Merge branch 'devicetree/next-console' into devicetree/next

[firefly-linux-kernel-4.4.55.git] / fs / kernfs / file.c

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index e3d37f607f975dd06f6c9534b2dc929c3fa5fa21..d895b4b7b66116f47ef68ed6ef5b3d46d31980ab 100644 (file)
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -39,6 +39,19 @@ struct kernfs_open_node {
        struct list_head        files; /* goes through kernfs_open_file.list */
 };
 
+/*
+ * kernfs_notify() may be called from any context and bounces notifications
+ * through a work item.  To minimize space overhead in kernfs_node, the
+ * pending queue is implemented as a singly linked list of kernfs_nodes.
+ * The list is terminated with the self pointer so that whether a
+ * kernfs_node is on the list or not can be determined by testing the next
+ * pointer for NULL.
+ */
+#define KERNFS_NOTIFY_EOL                      ((void *)&kernfs_notify_list)
+
+static DEFINE_SPINLOCK(kernfs_notify_lock);
+static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
+
 static struct kernfs_open_file *kernfs_of(struct file *file)
 {
        return ((struct seq_file *)file->private_data)->private;
@@ -783,24 +796,25 @@ static unsigned int kernfs_fop_poll(struct file *filp, poll_table *wait)
        return DEFAULT_POLLMASK|POLLERR|POLLPRI;
 }
 
-/**
- * kernfs_notify - notify a kernfs file
- * @kn: file to notify
- *
- * Notify @kn such that poll(2) on @kn wakes up.
- */
-void kernfs_notify(struct kernfs_node *kn)
+static void kernfs_notify_workfn(struct work_struct *work)
 {
-       struct kernfs_root *root = kernfs_root(kn);
+       struct kernfs_node *kn;
        struct kernfs_open_node *on;
        struct kernfs_super_info *info;
-       unsigned long flags;
-
-       if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
+repeat:
+       /* pop one off the notify_list */
+       spin_lock_irq(&kernfs_notify_lock);
+       kn = kernfs_notify_list;
+       if (kn == KERNFS_NOTIFY_EOL) {
+               spin_unlock_irq(&kernfs_notify_lock);
                return;
+       }
+       kernfs_notify_list = kn->attr.notify_next;
+       kn->attr.notify_next = NULL;
+       spin_unlock_irq(&kernfs_notify_lock);
 
        /* kick poll */
-       spin_lock_irqsave(&kernfs_open_node_lock, flags);
+       spin_lock_irq(&kernfs_open_node_lock);
 
        on = kn->attr.open;
        if (on) {
@@ -808,12 +822,12 @@ void kernfs_notify(struct kernfs_node *kn)
                wake_up_interruptible(&on->poll);
        }
 
-       spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
+       spin_unlock_irq(&kernfs_open_node_lock);
 
        /* kick fsnotify */
        mutex_lock(&kernfs_mutex);
 
-       list_for_each_entry(info, &root->supers, node) {
+       list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
                struct inode *inode;
                struct dentry *dentry;
 
@@ -833,6 +847,33 @@ void kernfs_notify(struct kernfs_node *kn)
        }
 
        mutex_unlock(&kernfs_mutex);
+       kernfs_put(kn);
+       goto repeat;
+}
+
+/**
+ * kernfs_notify - notify a kernfs file
+ * @kn: file to notify
+ *
+ * Notify @kn such that poll(2) on @kn wakes up.  Maybe be called from any
+ * context.
+ */
+void kernfs_notify(struct kernfs_node *kn)
+{
+       static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
+       unsigned long flags;
+
+       if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
+               return;
+
+       spin_lock_irqsave(&kernfs_notify_lock, flags);
+       if (!kn->attr.notify_next) {
+               kernfs_get(kn);
+               kn->attr.notify_next = kernfs_notify_list;
+               kernfs_notify_list = kn;
+               schedule_work(&kernfs_notify_work);
+       }
+       spin_unlock_irqrestore(&kernfs_notify_lock, flags);
 }
 EXPORT_SYMBOL_GPL(kernfs_notify);