[PATCH] xen-blkfront: emit KOBJ_OFFLINE uevent when detaching device

From: Vincent Legout
Date: Tue Jul 04 2017 - 07:58:16 EST

Devices are not unmounted inside a domU after a xl block-detach.

After xl block-detach, blkfront_closing() is called with state ==
XenbusStateConnected, it detects that the device is still in use and
only switches state to XenbusStateClosing. blkfront_closing() is called
a second time but returns immediately because state ==
XenbusStateClosing. Thus the device keeps being mounted inside the domU.

To fix this, emit a KOBJ_OFFLINE uevent even if the device has users.

With this patch, inside domU, udev has:

KERNEL[16994.526789] offline /devices/vbd-51728/block/xvdb (block)
KERNEL[16994.796197] remove /devices/virtual/bdi/202:16 (bdi)
KERNEL[16994.797167] remove /devices/vbd-51728/block/xvdb (block)
UDEV [16994.798035] remove /devices/virtual/bdi/202:16 (bdi)
UDEV [16994.809429] offline /devices/vbd-51728/block/xvdb (block)
UDEV [16994.842365] remove /devices/vbd-51728/block/xvdb (block)
KERNEL[16995.461991] remove /devices/vbd-51728 (xen)
UDEV [16995.462549] remove /devices/vbd-51728 (xen)

While without, it had:

KERNEL[30.862764] remove /devices/vbd-51728 (xen)
UDEV [30.867838] remove /devices/vbd-51728 (xen)

Signed-off-by: Pascal Bouchareine <pascal@xxxxxxxxx>
Signed-off-by: Fatih Acar <fatih.acar@xxxxxxxxx>
Signed-off-by: Vincent Legout <vincent.legout@xxxxxxxxx>
drivers/block/xen-blkfront.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 39459631667c..da0b0444ee1f 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2185,8 +2185,10 @@ static void blkfront_closing(struct blkfront_info *info)

if (bdev->bd_openers) {
- xenbus_dev_error(xbdev, -EBUSY,
- "Device in use; refusing to close");
+ dev_warn(disk_to_dev(info->gd),
+ "detaching %s with pending users\n",
+ xbdev->nodename);
+ kobject_uevent(&disk_to_dev(info->gd)->kobj, KOBJ_OFFLINE);
xenbus_switch_state(xbdev, XenbusStateClosing);
} else {