* [PATCH] virtio-blk: Generate uevent after attribute available
@ 2016-06-28 2:39 Fam Zheng
2016-06-28 11:45 ` Christoph Hellwig
0 siblings, 1 reply; 5+ messages in thread
From: Fam Zheng @ 2016-06-28 2:39 UTC (permalink / raw)
To: linux-kernel; +Cc: Michael S. Tsirkin, virtualization, famz
Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that
point we haven't created the serial attribute file, therefore depending
on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get
created.
This race condition can be easily reproduced by hot plugging a number of
virtio-blk disks.
Also in systemd, there used to be a related workaround in udev rules
called 'WAIT_FOR="serial"', but it is removed in later versions.
Now let's generate a KOBJ_CHANGE event after the attributes are ready.
Signed-off-by: Fam Zheng <famz@redhat.com>
---
drivers/block/virtio_blk.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 42758b5..5056007 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -567,6 +567,7 @@ static int virtblk_probe(struct virtio_device *vdev)
{
struct virtio_blk *vblk;
struct request_queue *q;
+ struct device *ddev;
int err, index;
u64 cap;
@@ -746,6 +747,8 @@ static int virtblk_probe(struct virtio_device *vdev)
&dev_attr_cache_type_ro);
if (err)
goto out_del_disk;
+ ddev = disk_to_dev(vblk->disk);
+ kobject_uevent(&ddev->kobj, KOBJ_CHANGE);
return 0;
out_del_disk:
--
2.9.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] virtio-blk: Generate uevent after attribute available
2016-06-28 2:39 [PATCH] virtio-blk: Generate uevent after attribute available Fam Zheng
@ 2016-06-28 11:45 ` Christoph Hellwig
2016-06-29 1:24 ` Fam Zheng
0 siblings, 1 reply; 5+ messages in thread
From: Christoph Hellwig @ 2016-06-28 11:45 UTC (permalink / raw)
To: Fam Zheng; +Cc: linux-kernel, Michael S. Tsirkin, virtualization
On Tue, Jun 28, 2016 at 10:39:15AM +0800, Fam Zheng wrote:
> Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that
> point we haven't created the serial attribute file, therefore depending
> on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get
> created.
>
> This race condition can be easily reproduced by hot plugging a number of
> virtio-blk disks.
>
> Also in systemd, there used to be a related workaround in udev rules
> called 'WAIT_FOR="serial"', but it is removed in later versions.
>
> Now let's generate a KOBJ_CHANGE event after the attributes are ready.
The same race is present in other drivers as well, e.g. nvme. Please
find a way to make this work properly without needing to hack every
driver to send events manually.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] virtio-blk: Generate uevent after attribute available
2016-06-28 11:45 ` Christoph Hellwig
@ 2016-06-29 1:24 ` Fam Zheng
2016-09-02 22:56 ` Michael S. Tsirkin
0 siblings, 1 reply; 5+ messages in thread
From: Fam Zheng @ 2016-06-29 1:24 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: linux-kernel, Michael S. Tsirkin, virtualization
On Tue, 06/28 04:45, Christoph Hellwig wrote:
> On Tue, Jun 28, 2016 at 10:39:15AM +0800, Fam Zheng wrote:
> > Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that
> > point we haven't created the serial attribute file, therefore depending
> > on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get
> > created.
> >
> > This race condition can be easily reproduced by hot plugging a number of
> > virtio-blk disks.
> >
> > Also in systemd, there used to be a related workaround in udev rules
> > called 'WAIT_FOR="serial"', but it is removed in later versions.
> >
> > Now let's generate a KOBJ_CHANGE event after the attributes are ready.
>
> The same race is present in other drivers as well, e.g. nvme. Please
> find a way to make this work properly without needing to hack every
> driver to send events manually.
OK, I'll take a look today!
Fam
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] virtio-blk: Generate uevent after attribute available
2016-06-29 1:24 ` Fam Zheng
@ 2016-09-02 22:56 ` Michael S. Tsirkin
2016-09-03 7:08 ` Fam Zheng
0 siblings, 1 reply; 5+ messages in thread
From: Michael S. Tsirkin @ 2016-09-02 22:56 UTC (permalink / raw)
To: Fam Zheng; +Cc: Christoph Hellwig, linux-kernel, virtualization
On Wed, Jun 29, 2016 at 09:24:15AM +0800, Fam Zheng wrote:
> On Tue, 06/28 04:45, Christoph Hellwig wrote:
> > On Tue, Jun 28, 2016 at 10:39:15AM +0800, Fam Zheng wrote:
> > > Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that
> > > point we haven't created the serial attribute file, therefore depending
> > > on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get
> > > created.
> > >
> > > This race condition can be easily reproduced by hot plugging a number of
> > > virtio-blk disks.
> > >
> > > Also in systemd, there used to be a related workaround in udev rules
> > > called 'WAIT_FOR="serial"', but it is removed in later versions.
> > >
> > > Now let's generate a KOBJ_CHANGE event after the attributes are ready.
> >
> > The same race is present in other drivers as well, e.g. nvme. Please
> > find a way to make this work properly without needing to hack every
> > driver to send events manually.
>
> OK, I'll take a look today!
>
> Fam
Was this fixed in the generic code?
--
MST
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] virtio-blk: Generate uevent after attribute available
2016-09-02 22:56 ` Michael S. Tsirkin
@ 2016-09-03 7:08 ` Fam Zheng
0 siblings, 0 replies; 5+ messages in thread
From: Fam Zheng @ 2016-09-03 7:08 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: Christoph Hellwig, linux-kernel, virtualization
On Sat, 09/03 01:56, Michael S. Tsirkin wrote:
> On Wed, Jun 29, 2016 at 09:24:15AM +0800, Fam Zheng wrote:
> > On Tue, 06/28 04:45, Christoph Hellwig wrote:
> > > On Tue, Jun 28, 2016 at 10:39:15AM +0800, Fam Zheng wrote:
> > > > Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that
> > > > point we haven't created the serial attribute file, therefore depending
> > > > on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get
> > > > created.
> > > >
> > > > This race condition can be easily reproduced by hot plugging a number of
> > > > virtio-blk disks.
> > > >
> > > > Also in systemd, there used to be a related workaround in udev rules
> > > > called 'WAIT_FOR="serial"', but it is removed in later versions.
> > > >
> > > > Now let's generate a KOBJ_CHANGE event after the attributes are ready.
> > >
> > > The same race is present in other drivers as well, e.g. nvme. Please
> > > find a way to make this work properly without needing to hack every
> > > driver to send events manually.
> >
> > OK, I'll take a look today!
> >
> > Fam
>
> Was this fixed in the generic code?
A proposed fix is:
https://lkml.org/lkml/2016/8/17/81
Fam
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2016-09-03 7:15 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2016-06-28 2:39 [PATCH] virtio-blk: Generate uevent after attribute available Fam Zheng
2016-06-28 11:45 ` Christoph Hellwig
2016-06-29 1:24 ` Fam Zheng
2016-09-02 22:56 ` Michael S. Tsirkin
2016-09-03 7:08 ` Fam Zheng
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