it should be possible to set info->reconfiguring and wait for the
> >>> backend to switch to state Closed, at that point we should call blkif_resume
> >>> (from blkback_changed) and the backend will follow the reconection.
> >>>
> >>
> >> Okay, I get your point. Yes, that's an option.
> >>
> >> But this will make 'dynamic configuration' to be async, I'm worry about the end-user will get panic.
> >> E.g
> >> A end-user "echo <new value> > /sys/devices/vbd-xxx/max_indirect_segs",
> >> but then the device will be Closed and disappeared, the user have to wait for a random time so that the device can resume.
> >
> > That should not happen, AFAICT on migration the device never dissapears.
>
> Oh, yes.
>
> > alloc_disk and friends should not be called on resume from migration (see
> > the switch in blkfront_connect, you should take the BLKIF_STATE_SUSPENDED
> > path for the reconfiguration).
> >
>
> What about if the end-user starts I/O immediately after writing new value to /sys?
> But the resume is still in progress.
blkif_free already stops the queues by calling blk_mq_stop_hw_queues, and
blkif_queue_request will refuse to put anything on the ring if the state
is different than connected, which in turn makes blkif_queue_rq call
blk_mq_stop_hw_queue to stop the queue, so it should be safe.
Roger.
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH 1/3] xen-blkfront: fix places not updated after introducing 64KB page granularity Bob Liu <bob.liu@oracle.com> - 2016-07-15 11:40 +0200
[PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-15 11:40 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-21 11:00 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-21 12:10 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-22 09:50 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-22 10:20 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-22 11:40 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-22 11:50 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-22 13:50 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-23 00:20 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-25 11:30 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-25 12:30 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-25 13:00 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-25 13:10 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Roger Pau Monné <roger.pau@citrix.com> - 2016-07-25 14:20 +0200
Re: [PATCH 3/3] xen-blkfront: dynamic configuration of per-vbd resources Bob Liu <bob.liu@oracle.com> - 2016-07-25 14:30 +0200
[PATCH 2/3] xen-blkfront: introduce blkif_set_queue_limits() Bob Liu <bob.liu@oracle.com> - 2016-07-15 11:40 +0200
Re: [PATCH 2/3] xen-blkfront: introduce blkif_set_queue_limits() Roger Pau Monné <roger.pau@citrix.com> - 2016-07-21 10:30 +0200
Re: [PATCH 2/3] xen-blkfront: introduce blkif_set_queue_limits() Bob Liu <bob.liu@oracle.com> - 2016-07-21 11:50 +0200
Re: [PATCH 1/3] xen-blkfront: fix places not updated after introducing 64KB page granularity Roger Pau Monné <roger.pau@citrix.com> - 2016-07-21 10:10 +0200
csiph-web