1 files changed, 59 insertions, 5 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 8d4d839a9d88..fc4633378dc0 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -168,12 +168,12 @@ sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
         ssize_t retval = 0;
 
         down(&buffer->sem);
-        if (buffer->orphaned) {
-                retval = -ENODEV;
-                goto out;
-        }
         if (buffer->needs_read_fill) {
-                if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
+                if (buffer->orphaned)
+                        retval = -ENODEV;
+                else
+                        retval = fill_read_buffer(file->f_path.dentry,buffer);
+                if (retval)
                         goto out;
         }
         pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
@@ -629,6 +629,60 @@ void sysfs_remove_file_from_group(struct kobject *kobj,
 }
 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 
+struct sysfs_schedule_callback_struct {
+        struct kobject          *kobj;
+        void                    (*func)(void *);
+        void                    *data;
+        struct work_struct      work;
+};
+
+static void sysfs_schedule_callback_work(struct work_struct *work)
+{
+        struct sysfs_schedule_callback_struct *ss = container_of(work,
+                        struct sysfs_schedule_callback_struct, work);
+
+        (ss->func)(ss->data);
+        kobject_put(ss->kobj);
+        kfree(ss);
+}
+
+/**
+ * sysfs_schedule_callback - helper to schedule a callback for a kobject
+ * @kobj: object we're acting for.
+ * @func: callback function to invoke later.
+ * @data: argument to pass to @func.
+ *
+ * sysfs attribute methods must not unregister themselves or their parent
+ * kobject (which would amount to the same thing).  Attempts to do so will
+ * deadlock, since unregistration is mutually exclusive with driver
+ * callbacks.
+ *
+ * Instead methods can call this routine, which will attempt to allocate
+ * and schedule a workqueue request to call back @func with @data as its
+ * argument in the workqueue's process context.  @kobj will be pinned
+ * until @func returns.
+ *
+ * Returns 0 if the request was submitted, -ENOMEM if storage could not
+ * be allocated.
+ */
+int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
+                void *data)
+{
+        struct sysfs_schedule_callback_struct *ss;
+
+        ss = kmalloc(sizeof(*ss), GFP_KERNEL);
+        if (!ss)
+                return -ENOMEM;
+        kobject_get(kobj);
+        ss->kobj = kobj;
+        ss->func = func;
+        ss->data = data;
+        INIT_WORK(&ss->work, sysfs_schedule_callback_work);
+        schedule_work(&ss->work);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
+
 
 EXPORT_SYMBOL_GPL(sysfs_create_file);
 EXPORT_SYMBOL_GPL(sysfs_remove_file);