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Commit 2f0157f1 authored by Dmitry Torokhov's avatar Dmitry Torokhov Committed by Linus Torvalds
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char_dev: pin parent kobject 



In certain cases (for example when a cdev structure is embedded into
another object whose lifetime is controlled by a separate kobject) it is
beneficial to tie lifetime of another object to the lifetime of
character device so that related object is not freed until after
char_dev object is freed.

To achieve this let's pin kobject's parent when doing cdev_add() and
unpin when last reference to cdev structure is being released.

Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6f0c0580

fs/char_dev.c

+17 −1
Original line number Diff line number Diff line
@@ -471,9 +471,19 @@ static int exact_lock(dev_t dev, void *data) 
 */

int cdev_add(struct cdev *p, dev_t dev, unsigned count)

{

	int error;



	p->dev = dev;

	p->count = count;

	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);



	error = kobj_map(cdev_map, dev, count, NULL,

			 exact_match, exact_lock, p);

	if (error)

		return error;



	kobject_get(p->kobj.parent);



	return 0;

}



static void cdev_unmap(dev_t dev, unsigned count)
@@ -498,14 +508,20 @@ void cdev_del(struct cdev *p) 
static void cdev_default_release(struct kobject *kobj)

{

	struct cdev *p = container_of(kobj, struct cdev, kobj);

	struct kobject *parent = kobj->parent;



	cdev_purge(p);

	kobject_put(parent);

}



static void cdev_dynamic_release(struct kobject *kobj)

{

	struct cdev *p = container_of(kobj, struct cdev, kobj);

	struct kobject *parent = kobj->parent;



	cdev_purge(p);

	kfree(p);

	kobject_put(parent);

}



static struct kobj_type ktype_cdev_default = {