[PATCHv2] base: force NOIO allocations during unplug

[PATCHv2] base: force NOIO allocations during unplug

[Oliver Neukum]

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.

v2: extended section for NOIO until after second notifier chain

Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/base/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index bb5806a2bd4c..b79783454293 100644
--- a/drivers/base/core.c
+++ b/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);
-- 
2.16.4

Re: [PATCHv2] base: force NOIO allocations during unplug

[Greg KH]

On Wed, Sep 16, 2020 at 09:15:44PM +0200, Oliver Neukum wrote:
> 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.
> 
> v2: extended section for NOIO until after second notifier chain
> 
> Signed-off-by: Oliver Neukum <oneukum@suse.com>
> ---
>  drivers/base/core.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index bb5806a2bd4c..b79783454293 100644
> --- a/drivers/base/core.c
> +++ b/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);
> -- 
> 2.16.4
> 

Thanks, now queued up.

greg k-h