linux-kernel - Re: [fixup][PATCH 2/6] ACPI / hotplug: Refuse to hot-remove all objects with disabled hotplug

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Date:	Wed, 06 Nov 2013 02:35:23 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Toshi Kani <toshi.kani@...com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [fixup][PATCH 2/6] ACPI / hotplug: Refuse to hot-remove all objects with disabled hotplug

On Tuesday, November 05, 2013 05:39:27 PM Toshi Kani wrote:
> On Wed, 2013-11-06 at 00:27 +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > In theory, an ACPI device object may be the parent of another
> > device object whose hotplug is disabled by user space through its
> > scan handler.  In that case, the eject operation targeting the
> > parent should fail as though the parent's own hotplug was disabled,
> > but currently this is not the case, because acpi_scan_hot_remove()
> > doesn't check the disable/enable hotplug status of the children
> > of the top-most object passed to it.
> > 
> > To fix this, modify acpi_bus_offline_companions() to return an
> > error code if hotplug is disabled for the given device object.
> > [Also change the name of the function to acpi_bus_offline(),
> > because it is not only about companions any more, and change
> > the name of acpi_bus_online_companions() accordingly.]  Make
> > acpi_scan_hot_remove() propagate that error to its callers.
> > 
>  :
> > +static acpi_status acpi_bus_online(acpi_handle handle, u32 lvl, void *data,
> > +				   void **ret_p)
> >  {
> >  	struct acpi_device *device = NULL;
> >  	struct acpi_device_physical_node *pn;
> > @@ -214,26 +220,32 @@ static int acpi_scan_hot_remove(struct a
> >  	 * If the first pass is successful, the second one isn't needed, though.
> >  	 */
> >  	errdev = NULL;
> > -	acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
> > -			    NULL, acpi_bus_offline_companions,
> > -			    (void *)false, (void **)&errdev);
> > -	acpi_bus_offline_companions(handle, 0, (void *)false, (void **)&errdev);
> > +	status = acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
> > +				     NULL, acpi_bus_offline, (void *)false,
> > +				     (void **)&errdev);
> > +	if (status == AE_SUPPORT) {
> > +		dev_warn(errdev, "Offline disabled.\n");
> > +		acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
> > +				    acpi_bus_online, NULL, NULL, NULL);
> > +		put_device(&device->dev);
> > +		return -EPERM;
> > +	}
> > +	acpi_bus_offline(handle, 0, (void *)false, (void **)&errdev);
> >  	if (errdev) {
> 
> If the target object failed with AE_SUPPORT, shouldn't we skip the 2nd
> pass and return with -EPERM after rollback?

We've checked the target object already in acpi_hotplug_notify_cb() or in
acpi_eject_store().

Which is telling me that the previous version of the patch was better after
all, because the hotplug.enabled thing takes precedence over
acpi_force_hot_remove in the other places.  So this:

https://patchwork.kernel.org/patch/3135841/

is the right version.  Sorry for the confusion.

Thanks,
Rafael

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