Commit 7c1ef338 authored by Gabriel Krisman Bertazi's avatar Gabriel Krisman Bertazi Committed by Martin K. Petersen
Browse files

scsi: drivers: base: Support atomic version of attribute_container_device_trigger 

attribute_container_device_trigger invokes callbacks that may fail for one
or more classdevs, for instance, the transport_add_class_device callback,
called during transport creation, does memory allocation.  This
information, though, is not propagated to upper layers, and any driver
using the attribute_container_device_trigger API will not know whether any,
some, or all callbacks succeeded.

This patch implements a safe version of this dispatcher, to either succeed
all the callbacks or revert to the original state.

Link: https://lore.kernel.org/r/20200106185817.640331-2-krisman@collabora.com


Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarGabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 54155ed4

drivers/base/attribute_container.c

+103 −0
Original line number Diff line number Diff line
@@ -236,6 +236,109 @@ attribute_container_remove_device(struct device *dev, 
	mutex_unlock(&attribute_container_mutex);

}



static int

do_attribute_container_device_trigger_safe(struct device *dev,

					   struct attribute_container *cont,

					   int (*fn)(struct attribute_container *,

						     struct device *, struct device *),

					   int (*undo)(struct attribute_container *,

						       struct device *, struct device *))

{

	int ret;

	struct internal_container *ic, *failed;

	struct klist_iter iter;



	if (attribute_container_no_classdevs(cont))

		return fn(cont, dev, NULL);



	klist_for_each_entry(ic, &cont->containers, node, &iter) {

		if (dev == ic->classdev.parent) {

			ret = fn(cont, dev, &ic->classdev);

			if (ret) {

				failed = ic;

				klist_iter_exit(&iter);

				goto fail;

			}

		}

	}

	return 0;



fail:

	if (!undo)

		return ret;



	/* Attempt to undo the work partially done. */

	klist_for_each_entry(ic, &cont->containers, node, &iter) {

		if (ic == failed) {

			klist_iter_exit(&iter);

			break;

		}

		if (dev == ic->classdev.parent)

			undo(cont, dev, &ic->classdev);

	}

	return ret;

}



/**

 * attribute_container_device_trigger_safe - execute a trigger for each

 * matching classdev or fail all of them.

 *

 * @dev:  The generic device to run the trigger for

 * @fn	  the function to execute for each classdev.

 * @undo  A function to undo the work previously done in case of error

 *

 * This function is a safe version of

 * attribute_container_device_trigger. It stops on the first error and

 * undo the partial work that has been done, on previous classdev.  It

 * is guaranteed that either they all succeeded, or none of them

 * succeeded.

 */

int

attribute_container_device_trigger_safe(struct device *dev,

					int (*fn)(struct attribute_container *,

						  struct device *,

						  struct device *),

					int (*undo)(struct attribute_container *,

						    struct device *,

						    struct device *))

{

	struct attribute_container *cont, *failed = NULL;

	int ret = 0;



	mutex_lock(&attribute_container_mutex);



	list_for_each_entry(cont, &attribute_container_list, node) {



		if (!cont->match(cont, dev))

			continue;



		ret = do_attribute_container_device_trigger_safe(dev, cont,

								 fn, undo);

		if (ret) {

			failed = cont;

			break;

		}

	}



	if (ret && !WARN_ON(!undo)) {

		list_for_each_entry(cont, &attribute_container_list, node) {



			if (failed == cont)

				break;



			if (!cont->match(cont, dev))

				continue;



			do_attribute_container_device_trigger_safe(dev, cont,

								   undo, NULL);

		}

	}



	mutex_unlock(&attribute_container_mutex);

	return ret;



}



/**

 * attribute_container_device_trigger - execute a trigger for each matching classdev

 *

include/linux/attribute_container.h

+7 −0
Original line number Diff line number Diff line
@@ -54,6 +54,13 @@ void attribute_container_device_trigger(struct device *dev, 
					int (*fn)(struct attribute_container *,

						  struct device *,

						  struct device *));

int attribute_container_device_trigger_safe(struct device *dev,

					    int (*fn)(struct attribute_container *,

						      struct device *,

						      struct device *),

					    int (*undo)(struct attribute_container *,

							struct device *,

							struct device *));

void attribute_container_trigger(struct device *dev, 

				 int (*fn)(struct attribute_container *,

					   struct device *));