linux-kernel - [PATCH 1/2] driver core: tell caller if the device/kboject is really released

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Date:   Thu, 30 Sep 2021 13:20:27 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     Changhui Zhong <czhong@...hat.com>, Yi Zhang <yi.zhang@...hat.com>,
        Ming Lei <ming.lei@...hat.com>
Subject: [PATCH 1/2] driver core: tell caller if the device/kboject is really released

Return if the device/kobject is really released to caller.

One use case is scsi_device_put() and the scsi device's release handler
runs async work to clean up things. We have to piggyback the module_put()
into the async work for avoiding to touch unmapped module page.

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 drivers/base/core.c     | 5 +++--
 include/linux/device.h  | 2 +-
 include/linux/kobject.h | 2 +-
 lib/kobject.c           | 5 +++--
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index e65dd803a453..cd1365a934b9 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3459,11 +3459,12 @@ EXPORT_SYMBOL_GPL(get_device);
  * put_device - decrement reference count.
  * @dev: device in question.
  */
-void put_device(struct device *dev)
+int put_device(struct device *dev)
 {
 	/* might_sleep(); */
 	if (dev)
-		kobject_put(&dev->kobj);
+		return kobject_put(&dev->kobj);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(put_device);
 
diff --git a/include/linux/device.h b/include/linux/device.h
index e270cb740b9e..ab089d743667 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -949,7 +949,7 @@ extern int (*platform_notify_remove)(struct device *dev);
  *
  */
 struct device *get_device(struct device *dev);
-void put_device(struct device *dev);
+int put_device(struct device *dev);
 bool kill_device(struct device *dev);
 
 #ifdef CONFIG_DEVTMPFS
diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index ea30529fba08..c83cc8a7a170 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -111,7 +111,7 @@ extern int __must_check kobject_move(struct kobject *, struct kobject *);
 extern struct kobject *kobject_get(struct kobject *kobj);
 extern struct kobject * __must_check kobject_get_unless_zero(
 						struct kobject *kobj);
-extern void kobject_put(struct kobject *kobj);
+extern int kobject_put(struct kobject *kobj);
 
 extern const void *kobject_namespace(struct kobject *kobj);
 extern void kobject_get_ownership(struct kobject *kobj,
diff --git a/lib/kobject.c b/lib/kobject.c
index ea53b30cf483..7ebdd6b99064 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -743,15 +743,16 @@ static void kobject_release(struct kref *kref)
  *
  * Decrement the refcount, and if 0, call kobject_cleanup().
  */
-void kobject_put(struct kobject *kobj)
+int kobject_put(struct kobject *kobj)
 {
 	if (kobj) {
 		if (!kobj->state_initialized)
 			WARN(1, KERN_WARNING
 				"kobject: '%s' (%p): is not initialized, yet kobject_put() is being called.\n",
 			     kobject_name(kobj), kobj);
-		kref_put(&kobj->kref, kobject_release);
+		return kref_put(&kobj->kref, kobject_release);
 	}
+	return 0;
 }
 EXPORT_SYMBOL(kobject_put);
 
-- 
2.31.1