[PATCH RESEND] char_dev: add cdev->release() and convert cdev_alloc()to use it

[Tejun Heo]

Add cdev->release() so that cdev can be considered in more involved
object lifetime management.  cdev_alloc() used a separate ktype for
auto-free release().  This patch converts it to use cdev->release() so
that there's no need for separate ktype and cdev_init() can be used
for auto-free variant too.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
 fs/char_dev.c        |   30 +++++++++++++-----------------
 include/linux/cdev.h |    1 +
 2 files changed, 14 insertions(+), 17 deletions(-)

Index: work/fs/char_dev.c
===================================================================
--- work.orig/fs/char_dev.c
+++ work/fs/char_dev.c
@@ -482,26 +482,22 @@ void cdev_del(struct cdev *p)
 }
 
 
-static void cdev_default_release(struct kobject *kobj)
+static void cdev_release(struct kobject *kobj)
 {
 	struct cdev *p = container_of(kobj, struct cdev, kobj);
 	cdev_purge(p);
+	if (p->release)
+		p->release(p);
 }
 
-static void cdev_dynamic_release(struct kobject *kobj)
-{
-	struct cdev *p = container_of(kobj, struct cdev, kobj);
-	cdev_purge(p);
-	kfree(p);
-}
-
-static struct kobj_type ktype_cdev_default = {
-	.release	= cdev_default_release,
+static struct kobj_type cdev_ktype = {
+	.release	= cdev_release,
 };
 
-static struct kobj_type ktype_cdev_dynamic = {
-	.release	= cdev_dynamic_release,
-};
+static void cdev_alloc_release(struct cdev *cdev)
+{
+	kfree(cdev);
+}
 
 /**
  * cdev_alloc() - allocate a cdev structure
@@ -510,10 +506,10 @@ static struct kobj_type ktype_cdev_dynam
  */
 struct cdev *cdev_alloc(void)
 {
-	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
+	struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
 	if (p) {
-		INIT_LIST_HEAD(&p->list);
-		kobject_init(&p->kobj, &ktype_cdev_dynamic);
+		cdev_init(p, NULL);
+		p->release = cdev_alloc_release;
 	}
 	return p;
 }
@@ -530,7 +526,7 @@ void cdev_init(struct cdev *cdev, const
 {
 	memset(cdev, 0, sizeof *cdev);
 	INIT_LIST_HEAD(&cdev->list);
-	kobject_init(&cdev->kobj, &ktype_cdev_default);
+	kobject_init(&cdev->kobj, &cdev_ktype);
 	cdev->ops = fops;
 }
 
Index: work/include/linux/cdev.h
===================================================================
--- work.orig/include/linux/cdev.h
+++ work/include/linux/cdev.h
@@ -16,6 +16,7 @@ struct cdev {
 	struct list_head list;
 	dev_t dev;
 	unsigned int count;
+	void (*release)(struct cdev *);
 };
 
 void cdev_init(struct cdev *, const struct file_operations *);
--
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