scsi: sysfs: Introduce sysfs_{un,}break_active_protection()

[mirror_ubuntu-bionic-kernel.git] / fs / sysfs / file.c

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index fbd090a10fd96b5afde589e780fa3a4fad872f5e..adc2eeba1c04164db6aa7f410c0db9f0cb18809e 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -411,6 +411,50 @@ int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 }
 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 
+/**
+ * sysfs_break_active_protection - break "active" protection
+ * @kobj: The kernel object @attr is associated with.
+ * @attr: The attribute to break the "active" protection for.
+ *
+ * With sysfs, just like kernfs, deletion of an attribute is postponed until
+ * all active .show() and .store() callbacks have finished unless this function
+ * is called. Hence this function is useful in methods that implement self
+ * deletion.
+ */
+struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
+                                                 const struct attribute *attr)
+{
+       struct kernfs_node *kn;
+
+       kobject_get(kobj);
+       kn = kernfs_find_and_get(kobj->sd, attr->name);
+       if (kn)
+               kernfs_break_active_protection(kn);
+       return kn;
+}
+EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
+
+/**
+ * sysfs_unbreak_active_protection - restore "active" protection
+ * @kn: Pointer returned by sysfs_break_active_protection().
+ *
+ * Undo the effects of sysfs_break_active_protection(). Since this function
+ * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
+ * argument passed to sysfs_break_active_protection() that attribute may have
+ * been removed between the sysfs_break_active_protection() and
+ * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
+ * this function has returned.
+ */
+void sysfs_unbreak_active_protection(struct kernfs_node *kn)
+{
+       struct kobject *kobj = kn->parent->priv;
+
+       kernfs_unbreak_active_protection(kn);
+       kernfs_put(kn);
+       kobject_put(kobj);
+}
+EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
+
 /**
  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
  * @kobj: object we're acting for