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-rw-r--r--fs/kernfs/file.c69
1 files changed, 55 insertions, 14 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index e3d37f6..d895b4b 100644
--- 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);
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