diff mbox series

[v2,1/6] drivers/base/devres: Introduce devm_release_action()

Message ID 155727336530.292046.2926860263201336366.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive)
State New, archived
Headers show
Series mm/devm_memremap_pages: Fix page release race | expand

Commit Message

Dan Williams May 7, 2019, 11:56 p.m. UTC 
The devm_add_action() facility allows a resource allocation routine to
add custom devm semantics. One such user is devm_memremap_pages().

There is now a need to manually trigger devm_memremap_pages_release().
Introduce devm_release_action() so the release action can be triggered
via a new devm_memunmap_pages() api in a follow-on change.

Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/base/devres.c  |   24 +++++++++++++++++++++++-
 include/linux/device.h |    1 +
 2 files changed, 24 insertions(+), 1 deletion(-)

Comments

Greg Kroah-Hartman May 14, 2019, 7:12 p.m. UTC | #1 
On Tue, May 07, 2019 at 04:56:05PM -0700, Dan Williams wrote:
> The devm_add_action() facility allows a resource allocation routine to
> add custom devm semantics. One such user is devm_memremap_pages().
> 
> There is now a need to manually trigger devm_memremap_pages_release().
> Introduce devm_release_action() so the release action can be triggered
> via a new devm_memunmap_pages() api in a follow-on change.
> 
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/base/devres.c  |   24 +++++++++++++++++++++++-
>  include/linux/device.h |    1 +
>  2 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index e038e2b3b7ea..0bbb328bd17f 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -755,10 +755,32 @@ void devm_remove_action(struct device *dev, void (*action)(void *), void *data)
>  
>  	WARN_ON(devres_destroy(dev, devm_action_release, devm_action_match,
>  			       &devres));
> -
>  }
>  EXPORT_SYMBOL_GPL(devm_remove_action);
>  
> +/**
> + * devm_release_action() - release previously added custom action
> + * @dev: Device that owns the action
> + * @action: Function implementing the action
> + * @data: Pointer to data passed to @action implementation
> + *
> + * Releases and removes instance of @action previously added by
> + * devm_add_action().  Both action and data should match one of the
> + * existing entries.
> + */
> +void devm_release_action(struct device *dev, void (*action)(void *), void *data)
> +{
> +	struct action_devres devres = {
> +		.data = data,
> +		.action = action,
> +	};
> +
> +	WARN_ON(devres_release(dev, devm_action_release, devm_action_match,
> +			       &devres));

What does WARN_ON help here?  are we going to start getting syzbot
reports of this happening?

How can this fail?

thanks,

greg k-h
Dan Williams May 14, 2019, 7:24 p.m. UTC | #2 
On Tue, May 14, 2019 at 12:12 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Tue, May 07, 2019 at 04:56:05PM -0700, Dan Williams wrote:
> > The devm_add_action() facility allows a resource allocation routine to
> > add custom devm semantics. One such user is devm_memremap_pages().
> >
> > There is now a need to manually trigger devm_memremap_pages_release().
> > Introduce devm_release_action() so the release action can be triggered
> > via a new devm_memunmap_pages() api in a follow-on change.
> >
> > Cc: Logan Gunthorpe <logang@deltatee.com>
> > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >  drivers/base/devres.c  |   24 +++++++++++++++++++++++-
> >  include/linux/device.h |    1 +
> >  2 files changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> > index e038e2b3b7ea..0bbb328bd17f 100644
> > --- a/drivers/base/devres.c
> > +++ b/drivers/base/devres.c
> > @@ -755,10 +755,32 @@ void devm_remove_action(struct device *dev, void (*action)(void *), void *data)
> >
> >       WARN_ON(devres_destroy(dev, devm_action_release, devm_action_match,
> >                              &devres));
> > -
> >  }
> >  EXPORT_SYMBOL_GPL(devm_remove_action);
> >
> > +/**
> > + * devm_release_action() - release previously added custom action
> > + * @dev: Device that owns the action
> > + * @action: Function implementing the action
> > + * @data: Pointer to data passed to @action implementation
> > + *
> > + * Releases and removes instance of @action previously added by
> > + * devm_add_action().  Both action and data should match one of the
> > + * existing entries.
> > + */
> > +void devm_release_action(struct device *dev, void (*action)(void *), void *data)
> > +{
> > +     struct action_devres devres = {
> > +             .data = data,
> > +             .action = action,
> > +     };
> > +
> > +     WARN_ON(devres_release(dev, devm_action_release, devm_action_match,
> > +                            &devres));
>
> What does WARN_ON help here?  are we going to start getting syzbot
> reports of this happening?

Hopefully, yes, if developers misuse the api they get a loud
notification similar to devm_remove_action() misuse.

> How can this fail?

It's a catch to make sure that @dev actually has a live devres
resource that can be found via @action and @data.
diff mbox series

Patch

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index e038e2b3b7ea..0bbb328bd17f 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -755,10 +755,32 @@  void devm_remove_action(struct device *dev, void (*action)(void *), void *data)
 
 	WARN_ON(devres_destroy(dev, devm_action_release, devm_action_match,
 			       &devres));
-
 }
 EXPORT_SYMBOL_GPL(devm_remove_action);
 
+/**
+ * devm_release_action() - release previously added custom action
+ * @dev: Device that owns the action
+ * @action: Function implementing the action
+ * @data: Pointer to data passed to @action implementation
+ *
+ * Releases and removes instance of @action previously added by
+ * devm_add_action().  Both action and data should match one of the
+ * existing entries.
+ */
+void devm_release_action(struct device *dev, void (*action)(void *), void *data)
+{
+	struct action_devres devres = {
+		.data = data,
+		.action = action,
+	};
+
+	WARN_ON(devres_release(dev, devm_action_release, devm_action_match,
+			       &devres));
+
+}
+EXPORT_SYMBOL_GPL(devm_release_action);
+
 /*
  * Managed kmalloc/kfree
  */
diff --git a/include/linux/device.h b/include/linux/device.h
index 4e6987e11f68..6d7fd5370f3d 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -713,6 +713,7 @@  void __iomem *devm_of_iomap(struct device *dev,
 /* allows to add/remove a custom action to devres stack */
 int devm_add_action(struct device *dev, void (*action)(void *), void *data);
 void devm_remove_action(struct device *dev, void (*action)(void *), void *data);
+void devm_release_action(struct device *dev, void (*action)(void *), void *data);
 
 static inline int devm_add_action_or_reset(struct device *dev,
 					   void (*action)(void *), void *data)