driver core: force NOIO allocations during unplug

There is one overlooked situation under which a driver must not do IO to
allocate memory. You cannot do that while disconnecting a device. A
device being disconnected is no longer functional in most cases, yet IO
may fail only when the handler runs.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20200916191544.5104-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -26,6 +26,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/netdevice.h>
 #include <linux/sched/signal.h>
+#include <linux/sched/mm.h>
 #include <linux/sysfs.h>
 
 #include "base.h"
@@ -3062,6 +3063,7 @@ void device_del(struct device *dev)
 	struct device *parent = dev->parent;
 	struct kobject *glue_dir = NULL;
 	struct class_interface *class_intf;
+	unsigned int noio_flag;
 
 	device_lock(dev);
 	kill_device(dev);
@@ -3073,6 +3075,7 @@ void device_del(struct device *dev)
 	/* Notify clients of device removal.  This call must come
 	 * before dpm_sysfs_remove().
 	 */
+	noio_flag = memalloc_noio_save();
 	if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_DEL_DEVICE, dev);
@@ -3114,6 +3117,7 @@ void device_del(struct device *dev)
 	glue_dir = get_glue_dir(dev);
 	kobject_del(&dev->kobj);
 	cleanup_glue_dir(dev, glue_dir);
+	memalloc_noio_restore(noio_flag);
 	put_device(parent);
 }
 EXPORT_SYMBOL_GPL(device_del);