s390: use device_remove_file_self() instead of device_schedule_callback()

driver-core now supports synchrnous self-deletion of attributes and
the asynchrnous removal mechanism is scheduled for removal.  Use it
instead of device_schedule_callback().

* Conversions in arch/s390/pci/pci_sysfs.c and
  drivers/s390/block/dcssblk.c are straightforward.

* drivers/s390/cio/ccwgroup.c is a bit more tricky because
  ccwgroup_notifier() was (ab)using device_schedule_callback() to
  purely obtain a process context to kick off ungroup operation which
  may block from a notifier callback.

  Rename ccwgroup_ungroup_callback() to ccwgroup_ungroup() and make it
  take ccwgroup_device * instead.  The new function is now called
  directly from ccwgroup_ungroup_store().

  ccwgroup_notifier() chain is updated to explicitly bounce through
  ccwgroup_device->ungroup_work.  This also removes possible failure
  from memory pressure.

Only compile-tested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 32 insertions, 27 deletions

diff --git a/arch/s390/include/asm/ccwgroup.h b/arch/s390/include/asm/ccwgroup.h
index 23723ce5ca7a..6e670f88d125 100644
--- a/arch/s390/include/asm/ccwgroup.h
+++ b/arch/s390/include/asm/ccwgroup.h
@@ -23,6 +23,7 @@ struct ccwgroup_device {
         unsigned int count;
         struct device   dev;
         struct ccw_device *cdev[0];
+        struct work_struct ungroup_work;
 };
 
 /**
diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c
index cf8a12ff733b..ab4a91393005 100644
--- a/arch/s390/pci/pci_sysfs.c
+++ b/arch/s390/pci/pci_sysfs.c
@@ -48,29 +48,27 @@ static ssize_t show_pfgid(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR(pfgid, S_IRUGO, show_pfgid, NULL);
 
-static void recover_callback(struct device *dev)
+static ssize_t store_recover(struct device *dev, struct device_attribute *attr,
+                             const char *buf, size_t count)
 {
         struct pci_dev *pdev = to_pci_dev(dev);
         struct zpci_dev *zdev = get_zdev(pdev);
         int ret;
 
+        if (!device_remove_file_self(dev, attr))
+                return count;
+
         pci_stop_and_remove_bus_device(pdev);
         ret = zpci_disable_device(zdev);
         if (ret)
-                return;
+                return ret;
 
         ret = zpci_enable_device(zdev);
         if (ret)
-                return;
+                return ret;
 
         pci_rescan_bus(zdev->bus);
-}
-
-static ssize_t store_recover(struct device *dev, struct device_attribute *attr,
-                             const char *buf, size_t count)
-{
-        int rc = device_schedule_callback(dev, recover_callback);
-        return rc ? rc : count;
+        return count;
 }
 static DEVICE_ATTR(recover, S_IWUSR, NULL, store_recover);
 
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index ebf41e228e55..ee0e85abe1fd 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -304,12 +304,6 @@ dcssblk_load_segment(char *name, struct segment_info **seg_info)
         return rc;
 }
 
-static void dcssblk_unregister_callback(struct device *dev)
-{
-        device_unregister(dev);
-        put_device(dev);
-}
-
 /*
  * device attribute for switching shared/nonshared (exclusive)
  * operation (show + store)
@@ -397,7 +391,13 @@ removeseg:
         blk_cleanup_queue(dev_info->dcssblk_queue);
         dev_info->gd->queue = NULL;
         put_disk(dev_info->gd);
-        rc = device_schedule_callback(dev, dcssblk_unregister_callback);
+        up_write(&dcssblk_devices_sem);
+
+        if (device_remove_file_self(dev, attr)) {
+                device_unregister(dev);
+                put_device(dev);
+        }
+        return rc;
 out:
         up_write(&dcssblk_devices_sem);
         return rc;
diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
index fd3367a1dc7a..dfd7bc681c25 100644
--- a/drivers/s390/cio/ccwgroup.c
+++ b/drivers/s390/cio/ccwgroup.c
@@ -168,14 +168,12 @@ static ssize_t ccwgroup_online_show(struct device *dev,
  * Provide an 'ungroup' attribute so the user can remove group devices no
  * longer needed or accidentially created. Saves memory :)
  */
-static void ccwgroup_ungroup_callback(struct device *dev)
+static void ccwgroup_ungroup(struct ccwgroup_device *gdev)
 {
-        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
-
         mutex_lock(&gdev->reg_mutex);
         if (device_is_registered(&gdev->dev)) {
                 __ccwgroup_remove_symlinks(gdev);
-                device_unregister(dev);
+                device_unregister(&gdev->dev);
                 __ccwgroup_remove_cdev_refs(gdev);
         }
         mutex_unlock(&gdev->reg_mutex);
@@ -195,10 +193,9 @@ static ssize_t ccwgroup_ungroup_store(struct device *dev,
                 rc = -EINVAL;
                 goto out;
         }
-        /* Note that we cannot unregister the device from one of its
-         * attribute methods, so we have to use this roundabout approach.
-         */
-        rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
+
+        if (device_remove_file_self(dev, attr))
+                ccwgroup_ungroup(gdev);
 out:
         if (rc) {
                 if (rc != -EAGAIN)
@@ -224,6 +221,14 @@ static const struct attribute_group *ccwgroup_attr_groups[] = {
         NULL,
 };
 
+static void ccwgroup_ungroup_workfn(struct work_struct *work)
+{
+        struct ccwgroup_device *gdev =
+                container_of(work, struct ccwgroup_device, ungroup_work);
+
+        ccwgroup_ungroup(gdev);
+}
+
 static void ccwgroup_release(struct device *dev)
 {
         kfree(to_ccwgroupdev(dev));
@@ -323,6 +328,7 @@ int ccwgroup_create_dev(struct device *parent, struct ccwgroup_driver *gdrv,
         atomic_set(&gdev->onoff, 0);
         mutex_init(&gdev->reg_mutex);
         mutex_lock(&gdev->reg_mutex);
+        INIT_WORK(&gdev->ungroup_work, ccwgroup_ungroup_workfn);
         gdev->count = num_devices;
         gdev->dev.bus = &ccwgroup_bus_type;
         gdev->dev.parent = parent;
@@ -404,10 +410,10 @@ EXPORT_SYMBOL(ccwgroup_create_dev);
 static int ccwgroup_notifier(struct notifier_block *nb, unsigned long action,
                              void *data)
 {
-        struct device *dev = data;
+        struct ccwgroup_device *gdev = to_ccwgroupdev(data);
 
         if (action == BUS_NOTIFY_UNBIND_DRIVER)
-                device_schedule_callback(dev, ccwgroup_ungroup_callback);
+                schedule_work(&gdev->ungroup_work);
 
         return NOTIFY_OK;
 }