[patch 48/52] [PATCH] cio: handle busy subchannel in ccw_device_move_to_sch

Martin Schwidefsky
2009-11-13T15:15:21Z

[-- Attachment #1: 147-cio-handle-busy-subchannel.diff --]
[-- Type: text/plain, Size: 2211 bytes --]

From: Sebastian Ott <sebott@linux.vnet.ibm.com>

Try to disable the old subchannel before we ask the driver core
to move the attached device to a new parent. This way we can use
the QUIESCE state during shutdown which prevents a possible use
after free situation in some error cases.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

drivers/s390/cio/device.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

Index: quilt-2.6/drivers/s390/cio/device.c
===================================================================
--- quilt-2.6.orig/drivers/s390/cio/device.c 2009-11-13 16:08:22.000000000 +0100
+++ quilt-2.6/drivers/s390/cio/device.c 2009-11-13 16:08:22.000000000 +0100
@@ -892,12 +892,27 @@
struct subchannel *sch)
{
struct subchannel *old_sch;
- int rc;
+ int rc, old_enabled = 0;

old_sch = to_subchannel(cdev->dev.parent);
/* Obtain child reference for new parent. */
if (!get_device(&sch->dev))
return -ENODEV;
+
+ if (!sch_is_pseudo_sch(old_sch)) {
+ spin_lock_irq(old_sch->lock);
+ old_enabled = old_sch->schib.pmcw.ena;
+ rc = 0;
+ if (old_enabled)
+ rc = cio_disable_subchannel(old_sch);
+ spin_unlock_irq(old_sch->lock);
+ if (rc == -EBUSY) {
+ /* Release child reference for new parent. */
+ put_device(&sch->dev);
+ return rc;
+ }
+ }
+
mutex_lock(&sch->reg_mutex);
rc = device_move(&cdev->dev, &sch->dev, DPM_ORDER_PARENT_BEFORE_DEV);
mutex_unlock(&sch->reg_mutex);
@@ -906,6 +921,12 @@
cdev->private->dev_id.ssid,
cdev->private->dev_id.devno, sch->schid.ssid,
sch->schib.pmcw.dev, rc);
+ if (old_enabled) {
+ /* Try to reenable the old subchannel. */
+ spin_lock_irq(old_sch->lock);
+ cio_enable_subchannel(old_sch, (u32)(addr_t)old_sch);
+ spin_unlock_irq(old_sch->lock);
+ }
/* Release child reference for new parent. */
put_device(&sch->dev);
return rc;
@@ -914,7 +935,6 @@
if (!sch_is_pseudo_sch(old_sch)) {
spin_lock_irq(old_sch->lock);
sch_set_cdev(old_sch, NULL);
- cio_disable_subchannel(old_sch);
spin_unlock_irq(old_sch->lock);
css_schedule_eval(old_sch->schid);
}